Class 
 Book. 
 
 Copyrights 
 
 COPYRIGHT DEPOSIT. 
 
NOTES ON SOILS 
 
 An Outline for an Elementary Course 
 in Soils 
 
 BY 
 
 A. R. WHITSON 
 
 Professor of Soils, The University of Wisconsin 
 
 H. L. WALSTER 
 
 Instructor in Soils, The University of Wisconsin 
 
 Published by the Authors 
 Madison, Wisconsin 
 
Copyright, 1909, 
 
 BY 
 
 A. K. Willi SON AND li. I>. WALSTBB. 
 
 JEMOCRAT PRINTING COMPANY. M»OISOf 
 
 © CI. A 2533 35 
 
PREFACE 
 
 The aim in the pages that follow has been to present 
 a brief outline of work in Soils, adapted to the needs 
 of students pursuing short courses in Agriculture. The 
 present volume has been hastily prepared, and therefore 
 many errors may have been overlooked. Much valuable 
 data, not included in these pages, will be found in the 
 bulletins listed in the appendix, and in the larger text 
 books upon the subject of Soils. Acknowledgment is 
 due Mr. Stuart L. Clark for his careful preparation of 
 the line drawings. 
 
 A. R. W. 
 
 H. L. W. 
 The University of Wisconsin, 
 
 College of Agriculture, 
 
 December, 1909. 
 
CONTENTS 
 
 Chapter Page 
 
 I. Conditions essential for Plant Growth 1 
 
 II. The Origin of Soil -Material 19 
 
 III. The Supply of Chemical Elements 26 
 
 I V. II minis '■'>- 
 
 V. Acidity and Liming 42 
 
 V I . Nitrogen 47 
 
 VII. Phosphorus and Potash 58 
 
 VIII. .Mechanical Composition, Texture and Tilth.... 6S 
 
 IX. Water-Holding Capacity of Soils 7.", 
 
 X. Movements of Soil Water 79 
 
 XI. Temperature of Soils 83 
 
 XII. Ventilation of Soils 88 
 
 XIII. Tillage 90 
 
 XIV. Barnyard Manure 95 
 
 XV Classification of Soils 101 
 
 XVI. Conditions of Climate and Soils Needed by 
 
 XVII. Rotation of Crops 122 
 
 XVIII. Types of Sandy Soils and their Management 125 
 
 XiX. Types and Management of Clay Soils of Humid 
 
 Regions 131 
 
 XX. Marsh Soils 136 
 
 Appendix 140 
 
NOTES ON SOILS 
 
 CHAPTER I. 
 
 CONDITIONS ESSENTIAL FOR PLANT GROWTH. 
 
 In studying the growth of the plant it is convenient 
 to divide its life history into three periods: First, the 
 period of germination ; second, the period of vegetative 
 growth, and third, the period of fruition. It is, of 
 course, true that these periods shade one into the other 
 or overlap to a certain extent, but it is nevertheless 
 helpful to study the effect of conditions on plants from 
 the standpoint of this threefold division. Some condi- 
 tions are essential to the life of the plant at all times 
 while others apply to only one or two of its periods of 
 development. 
 
 Conditions Necessary for Germination. 
 
 ( 1 ) Absorption of Water. The first act in the 
 germination of seed is the absorption of moisture. The 
 factors which influence this process are : Temperature, 
 closeness of contact between the soil and seed, amount 
 of moisture in the soil and the amount of soluble salts 
 in the soil. 
 
2 NOTES ON SOILS. 
 
 (2) Temperature. By placing beans or peas in 
 warm and in cold water the greater rapidity with which 
 
 the warm wain- is absorbed can be readily determined. 
 It is for this reason, in part, that seeds germinate in 
 warm soil faster than in cold soil. But, besides influenc- 
 ing the rate at which water is absorbed, the temperature 
 also influences the chemical changes which take place in 
 the seed during germination. 
 
 The influence of temperature on germination has been 
 studied by a number of experimenters and the averages 
 of their determinations of the best and of the lowest 
 temperatures, for the germination of the seeds of a few 
 crops, are given in the following table. 
 
 Best. . . . 
 Lowest . 
 
 Wheal and 
 Barlej . 
 
 Red 
 
 ( lover. 
 
 Corn. 
 
 Rape. 
 
 75 deg. 
 40 deg. 
 
 70 deg. 
 lo deg. 
 
 90 deg. 
 is deg. 
 
 90 deg. 
 to deg. 
 
 There is usually little gained by sowing seeds in the 
 spring too early and while the ground is loo cold for 
 the respective crops, although for some seeds, as for in- 
 stance Red Clover, the moisture conditions may be bet- 
 ter earlier. 
 
 The ways in which the temperature of the soil can be 
 influenced will be studied in ;i later chapter. 
 
 (3) Contact of Seed and Soil. The ease with 
 which water can lie absorbed from the soil by the seed 
 will also depend on the number of points of contact be- 
 tween the soil and seed. This will depend on the fine- 
 
CONDITIONS ESSENTIAL FOR PLANT GROWTH. 3 
 
 ness of the soil and on the firmness with which it is 
 pressed down on the seed. 
 
 It is for this reason that so much depends on the care 
 taken in the preparation of the seed lied and in firm- 
 ing the soil by rolling after the seed is planted. And 
 the fineness depends very largely on the condition of 
 the soil when cultivated, as will be shown in a later 
 chapter. 
 
 The degree of fineness necessary for good germina- 
 tion depends also on the kind and size of seed. The 
 smaller seeds, such as those of the grasses and clovers, 
 require a finer seed lied than is essential for corn and 
 peas. 
 
 (4) Influence of Salts. On account of the attrac- 
 tion between salts and water the presence of a consid- 
 eral Le amount of soluble salts in the soil will prevent 
 the seed from absorbing water. This can be shown by 
 placing 1 cans or peas in two cups of water — one of 
 which contains a small amount of common salt while the 
 other contains none. The salt will partly or entirely 
 prevent tie absorption of water by the seed. It is in 
 this way that the large amounts of salts in the soil of 
 arid regions often prevent the germination of seedi 
 Some salts are actually poisonous to plants even in 
 small amounts while others simply act to prevent the 
 water from entering the seed and are not injurious ex- 
 cept when present in considerable quantities. 
 
 ( 5 ) Oxygen. The work of constructing new tissues 
 and of forcing the newly formed root into the soil is 
 done by the energy resulting from oxidation of food 
 stored in seed and therefore, the germinating seed re- 
 quires a supply of available oxygen, just as the energy 
 
4 NOTES ON soils. 
 
 which a man uses in doing "work comes from the food 
 which he consumes when oxidized iii the muscle tissue. 
 It is therefore necessary that the soil iii which the 
 seed is germinating allow the air to reach it. otherwise 
 the seed will rot without germination. The access of air 
 to the seed is frequently prevented by loo much water in 
 the soil and by puddling of the soil as will he described 
 later. 
 
 (6) Mineral Elements not Needed for Germina- 
 tion. It is often noticed that seed will germinate and 
 grow for a short time better in poor, sandy soil than in 
 fertile soil and even better in sawdust or other loose ma- 
 terial. This shows that nothing hut water and air need 
 he taken in by the seed in germination and in the early 
 growth of the seedling. 
 
 The amount of growth made by the seedling develop- 
 ing in sawdust or in the air alone under suitable con- 
 ditions of moisture, temperature and light depends on 
 the amount of material stored in the seed. Small seeds 
 such as those of most grasses will allow but little growth 
 while larger seeds such as those of pea and hean may 
 allow the seedling to attain considerable size; in some 
 e;ises half the size usually attained in ordinary soil, and 
 even produce flowers. 
 
 Conditions Essential for Vegetal ire Growth. 
 
 (7) Mineral Elements Taken from the Soil. 
 
 While tin' seed will germinate readily and the seedling 
 grow rapidly for a short time in pure sand or sawdust 
 il soon begins to lose its healthy green color and finally 
 stops growing. On the other hand, while the field soil 
 
CONDITIONS ESSENTIAL FOR PLANT GROWTH. 5 
 
 may not allow the seed to germinate as rapidly as the 
 pure sand or saw-dust, it does allow it to continue its 
 growth to maturity. 
 
 The reason for this is that it furnishes material which 
 is necessary for continued growth although not neces- 
 sary for germination. 
 
 When plants are analyzed the following elements 
 taken from the soil are usually found: sodium, potas- 
 sium, calcium, magnesium, iron, silicon, chlorine, sul- 
 phur, phosphorus and nitrogen. With the exception of 
 the nitrogen these are almost entirely left in the ash on 
 burning. Besides these elements there are a number of 
 others which are often found. 
 
 Part of the above list of elements are not entirely 
 necessary to growth, as has been shown by growing 
 plants to maturity in a solution not containing them. 
 Those which do not seem to be essential are sodium, sili- 
 ccn and chlorine. All of the remaining ones must be 
 present or growth will cease before maturity. 
 
 (8) The Amount of Salts Taken up by Plants. 
 The amount of the various elements taken up by plants 
 depends on three factors: first, the relative amount 
 present in the soil in a form which can be taken up by 
 the plant; second, on the combination it makes in the 
 plant, and third, on the kind of plant. 
 
 More salts will be taken up from a soil rich in soluble 
 salts than from one poor in them. If a given element 
 combines with other substances in the plant much more 
 of it will be taken up, than if no such combination is 
 made. 
 
 There is therefore quite a range in the amounts of 
 different elements found in the plant, and also in the 
 
<i NOTES ON Si ll I. S. 
 
 total amount of ash. Again, different plants growing 
 dti the same soil will take from it different amounts of 
 i he various elements. 
 
 (9) Variation in Fertilizing Constituents at 
 Different Stages of Growth. Different plants not 
 only use different amounts of plaid food, but the same 
 plaid lias a varying composition at different stages of 
 growth. This matter lias received careful attention at 
 the Ducal Agricultural Experiment Station in Bern- 
 burg, Germany, and some of their results will he given 
 here. 
 
 The amount of potash in the crop from one acre of 
 wheat was SS lbs. at a very early stage, 123 lbs. when 
 jusl heading out. 122 lbs. when fully headed out but 
 green, and decreased to 72 lbs. at the ripening stage, less 
 than at a very early stage, showing that the plant had 
 taken up large amounts of potash, used it in life proc- 
 esses, and then returned it to the soil, either by way of 
 the roots or by excretion on the surface of the leaves and 
 stems to be washed off by rain and dew. The same gen- 
 eral relation holds for nitrogen in the case of the wheat 
 plant, while phosphorus, on the other hand, reaches its 
 maximum when the plant is fully headed out. and does 
 nut materially decrease ;it maturity. Analyses of an- 
 other cereal, barley, at different stages in its growth 
 showed the same general tendencies, although the abso- 
 lute amounts are different. 
 
 Quite different results were obtained with the potato. 
 The amount of potash in the tubers, leaves, and sleius 
 from one acre of potatoes was 47 lbs., when tubers were 
 just beginning to set (June 17). 78 lbs. one month 
 l;tcr (July 16). 112 lbs. two months later (Aug. 18), 
 
CONDITIONS ESSENTIAL FOR PLANT GROWTH. 7 
 
 and when the potatoes were fully ripe (Oct 5), 143 lbs. 
 showing a continual increase in amount of potash ab- 
 sorbed. Similarly phosphorus increased from 8 lbs. at 
 an early stage to 28 lbs. at ripening stage, and nitrogen 
 from 45 to 111 lbs. This great difference between the 
 cereals and the potato is probably due to the fact that 
 the potato does not dry out on maturing as do the 
 cereal crops. 
 
 It should be remembered that the experimental work 
 here discussed was carried on under a particular set of 
 conditions and with a particular soil. The results ob- 
 tained might have been quite different under different 
 conditions, for we have pointed out in the previous 
 paragraph that the amount of an element taken up by a 
 plant depends upon the relative amount in the soil in 
 an available form. This general conclusion can be 
 drawn, that the composition of a plant at maturity does 
 not necessarily show the amount of plant food it may 
 have absorbed during its growth. 
 
 (10) Average Amount of Salts Removed by 
 Crops. While, as stated in previous paragraphs, the 
 amount of various salts absorbed by plants from the soil 
 varies greatly during different stages of growth still 
 the amount of the three most important elements, Nitro- 
 gen (N), Phosphoric Acid (P 2 5 ), and potash (K 2 0), 
 found in mature crops grown on ordinary clay loam soil 
 is quite constant. Since these are the amounts removed 
 from the soil by crops when harvested, they are very 
 important to bear in mind. 
 
 The following table, taken from Bulletin 47 of the 
 Minnesota Experiment Station, shows the amount of the 
 
b NOTES ON SOILS. 
 
 more importanl elements taken by different crops from 
 clav loam soil. 
 
 Tdbli showing the Plant Food material removed by the crops in 
 pounds per acn . 
 
 Crop. 
 
 ( tress 
 Weight. 
 
 Nitro- 
 gen. 
 
 Phos- 
 phoric 
 Acid. 
 
 Pot- 
 ash. 
 
 Lime. 
 
 Wheat, 20 bu 
 
 1200 
 2000 
 
 25 
 10 
 
 12.5 
 7.5 
 
 7 
 28 
 
 1 
 7 
 
 
 
 Total 
 
 
 35 
 
 20 
 
 35 
 
 8 
 
 
 
 
 Barley, 40 bu 
 
 11)20 
 3000 
 
 28 
 12 
 
 15 
 5 
 
 8 1 
 30 ' 8 
 
 
 
 Total 
 
 
 40 
 
 20 
 
 38 1 9 
 
 
 
 
 ( >al s 50 bu 
 
 1 COO 
 3000 
 
 35 
 
 15 
 
 12 
 6 
 
 10 
 35 
 
 1.5 
 
 Straw 
 
 9.5 
 
 Total 
 
 
 50 
 
 18 
 
 45 
 
 11 
 
 
 
 
 Corn, 65 bu 
 
 Stalks 
 
 2200 
 
 (JO00 
 
 40 
 15 
 
 18 
 
 14 
 
 15 
 80 
 
 1 
 •jo 
 
 
 
 Total . 
 
 
 85 
 
 32 
 
 95 
 
 21 
 
 
 
 
 Peas, 30 bu 
 
 St raw 
 
 1800 
 3500 
 
 
 18 
 
 7 
 
 22 
 
 38 
 
 4 
 
 ;i 
 
 
 
 Total 
 
 
 
 25 
 
 GO 
 
 75 
 
 
 
 
 
 Flax, 15 im 
 
 900 
 1800 
 
 39 
 15 
 
 15 
 
 :; 
 
 8 
 
 1!) 
 
 ;; 
 
 Straw 
 
 13 
 
 
 
 
 Total 
 
 
 5J 
 
 18 27 
 
 1(5 
 
 
 
 
 Potatoes. 300 bu 
 
 Mangels, 10 tons. . . . 
 
 2000 
 1000 
 
 |S(I()(I 
 
 20000 
 
 30 
 
 80 
 
 20 
 28 
 10 
 35 
 
 15 12 
 
 66 75 
 
 150 50 
 
 150 30 
 
CONDITIONS ESSENTIAL FOR PLANT GROWTH. 9 
 
 (11) Distribution of Elements in Plant. Study 
 -of the foregoing table will show that nitrogen and phos- 
 phoric acid go chiefly to the seed or grain of crops, while 
 potash and lime are largely found in the stalks or straw. 
 From this we are able to determine the probable losses 
 when either the grain or straw or both are sold. 
 
 (12) Food Constituents of Plants. The chemist 
 divides the chief food compounds produced in plants 
 into three classes : carbohydrates, fats and proteids. The 
 carbohydrates, such as starch, sugar and a large part 
 of crude fibre and the fats and oils of the plant are 
 made up of only three chemical elements : carbon, oxy- 
 gen and hydrogen. These are derived from carbon- 
 dioxide of the air and from water absorbed by the root. 
 The proteids. however, which form the most valuable 
 part of the food contain considerable nitrogen, small 
 amounts of sulphur and in some cases phosphorus. 
 These three elements are taken from the soil. 
 
 (13) Variation in Composition During Growth. 
 Since young plants and growing parts of older plants 
 have thin walled cells filled with protoplasm, they have 
 a high per cent of protein and a low per cent of crude 
 fiber or cellulose. Crops cut very green are therefore 
 richer in protein than mature crops. Moreover, if crops 
 are prevented from making full growth, the stunted 
 crop is usually richer in protein than the crop making 
 a larger growth. There is an exception to this when the 
 failure to grow is due to lack of available nitrogen as 
 mentioned in paragraph 15. 
 
 (14) Function of Elements. Although it is com- 
 paratively easy to determine which of the elements 
 
10 NOTES ON SOILS. 
 
 found in the plant arc essential and which are unes- 
 sential to the growth of the plant it is very difficult to 
 find out just what the use of the essential elements is 
 to the plant. There are specific functions which each of 
 the essential elements have to perform and there are 
 more general functions which various elements can 
 perform. While a certain minimum amount of each of 
 the essential elements must be present for' the specific 
 functions, there must be larger amounts of some of the 
 essentia] elements or of the non-essential elements to 
 produce the best growth. A soil which is poor in all 
 the essential elements will often be helped to a certain 
 extent by an addition of any one while it is much more 
 benefited by the addition of all those lacking. 
 
 One of the special functions of potash seems to be- 
 to aid in the process of starch formation. Corn grow- 
 ing on the marsh lands of our state has been greatly 
 benefited by potash fertilizer and in all cases the in- 
 crease of grain — containing a large amount of starch — 
 has been greater than the gain in the stalks. The 
 formation of starch takes place in the leaves, it being 
 then carried to the seed and the potash is chiefly found 
 in the Leaves and stems of plants. 
 
 The phosphorus is necessary to the formation of 
 some proteids, and since the proteids form a larger per 
 eon of the seed than of the stalk and leaves, the phos- 
 phorus is found in larger amounts in the seed or grain 
 than in the stalk and leaves. 
 
 Calcium or lime seems necessary for the development 
 of leaves, for plants grown in solutions free from cal- 
 cium do not develop leaves readily. 
 
CONDITIONS ESSENTIAL FOR PLANT GROWTH. 
 
 11 
 
 Nitrogen is absolutely essential for the formation of 
 prot cids and the relative amount of protein found in 
 the plant depends partly on the relative amount of ni- 
 trogen in the soil in an available form, as well as on 
 the nature of the plant. 
 
 (15) Relation Between Composition of Plant 
 and Amount of Food Material Available to it. The 
 composition of the plant is to a certain extent depend- 
 ent on the relative amount of the necessary elements 
 available to it. When the amount of available nitrogen 
 is small the plant cannot produce as much protein as 
 it does ordinarily. The crop grown on soil very low in 
 available nitrogen is therefore often low in proteid, the 
 most valuable food material. 
 
 Experiments made by growing corn, oats and rape 
 on three sand plots to which had been added different 
 amounts of nitrates showed the following per cent of 
 protein where plot one received no nitrates; plot two, 
 a medium amount; and plot three, double this amount. 
 
 
 Oats. 
 
 Corn. 
 
 Rape. 
 
 Plot 1 
 
 Plot 2 
 
 Plot 3. . . 
 
 12.00 per cent. 
 15.81 per cent. 
 16.63 per cent. 
 
 S.44 per cent. 
 
 S».94 per cent. 
 
 1 1.25 per cent. 
 
 12.56 per cent. 
 14.00 per cent. 
 14.25 per cent. 
 
 
 These crops were cut green, as they would be used for 
 soiling. 
 
 These experiments, with others, show that not only is 
 the crop on fertile soil larger than that on poor soil ; 
 but it is richer in the most valuable food constituent. 
 
12 NOTES ON SOILS. 
 
 The composition of plants is also influenced by their 
 rate of growth and varies at differenl stages of growth. 
 This is discussed in paragraph 20. 
 
 The influence which climate and soil have on the per 
 cent of protein in wheat has been investigated by De- 
 herain in France and by Sonic in Tennessee. 
 
 During the period of most rapid growth of the cereals 
 comparatively little starch is transmitted to the seed, 
 most of it collecting in the upper part of the stem dur- 
 ing this period and being carried to the seed during the 
 ripening stage. 
 
 If therefore the weather becomes dry during the rip- 
 ening stage less starch is carried to the seed and it has a 
 relatively high protein content. 
 
 (16) Chemical Requirements of Different Crops. 
 Since different plants produce different relative amounts 
 of carbohydrates, fats and proteids, we should expect 
 that they would need somewhat different relative 
 amounts of the various elements. Those plants which 
 produce a relatively large amount of starch, such as corn 
 and potatoes, require considerable available potassium 
 while those which produce a relatively large amount 
 of proteid should require considerable available nitro- 
 gen. This is found to he home out by experience, but in 
 addition to these facts which we can explain in this way. 
 there are other cases where certain plants require rela- 
 tively large amounts of certain elements for reasons we 
 do not yet know. It will be helpful in studying the 
 relation of the various crops to the soil and of their 
 tieatment with fertilizers to lirst study some of the most 
 important cases of this varying requirement. 
 
CONDITIONS ESSENTIAL FOR PLANT GROWTH. 13 
 
 Cereals, such as wheat, oats and barley, need rela- 
 tively large amounts of nitrates and phosphates, while 
 not a very large amount of potassium is necessary. Corn 
 iu addition to available nitrogen and phosphate must 
 have considerable available potassium, possibly on ac- 
 count of the large amount of starch which is produced. 
 Potatoes also, both white and sweet, require considerable 
 potassium. Timothy and most grasses require also large 
 amounts of available nitrogen. Turnips do best when the 
 amount of available phosphorus is large, while beets 
 and carrots require more nitrogen. These are some of 
 the facts which have been learned from experience, but 
 our knowledge of this subject is still very incomplete. 
 
 (17) Uses of Water to the Plant and Amount 
 Required. There are a number of Afays in which water 
 is of service 1 in the growth of plants, among the most im- 
 portant of which are the following: (1) to keep the cell 
 Avails of the leaves moist so they can absorb carbon di- 
 oxide; (2) to evaporate from the surface and so pre- 
 vent the plant from getting too hot, just as the evapora- 
 tion of perspiration from the human body tends to keep 
 it cool; (3) 'to furnish the small amount of water needed 
 for building the various tissues in the plant; (4) to carry 
 the salts from the soil into the plant and to the leaves 
 where they are chiefly used in the chemical changes 
 taking place there. 
 
 This current of water into the plant roots, up the 
 stem and out of the leaves is called the transpiration 
 current. 
 
 The rate of transpiration depends chiefly on the 
 amount of moisture in the air, on the temperature, on 
 
14 xo'i i:s ox soils. 
 
 the strength of Lighl and on the character of the plant. 
 Moisture in the air lessens it; warmth increases and cold 
 decreases il : strong Lighl increases and darkness greatly 
 
 retards it: and some plants transpire nmeli less than 
 others under the same conditions because they are pro- 
 tected in various ways or have fewer stomata. 
 
 A aumber of experiments have been made by differ- 
 ent men to determine the number of pounds of water 
 lost by the plant for each pound of dry matter formed 
 by the plant. An average of these would be approxi- 
 mately as follows: Barley, 465; Oats. 500; Corn. 27-"); 
 Clover, 575; Peas. 47-"); Potatoes, 385. 
 
 A single determination of soy bean shows that it used 
 527 pounds for each pound of dry matter. From these 
 figures we would conclude that if no water ran off the 
 surface or drained away a crop of 2(1 bushels of wheat 
 would require only six inches of rain during the grow- 
 ing season ; or a crop of 50 bushels of oats only eighl 
 inches; 60 bushels of corn, ten inches; 300 bushels of 
 potatoes, six and one-fourth inches; two tons of clover 
 hay. nine inches. 
 
 (18) Relation of Light to Plant Growth. In the 
 development of the plant there are two processes going 
 on; one is the process of forming starch, fats and pro- 
 t< ids either for the plant itself or to be stored in some 
 part of the plant, such as the seed or root. The other 
 process is that of growth or the development of new tis- 
 sue and parts. This latter process is carried on by the 
 use of some of the material produced in the first process. 
 Prom this we see thai the plant differs from the animal 
 in that the plant produces as well as uses food, while 
 
CONDITIONS ESSENTIAL FOR PLANT GROWTH. 15 
 
 the animal uses food only and must be supplied with it 
 from outside 
 
 Now the production of starch, fats and proteids re- 
 quires light, while their use in growth and movement 
 does not require light. We have all noticed the growth 
 which potato vines will make from material stored in 
 the tuber in the entire absence of light and not only is 
 light not necessary but to a certain extent it retards 
 growth. The tendency of plants to turn towards light 
 .is due to the fact that the side away from the light 
 grows more rapidly than the other and pushes it over 
 towaids the light. The question as to the amount of 
 light necessary for producing the greatest amount of 
 Pood is not entirely understood, but it is known that the 
 strength of light received on the earth's surface in our 
 latitude during mid-day hours of the summer is as great 
 as can be used by most plants. Moreover in all prob- 
 ability the intensity of light at five o'clock during clear 
 days in the summer is as great as can be used by our 
 crops. 
 
 It will therefore be seen that the intensity of light is 
 not of so much importance as its duration. During the 
 long summer days of Northern latitude much more 
 rapid growth is possible than in the regions near the 
 « quator, because more food material is produced. The 
 starches and sugars in particular require light to pro- 
 duce them and hence relatively larger amounts of these 
 substances are produced in those regions where there are 
 few clouds to interrupt the sunshine, than in those re- 
 gions where there is much cloudiness. This is probably, 
 in part, the reason why the sugar beet produces a rela- 
 tively larger amount of sugar in Colorado where there 
 
16 NOTES ON SOILS. 
 
 is much more sunshine than in the Mississippi Valley 
 where there is more cloudiness. 
 
 (19) Relation of Temperature to Plant Growth. 
 The most favorable temperature for formation of food 
 by the plant is usually the most favorable for growth 
 also. When the amount of material produced by the 
 plant is studied at different temperatures, it is found 
 that it increases with increase in temperature up to a 
 certain point and then decreases; that is. the production 
 of food in the plant is lower at too high as well as too 
 low temperatures. Probably the most favorable tem- 
 peratures for our field crops art 1 between seventy and 
 seventy-five degrees Fahrenheit. Even corn, which is 
 often supposed to need much heat, will make its very 
 best growth without rising higher than seventy-five de- 
 grees. Since growth goes on during the night as well 
 as day. the influence of warm nights is very great. 
 
 (20) Relation of Character of Plant to Rate of 
 Growth. It is frequently noticed that plants which are 
 growing very rapidly lack in stiffness of stem. This is 
 because the cell walls of the tissues are thin in rapidly 
 growing plants, as was remarked in a former paragraph, 
 and the growth is more rapid in either complete or 
 partial absence of light than where it is intense. The 
 result of this is' that those plaids or those parts of plants 
 which grow in partial darkness are softer and less rigid 
 than those which grow in strong light. The succulence 
 of good vegetables is. therefore, largely caused by their 
 rapid growth and so in the production of vegetables it 
 is essential to hasten the growth in every way possible 
 by supplying them with the best condition of moisture, 
 light, temperature and food material. 
 
CONDITIONS ESSENTIAL FOR PLANT GROWTH. 17 
 
 (21) Lodging". The weakness of the stem of grain 
 which causes it to lodge, is due to the rapid growth 
 made when there are large amounts of water available 
 and when the light is partly excluded either by cloudi- 
 ness or by thickness of planting. It has been supposed 
 that the degree of stiffness of the straw was determined 
 by the amount of silica present, but this is probably not 
 true There is very little tendency in grain to lodge in 
 dry regions even when large quantities of water are used 
 in their irrigation, probably because of the continuous 
 sunshine, although it may in part lie due to the larger 
 amounts of salts such as potash and phosphates in the 
 soil. 
 
 Conditions Influencing Fruition. 
 
 (22) Translocation of Material in Plant. The 
 object of the plant in the production of seed is to secure 
 the reproduction of itself. As a general rule plants 
 tend to form seed when the conditions become unfavor- 
 able to continued rapid growth of vegetative parts. On 
 the other hand if the conditions for vegetative growth 
 remain very favorable, the formation of seed is retarded 
 and the seed when formed is often not so well matured. 
 The conditions most favorable to the formation of seeds 
 are, therefore, different in some respects from those 
 most favorable to vegetative growth, although, pf course, 
 a certain amount of growth is necessary to allow the 
 plant to produce the seed in full maturity. It is very 
 important for the farmer to realize the difference in the 
 conditions necessary to the production of the largest 
 amount of stalk and leaves on the one hand and of 
 
18 NOTES ON Soll.s. 
 
 seed mi the other. In growing fodder and hay. a heavy 
 growth of stalk and leaves is wanted, while in raising 
 grain, a heavy yield of mature seed is the object. 
 
 The formation of material stored in the seed and fruit 
 is largely the result of moving it from the stalk and 
 leaves where it is produced to the seed or fruit where it 
 is stored. In most of our farm plants growing under 
 favorable conditions there is nearly enough of this ma- 
 terial in the stalks and leaves at the time of tlowering 
 l<i reproduce the mature fruit and seed. Some water 
 must, of course, be available to the plant during the 
 ripening period, hut little else is accessary. It' now. 
 there is an excess of water and especially of available 
 nitrogen, there is a strong tendency to continue veg- 
 etative growth which retards and in some cases prac- 
 tically prevents the formation of seed. It is essential. 
 therefore, to the besl development of fruit and seed that 
 the amount of these substances available to the plant be 
 limited during the period of maturity. This principle 
 is very important in planning a rotation of crops and 
 will he referred to later when that subject is discussed. 
 
 (23) Relation of Growth to Soil. On account of 
 the many ways in which the soil affects the plant's 
 growth the importance of its study is very great. It 
 supplies it with those chemical elements necessary, and 
 with water. Then since a considerable part of the plant 
 must grow under ground for these materials the tem- 
 perature of the soil and its ventilation are important 
 factors. 
 
THE ORIGIN OF SOIL MATERIAL. 19 
 
 CHAPTER II. 
 THE ORIGIN OF SOIL MATERIAL. 
 
 In order to understand the distribution of the various 
 kinds of soils and also the processes by which the ele- 
 ments in them become available to plants it is necessary 
 to study their origin. 
 
 If we examine any soil carefully we find that it is 
 made up of two different kinds of material. The first 
 kind includes gravel, sand and clay and is derived en- 
 tirely from rocks. The second, which forms the black 
 or organic material and is called hum us, is derived from 
 the decomposition of animal and plant organisms which 
 have grown in the soil. 
 
 (24) Soil-forming Rocks and Minerals. There 
 are three chief classes of rocks in Wisconsin : granite 
 and related rocks, limestone and sandstone. The granite 
 occurs in the North Central part of the state. It is a 
 crystalline rock composed of various minerals, the chief 
 of which are quartz, feldspar, mica and hornblende. 
 The quartz is white, the feldspar has flat surfaces and is 
 pink or flesh colored. There are two kinds of mica, one 
 white and the other black, but both are characterized by 
 being in very thin* layers which can be easily separated 
 with the point of a knife blade. The hornblende is 
 black, very hard, and usually occurs as more or less 
 needle-like crystals. 
 
20 NOTES ON SOILS. 
 
 'Plic quartz contains only silica. The feldspar con- 
 tains silica, alumina, potash, soda and smaller amounts 
 of Lime. The while mica contains besides silica and 
 alumina, potash and the black mica, iron and magnesia. 
 The hornblende contains silica, alumina, iron and mag- 
 nesia chiefly. Very small amounts of a mineral called 
 apatiti which contains calcium and phosphoric acid are 
 also found in granite. When the fresh granite rock is 
 analyzed it is found to contain about 72% of silica, 
 It'.', of alumina. 6.5$ of potash. 2.5% of soda. l.o'v, 
 o! lime, 0.5$ of magnesia, 1.5$ of iron oxide and very 
 small amounts of phosphorus, chlorine and sulphur. 
 
 (25) Residual Soils. The action of frost, heat, 
 water, especially when containing carbon, dioxide, plant 
 roots, etc., tends to decompose the minerals of the gran- 
 ite. The rock is in this way decomposed and what 
 can be dissolved is carried away in the water soaking 
 through it. The quartz is not dissolved much hut 
 bieaks up more or less and forms the sand of the soil. 
 The feldspar, which forms a Large part of the granite, 
 gives rise to kaolin, the chief material in clay, while 
 part of the silica and most of the potash, soda and lime 
 ii contains are dissolved and carried away. The iron 
 and phosphoric acid are mostly left in the soil. 
 
 It will therefore be seen that the soil derived from 
 granite differs wvy much in chemical composition from 
 the rock. The chief differences are that the soil con- 
 tains most of the silica, both as quartz sand and kao- 
 lin or clay, relatively more alumina, iron and phos- 
 phoric acid, but very much less potash, soda, lime and 
 magnesia. 
 
THE ORIGIN OF SOIL MATERIAL. 21 
 
 There is another class of crystalline rocks called 
 basalt, which occurs north of the area of granite and in 
 small areas within the granite region. 
 
 These rocks are similar to the granite but are black 
 or gray in color and contain less silica, alumina and 
 potash but much more iron and magnesia. The process 
 of decomposition of the basalts is similar to that of the 
 granite and the soil is similar though as the rock has 
 little or no quartz there is very little sand in the soil. 
 
 The other two classes of rock, sandstone and limestone, 
 are called sedimentary because they were formed from 
 sediment deposited in the water of the shallow ocean 
 which once covered a large part of the continent. 
 
 The sandstone was formed chiefly from sand derived 
 from the quartz in the granite, with small amounts of 
 undecomposed feldspar, mica and hornblende. This 
 sand was deposited along the shore of the islands of 
 granite rocks and as far out as the current of streams 
 and waves could carry it. 
 
 The limestone was formed farther out from shore, 
 partly as a deposit of what had been brought out in 
 solution from the land and partly as the remains of the 
 shells of mollusks, corals, etc. They therefore consist 
 almost entirely of carbonates of lime and magnesia, but 
 also contain small amounts of clay and fine silt which 
 remained suspended in the water of streams running 
 into the sea long enough to be carried out so far. This 
 clay and silt, derived from the granite, contains the 
 small amounts of potash, phosphoric acid and iron 
 found in the limestone. 
 
 After these sedimentary rocks were raised above the 
 
22 NOTES ON SOILS. 
 
 water the same agencies which act on the granite began 
 to ad on them. The sandstone od the surface was acted 
 mi by the frost and heat which tended to loosen the 
 grains and leave them on the surface as sand. 
 
 The carbonate of lime and magnesia in the Limestone 
 is soluble in water containing carbon dioxide while the 
 clay and silt is not soluble. The carbonate of lime and 
 magnesia was therefore dissolved by the water and car- 
 ried away while the small amount of clay and silt was 
 left and collected as a layer of soil over the limestone. 
 The amount of this clay and silt in the limestone is only 
 two to eight per cent so that a layer a hundred feet 
 thick of limestone would leave only two to eight feet of 
 soil. Since this clay and silt soil left on top of the lime- 
 stone originally came from the soil of the granite islands 
 it is easy to understand why the soil from limestone and 
 from granite are so much alike. 
 
 The soil on the granite, however, contains quartz 
 grains, or sand which is coarser than any in the soil 
 from the limestone, while the latter contains sharp, angu- 
 lar pieces of Hint or chert. 
 
 These, then, ale the kinds of residual soil we should 
 find on the rocks of the state: clay on the granite and 
 limestone, and sand on the sandstone. 
 
 (26) Alkali Soils. In regions where the rainfall is 
 very light and is all evaporated, the salts formed by 
 weathering are not washed out of the soil as they are 
 in humid regions, bu1 colled in the soil. These salts 
 usually have an alkaline nature and the soils contain- 
 ing them are called A I hall soils. 
 
 (27) Glacial Soils. When we examine the soils of 
 
THE ORIGIN OF SOIL MATERIAL. 23 
 
 most of the "Northern part of the United States we find 
 that they contain stones which are not like those found 
 in quarries of the region, but are like those found in 
 quarries at a distance north from one to five hundred 
 miles. The soil also in many cases contains much more 
 lime than residual soils. Geologists have shown that 
 all this is due to a remarkable glacial ice sheet which 
 collected in the region of Hudson's Bay and flowed 
 south from the northern part of the United States and 
 scraped off a great deal of soil from the rocks over which 
 it passed and carried it to the country to the south, 
 it brought blocks of granite and basalt away down to 
 the southern part of the state and into Illinois. It 
 ground off the limestone hills' making a fine rock flour 
 of it. The water formed when the ice melted sorted 
 this material, carrying part of the finer portion far 
 down the Mississippi river while gravel and sand were 
 left as great terraces along the streams in the state. 
 
 Strangely enough, however, the ice flowed around a 
 large area in the southwestern part of the state extend- 
 ing from a few miles west of Madison across the Miss- 
 issippi river a little way into Iowa and Minnesota and 
 from near Eau Claire south into northern Illinois. 
 Within this unglaciated area the soils are derived from 
 the limestone and sandstone underneath them and 
 are therefore residual, while those over the area covered 
 by the ice are glacial soils. 
 
 It will lie seen that the character of the glacial soils 
 depends very largely on the character of the soil and 
 rocks over which the ice passed. In some regions in 
 the northern part of the state where the rock was 
 granite and the soil clay the ice removed the soil to a 
 
24 NOTES ON SOILS. 
 
 considerable extent often leaving only a very thin layer 
 over the granite rock. 
 
 In the southern and eastern part of the state most of 
 the glacial soil contains ground limestone mixed with 
 sand and clay. Throughout the area covered by the ice 
 there are hikes, ponds and marshes resulting from its 
 making undrained depressions in which the water ac- 
 cumulated. 
 
 It will be seen, therefore, that within the glacial area 
 there is a very great diversity in the character of the 
 soil. In the southeastern part of the state the glacial 
 soil contains large amounts of lime carbonate while this 
 has been almost completely dissolved away in the forma- 
 tion of the residual soils of the southwestern part. 
 
 (28) Wind Formed or Loess Soils. Over a large 
 area in the Mississippi Valley is a kind of soil which 
 is thoughl by geologists to have been brought to its 
 present position by the wind. This soil, called Loess, 
 is YiTv fertile and covers large areas in Iowa, some in 
 Illinois, Missouri and other states. In Wisconsin it oc- 
 curs in the southeastern part of the state, extending in 
 patches as far north as Chippewa Falls. 
 
 (2 9) Origin of Humus. The incomplete decompo- 
 sition of vegetable matter, such as roots, leaves, etc., 
 give rise to the black, waxy organic matter in soils, 
 called hum us. This part of the soil will be fully dis- 
 eussed in a later chapter. 
 
 (3 0) Soil and Subsoil. In many places in plowing 
 or in digging, earth is turned up which is of a lighter 
 color than that of the surface. The surface is made 
 dark by humus, while its absence in the lower layer 
 haves it of a lighter color. Where this difference be- 
 
THE ORIGIN OF SOIL MATERIAL. 25 
 
 tween the upper and lower layers is found, the surface 
 is called the soil, and the lower layer the subsoil. 
 "Where, however, little or no humus is found in the sur- 
 face it is still called the soil, but there is no distinction 
 between the soil and subsoil. This occurs in most sandy 
 regions and very generally in warm countries, even on 
 «lay soils, because the humus is largely oxidized. 
 
26 NOTES ON SOILS. 
 
 CHAPTER III. 
 TIIH SUPPLY OF CHEMICAL ELEMENTS. 
 
 In Chapter I we have seen that all plants require cer- 
 tain chemical elements for their growth. With the ex- 
 ception of carbon dioxide, "which is absorbed from the 
 atmosphere by the leaves, and water, falling as rain, 
 and, in the case of a leguminous plant, nitrogen which 
 is absorbed from the air by certain bacteria in the soil, 
 all of these elements are absorbed from the soil. We 
 must now examine the soil carefully as a source of these 
 essential elements. 
 
 (31) The Revolving Fund of Soil Fertility. The 
 first thing to notice is that this material which is ab- 
 sorbed by the plants is used by them during their grow- 
 ing period, and that part of these materials which is not 
 built up into the tissues of the plant is allowed to pass 
 hack out of the plant into the soil during the ripen- 
 ing stage as explained in paragraph 9. Moreover in 
 the virgin condition the native vegetation falls to the 
 ground and by, decaying permits a large part of the ma- 
 terial it contains to be reabsorbed by the fresh vegeta- 
 tion of the succeeding year. In this way it is seen that 
 the soil is provided with a revolving fund of material 
 which is used over and over again. When crops are 
 removed from the land, however, this fund of revolving 
 
THE SUPPLY OF CHEMICAL ELEMENTS. 27 
 
 material is - gradually reduced and it is a well known 
 fact that virgin soils under crop lose their fertility in a 
 longer or shorter period unless this material is replaced 
 in some form of fertilizer. 
 
 A small amount of the essential mineral elements be- 
 comes available from the weathering and decomposition 
 of the rock particles in the soil each year and is ab- 
 sorbed by the growing plants and thereby added to the 
 revolving fund. This, however, is in part counterbal- 
 anced by the leaching of small amounts of soluble ma- 
 terial from the soil each year. 
 
 Under cultivated conditions a portion of the fertility 
 of the soil is removed in products sold from the farm 
 which may be either vegetable, as when grain or hay is 
 sold directly, or animal, as in the bones and meat of fat 
 stock or dairy products. 
 
 All of these relations are expressed in the accompany- 
 ing illustration (Fig. 1). 
 
 A full understanding of the value of this rotating 
 fund to soil fertility is of the utmost importance. 
 While most soils contain a considerable supply of the 
 essential elements, they can be thought of only as a store 
 house from which but very small amounts may be with- 
 drawn from year to year. The rapid growth of crops 
 during the summer season must ordinarily be supplied 
 almost entirely by the rotating fund. The vegetable 
 matter left in the ground in the form of roots and 
 stubble or returned in the form of manure is a very 
 important portion of this rotating fund. It decomposes 
 with sufficient rapidity to set free most of its content 
 of the essential elements rapidly enough to supply good 
 growth under favorable conditions, and not so rapidly 
 
28 
 
 NOTES ON SOILS. 
 
 as to endanger serious loss by leaching before it can be 
 absorbed by the crop. Moreover, this decomposition 
 supplies the carbon dioxide which, absorbed in the mois- 
 ture of the soil, acts as an acid on the inorganic or 
 mineral portion of the soil causing this to decompose 
 or weather. The action of the carbonic acid of the 
 
 ANIMAL PRODUCTS 
 TO MARKET 
 
 TO STABLE 
 
 LOST BY 
 LEACH I 
 
 BY 1 *- 
 NG J 
 
 "z CROP 
 
 GRAIN AND VEGETABLES 
 ~~ *TO MARKET 
 
 COMMERCIAL FERTILIZER 
 
 ATMOSPHERIC NITROGEN 
 
 LOSS OF CO z TO 
 ATMOSPHERE 
 
 REVOLVING FUND 
 
 MINERAL BASE OF SOIL 
 
 Fir,. 1. — Indicating the factors which influence soil fertility. 
 
 soil is most rapid on limestones or lime carbonate in the 
 soil, which is rapidly removed by leaching into the 
 deeper waters, such as are drawn on by wells and into 
 streams. This latter process is to a certain extent in- 
 jurious, since soils from which the limestone has been 
 in this way largely removed become acid and unsuit- 
 able for certain helpful bacteria, as will be seen in a 
 
THE SUPPLY OP CHEMICAL ELEMENTS. 29 
 
 later chapter. Besides the vegetable portion of the re- 
 volving fund in the soil there is a considerable amount 
 of various salts which are quite readily soluble in wa- 
 ter, and yet are held physically by the fine soil grains, 
 so that while they can be absorbed gradually by the 
 fine root hairs of plants they are not readily leached 
 out. Fertile soils subjected to percolation will continue 
 to give up appreciable quantities of soluble matter un- 
 til several times their volume of water has been allowed 
 to percolate through them. This matter is probably 
 held by the attraction of the soil grains, so that the 
 moisture of the soil is in a more highly concentrated 
 condition in the layer in contact with the soil grains 
 than it it at some distance out from the surface of the 
 soil grains. 
 
 (32) Limiting Factors in Soil Fertility. While 
 all of the essential elements mentioned in Chapter I are 
 absolutely necessary for the growth of crops, it is true 
 that a few of them only are apt to be deficient in or- 
 dinary soils. Others are generally so abundant that 
 we need give no particular care concerning them. Ni- 
 trogen, phosphorus, and less often potassium are in some 
 soils so deficient that they must be given especial at- 
 tention by the farmer, and they will therefore be dis- 
 cussed fully in succeeding chapters. The condition of 
 acidity, referred to above, has a particular bearing on 
 the fixation of nitrogen in the soil by bacteria and will 
 therefore be discussed in a chapter on that subject. 
 
 Since all plants must be supplied with all of these 
 essential conditions before satisfactory growth can oc- 
 cur, it is evident that failure in any one respect be- 
 comes critical. It is very commonly true that the maxi- 
 
30 
 
 NOTES ON SOILS. 
 
 mum yield of any particular field is determined by some 
 one factor which thereby becomes the limiting factor for 
 that soil. This may be the supply of the element ni- 
 trogen or phosphorus or potassium, the amount of mois- 
 ture available, or of oxygen in a highly saturated soil, 
 or the temperature during a cold season or In a cold 
 
 Fig. 2. — Illustrating the principle of limiting factors in soil 
 
 fertility. 
 
 climate, or other factors. This relation is expressed in 
 figure 2 devised by Dr. Dobenecks. The amount 
 of water which the barrel can hold is determined 
 by the height of the lowest stave. If the length 
 
 of this stave is increased then the next shortest 
 stave will determine the capacity of the barrel and so 
 
THE SUPPLY OF CHEMICAL ELEMENTS. 31 
 
 •on until all are of equal length. The same relation 
 holds among the factors determining the fertility of the 
 soil. Supplying a certain element which at one time 
 is the limiting factor will increase the yield and if all 
 the other conditions have been very favorable the in- 
 crease in the yield from supplying the single factor may 
 be very great. If, however, there are one or more other 
 factors which are also low m value then they must in 
 turn be improved before the highest yields can be 
 reached. 
 
32 NOTES ON SOILS. 
 
 CHAPTEK IV. 
 
 HUMUS. 
 
 If you examine the soil grains closely you Avill find 
 that they are usually coated with a black, waxy sub- 
 stance, largely organic in nature, which Ave call humus. 
 In addition to this true humus, which has been formed 
 by the partial decay of organic material returned to 
 the soil, there is vegetable matter in practically all 
 stages of decomposition, from that almost entirely un- 
 decomposed, to that which we call true humus. 
 
 (33) Composition of Humus. If humus is sub- 
 jected to a chemical analysis, it will be found to contain 
 the elements carbon, hydrogen, oxygen, and nitrogen, 
 with small amounts of potash and phosphorus. If the 
 composition of humus is compared with the composition 
 of fresh organic matter, you will discover that the mak- 
 ing of humus from fresh organic matter has meant an 
 increase of carbon and nitrogen and a decrease of oxy- 
 gen and hydrogen. There is reason to believe that not 
 all of* the fresh organic matter returned to the soil ever 
 goes through this complex process of oxidation. .Most 
 organic matter oxidizes too rapidly to contribute any- 
 thing to this store of inert, waxy material that we call 
 humus. It has taken ages and generations for a very 
 small residue of incompletely oxidized organic matter 
 
HUMUS. 33 
 
 to accumulate, and form true humus. The various 
 kinds of partly decomposed vegetable matter in the soil 
 grade into each other so gradually, however, that it will 
 be best for us to consider it all under the general term 
 humus. 
 
 (34) Rate of Decomposition of Vegetable Ma- 
 terial. We may have vegetable matter decomposing so 
 rapidly in the air, if ignited, that we call the process 
 combustion, or rapid burning. In this manner thou- 
 sands of tons of straw were destroyed during the early 
 farming days in the middle "West. The rate of decom- 
 position in the soil leading to the making of humus 
 varies greatly. The principal factors affecting the rate 
 of humus-forming are (1) access of air, (2) tempera- 
 ture, (3) kind of vegetation, (4) reaction of the soil. 
 
 (35) Access of Air. The rate of decomposition of 
 vegetation usually increases as the amount of water in 
 the soil decreases. If the vegetation grows on very wet 
 ground, as in a marsh, and on falling down, is largely 
 covered by water which excludes the air. it will decom- 
 pose very slowly. Indeed if it is kept entirely covered 
 with water, it may remain almost entirely undecomposed 
 and collect as peat. If the marsh becomes partly dried 
 i\ part of the year, then the material will partly decom- 
 pose and form muck. If the vegetation grows on land 
 which is comparatively dry most of the year, then it 
 may decompose more completely to form the true humus 
 coating the mineral particles of the soil. 
 
 It is generally known that very sandy soils contain lit- 
 tle humus, for the air can penetrate so rapidly and so 
 completely that the humus is almost entirely decom- 
 
3 ! NOTES ON SOILS. 
 
 posed. The low water-holding capacity of sands makes 
 them drier, hence less vegetation accumulates, and cor- 
 respondingly less material is available for humus form- 
 ing. 
 
 (36) Effect of Temperature. High temperatures 
 promote rapid oxidation of organic material, and low 
 temperatures retard the process. This explains the dif- 
 ficulty that farmers in warm countries have in main- 
 taining a supply of humus. This fact should also lend 
 confidence to farmers in the cooler climates in their ef- 
 
 to maintain a supply of humus. Oxidation of the 
 table material in soil is so rapid in many of our 
 Southern states that it is absolutely essential to turn 
 under green manuring crops practically every year. 
 
 (37) Effect of Kind of Vegetation. Sphagnum 
 moss, and other mosses, such as grow in the marshes of 
 Wisconsin decompose very slowly, while, on the other 
 hand, the tissues of such succulent plants as peas. rape. 
 etc., decompose very rapidly. Different portions of the 
 
 plant resist decomposition differently, thus leaves 
 and fleshy stems decay quickly, while the fine woody 
 roots decompose slowly. Hence it is that in forests, the 
 fallen Leaves decompose so rapidly, while the roots of the 
 prairii es decompose slowly. Of course, in the 
 
 ' the leaves, being on top of the soil are more ex- 
 posed to the aii- than the roots of the prairie grasses 
 growing in the rather poorly drained soil of a level 
 country. The difference between prairie and forest is 
 so pronounced that on prairies we find deep black soils, 
 humus coating the soil grains often to the depth of 
 several feet, while in the forests, especially in the up- 
 
HUMUS. 35 
 
 lands, we find light colored, shallow soils, the humus 
 coating extending to the depth of only a few inches. 
 
 (38) Reaction of the Soil. Sour or acid soils pos- 
 sess such antiseptic properties that decay goes on very 
 slowly. Thus many of our peat marshes are so highly 
 acid that complete neutralization is impossible with 
 moderate amounts of lime. On such soils, crops must 
 be found that can adapt themselves to an acid condition 
 of the soil. 
 
 (39) Function of Humus. Some one has said that 
 ' ' Humus is the life of the soil. ' ' Let us therefore in- 
 quire into the ways in which humus benefits the soil. 
 Bulletin 135 of the Vermont Experiment Station sum- 
 marizes these benefits in the following brief statement: 
 
 Humus serves 
 
 1. As a nitrogen supply, 
 
 2. As a mineral plant food supply, 
 
 3. As a store house for water, 
 
 4. As a source of warmth, 
 
 5. As an improver of texture, 
 
 6. As an aid to bacterial and other micro-organic 
 
 growth in the soil. 
 
 (40) Nitrogen. We have previously pointed out 
 that the process of humus making from fresh organic 
 matter has meant an accumulation of nitrogen. The 
 method by which this humus nitrogen becomes available 
 to plants will be discussed in chapter VI. 
 
 (41) Mineral Plant Food in Humus. Practically 
 all plant residues returned to the soil contain mineral 
 plant food, originally obtained from the soil. The por- 
 tion of the vegetable material, which is quickly oxidized, 
 and does not go to form the inert, structureless humus, 
 
36 NOTES ON SOILS. 
 
 yields up its ash contenl readily. M is this rapid avail- 
 ability of the ash contenl of planl residues that helps 
 maintain the revolving fund discussed in a previous 
 chapter. Some of the material thus quickly set free 
 may be Los1 to the subsequent crops by leaching, or by 
 oilier processes. When, however, the potash and phos- 
 phoric acid of the. decaying vegetable matter, enter into 
 the more or less "tight" waxy humus compound, it is 
 probable, because of the difficulty in oxidizing this true 
 humus thai the ash contenl becomes vrvy slowly avail- 
 able, if a1 all. 
 
 It is held by some investigators that the humus in the 
 soil may act as an acid and combine with the mineral 
 elements from the soil grains to form humates, which 
 although not directly soluble in water, may decompose 
 and become available to plants. The true chemical na- 
 ture of humus is so little understood, however, that it 
 is impossible to make definite statements concerning the 
 action of the so-called humus acids. 
 
 Again, the oxidation of both true humus, and of un- 
 humified vegetable matter, sets free carbon dioxide, 
 which combines with the soil water to form carbonic 
 acid, a very powerful solvent of soil minerals. Thus 
 it is thai addition of manure benefits the soil in two 
 ways, in the plant food that it itself contains, and the 
 planl food that, by its decay, is set free from the soil 
 g] ains. 
 
 (42) Humus and Water-Holding Capacity. The 
 black waxy coating of soil grains becomes somewhat 
 gelatinous when wet, and like all such bodies, has the 
 power of absorbing large quantities of water. It is 
 hardly necessary to state that the high water-holding 
 
HUMUS. 37 
 
 capacity of our muck and loam soils is due to their high 
 content of humus. Hilgard has pointed out that "Dry 
 humus swells up visibly when wetted, the volume weight 
 increasing to the extent of two to eight times; so that 
 humus stand foremost in this respect among the soil 
 constituents." This power of humus to retain moisture 
 will he referred to again in connection with the general 
 subject of water-holding capacity of soils. 
 
 (43) Effect of Humus on Temperature. Humus 
 is able to affect the temperature of the soil in two quite 
 distinct ways. In the first place, humus is a black ma- 
 terial, so that an abundance of humus means that more 
 lna I will be absorbed from the sun, black colors being 
 able to absorb more heat than lighter colors. In the 
 second place, the various decay and oxidation processes, 
 incident to the destruction of vegetable matter in the 
 soil, give rise to considerable heat. "We have all no- 
 ticed this same process in the fermentation and heating 
 of a manure heap, although, in such a case much more 
 heat is evolved, and higher temperatures reached in a 
 limited amount of material, than in the same amount of 
 soil. The same amount of heat is evolved in the decay 
 of the manure when spread over an acre of soil, but 
 since it is spread out so thinly we are not able to detect • 
 the rise of temperature. 
 
 (44) Improver of Texture. The humus coating 
 ot' the soil grains causes them to adhere to one another, 
 so that, instead of a. soil being made up of an infinite 
 number of isolated soil grains, it is made up of groups 
 of soil grains or soil aggregates, as they are sometimes 
 called. The development of this crumb structure is 
 particularly noticeable in soils containing large amounts 
 
38 NOTES ON SOILS. 
 
 of true humus, such as our loamy soils. Further, we 
 find this crumb structure disappearing from soils, as 
 Hi*' humus is destroyed by poor methods of farming. 
 
 (45) Aid to Growth of Microscopic Soil Organ- 
 isms. Our soils contain thousands of tiny organisms, 
 such as bacteria and moulds. These bacteria and 
 moulds depend upon the vegetable matter in the soil for 
 their food supply. The soil organisms perform an im- 
 mense amount of work in helping to bring about the 
 decay of the plant residues returned, therefore they 
 must obtain the necessary energy for this work from the 
 oxidation of this vast organic I'ood supply. Different 
 organisms attack different kinds of vegetable matter or 
 different elements in it. but there is such a complex 
 array of material at hand, that each different organism 
 finds a suitable food supply. 
 
 (46) Loss of Humus. We have mentioned various 
 ways in which humus benefits the soil. Let us now in- 
 quire into how humus may be lost, so that Ave may learn 
 to avoid such methods. Probably the single greatest 
 cause of loss of humus is in the continuous growth of 
 tilled crops. Determinations made at the Wisconsin Sta- 
 tion, show that when a tilled crop, such as corn or to- 
 bacco has been grown for a period of 10 to 25 years con- 
 tinuously that there has been no increase in the total 
 
 table matter in the cropped soil as compared to the 
 amount in a comparable virgin soil even though large 
 amounts of manure have been annually returned to the 
 soil. Several cases show an actual decrease in the 
 amount of organic matter in the soil. When, therefore, 
 there is an addition of manure, or some other vegetable 
 natter, how great must be the total loss! In fad we 
 
HUMUS. 3S 
 
 find many eases, where excessive tillage and cropping 
 lias reduced the supply of vegetable matter in the soil 
 from 5 or 6 per cent to a few tenths of a per cent. It 
 should he pointed out here that a mere avoidance of 
 tilled crops will not maintain a humus supply, for a ro- 
 tation of only cereal crops is also destructive. . 
 
 The rate of loss of humus, is. of course, affected by 
 the type of soil, sands losing their humus much more 
 rapidly because of the easy entrance of air, than other 
 soils. 
 
 Humus is also destroyed by great forest and prairie 
 fires, but these sudden losses of humus are certainly not 
 as alarming, as the sIoav, insidious oxidation in tilled 
 soils. 
 
 (47) Maintenance of Humus. Since humus may 
 be lost so readily, it is necessary to know what practices 
 will aid us in maintaining and increasing our supply 
 of humus. The current farm practices tending to keep 
 up the humus supply are as follows: (1) Maintenance 
 of permanent pastures and meadows, (2) green manur- 
 ing, especially with the clovers and other legumes, (3) 
 use of farm manures, and (4) crop rotation. 
 
 (48) Permanent Pastures and Meadows. The 
 growing of such crops as the grasses, especially Ken- 
 tucky blue grass, fills the soil full of tiny roots. Vir- 
 gin prairie soils often contain 8 to 10% of total organic 
 matter, which has accumulated because of the large* 
 amount of roots present. Similarly, soils that have 
 been kept in pasture, or meadow, for a considerable 
 number of years are not found to decrease to any great 
 extent in their total organic matter, especially if such 
 fields are supplemented with top dressings of the min- 
 
40 Xo'l ES ON SOILS. 
 
 eral, fertilizers. This supplementary top dressing is 
 often practiced in England which is noted for the fer- 
 tility of her permanenl pastures. On meadows, where 
 the hay crop is annually removed, the humus supply 
 will decrease more rapidly 1h;in in the permanenl pas- 
 ture, luil this may be avoided by occasionally turning 
 under a green crop. 
 
 (49) Green Manuring. In Circular 120 of the 
 Illinois Experimenl Station, Dr. Cyril G. Hopkins 
 states thai the humus in Illinois soils musl be main- 
 tained by plowing under manure, or clover and crop 
 residues. In comparing green manuring with farm 
 manure, he makes the following significant statement: 
 
 '"As an average animals digest, and thus destroy, two- 
 thirds of the dry matter in the food they eat, so that 
 • me ton of clover hay plowed under will add as much 
 humus to the soil as the manure made from three tons 
 of clover hauled off and fed, even if all the manure is 
 returned to the land without loss by fermentation." 
 The above striking illustration emphasizes the fact that 
 we are not returning every thing to the soil, no matter 
 how carefully we handle our manure supply. 
 
 The crops used for green manuring should be the 
 leguminous crops such as clover, alfalfa, and where 
 adapted, such legumes as the vetches, lupines. serra- 
 della, cow peas, and soy beans. These crops are recom- 
 mended for use because of their power of obtaining 
 nitrogen from the air through the agency of the bac- 
 ti ria inhabiting the tubercles, or nodules on their roots. 
 [f clover does not thrive well, and other conditions are 
 suitable, it is probable thai the soil is acid, which con- 
 dition should be corrected by the use of ground lime- 
 
HUMUS. 41 
 
 stone, marl, or slacked lime. • Certain legumes seem to 
 thrive in acid soils, and should be used as green ma- 
 nures on those soils, provided it is impossible, or un- 
 profitable to correct the acidity of such soils. 
 
 (50) Farm Manures. Farm manure consists 
 largely of vegetable matter, and as such, aids in restor- 
 ing humus, but as has been pointed out this partially 
 decayed material, is in an easily oxidizable condition, 
 so that only a small portion accumulates as true humus. 
 This seems to be especially true where excessive amounts 
 of manure are used on tilled crops without rotation. 
 The use of smaller amounts of manure, spread over 
 larger areas is the economical way to apply manure. 
 
 (51) Crop Rotations. Crop rotations alone will 
 neither maintain nor increase the supply of humus in 
 the soil. A crop rotation which consists merely of a 
 succession of corn and oats, or of a rotation of various 
 cereals is not calculated to build up humus. On the 
 contrary a rotation which embodies the practices here- 
 tofore mentioned, pasture, meadow, turning under of 
 a green manuring crop, and an intelligent use of farm 
 manures with the various crops raised, is calculated to 
 maintain or even increase the supply of humus. The 
 proper combination of these practices will have to be 
 worked out by the individual farmer on his own soil, 
 under the particular set of conditions operative on his 
 farm. 
 
42 NOTES ON SOILS. 
 
 CHAPTEK V. 
 ACIDITY AND LIMING. 
 
 (52) Prevalence of Acid Soils. Sour or acid 
 soils are to be found in widely separated parts of the 
 earth. "We have descriptions of the "sour land" of 
 Alaska, the sour "veld" of South Africa, the "Siiure 
 Sandboden" of Germany, the acid sandy soils of 
 France, the acid uplands of Rhode Island, and the acid 
 marshes and uplands of "Wisconsin, and they undoubt- 
 edly exist in many places not ye) described. Neither 
 is acidity confined to any particular type of soil. Tests 
 in Wisconsin have shown the existence of acidity in 
 both virgin and cultivated soils; in clay, sand, clay 
 loam, and marsh soils. 
 
 (53) Test for Acidity. So important is the recog- 
 nition of soil acidity as a factor in soil fertility that 
 Hilgard says, "A test never to be omitted is that of 
 the reaction of soil on litmus or other test paper to as- 
 certain its acid, neutral, or alkaline reaction." The 
 Litmus paper test for acidity is performed as follows: 
 Having procured a few pieces of sensitive blue litmus 
 paper from a drug store, place the paper between por- 
 tions of moist soil, allow the paper to remain in con- 
 tact with the moist soil about five minutes, then remove 
 the paper and examine for red spots. Any reddening 
 
ACIDITY AND LIMING. 43 
 
 of the test paper indicates an acid soil. The test should 
 be performed shortly after a rain before the soil be- 
 comes too dry. The use of well or cistern water to 
 ten the soil should be avoided, for such water may 
 be cither acid or alkaline, so that its use would lead to 
 wrong conclusions. Avoid touching the litmus paper 
 with the hands as much as possible for the natural 
 moisture of the hands is ordinarily acid. 
 
 (54) Origin of Acidity. Results in "Wisconsin point 
 to two kinds of acidity, namely, that developing in 
 the peat marshes, and that developing on the uplands 
 and prairies of the state, especially in soils that have 
 been cropped for a comparatively long time. Soils like 
 the peat marshes contain large amounts of vegetable 
 matter, which, in decaying sets free organic acids. This 
 acidity prevents rapid decay of the vegetable matter, 
 and the peat therefore accumulates. 
 
 The cause of acidity in upland soils is not so well 
 understood. It is, of course, always associated with a 
 lack of lime in the soil. It is probable that in the ab- 
 sence of sufficient lime, the oxidation of the vegetable 
 matter in the soil gives rise to acids. A combination of 
 causes may be at work, including the development of 
 small amounts of mineral acids, and their acid salts. 
 The use of ammonium sulphate, as a nitrogen fertilizer, 
 unless supplemented with lime, has also been found to 
 cause acidity. The primary fact to be remembered in 
 connection with acidity is that it means a lack of lime 
 in the soil. 
 
 (55) Harmful Effects of Acidity. 1. It hinders 
 nitrogen fixation by the legumes, and is therefore espe- 
 
44 NOTES ON SOILS. 
 
 chilly harmful when such crops as clover and alfalfa 
 are to be grown. 
 
 2. It makes the process of nitrification wry slow 
 i Sec Chapter VI), although nitrification may progress, 
 ii there arc large amounts of organic nitrogen present, 
 as in peal soils. On such soils applications of lime 
 hasten nitrification. 
 
 )i. It is commonly associated with, and is undoubt- 
 edly related to a deficiency in available phosphates 
 (See ' 77). 
 
 4. It favors the growth of certain acid tolerating 
 weeds, notably common sorrel, and the horsetail rush. 
 
 In considering the effeel of acidity alone we must be 
 careful not to ascribe to acidity certain harmful effects 
 thai may be due to lack of drainage, or absence of 
 available phosphates. 
 
 (56) Effect upon Different Kinds of Plants. 
 Not all plants are injuriously affected by an acid con- 
 dition o!' tin 1 soil. One of our weeds, usually known as 
 the common sorrel (Rumex acetosella) prefers acid soils, 
 and its presence is practically a s\^vc indication of an 
 acid condition. The presence of the common horsetail 
 rush (Equisetum) also indicates acidity. Cranberries 
 and certain of the marsh grasses are also able to thrive 
 under acid conditions. Of the cultivated crops, red 
 clover, alfalfa, and sugar heels are peculiarly sensitive 
 to acidity, while corn, oats, potatoes, and alsike clover 
 are not so badly affected. Alsike clover has often made 
 a good stand on fields too acid \'<>v the growth of red 
 clover. Large yields of potatoes have been obtained on 
 acid soils, where of course there were suitable amounts 
 of potash and phosphate present. 
 
ACIDITY AND LIMING. 45 
 
 (57) Remedial Treatment for Acid Soils. The 
 treatment for acid soils universally recommended is the 
 application of lime, provided, of course, that such treat- 
 ment may he expected to yield a profit upon the in- 
 vestment. The forms of lime available to the farmer 
 are ordinary quick lime, ground limestone, marl, and 
 various by-products, such as lime refuse from sugar 
 beet factories, marine dust, and shell refuse. The 
 Rhode Island Experiment Station has shown that par- 
 tial neutralization of the acid in the soil is often as 
 effective as complete neutralization. 
 
 (58) Lime. Ordinary lime (the commercial prod- 
 uct | should be applied in the water or air slaked form 
 during the fall since it would be injurious to the seed 
 if applied at the time of planting, or even shortly be- 
 fore. For the lighter soils, such as sands and sandy 
 loams, apply at the rate of 10 to 15 bushels fresh lime 
 (equivalent to nearly twice that of water or air slaked 
 lime) per acre. For the heavier soils, such as the clays 
 and clay loams, 25 to 30 bushels of fresh lime may be 
 used. It is essential that the lime should be well slaked 
 in order to avoid any caustic action upon the humus 
 in the soil. For this reason, ground limestone, where 
 the lime is in the carbonate form, is preferable to or- 
 dinary lime. If possible, the lime should be applied 
 with some form of fertilizer drill, to insure an even dis- 
 tribution over the field. It should be applied after 
 plowing and then be thoroughly mixed with the soil 
 by harrowing. If it is not desirable to harrow the field, 
 the lime may be left on the rough furrows. 
 
 (59) Ground Limestone. When available, ground 
 limestone is to be preferred to lime, especially for the 
 
NOTES ON SOILS. 
 
 lighter soils, or for soils very low in vegetable matter. 
 Limestone ought to be the cheapest form in which to 
 supply lime. Heavy applications, from 1,000 pounds 
 to a ton per acre should be used. It is best applied in 
 ill before seeding to clover. This application 
 should be repeated i-vny fourth or fifth year, in order 
 to maintain a good supply of lime carbonate in the 
 soil. The limestone should be so finely ground that 
 three-fourths of it will pass a 40-60 mesh sieve. If 
 much coarser than this heavier applications can be 
 used, but this is unprofitable where a long haul is neces- 
 sary. 
 
 (60) Marl — Lime Refuse. Wherever deposits of 
 marl occur these should be utilized, for marl usually 
 coul a ins a high percentage of lime carbonate. If the 
 marl is thrown out, and partly dried, so that it crum- 
 bles readily, it can lie applied at the same rate' as 
 ground limestone. Lime wastes from sugar beet fac- 
 tories arc available, if properly dried, so that they can 
 
 spread evenly over the fields. 
 
NITROGEN. 47 
 
 CHAPTER VI. 
 NITROGEN. 
 
 (61) Amount and Kinds of Nitrogen in the Soil. 
 
 Determinations at the Wisconsin Station of the amount 
 of nitrogen in 21 samples of cropped clay loam soils 
 showed an average of .106%, or 2,120 lbs. per acre 8 
 inches, while corresponding virgin soils contained .169% 
 or 3,380 lbs. per acre 8 inches. Wisconsin peats 
 usually have about 3% nitrogen, but since they are 
 light soils, that amounts to only 1,100 lbs. per acre eight 
 inches. Sandy soils vary in their nitrogen content de- 
 pending upon the amount of organic matter present. 
 Some sands run as low as .05% or about 100 lbs. per 
 acre 8 inches up to as high good clay loam soils. 
 Constant cropping may deplete the nitrogen in clay 
 soils to the amount found in poor sands. 
 
 Most of the nitrogen in the soil is present as humus 
 nitrogen, derived from the decay of vegetable matter. 
 Under normal conditions all soils contain varying 
 amounts of nitrate nitrogen, as well as a small quan- 
 tity of ammonia compounds. Before humus nitrogen 
 is formed, the fresh vegetable matter containing pro- 
 tein, the principal nitrogenous substances in all plants, 
 must pass through various stages of oxidation and de- 
 cay. These stages constitute the nitrogen cycle. 
 
L8 
 
 XOTKS OX .SOILS. 
 
 (62) Nitrogen Cycle. Nitrogen is one of the most 
 importanl elements in plants, and although it consti- 
 tutes four-fifths of the air, i1 is not available to most 
 plants in that form. Most plants take their nitrogen 
 from the soil in the form of nitrates. 
 
 ^o- s9 4!- , 4/u 
 
 "*/- 
 
 -6 
 C 
 
 CD 
 
 a. 
 
 
 NITROGEN CYCLE 
 in +he 
 SOIL 
 
 o 
 o 
 0- 
 
 o 
 o 
 
 o 
 
 c 
 o 
 
 
 
 d> T. 
 
 V 
 
 V 
 
 0r 9oASc Nitroqe^" 
 
 d 6C 
 
 X 
 
 Pig. 
 
 -The Nitrogen Cycle in the soil. 
 
NITROGEN. 49 
 
 When plants die their dead roots, stalks, leaves, and 
 fruit are returned to the soil, where their decomposi- 
 tion is brought about through the agency of molds, bac- 
 teria, and other low forms of plant life. Of course 
 plants may be used to feed animals, but even then we 
 have a great residue of partially oxidized vegetable mat- 
 ter returned to the soil as manure. These various 
 forms of nitrogen-containing vegetable matter cannot 
 be used directly by the plant as food, but must undergo 
 a process called nitrification. This nitrification or build- 
 ing of nitrates is carried on by bacteria in the soil. The 
 process consists of three stages (see cycle in accompany- 
 ing diagram), a different set of bacteria being at work 
 in each stage. We first have the ammonifying bacteria 
 converting the humus in the soil into ammonia. This 
 ammonia then furnishes a food supply for the nitrite 
 bacteria, with the resulting formation of nitrites, while 
 a third class of bacteria use the nitrites as food, there- 
 by producing nitrates. These nitrates are what the 
 chemist calls a salt, that is a compound of a mineral 
 element and an acid, the acid in this case being nitric 
 acid. In fact, the nitrate bacteria do not actually build 
 nitrates but build instead nitric acid, this then imme- 
 diately unites with a mineral element, usually calcium, 
 magnesium or potassium, to form nitrates. These ni- 
 trates are readily soluble in water and are therefore 
 easily taken up by plants. 
 
 (63) Factors Influencing Rate of Nitrification. 
 The principal factors influencing the building of ni- 
 trates are as follows: 
 
 (1) Aeration. 
 
 (2) Temperature. 
 
 4 
 
•">•' NOTES ON SOILS. 
 
 (3] Moisture. 
 
 ! i Reaction of the soil. 
 (5) Character of the humus. 
 
 (64) Aeration. The soil bacteria that form ni- 
 trates require an abundance of oxygen, and are there- 
 fore largely confined to the firsl four or five feet of 
 soil. Nitrification is more rapid when the soil is loose 
 enough to allow access of air than when too compact. 
 Cultivation of the surface soil therefore promotes nitri- 
 cation. In order to insure good aeration of the soil, 
 ■ must have good drainage, for an excess of water 
 excludes the air. Excess of moisture and absence of 
 air in fact cause loss of nitrates, as will be shown in 
 paragraph 74. 
 
 (65) Temperature. Nitrification is hastened by 
 warm temperatures. The rate of nitrification is twice 
 as meat as 70° F. as at 50°, and twice as great at 90° 
 as at 70°. The factors influencing soil temperatures 
 will be treated under thai head (See Chapter XI). 
 Very Low temperatures arrest nitrification, so that for 
 ( xample, but little nitrate is formed during the winter 
 in a climate like that of Wisconsin. In warmer cli- 
 mates, as in our southern stales, humus nitrogen is 
 quickly changed to nitrates and may be leached out of 
 the soil by heavy winter rains. In order to prevent 
 this loss cover crops are sown to absorb the nitrates 
 and thus hold them for the next summer's crop. 
 
 (66) Moisture. The most favorable amount of 
 moisture for nitrification is thai amount most favorable 
 to the growth of crops. When all the space between the 
 soil grains is full of water, as in saturated soil, no air 
 can gel to the nitrifying bacteria and they become in- 
 
NITROGEN. 51 
 
 active. Excessive amounts of moisture, such as we 
 have iu undrained lands, favor the growth of certain 
 bacteria, called denitrifiers, which have the power of 
 setting free gaseous nitrogen from nitrates. 
 
 (67) Reaction. Nitrification is probably most ac- 
 tive in a slightly alkaline soil. The nitric acid pro- 
 duced also requires some base such as lime, to neutral- 
 ize it, in order that nitrates may be formed. Nitrifica- 
 tion is not entirely prevented under acid conditions of 
 the soil, for we have some acid peat soils that are well 
 able to supply the necessary nitrate to their crops. A 
 sufficient supply of potash and phosphate is as essen- 
 tial for the growth of these nitrate forming bacteria as 
 il is for the higher plants. "We must be certain that all 
 other conditions are at their best before we can safely 
 assert that any one factor is limiting nitrification. 
 
 (68) Character of the Humus. The development 
 of nitrates also depends very much upon the character 
 of the humus and vegetable matter in the soil. Some 
 humus is readily acted upon, while the remainder is 
 only slowly used. For this reason, when a piece of 
 land is cropped several years without the addition of 
 manure the humus most easily acted on is used first, 
 and nitrates are formed rapidly ; while after a few 
 years, when this has been used up, the process of ni- 
 trification becomes much slower, and crops suffer for 
 want of available nitrogen. Fresh succulent vegetable 
 matter, like that turned under in clover, is easily trans- 
 formed into nitrates so that a clover sod when plowed 
 and cultivated usually becomes rich in nitrates. 
 
 (69) Close Use of Nitrates by Plants. The ex- 
 tent to which plants can reduce the nitrate supply in 
 
52 NOTES ON SOILS. 
 
 the soil is appreciated when wo compare the amount 
 o1 nitrate in the soil under a rapidly growing crop, 
 and the amount in an adjacent fallowed plot of soil. 
 Bulletin 93 of the Wisconsin Experiment Station states 
 thai on July 9 the ground under oats contained 3.32 
 lbs. of nitrates per acre in the first foot of soil, while 
 adjacent fallowed soil contained 57.8 lbs. per acre in 
 the first foot. Plants quickly respond to a poor nitrate 
 supply. Every farmer has noticed the yellowing of 
 ■ ■ in plants after a few days of cold, wet weather. The 
 cold, wet weather causes a slow rate of nitrification, or 
 even loss of nitrates, so that the corn is deprived of an 
 essential part of its food supply and consequently turns 
 
 \ el low. 
 
 (70) Nitrogen Fixation. The diagram on page 
 48 indicates that certain plants, the legumes, can ob- 
 tain nitrogen from the air. Nitrogen gathering bac- 
 teria inhabit the tubercles, or nodules, which develop 
 on the roots of the clover, alfalfa and other plants of 
 the legume family. The nitrogen of the air is trans- 
 formed by these bacteria into organic nitrogen. 
 Whether I his organic nitrogen is directly absorbed by 
 the plant, or whether it first passes through all the 
 stages of oxidation, as does organic nitrogen from other 
 sources, is not known. The diagram indicates this un- 
 ci rtainty by the use of two arrows proceeding from the 
 words "Nitrogen of the Air," one indicating the or- 
 dinary route, the dotted arrow indicating the possibil- 
 ity of the direct absorption of the organic nitrogen by 
 1b( plant. 
 
 Some nitrogen is fixed in the soil by bacteria no1 at- 
 tached to the roots of plants, but the amounts of nitro- 
 
NITROGEN. 53 
 
 gen fixed by' these bacteria under actual soil conditions 
 is not known. The distribution of these organisms, and 
 their importance, is at present engaging the attention 
 of many soil bacteriologists. The diagram used also in- 
 cludes this class of bacteria. 
 
 (71) Amounts of Nitrogen Fixed. Plots of land 
 at the Rothamsted Experiment Station growing le- 
 gumes, such as clover, vetches, and alfalfa for 21 years 
 continuously had 757 pounds per acre more nitrogen 
 than a similar plot in wheat for the same time. Or- 
 dinarily a crop of clover may be expected to add forty 
 pounds of nitrogen per acre foot to the soil the first 
 year, and 75 to 100 pounds more the second year, be- 
 sides what is taken off in the hay crop. This, if changed 
 without loss into nitrates, would be enough for a good 
 crop of grain, corn or potatoes. It must not be for- 
 gotten, however, that clover and other legumes take 
 other elements from the soil just as other crops do, so 
 that fertilizers containing potash and phosphoric acid, 
 especially the latter, must be used if clover or other 
 legumes are to be grown continually. Many soils do 
 not contain sufficient available phosphoric acid for a 
 maximum crop of clover. 
 
 (72) Conditions Favoring Nitrogen Fixation by 
 Legumes. In order to obtain the maximum amount 
 oi nitrogen from the air, when growing clover, or other 
 legumes the soil should have 
 
 (1) good drainage, 
 
 (2) a neutral or slightly alkaline reaction which 
 means an abundant supply of lime. 
 
 (3). an abundant supply of all the essential elements, 
 especially of phosphoric acid. 
 
5 i NOTES ON SOILS. 
 
 I and a suitable inoculation with the bacteria as- 
 sociated with the particular Legume to be grown. 
 
 (73) Soil Inoculation. Alter the firsl three of the 
 above conditions have been provided we must still he 
 sure thai our soil is well inoculated. In this part of 
 the United States it is hardly necessary to inoculate 
 the soil for the growth of common red clover. Many 
 soils, however, are not adapted to alfalfa and other less 
 common Legumes because of this lack' of inoculation. 
 The upland acid soils of Wisconsin rarely contain the 
 necessary alfalfa organisms. Various forms of artificial 
 inoculation of the soil by so-called "liquid cultures," 
 "Nitragin," and "dried cultures" have been tried, hut 
 
 none have 1 n successful enough to be called practical 
 
 although better results are constantly expected. The 
 only practical method of inoculating the soil is the 
 actual transference of stone soil from a. field that has 
 previously grown the legume. In the case of alfalfa. 
 inoculation with soil from patches of sweet clover is 
 equally effectual. If a small portion of a field is well 
 inoculated, soil will then lie at hand for inoculating the 
 remainder of the farm. After a new legume is once 
 started, farm operations of cultivating, plowing, etc., 
 soon spread the bacteria. "Where it is impractical 
 to inoculate with soil, alfalfa, for example, has often 
 been finally successfully grown by constantly seeding 
 small portions of alfalfa with the clover. Success in 
 this case depends upon the fact that some of the alfalfa 
 seeds have a few of the necessary bacteria clinging to 
 them and thus some of the plants are inoculated. If 
 this procedure is kept up. the inoculation will soon 
 spread. 
 
NITROGEN. 55 
 
 (74) Losses of Nitrogen. Nitrogen may be re- 
 moved from the soil by 
 
 1. Leaching, 
 
 2. Cropping, 
 
 3 Denitrification. 
 Any treatment of the soil which promotes nitrification 
 causes a loss of nitrates by leaching. Soils constantly 
 cultivated are therefore more subject to this loss than 
 soils kept in sod. Losses by leaching may be consider- 
 able and are probably relatively greater in a soil kept 
 in a high state of fertility than in soils in a moderate 
 state of fertility. 
 
 In a study of the nitrogen content of virgin and 
 cropped soils, reported in the 23d Annual Report of the 
 Wisconsin Station, the conclusion was reached that in 
 day Loam soils of moderate fertility more than four-fifths 
 of the nitrogen lost is removed by crops. Recent results 
 obtained at the same station indicate that there is a 
 considerable loss of nitrogen above that removed by 
 crops, when soils have been fertilized with large 
 amounts of barnyard manure, and have been cropped 
 without rotation to some intensive crop, like tobacco or 
 other truck crops. 
 
 Denitrification, as indicated in the diagram, consists 
 chiefly in the loss of gaseous nitrogen from the nitrate 
 nitrogen in the soil. The bacteria causing denitrifica- 
 tion do not require the oxygen of the air, but obtain 
 their oxygen from the soil nitrates. These bacteria are 
 inactive when the soil is well aerated. Poor drainage, 
 and consequently little aeration, and insufficient cul- 
 tivation, or cultivation when the soil is too wet, tend to 
 promote denitrification. It is difficult to measure losses 
 
56 NOTES ON SOILS. 
 
 by denitrification under actual field conditions, and 
 such losses have probably been over-emphasized. 
 
 ll is evident thai the nitrogen content of soils is pro- 
 foundly affected by the method of Winning. The nitro- 
 gen containing substances in the soil are constantly un- 
 dergoing changes, and at practically every stage are 
 subject to losses unless used by the crops. 
 
 (75) Nitrogen Fertilizers. The two most import- 
 ant sources of soil uitrogen are that obtained from the 
 aii- by Legumes, and barnyard manure. When we recall 
 that nitrogen in artificial manures is rated at 15 to 18 
 cents per pound, we can appreciate how invaluable are 
 ihese two sources of nitrogen. Average barnyard ma- 
 nuie contains about five-tenths per cent of nitrogen. 
 Using the above valuation, a ten ton application of ma- 
 rine per acre, or the nitrogen remaining in the soil as 
 the result of a good crop of clover is worth eighteen 
 dollars. 
 
 The important commercial nitrogen fertilizers are 
 sodium nitrate (Chile salt peter), ammonium sulphate, 
 obtained as a by-product in the manufacture of coke 
 and gas, dried blood, and other packing house products, 
 and electrically fixed nitrogen, the latter not of com- 
 mercial importance in the United States as yet. It 
 should not be forgotten that all of these artificial fer- 
 tilizers are expensive, and that nitrogen can be obtained 
 from the air practically without cost. 
 
 Salts like sodium nitrate and ammonium sulphate are 
 very soluble in water, and therefore tend to leach out of 
 the soil, unless the crop is at hand to absorb them. Am- 
 monium sulphate is retained by the soil more completely 
 than sodium nitrate. These fertilizers are particularly 
 
NITROGEN. 57 
 
 adapted to" forcing the truck crops. Grass crops, which 
 always tend to reduce the nitrate supply in the soil to 
 a small amount, respond quickly to applications of such 
 fertilizers. In order to avoid losses by leaching, these 
 salts are applied at different times during the growing 
 season. Seventy-five pounds per acre is the lowest 
 quantity of these salts usually applied, while this quan- 
 tity may be increased to 150 or 200 pounds per acre, 
 depending upon the crop, and the condition of the soil. 
 
 Dried blood is ordinarly applied at the rate of 300 to 
 400 lbs. per acre. Dried blood becomes available to the 
 plants more slowly and therefore there is not so much 
 loss by leaching. 
 
 The great peat marshes of Wisconsin furnish an im- 
 portant nitrogen fertilizer. Peat may contain from two 
 to three per cent of nitrogen in the dried condition, and 
 i: well adapted to use on sandy or clay soils. It should 
 be partly dried so that it will spread easily, and then 
 should be applied at the rate of at least 20 loads to the 
 acre. 
 
58 NOTES ON SOILS. 
 
 CHAPTER VII. 
 PHOSPHORUS AND POTASH. 
 
 Phosphorus. 
 
 (76) Occurrence and Amount of Phosphorus. 
 The elemenl phosphorus occurs chiefly in the mineral 
 apatite in practically all rocks from which the soil 
 grains are formed. It is customary to report the 
 amount of phosphorus in the form of phosphoric pent- 
 oxide (P,0 5 ), although it is not intended to imply 
 thereby thai the phosphorus is absorbed in this form by 
 plants or exists in this form in the rock. It usually, 
 as a matter of fact, exists as a chemical compound of 
 calcium, iron or aluminum. The total amount of phos- 
 phoric acid (P 2 5 ) in most soils varies between .05 and 
 .25 of a per cent though not infrequently soils are met 
 which contain less than .<)•"> of a per cent and a few 
 which contain more than .25. From this it will be seen 
 thai the total quantity of this element in many soils is 
 so small that a comparatively small number of crops, 
 if entirely removed from the land, would exhaust the 
 original supply. .Moreover this element occurs in those 
 substances in the plant, chiefly in the grains of cereals, 
 which are used directly for human food or indirectly 
 through animals and later used as human food and 
 thereby removed from the land. It is therefore abso- 
 
PHOSPHORUS AND POTASH. 59 
 
 lutely necessary to return this element to the land in 
 some form as fertilizer. 
 
 (77) Soil Acidity and Availability of Phos- 
 phates. While the total supply of this element in most 
 soils is sufficient for a considerable number of crops, 
 it often becomes available too slowly to permit a good 
 growth. This is particularly true in soils which have 
 become acid. In fact it can he set down as a rule that 
 acid soils are deficient in available phosphorus and a 
 tes.1 for acidity (sec paragraph 53) becomes a ready 
 method for determining the needs of the soil in this 
 respect. Just what the explanation of this fact is has 
 not yet been determined. It is possibly because the 
 calcium carbonate of the soil has been largely removed, 
 so that it is not present to aid in the formation of cal- 
 cium phosphates which are more readily soluble and 
 avail;! He to plants than iron and aluminum phosphates 
 which are not removed by the acid condition. 
 
 (78) Classes of Soil Deficient in Phosphorus. 
 Lack of available phosphorus in the soil is found to exist 
 first in very acid marsh soils and second in upland well 
 drained soils which have become exhausted and have 
 usually become acid after a considerable portion of the 
 rotating fund of available material has been removed by 
 a longer or shorter period of cropping. 
 
 In the case of th'e acid marsh soils, usually of a peaty 
 nature, the acidity is frequently present to such an ex- 
 tent that it would be impracticable to neutralize it by 
 any form of lime. In this case it is necessary to sup- 
 ply the phosphorus in an available form every year or 
 in a form -which will become available gradually and 
 be taken up by succeeding crops. In the case of up- 
 
60 NOTES ON SOILS. 
 
 land soils it is usually desirable to neutralize the acidity 
 in order to secure better growth of legumes, as has been 
 explained in paragraph 55, ;md the lime for this pur- 
 nose will undoubtedly be helpful in retaining the phos- 
 phorus iu the form of calcium phosphate. It is, however, 
 necessary to supply this elemenl as a fertilizer to main- 
 tain good growth on many of the upland clay loam 
 soils, ordinarily of high fertility, after they have had 
 from l/, to y 2 of their total original supply of this ele- 
 ment removed by a period of from forty to sixty years 
 of grain farming. 
 
 (79) Influence of Method of Farming. Since the 
 element phosphorus goes chiefly into the grains of 
 c< nals. a system of farming in which the grains are 
 sold directly is most exhaustive in its effect on this ele- 
 ment in the soil. On the other hand, where these grains 
 and other parts of the plant are fed to stock on the 
 farm a considerable portion is returned directly to the 
 land in the manure. The amount sold from the farm 
 in animal products varies considerably. Where only 
 butter is sold the amount is reduced to the minimum. 
 Where milk is sold a very important amount of phos- 
 phorus is removed from the milk and where fat stock, 
 the bones of which contain a large amount of phos- 
 phorus, are sold the amount removed is very consider- 
 able. Moreover unless great precaution is taken a con- 
 siderable amount of the phosphorus of the manure is 
 losl by leaching before it is returned to the land. When 
 carefully handled the loss need not be allowed to exceed 
 1<> per cent of that in the manure, but where there is 
 much leaching it may be 25 to 30 per cent or more. 
 Where considerable quantities of feed are purchased for 
 
PHOSPHORUS AND POTASH. 61 
 
 consumption on the farm the loss in animal products 
 by leaching of manure may be counterbalanced or even 
 more than equaled so that a gain actually results. 
 However, it is only on the very highest types of dairy 
 farms that this takes place. The following tables are 
 drawn up to show the income and outgo of phosphoric 
 acid from a general grain farm and from a good average 
 dairy farm, as they exist in the north central part of 
 our country. 
 
 Exchange of Phosphoric Acid on a 100 Acre Dairy Farm 
 
 I. Consumed on farm by 20 milch cows, Whogs, 
 W neat cattle mnl 4 horses: 
 
 
 Phosphoric 
 
 acid, lbs. 
 
 450 
 
 2. Clover and timothy 16 acres 
 
 350 
 
 400 
 
 
 160 
 
 
 40 
 
 
 
 Total 
 
 1.400 
 
 
 210 
 
 II. Sold from the farm each year: 
 
 1. Barley 8 acres 
 
 2. l-i cows 
 
 120 
 60 
 
 
 100 
 
 4. 20 hogs 
 
 50 
 
 
 330 
 
 III. Feeds purchased : 
 
 10 tons wheat bran 600 
 
 Loss, about 15 per tent, on reeds purchased 90 
 
 Total loss 630 
 
 €iain on feeds purchased 600 
 
 Net loss 30 
 
62 NOTES ON SOILS. 
 
 Km iiam.i; of Phosphoric A.cid on a LOO Acre Grain Farm. 
 
 /. Consumedon farm by six milch cows, Bhorses, 
 luhogs and 4 neat cattle: 
 
 Phosphoric 
 
 acid. Il». 
 
 1. Corn 10 acres 280 
 
 2. Oats 25 " 450 
 
 •"• Clover / - .. . 
 
 4. Clover ami timothy ! ' ' 
 
 5. Straw 35tor>s 125 
 
 6. Pasture and wood lot. 25 acres 
 
 'Petal . 1.155 
 
 Loss, about 15 percent, on reeds consumed 17<> 
 
 //. Sold from farm each year: 
 
 I. Barley 25 acres :s:;> 
 
 ■ 2. 10 hoys 2,") 
 
 '■'<. 3 neat cattle 4r> 
 
 Total loss on products *ol<l 445 
 
 Total loss io ih«' farm 615 
 
 From these tables it is evident that it will be neces- 
 sary Io purchase phosphate fertilizers in order to main- 
 tain the yield of crops on the great majority of farms. 
 In all probability the outgo of phosphorus from the 
 soil on 90 per cent of the farms of the country is 
 greater than that returned in feed purchased. 
 
 (80) Phosphate Fertilizers. There are three prin- 
 cipal sources of phosphate for use as fertilizers: (1) 
 Tin- hones of animals killed at the stock yards, (2) 
 Mineral deposits of the tri-calcium phosphate, (3) basic 
 slag from furnaces in which iron ores which contain 
 considerable phosphorus are reduced. Besides these 
 SGurces considerable phosphoric acid is found in fish 
 scrap, dried blood, tankage, and other refuse products. 
 Basic slag is qo1 produced in this country, but is im- 
 ported by the Atlantic coast states to a considerable ex- 
 tent from England where large amounts are produced 
 
PHOSPHORUS AND POTASH. 63 
 
 and from which it is largely shipped to other European 
 countries. 
 
 Our two chief sources are therefore the stock yards 
 and the phosphate mines. Bones are treated in three 
 different ways to prepare them as fertilizers: (1) simply 
 ground and sold as raw bone meal, (2) steamed to re- 
 move grease, etc., and sold as steamed bone meal, and 
 (3) treated with acid to render the phosphorus more 
 soluble and available to plants and sold as acidulated 
 bone meal. The mineral phosphates are either simply 
 ground to a flour-like condition and sold as raw rock 
 phosphate or floats or it is treated with an equal weight 
 of sulphuric acid to make it more soluble and available 
 and sold as acid phosphate. Manufacturers give their 
 products brand names, but they still belong to the above 
 given classes. Mixed fertilizers are also prepared con- 
 taining nitrogen and potash as well as phosphate in 
 various proportions and given trade names, such as 
 Tobacco Special, Potato Grower, etc., etc. 
 
 (81) Raw Bone Meal. This fertilizer contains 21 
 to 23 per cent of phosphoric acid and 3 to 4 per cent of 
 nitrogen. It becomes available rather slowly and so a 
 heavy application should be made at orfe time to become 
 available during the nest few years. It usually costs 
 about $22 a ton in Chicago and a good application is 
 from 300 to 500 pounds per acre depending upon the 
 crops to be grown, more being applied for truck crops 
 than for general farm crops. This application is usu- 
 ally sufficient for three to four years. 
 
 (82) Steamed Bone Meal. This contains 28 to 
 30 per cent of P,0 5 , costs about $26 per ton in Chicago 
 
64 NOTES ON SOILS. 
 
 and is used in the same way as the raw bone meal, but 
 is more desirable. 
 
 (83) Acidulated Bone. Acidulated bone varies 
 with differenl manufacturers in the amount of sul- 
 phuric acid used, and therefore in the amount rendered 
 readily available and in the price and amount to be 
 used. 
 
 (84) Raw Rock Phosphate or Floats. This con- 
 Li ins Prom 20 to 32 per cent of P 2 5 , is ground until 
 90 per cent will pass through a 60 or 80 mesh screen, 
 and costs at the Tennessee mines $3.50 to $5.00 a ton 
 in bulk in carload lots. It becomes available gradually 
 when mixed with manure, applied on a clover or alfalfa 
 sod, or to a soil highly charged with organic matter by 
 the decomposition of which organic acids are set free 
 to act on it. 
 
 Applied under these conditions at the rate of 600 to 
 1000 lbs. per acre for the first treatment of land ex- 
 hausted of available phosphates and at the rate of 300 
 to 500 lbs. per acre every three to five years thereafter, 
 it is probably the cheapest and best phosphate fertilizer 
 for general farm use. It is an excellent absorbent for 
 use in the stables and this is a good way to incorporate 
 it with the manure. 
 
 (85) Acid Phosphate. This is made by mixing 
 equal weight's of raw rock phosphate and sulphuric 
 acid and so contains only 12 to 16 per cent of P 2 5 , 
 but this is readily available without organic matter, 
 and so can be used under conditions where the raw rock 
 phosphate could not. 11 costs $12 to $15 per ton in 
 Chicago. Three to five hundred pounds per acre every 
 
PHOSPHORUS AND POTASH. 65 
 
 two or three years is needed when no other fertilizer 
 containing phosphorus is used. 
 
 potash. 
 
 (86) Amount of Potassium in Soils. The chemi- 
 cal symbol of potassium is K, but the amount of this 
 element contained in any substance is usually stated in 
 terms of the oxide, K 2 0, and this is called potash. 
 About six-sevenths of potash is potassium. Clay and 
 loam soils contain from one to two per cent of potash; 
 sandy soils, two-tenths to one per cent ; and peat and 
 muck, two-hundredths to five-tenths of a per cent. As- 
 suming the weight of the surface soil over an acre to a 
 depth of eight inches to be 2,000,000 pounds in the case 
 of clay, two and one-half million in the case of sand, 
 and one-half million in the case of peat and light muck, 
 it will be seen that these soils contain on the average 
 from twenty to forty thousand pounds per acre for the 
 clay loams to a depth of eight inches, five to twenty- 
 five thousand for sands, and one hundred to twenty-five 
 hundred for peats and mucks. It will be seen from 
 these figures that only peat and muck soils are de- 
 ficient in their total supply of potassium and that in 
 these soils it is absolutely necessary to add this element 
 to secure good crops where it is below two-tenths or 
 three-tenths of a per cent. In most soils the total sup- 
 ply of this element is sufficiently large for a long period 
 of cropping if it were in an available form or would 
 become available readily, but the potassium exists in 
 the soil largely in the form of grains of feldspar and 
 other minerals, which become soluble onlv with consider- 
 
6G NOTES ON SOILS. 
 
 able slowness, so that occasionally sands and even clay 
 soils are found deficienl in available potassium. Never- 
 theless, it is true that with very few exceptions, clay, 
 loam, and sandy soils hecome deficient in nitrogen or 
 phosphate before they do in potassium, and it is very 
 seldom that this elemenl is the limiting factor. 
 
 (87) Loss of Potassium from the Farm. From 
 a study of the composition of the different parts of the 
 plant as given in the table in paragraph 10, it will 
 be seen that most of this element goes to the stalk and 
 straw of a crop and comparatively little to the grain. 
 For this reason there is very much less loss of this ele- 
 ment from the farm in the crops than is the case with 
 phosphorus. Hay is about the only product of the 
 staple crops commonly sold which removes a consider- 
 able amount of potassium. 
 
 (88) Potash Fertilizers. The all-important source 
 of potash fertilizer is that of the Stassfurt mines in 
 Germany. Besides this, wood ashes, which are available 
 especially in the pineries- contain from four to six per 
 eenl of potash. The Stassfurt salts as mined in the 
 crude form contain from 12 to 15 per cent of potash 
 but are manufactured into sulphates and muriates or 
 chlorides in which process the potash is concentrated, 
 so that high grade muriate and sulphate of potash con- 
 tain from 48 to 50 per cent of potash. These last men- 
 tioned salts will, therefore bear a larger expense for 
 transportation than will a low grade salt of Avhich 
 kainit is an example. Muriate of potash is somewhat 
 cheaper than sulphate and is equally good for most 
 crops, hut for potatoes and tobacco and possibly some 
 other truck crops the sulphate is preferable. These 
 
PHOSPHORUS AND POTASH. 67 
 
 salts are both readily soluble in water and therefore 
 available to crops and may be applied on any land at 
 the time of preparation for seeding, although there is. 
 very little lost if applied some time in advance since the 
 potash is largely fixed in the soil. From 100 to 200^ 
 pounds of cither the sulphate or muriate is a good ap- 
 plication; the amount tends to vary with the crop, a 
 larger amount being used for such crops as cabbage, 
 sugar beets, or potatoes than would be necessary for 
 grain, and, of course, the amount would vary with the ■ 
 character of the soil, a point which will be discussed in, 
 a later chapter. 
 
08 
 
 NOTES ON SOILS. 
 
 CHAPTER VIII. 
 
 MECHANICAL COMPOSITION, TEXTURE AND 
 
 TILTH OP SOIL. 
 
 When we examine any soil in the field we find that 
 il is largely made up of lumps varying in size from 
 the size of a pin head to several inches in diameter. 
 If these Lumps be dried and crushed they are found to 
 be made up of particles of grains varying all the way 
 from a size much too small to be seen with the naked 
 eye up to coarse sand or gravel. The term mechanical 
 composition refers to these ultimate particles and the 
 term texture, to the way in which they are arranged 
 ami clustered into clumps. Both the mechanical com- 
 position and the texture of the soil vitally affect the 
 growth of plants in many ways and their study is there- 
 fore of much importance to the farmer. 
 
 (89) Mechanical Composition. When samples of 
 different kinds of soil are dried and the lumps crushed 
 and then sifted through sieves of different sizes, it is 
 found that while most samples contain grains of all 
 sizes, from the finest up to sand, the relative amounts 
 of the different sizes vary greatly. Clay soils contain 
 a large amount of the finest grains with small amounts 
 of the medium and coarser grains, while in sandy soils 
 this relation is reversed, in alluvial or silty soils there 
 is a large amount of the medium sized grains. 
 
COMPOSITION, TEXTURE AND TILTH OF SOIL. 
 
 69 
 
 It is customary in a scientific study of soils to call the 
 finest grains clay, the medium size grains silt, and the 
 coarsest, sand. When the grains of clay are measured 
 they are found to vary from sizes too small to measure, 
 up to .005 of a millimeter in diameter. The fine silt 
 varieties from .005 to .01 of a millimeter; the coarse 
 silt, from .01 to .05; fine sand from .05 to 0.2; coarse 
 sand from 0.2 to 1 ; fine gravel from 1 to 3 millimeters 
 in diameter. In this classification the only difference 
 between clay and sand is in the size of grain. Now, 
 it is true that part of the extremely fine particles of 
 clay are kaolin, resulting from the decomposition of 
 feldspar in granite, as described in paragraph 25, 
 nevertheless some of the finest particles of clay are pure 
 quartz like those found in sand. Moreover, if pure 
 quartz is ground fine enough, it has the plastic quality 
 of natural clay. The chief differences in character of 
 clay and sand are due to difference in size of grain. 
 The following table gives the mechanical composition 
 expressed in per cent of six different types of soil 
 found in England as described by Professor A. D. Hall. 
 
 Fine Gravel, 3 to 1 Mm . . . 
 Coarse Sand, 1 to 0.2 Mm . 
 Fine Sand, 0.2 to 0.05 Mm. 
 
 Silt, 0.05 to 0.01 Mm 
 
 Fine Silt, 0.01 to 0.005 Mm 
 Clay, below 0.005 Mm 
 
 ( loarse 
 Barren 
 
 Sand. 
 
 V- — — 
 
 it E - 
 O c$ 
 
 Fine 
 
 Sandy 
 Loam. 
 
 >'. si 
 
 0.2 
 
 7.6 
 
 0.5 
 
 2.8 
 
 22.6 
 
 44.11 
 
 15.0 
 
 14.1 
 
 60.8 
 
 23.1 
 
 49.0 
 
 31.2 
 
 4.8 
 
 4.3 
 
 15.3 
 
 17.4 
 
 0.6 
 
 2.9 
 
 3.9 
 
 6.9 
 
 1.8 
 
 11.7 
 
 9.7 
 
 18.5 
 
 o 
 
 0.4 
 
 0.8 
 
 6.4 
 
 18.6 
 
 13.6 
 
 42.2 
 
70 CTOTES ON soils. 
 
 The remainder of the soil in each case is made up of 
 humus, Lime carbonate and moisture. It will be seen 
 from the table that while all soils contain some grains 
 of each size, there is a relatively large amount of sand 
 both coarse and fine in the coarser soils and a rela- 
 tively small amount in the clay soils, while clay soils 
 contain a small amount of sand, but a relatively large 
 amount of clay. Many alluvial soils, such as the loess 
 of the Mississippi Valley, contain a much larger rela- 
 tive amount of silt size than any one of these six 
 samples, it will be seen later that the mechanical com- 
 position of soils influences very profoundly their tex- 
 ture and capacity for holding water. It also influences 
 the fertility to a certain extent, since the finer grained 
 particles will dissolve in soil water more rapidly than 
 the coarser grained, just as fine salt will dissolve more 
 rapidly than coarse. This is because there is more sur- 
 face on a given weight of the fine soil than of the 
 •eoarse. 
 
 The surface of an inch cube is six square inches. If 
 this cube he divided into cubes of a half inch on the 
 edge, there will be eight of them and the total area will 
 be twelve square inches. The area of the entire surface 
 will double each time the diameter is divided in two. 
 From this we see that the surface of all the grains of a 
 cubic inch of soil would be vvvy great and that the sur- 
 face of the grains in a cubic inch of clay would be very 
 much greater than in a cubic inch of sand. The follow- 
 ing table .irives the area in square feet of the grains in a 
 pound of sand, silt and clay of given diameters. 
 
COMPOSITION, TEXTURE AND TILTH OF SOIL. 71 
 
 Diameter of Grain. 
 
 Square Feet of Surface 
 in a Pound. 
 
 
 11.05 
 
 Fine Sand 1 Mm 
 
 110.54 
 
 Silt 01 Mm 
 
 1,105.38 
 
 Clav 001 Mm 
 
 11,053.81 
 
 Fine Clav 0001 Mm 
 
 1,100,538.10 
 
 
 
 (90) Texture and Tilth. Everyone who has culti- 
 vated soil realizes the influence of its texture on the 
 growth of the crop. On this texture depends the readi- 
 ness with which roots can penetrate it, the readiness 
 with which oxygen can enter it to be used by the roots, 
 and by the bacteria in developing nitrates and to oxidize 
 the humus producing carbon dioxide.. It also deter- 
 mines to a certain extent the water holding capacity of 
 the soil. 
 
 Now the texture of a soil or the arrangement of its 
 grains is affected by the following conditions : 
 
 1. Mechanical composition, 
 
 2. The amount of water it contains, 
 
 3. The cfiaracter of the soil water, 
 
 4. Humus, 
 
 5. The roots of crops, 
 
 6. Freezing and thawing. 
 
 7. Cultivation. 
 
 "When the texture is favorable to growth of the crop, 
 the soil is said to have a good tilth; when unfavorable, 
 to have a poor tilth. 
 
 (90a) Mechanical Composition and Texture. The 
 smaller the size of the grains, that is, the finer the me- 
 
72 
 
 NOTES ON SOILS. 
 
 chanieal composition, the greater is its tendency to cling 
 together so thai when cultivated it tends to break up 
 into lumps. The way in which these aggregates are 
 formed as the moisture dries out of the soil is illustrated 
 in fie. 4. It will be seen that as the films of water 
 
 Fie. 4. — Illustrating the formation of soil granules. 
 
 become thinner and the soil grains are drawn closer to- 
 gether large cracks are formed leaving the soil in a 
 granular condition. Sands composed of coarser grains 
 show very little of this tendency, but fall apart readily. 
 The mechanical composition of the soil will, therefore, 
 aid us to a certain extent, to predict its texture under 
 field conditions. 
 
 (91) Amount of Water. When soils are extremely 
 wet, that is, when saturated, the particles tend to fall 
 apai't or run. This effect is increased when the soil is 
 
COMPOSITION, TEXTURE AND TILTH OF SOIL. 73 
 
 stirred while Avet. As the soil dries, the particles tend 
 to adhere more and more firmly and when extremely 
 dry, the clays which have run while wet become very 
 hard and if cultivated in that condition break up into 
 lumps. The sands, not having sufficient adhesive power, 
 fall apart when entirely dry, while they are held in a 
 fine, crumb like texture while partly wet. 
 
 (92) Texture and Soil Solution. Many salts when 
 dissolved in water tend to make the soil grains gather 
 into clusters or flocculate. If for instance a little clay 
 be shaken with pure rain water it will remain in sus- 
 pension for ;i long time, making the water turbid. If, 
 however, a very little alum be dissolved in the water 
 it will cause the clay to flocculate and settle, leaving 
 the water perfectly clear. Salts occurring in the soil 
 have the same effect. Lime put on the soil often bene- 
 fits the soil by causing the grains to cluster, thus giv- 
 ing it a better texture, especially where it would other- 
 wise have a tendency to run. On the other hand some 
 salts and other substances tend to break down the clus- 
 ters of soil and make them run or puddle. Ammonia 
 or ammonium salts have this effect. 
 
 (93) Humus and Texture. As the vegetable ma- 
 terial in the soil decomposes, humus is produced. This 
 humus spreads over the surface of soil grains, often 
 covering them like a coat of black paint. In the case of 
 sand this has the effect of making the sand grains cling 
 together, thus giving it a firmer and closer texture which 
 prevents it from drying out so rapidly as well as greatly 
 increasing its water-holding capacity. In the case of 
 clay, on the other hand, the humus tends to weaken the 
 adhesiveness and so prevent the formation of large, hard 
 
M NOTES ON SOILS. 
 
 clods on drying, to a certain extent. Humus, therefore, 
 greatly improves the texture or tilth of both sandy soils 
 and clay soils. 
 
 The development of the root system of* plants causes 
 the liiovenienl of soil particles in contad with them 
 thus modifying their texture. The most important ef- 
 t'i ■el of the roots, however, is the result of their decay, 
 Leaving holes in the soil and subsoil. The amount of this 
 eti'eet depends largely on the character of the roots. 
 Such roots as those of alfalfa, which are often more than 
 a third of an inch in diameter and extend several feet 
 into the soil, often have a very decided effect in loosen- 
 ing a compact subsoil. The same result is produced by 
 earthworms. 
 
 (94) Freezing and Thawing. The effect of the 
 freezing- and of the expansion of the water contained 
 in the soil, is to separate the soil clusters, breaking 
 down the larger chunks. One of the chief benefits of 
 deep fall plowing is due to the fact that the exposure 
 to the surface where there is frequent freezing and 
 thawing breaks up the mass, giving it a better texture. 
 
 (95) Cultivation. One of the most important ob- 
 jects of cultivation is to improve the texture of the soil. 
 This will be discussed in the chapter on Principles of 
 Tillage. 
 
WATER-HOLDING CAPACITY OF SOILS. (O 
 
 CHAPTER IX. 
 WATER-HOLDING CAPACITY OF SOILS. 
 
 (96) Three Forms of Water in Soil. If sand is 
 placed in a stoppered funnel and water poured over 
 it until it is entirely soaked and then the stopper re- 
 moved part of the water will drain away while part re- 
 mains in the soil. The water which drains off is called 
 drain or gravitational water. If the soil is examined 
 after drainage it will be found that the water still in 
 the soil is in the form of films around the grains and 
 in the smaller angles between the grains. Since this 
 water is held by the grains of soil in the same way that 
 water is held in a capillary tube it is called capillary 
 water. Again, if soil is allowed to dry in the air as 
 completely as it will, it will be found that if it is put 
 in an oven and heated it will give up some water. If 
 after drying completely in this way it be allowed to 
 sland in the air it will again absorb some moisture. 
 This water is called hydroscopic moisture and of course 
 is usually small in amount. 
 
 (97) Use of Water in these Different Forms. It 
 would seem that the plant could use the water in all 
 forms equally well ; but when it is remembered that 
 "the soil must contain air for the growth of roots and for 
 the process of nitrification it will be seen that eondi- ' 
 lions will be better when part of the water is drained 
 
7(i NOTES ON SOILS. 
 
 off. [f the root hairs come in contad with the soil 
 grains to gel moisture they will act more strongly to 
 dissolve the grains. 
 
 (98) The Amount of Capillary Water Held by 
 Soils. Since the water is held ;is films around the soil 
 .mains, the amount so held depends in pari on the area 
 of the surface of the grains. Now, the area of the soil 
 grains depends on their size; the finer the soil the 
 greater the area of a given amount. The area of soil 
 grains is very Large. In one cubic foot of the finest 
 clay soil I here are 175,000 square feet of surface, or 
 more than four acres. In a cubic foot of sandy loam 
 Hie aiea is 35,000 square feet, or over three-fourths of 
 an acre, while in coarse sand it is only 6,000 to 8,000 
 square feet. 
 
 The importance of even small amounts of clay in 
 soils is shown hy the above data. In truck soils the 
 clay constitutes about !<> per cent; in wheat soils 20 per 
 cent, and in the best grass soils :!(> per cent. 
 
 Humus also has a very great power to hold water, 
 and Hie water-holding capacity of our loam soils is due 
 to a considerable extent to the humus. To show the 
 effect of clay and humus on the water-holding capacity 
 of soils a pint each of humus soil, of clay loam and 
 of sand soil was placed in percolating jars, water 
 poured on till it began to drip, then allowed to drain 
 twelve hours and the water still held determined. It 
 was found to be for the humus soil 315 c. e., for the 
 clay loam 230 c. e., and for the sand soil 153 c. c. 
 
 In the field after heavy rains have given the soil all 
 it can hold and it has rained few days, approximately 
 Hie fdl lowing amounts will he held: 
 
\\ ATER-HOLDING CAPACITY OF SOILS. 
 
 77 
 
 
 Sandy 
 loam. 
 
 Clay 
 loam. 
 
 Humus 
 
 soil. 
 
 
 3 in. 
 2 in. 
 
 VI in. 
 3 in. 
 
 5 in. 
 
 
 3| in. 
 
 
 
 Sand in clay soils has the effect of allowing a rain to 
 wet down farther than the pure clay would, because of 
 its much less capacity to hold water. Hence a small 
 rain will reach to the roots of plants in a sandy soil or 
 even in a clay soil containing sand, when it might not 
 reach them in a clay soil containing little sand. 
 
 (99) Availability of Soil Moisture to Plants. It 
 is, of course, impossible for the plant to extract all the 
 water from the soil and when plants wilt a sandy soil 
 will contain the least water, the clay loam more and 
 the humus most. Still, when the amount contained 
 when plants wilt is subtracted from what the soil can 
 hold, it will be found that the plants have taken least 
 from sand, more from clay loam and most from humus 
 soil. The amount of water in the first four feet of soil 
 which is available to crops is approximately as follows: 
 very sandy soils four inches, clay loam five inches and 
 very humus soils seven inches. 
 
 (100) Cultivation and Culture to Increase Wa- 
 ter Capacity of Soils. In a region like ours where the 
 rain is apt to be deficient it is desirable to improve the 
 water-holding capacity of soils. Fall plowing has an 
 advantage over spring plowing in that the loose con- 
 dition of the soil tends to hold the winter rain and 
 snow so that it soaks into the ground instead of running 
 
NOTES ON SOILS. 
 
 off. The direction of plowing with reference to the 
 slope also makes a difference in this respect. If the 
 furrow slice be turned up-hill it tends to hold water 
 better than when turned down. Subsoiling is another 
 method of increasing the amount of water the soil can 
 hold. This method of plowing is followed to quite an 
 extent in Europe, bu1 so Ear as tried in the west does 
 not seem to increase the crop enough to justify the ex- 
 tra labor. The looseness of soil produced by some 
 crops is quite important. Bui in all probability the 
 mosl effective method of increasing the water capacity 
 is by developing humus. This can be done by growing 
 and plowing under catch crops when the soil will not 
 be dried too much by this. i. e.. during a wet season, 
 and by pasturing-. A piece of very sandy land was 
 found in the summer to have 16,000 pounds more water 
 per acre where manure had been applied than where not. 
 
-MOVEMENTS OF SOIL WATER. 79 
 
 CHAPTER X. 
 MOVEMENTS OF SOIL WATER. 
 
 Since the entire pore space of soils must not be filled 
 by water or there will be a lack of air for the plant 
 loots and for the bacteria which carry on the process of 
 nitrification it is necessary that artificial means be used 
 to draw off the excess. This is the object of drainage. 
 Since the amount of water within the reach of plant 
 roots is often too small for their needs it is necessary 
 to take advantage of and increase the upward move- 
 ment of water through the soil penetrated by roots and 
 to prevent as much as possible its loss by evaporation 
 from the soil surface. 
 
 (101) Causes of Movements of Soil Water. 
 There are three causes of movements of water in soils. 
 The first is the force of gravitation ; second, surface ten- 
 sion causing capillary movement ; and third, heat. The 
 force of gravitation while acting in a line toward the 
 center of the earth will cause movements of water on 
 even very gentle inclines under the surface of the soil 
 as well as on it. Capillary movement may take place 
 in any direction. It tends to move the water from 
 places of greater towards places of less moisture and 
 to so distribute it that the films surrounding the grains 
 are of equal thickness and so the fine soils will hold 
 more than the coarse ones. The thermal or heat move- 
 
80 NOTES ON SOILS. 
 
 ments are due to the fact that when the soil is warmer 
 ;ii one point than at another the water will evaporate 
 where the soil is warmer and pass as vapor through the 
 soil to the cooler parts and there condense. Heat may 
 therefore cause movements of water in any direction in 
 the soil. When these forces act in the same direction 
 the water will move most rapidly. 
 
 (102) Ground Water. Of the water which falls 
 cm the ground, part runs oft' while part sinks in. Of 
 that which sinks in, pail is used by plants while the re- 
 mainder passes on down and accumulates as the ground 
 water entirely tilling the pore space hetween soil grains. 
 The surface of the saturated part is called the ground 
 watt r level. This surface however is not level but rises 
 and falls with the surface of the ground though being 
 Less uneven than the surface. 
 
 (103) Percolation and Seepage. The downward 
 and lateral movements of this ground water, produced 
 by gravitation either alone or together with capillary at- 
 ti act ion are called percolation and seepage, respect- 
 ively. The rate of these movements of water depends 
 on a number of factors, the most important of which 
 are: first, the size and arrangements of the soil grains; 
 second, the height of water pressure; third, the dis- 
 tance the water must flow before finding an outlet: and 
 fourth, the temperature of the water. 
 
 The tiow of water through sand or soil under simi- 
 lar conditions is approximately proportional to the 
 square of the diameter of grain, that is water will flow 
 four times as fast through a soil having a given diame- 
 ter of grain than through one having half that diameter, 
 etc. It may tiow 1000 times as fast through a coarse 
 
MOVEMENTS OP SOIL WATER. 81 
 
 sand as through a clay. The rate of flow is dependent 
 directly on the pressure head, that is if the ground 
 water surface falls one foot per rod the flow will be 
 twice what it would be if the fall were but 6 inches in 
 that distance. The warmer the temperature the more 
 rapid will the water move because the viscosity of the 
 water is less when warm than when cold. 
 
 The checks and cracks formed during the drying of 
 clay soils, and the holes left by the roots on decaying 
 are the chief channels in the movement of water through 
 heavy clay soil. 
 
 (104) The Advantages of Drainage. Some of 
 the more important advantages of drainage are the fol- 
 lowing: First, it increases the water available to plants; 
 second, allows humus to decompose more rapidly; third, 
 warms the soil by lessening the evaporation and by al- 
 lowing the warm rain to soak in ; fourth, it gives better 
 ventilation; and fifth, gives a larger mass of soil on 
 which the plants can draw for food material. 
 
 Soils continue to improve in texture for several years 
 after drains are put in because the drains allow the 
 water to escape from the checks and cracks formed dur- 
 ing dry periods in place of remaining and causing the 
 soil to run into the cracks and fill them up again. 
 
 (105) Capillary Rise of Water. The rate at 
 which water will rise in soils is greater the coarser the 
 grain. It is also more rapid in moist than in dry soils. 
 The height to which the water will rise is greater the 
 finer the soil, or what amounts to the same thing, the 
 greater its compactness. 
 
 There are two ways in which we must be able to con- 
 6 
 
82 NOTES ON SOILS. 
 
 tin] the movements of soil water. The firsl is that of 
 bringing it from lower layers to the seed during a dry 
 spring and second to prevent its loss from the surface, 
 it will lie seen from the above mentioned facts that the 
 most effective means of raising is compacting by t lie use 
 of a heavy roller. The prevention of loss by evapora- 
 tion can he accomplished by making the surface soil 
 thoroughly dry and loose, thai is by developing a soil 
 mulch. 
 
 The characteristics of a good mulch are that it 
 should he thoroughly dry, loose and not too fine. The 
 efficiency of the mulch is about as great when its thick- 
 ness is three inches as when greater. There is, there- 
 fere, nothing gained by deeper cultivation, in this re- 
 spect. Of course the crust developed by even a light 
 rain destroys the mulch and necessitates a new cultiva- 
 tion. The effect of light rains in this way is often to 
 cause loss of more water than they brought to the soil. 
 
TEMPERATURE OF SOILS. 83 
 
 CHAPTER XL 
 
 TEMPERATURE OF SOILS. 
 
 The influence of temperature on germination and 
 growth was discussed in the first chapter and its influ- 
 ence on the chemical and biological changes, including 
 nitrification, were mentioned in the sixth chapter. 
 As an illustration of the influence of temperature on 
 the growth of roots the following table from Hall giv- 
 ing the growth of roots of corn at different tempera- 
 tures, is quoted. 
 
 Temperature. 
 
 Millimeters. 
 
 <>)! degrees Fahrenheit 
 
 1.3 
 
 79 degrees Fahrenheit 
 
 21.5 
 
 92 degrees Fahrenheit 
 
 39. 
 
 93 degrees Fahrenheit 
 
 55. 
 
 101 degrees Fahrenheit 
 
 25.2 
 
 108.5 degrees Fahrenheit 
 
 5.9 
 
 It will be seen that there is an optimum temperature 
 at about 93 degrees. We have now to consider the 
 conditions which modify the temperature of the soil. 
 They are first, character of the soil, including color 
 and specific heat ; second, roughness of surface ; third, 
 
• s 1 NOTES ON SOILS. 
 
 amounl of water; fourth, slope and situation; fifth, de- 
 composition of organic material. 
 
 (106) Character of the Soil. The color of the 
 soil influences to a certain extenl the amount of heat ab- 
 sorbed from the sun. The black soils absorb more heat 
 than the red and the wd more than those of lighter 
 color. Tins is one of the ways in which the black 
 humus is helpful in the soil. The specific heat, or the 
 relative amount of heal necessary to give the same 
 weighl of different soils the same increase in temper- 
 ature, also has its influence. The amount of heat neces- 
 sary to raise the temperature of a pound of sand one 
 degree is only two-thirds of that necessary to raise a 
 pound of clay and only one-half of that needed to raise 
 ;i pound of humus one degree. However, the sandy 
 soils are much heavier, volume for volume, than the 
 humus soils, so that these two factors tend to offset each 
 other to a certain extenl and yet it will be seen that 
 a small amount of humus in the sandy soil will give it 
 a black surface to absorb the heat effectively, while the 
 sand is easily heated so that soils Of this type warm 
 up very much more rapidly in the sunshine than do 
 clear sands, clay or soils largely composed of humus. 
 
 (107) Amount of Water. Water in the soil 
 must, of course, be warmed when the soil is warmed, and 
 owing- to its high specific heat greatly retards the rate at 
 which the soil is warmed, but the most detrimental ef- 
 fect of water on the temperature of the soil is due to 
 The fad that its evaporation from the surface uses up 
 so much of the heat. The amount of heat necessary 
 to evaporate one-tenth of an inch of water over the 
 surface of a field would be enough to raise the tempera- 
 
TEMPERATURE OF SOILS. 85 
 
 ture of the wet soil to a depth of six inches over thirty 
 degrees if none were radiated to the air. The percent- 
 age of water in the soil is the most important factor 
 in soil temperature. Those soils which are relatively 
 dry are usually early, while those that are wet are late 
 not simply because the dry soils can he cultivated be- 
 fore the wet ones but because they are warmer and 
 seeds will germinate in them sooner than in the late 
 ones. 
 
 Undrained soils are often 10° to 12° colder than simi- 
 lar drained soils. This coldness of undrained soils has 
 much to do with the formation of frost on marshy 
 ground. 
 
 (108) Roughness of Surface. It follows from 
 the above that any condition which will prevent the 
 rise of water to the surface or its evaporation will allow 
 the soil to warm up so much the more rapidly. If the 
 texture is loose and open so that capillarity is inter- 
 rupted this will lessen the amount of water evaporated 
 from the surface and so tend to increase its temper- 
 ature. There is, however, another factor which must 
 be considered, namely the heat conductivity of the soil. 
 If the soil does not conduct the heat from the surface 
 downward, the surface itself may be very warm, while 
 the lower layers remain cold. Now looseness of tex- 
 ture greatly lessens the rate at which heat is trans- 
 mitted from the surface downward, while compacting 
 the soil as by rolling, will aid this process of conduc- 
 tion. It is found that soils that have been rolled may 
 be three or four degrees warmer at a depth of three 
 inches than unrolled soils, in spite of the fact that more 
 water is brought to the surface as a result of rolling. 
 
86 NOTES ON SOILS. 
 
 The best condition is' produced by rolling the ground 
 when necessary and then harrowing the surface to de- 
 velop a thin dry mulch to prevent evaporation. 
 
 [f the surface be somewhat rough, the evaporation 
 
 is lessened because the wind does tiol have as free play 
 over the surface as when the ground is smooth. Any 
 oilier shelter such as that of a hedge or woods which 
 Lessens the effect of the wind also allows the soil to be- 
 come warmer. The difference due to this may lie ;is 
 much as two or three degrees, which is quite an im- 
 portant amount in the germination of seed and growth 
 of roots. 
 
 (109) Slope and Situation. The south slope of 
 hills tends to become warmer than a flat surface and this 
 in turn warmer than the north side of the hill. This is 
 because the surface is more nearly perpendicular to 
 the sun's rays and hence a greater amount of heat is 
 received per square foot. The difference between the 
 south and north slope may he as much as two degrees. 
 The influence of situation whether on low lying ground 
 or on higher slopes or hilltops is also of importance. 
 The soils of the lower ground are usually considerably 
 colder than those of the hillsides and hilltops for sev- 
 eral reasons. There is usually more water in thejower 
 regions which tend to keep them cold as seen above. 
 There is also a tendency for the cold air to collect in 
 the low places which cools the soil. This is the most 
 important factor to be considered in the selection of 
 ground for crops such as fruit, vegetables, etc., which 
 are in serious danger of being affected by frost. It is 
 also of importance in selecting ground for corn rais- 
 in, «r in the northern part of the state. Frost is often 
 
TEMPERATURE OF SOILS. 87 
 
 experienced on marsh ground while the temperature on 
 high land, within a few miles, is as much as ten degrees 
 above freezing. 
 
 (110) Decomposition of Organic Material. The 
 decomposition of vegetable material is the result of 
 chemical and biological changes which produce heat. 
 When the amount of organic material is very large 
 and it is decomposed rapidly, the temperature may be 
 raised several degrees. 
 
 In the soil the organic material usually forms a small 
 part and its decomposition is so slow that the heat de- 
 veloped is not large. A very heavy dressing of manure 
 may have the effect of raising the temperature two or 
 three degrees for a short time. 
 
88 NOTES ON SOILS. 
 
 CHAPTER XII. 
 VENTILATION OF SOILS. 
 
 (111) Necessity of Ventilation. We have seen 
 thai ventilation of soil is necessary, first, to supply oxy- 
 gen used by bacteria in the process of nitrification and 
 by roots in growth: and second, to remove the carbon 
 dioxide which is produced by the decomposition of the 
 humus, so that it may not accumulate in quantities 
 large enough to injure the roots and so that it may be- 
 come available to the plant by absorption by the leaves. 
 One of the greatest objections to a large amount of 
 water in the soil is that this water logged condition 
 decs not allow access of air to the soil. 
 
 (112) Agencies Causing Ventilation. The 
 change of air in the soil is affected by first, expansion 
 and contraction due to changes in temperature; second, 
 l\ change in barometric pressure, third, by wind; and 
 fourth, by rain. 
 
 The expansion and contraction of air contained in 
 the soil as it is warmed during the day and cooled dur- 
 ing the night tends to force some air out in the day 
 and draw some fresh air in at night, producing a crude 
 -nf of breathing. 
 
 The constant change of barometric pressure also pro- 
 duces this resnlt. The unequal pressure of the wind, 
 blowing si mng at times and ceasing again, also tends 
 
VENTILATION OF SOILS. 89 
 
 to change the air in the soil particularly on hillsides 
 which are exposed to this action. A rainfall brings 
 fresh air into the soil in two ways: first, in solution 
 in the water, and second, by drawing it in after the 
 water percolates down into the soil. 
 
 Tillage affects the ventilation to the depth to which 
 the soil is cultivated. 
 
 (113) Excessive Ventilation. While a certain 
 amount of ventilation is necessary to supply oxygen 
 and to remove carbon dioxide, it is quite possible for it 
 to be so large as to oxidize the humus more rapidly than 
 it can be accumulated with the result that it disappears 
 almost entirely from the soil. This is the effect very 
 generally in extremely sandy soils which allow the air 
 a too ready access. Difficulty is also experienced in the 
 southern states in retaining humus in the soil where the 
 temperature being higher hastens its oxidation. Any- 
 thing' which will lessen the ventilation will also lessen 
 the oxidation of the humus. 
 
90 NOTES ON SOILS. 
 
 ( IIAPTER XIII. 
 TILLAGE. 
 
 The work of cultivation or tillage involves the 
 greater pari of the labor which the farmer has to do 
 in the production of crops. It is very important, there- 
 tore, thai he study carefully the objects to be gained 
 ami the methods of attaining them. 
 
 The most important objects of cultivation are: First, 
 to improve texture; second, to kill weeds; third, to con- 
 serve moisture, and fourth, to cover vegetation so as to 
 add humus to the soil. It very often happens that two 
 or more of these objects are attained at the same time, 
 but it is desirable that they be thought of distinctly 
 and that the effectiveness of the tillage be considered 
 from the standpoint of each object to be gained. 
 
 (114) Cultivation and Texture. The process of 
 plowing has for its chief object the improvement of 
 the texture or tilth of the soil. The effect of bending 
 the furrow slice by means of the mold board is to break 
 it up into larger or smaller lumps making it more open 
 and porous. The form of the mold board determines 
 the amount of this bending or crumpling. The long, 
 slightly curved mold board of the breaking plow may 
 allow the furrow slice to slide from it with compara- 
 tively little bending while a plow witli a steeper or 
 
TILLAGE. 91 
 
 more highly curved mold board will bend the furrow 
 slice so as to break it up very thoroughly. This is the 
 desired result and the best plowing in this respect is one 
 which leaves the ground rough and uneven. 
 
 The condition' of the ground at the time of plowing 
 with reference to its moisture content has a very great 
 influence on the texture developed. If the ground is 
 too wet the working of the soil by plowing tends to 
 puddle it so that on drying the soil is left in a very 
 bad condition. This applies particularly to clay soils. 
 Sandy and humus soils are not so badly affected and 
 can therefore be plowed when relatively much wetter 
 than clay soil. If the soil be too dry, on the other 
 hand, it will be hard so that not only is the draft of 
 the plow much greater but the furrow slice does not 
 break up so completely and large unbroken clods are 
 left. 
 
 It is extremely important to plow at just the proper 
 condition of moisture to produce a good tilth and the 
 farmer should study each field carefully and note the 
 results of plowing under different conditions till he rec- 
 ognizes the proper conditions to secure the best results. 
 
 The depth of plowing depends on the kind of soil to 
 some extent and also on the time of plowing. In gen- 
 eral, clay soils should be plowed more deeply than is 
 necessary or desirable for sandy soils. It is also de- 
 sirable that clay soils be plowed in the fall in order to 
 give time for the clay to acquire a good texture. 
 
 This is particularly important when the plowing is 
 deeper than usual, since if new clay soil be turned up 
 in the spring it will have a poor texture and tend to de- 
 velop a crust on the surface easily after rain, thus giv- 
 
NOTES ON SOILS. 
 
 in-; a poor tilth of the soil. After plowing in the 
 spring it is often very helpful in developing a good 
 texture to go over the ground with planker or a float 
 a1 the dose of each day's plowing while the lumps are 
 still moist enough so as to be readily broken. The re- 
 peated plowing of the soil to the same depth tends to 
 develop a hard-pan. This can be avoided by plowing 
 ;ii different depths different seasons. The disc plow 
 has some advantages over the ordinary mold board plow 
 in this respect; it does not leave the plowed land lying 
 upon a perfectly smooth surface without good contact 
 K-ith it as the ordinary plow often does. The disc plow- 
 does not clean well in clay soils unless they have some 
 s;; nd in I hem. In using the cultivator for improving 
 tilth, it is necessary to pay attention to the amount of 
 moisture in the soil as in the work of plowing. The 
 chief use of the cultivator so far as tilth is concerned is 
 to destroy the crust which develops after even a slight 
 rainfall. 
 
 (115) Cultivation to Kill Weeds. The time at 
 which weeds are most easily killed, is just as the seed is 
 germinating. By stirring the surface of the soil so as 
 to expose the germinating seed to the sun and air to 
 diy. it can readily he destroyed. Since not all seeds 
 germinate at the same time a repetition of this cultiva- 
 tion may he necessary. For light sandy soils a close 
 toothed weeder is the most effective, but for heavier 
 soils a light spiked toothed harrow will give better re- 
 sults. 
 
 (116) Cultivation to Conserve Moisture. A 
 Large part of tin 1 United States is subject to drought. 
 It is. therefore, important at such times to prevent the 
 
TILLAGE. 93 
 
 less of water as much as possible. Much can be clone 
 by proper cultivation to lessen the water lost by evapor- 
 ation from the surface. It was seen in Chapter X that 
 water cannot rise readily through dry soil nor through 
 one which is very open. 
 
 The loss of water can, therefore, to some extent be 
 prevented by stirring the surface of the soil so as to 
 dry it completely and leave it loose or in the form of a 
 mulch. It is not desirable that the mulch be broken 
 up so fine as to form dust, for the moisture will rise 
 through this more rapidly than if it is somewhat coarser, 
 but it is extremely important that it be thoroughly dry. 
 The depth to which the soil can be cultivated for this 
 purpose will depend somewhat on the crop though three 
 inches is usually as effective as a greater depth. It is 
 very important that the crust produced by rain be 
 broken as soon as possible, since this crust allows the 
 moisture to escape rapidly. 
 
 The wetness of a smooth surface of ground in the 
 spring is due usually not so much to rain or snow at 
 that time as it is to the moisture brought up from be- 
 low by capillarity. This does not evaporate so rapidly 
 in the spring while the soil is cold and hence leaves 
 the ground wet. By plowing so as to leave the sur- 
 face rough and uneven less water will be drawn up 
 from below and the ground will dry off more rapidly 
 and therefore get warm enough for planting at an 
 earlier date. 
 
 (117) Cultivation to Cover Vegetation. One of 
 the greatest benefits of plowing is that it turns under 
 the vegetable matter so as to keep it moist and allow 
 it to decay. Fall plowing has the advantage over 
 
f)4 NOTES ON SOILS. 
 
 spring plowing in that it allows decomposition of veg- 
 etation to go oil to a certain extenl during the winter. 
 Of course where green manuring is used it is often 
 desirable to allow it to grow for a while in the spring. 
 Care should be taken, however, that the green manur- 
 ing crop he not allowed to dry the soil beyond a good 
 growing condition for the crop which is to follow. 
 
 (118) Labor in Cultivation. A large part of the 
 expense involved in producing most crops is for the 
 Labor of preparing and cultivating the land. The in- 
 fluence of the texture of the soil on this labor is there- 
 fore extremely important. When two soils are equally 
 Fertile but one requires 25 per cent more labor than the 
 other the expense of the extra labor reduces the net 
 profit. 
 
BARNYARD MANURE. 95 
 
 CHAPTER XIV. 
 
 BARNYARD MANURE. 
 
 The all important fertilizer available on every farm is 
 barnyard manure. Progress in farming methods has 
 been marked just so far as a careful economical use 
 of farm manures has been practiced. 
 
 (119) Factors Affecting Value of Manure. The 
 principal conditions- affecting the value of manure are 
 as follows : 
 
 1. Food of the animal, 
 
 2. Age of the animal, 
 
 3. Kind of animal, 
 
 •4. Product from the animal, 
 
 5. Kind and amount of litter used. 
 
 6. Care of the manure. 
 
 (120) Food. Animals fed on food substances low 
 in fertilizing constituents will produce a manure of cor- 
 respondingly low value. For example, animals fed on 
 straw and timothy hay, which are low in nitrogen and 
 phosphorus, will produce a manure much lower in value 
 than if fed bran and clover hay, substances relatively 
 high in nitrogen and phosphorus. 
 
 (121) Age. Young animals are constantly remov- 
 ing from their food nitrogen to build up muscle, etc., 
 and lime and phosphorus to build up bones, while ma- 
 
96 
 
 notes on soils. 
 
 tured animals jusl maintaining themselves remove com- 
 paratively little of these fertilizing constituents. There- 
 fore manure from mature animals is more valuable than 
 thai from young growing animals. 
 
 (122) Kind. The following 1 table adapted from 
 
 Wolff shows the percentage composition of fresh manure 
 
 from various animals and its value per ton, figuring ni- 
 
 en ;il 15 cents per pound, and phosphoric acid and 
 
 ]><it;ish at 5 cents per pound. 
 
 Average Composition of Fresh Manure (Wolff). 
 
 
 Nitrogen. 
 % 
 
 Phosphoric 
 
 acid 
 % 
 
 Potash. 
 
 % 
 
 Value per 
 
 ion. 
 
 Cow 
 
 Pi-- 
 
 . 11 
 .58 
 .45 
 .83 
 
 0.16 
 
 0.28 
 O.li) 
 0.23 
 
 0.40 
 0.53 
 0.60 
 
 $1.89 
 2 . 55 
 2.14 
 
 
 3.39 
 
 The following table from Bulletin No. 56 of the Cor- 
 nell Station is even more instructive for it shows the 
 amount and value of manure per 1,000 lbs. of live 
 weight of animals. 
 
 
 Amoimi per 
 day. pounds. 
 
 Value per 
 day, cents. 
 
 Value per 
 year, dollars. 
 
 Sheep 
 
 :;i.l 
 67.8 
 56.2 
 
 ;i.i 
 
 48.8 
 
 ; . 2 
 
 6.7 
 
 10. 1 
 
 8.0 
 
 7.6 
 
 26.09 
 
 Calves 
 
 24.45 
 
 II s 
 
 37.96 
 
 
 ■in.-.'; 
 
 Horse 
 
 •jr.; i 
 
 
 
BARNYARD MANURE. 
 
 97 
 
 (123) Liquid and Solid Manure. The liquid por- 
 tion of the manure is of different composition than the' 
 solid portion. Urine contains a high per cent of nitro- 
 gen, but only a trace of phosphoric acid. Most of the 
 phosphoric acid is found in the solid excrement, while 
 the potash is largely confined to the urine. Nitrogen 
 is the most expensive fertilizer, yet it is in a form most 
 readily lost. The utmost care should be taken to pre- 
 serve the liquid manure by the use of absorbents, and 
 by thoroughly mixing it with the solid excrement. 
 
 •The following table adapted from the work of Ano- 
 dynaud and others, reported in Experiment Station 
 Record, Vol. 5. p. 142. shows the comparative composi- 
 tion of liquid and solid excrement. 
 
 Horse urine 
 
 Horse — solid excrement . 
 
 Cow urine 
 
 Cow — solid excrement.. . 
 
 Nitrogen. 
 
 Phosphoric 
 
 acid. 
 
 Potash. 
 
 1.52 
 .55 
 
 1.05 
 
 . i:: 
 
 trace 
 
 trace 
 
 .12 
 
 .1 
 1.36 
 
 .04 
 
 (124) Product. Manure from milch cows is rela- 
 tively lower in nitrogen and phosphorus than manure 
 from beef animals, or from animals being fed a main- 
 tenance ration. Vivian estimates that a cow giving an 
 annual yield of 5,000 lbs. of milk removes in the milk 
 fertilizing materials amounting in value to $4.98. 
 
 (125) Litter. Straw is the common absorbent 
 used. The effect of the litter upon the texture of the- 
 
 7 
 
98 NOTES ON SOILS. 
 
 manure is as an importanl consideration as its effect 
 upon the chemical composition. Coarse wheat or rye 
 straw will make a loose strawy manure, while oat straw 
 will lend to produce a more compact fertilizer. Finely 
 tut coin stover is therefore of more value ;is hedding 
 than the coarser stalks. 
 
 Well dried mossy peat is a good absorbenl and is also 
 a source of nitrogen. Wood shavings are commonly 
 used as litter in cities, where straw is expensive or un- 
 obtainable. They retard the decay of manure and tend 
 to cause drying out of soils on which they are applied. 
 Manure containing wood shavings should not lie ap- 
 plied to light sandy soils, but can lie safely applied as 
 light dressings on clay or clay loam soils. 
 
 (126) Care of Manure. Results at the Ohio Ex- 
 periment Station (see Ohio Bulletin No. 183) demon- 
 strate that the exposure of manure to the weather of 
 winter and early spring deprives it of about one-third 
 of its value. When applied to crops in the field a ton 
 of yard manure produced an increase of value of $2.15- 
 as a ten-year average, while a. ton of fresh manure pro- 
 duced an increase of $2.96 as a ten-year average, show- 
 ing a loss of 81 cents a ton. or 27 per cent due to ex- 
 posure. 
 
 (127) Handling Manure. Because of losses due to 
 exposure in the yard, where leaching and fermentation 
 may take place, it is more economical to use other meth- 
 od* in handling this material. Where the fields are not 
 too rough so as to cause side hill wash, it is most eco- 
 nomical to haul the fresh manure direetlv to the field as 
 fast as it is produced. This means hauling out a large 
 
BARNYARD MANURE. 99 
 
 amount of the manure in the winter and consequently 
 hand spreading. Because of the desirabilty of using a 
 manure spreader, it is a good plan to store the manure 
 in sheds where it must be kept compact and moist. 
 Where large quantities of well rotted manure are de- 
 sired by gardeners, the material can be composted. 
 Qomposting of manure, or even storing in deep stalls or 
 sheds, will aid in the killing of any weed seeds that there 
 might be in the manure. The deep stall method, al- 
 though unsanitary where dairy cows are kept, may well 
 be used in case of young cattle. 
 
 (128) Application of Manure. In the ordinary 
 farm rotations, it is usually found best to apply manure 
 to corn ground. It is often found advantageous to ap- 
 ply top dressings to grass land. Top dressings of ma- 
 nure on heavy clay soils will materially aid in making 
 such soils of lighter texture. The coarser manures, such 
 as rotted straw or horse manure, are w r ell adapted to 
 marsh soils, while the well rotted manures should be 
 used on sand soils. Coarse manure applied to sand 
 will cause loss of water. In all cases, and on all soils, 
 light and frequent applications of manure are more 
 economical than very heavy applications at greater in- 
 tervals. 
 
 (129) Re-inforcement of Manure. Average barn- 
 yard manure contains .5% of potash, .5% of nitrogen, 
 and .3 to .35% of phosphoric acid. It will be noticed 
 that the percentage of phosphoric acid is relatively low. 
 Because of this fact and because soils generally are be- 
 coming depleted in their phosphoric acid content, it has 
 become quite profitable to use ground rock phosphate 
 
100 NOTES ON SOILS. 
 
 (floats) as ;ni absorbent in the stables. The ground 
 rock phosphate not only acts as an absorbent to retain 
 the liquid portion of the manure, but is itself a source 
 of fertility. Although experimental evidence is some- 
 what conflicting concerning the effect of rotting manures 
 upon rock phosphate, field experience seems to show a 
 marked increase in the availability of the phosphate 
 where used with the manure. 
 
 (130) Long-time Effect of Manure. The effect 
 of an application of barnyard manure is felt much 
 longer than a single application of artificial fertilizer 
 containing the same amount of plant food. Every 
 farmer has noticed this effect of manure on a plot of 
 soil, three or even five years after its application. An 
 experiment at Rothamsted Station with barley showed 
 beneficial effects even after manuring had been discon- 
 tinued for 20 years. Every effort should be put forth 
 to conserve this store of plant food, and to return it to 
 the soil. 
 
CLASSIFICATION OP SOILS. 101 
 
 CHAPTER XV. 
 
 CLASSIFICATION OF SOILS. 
 
 Soils may be classified with reference to the follow- 
 ing different liases: 
 
 1. Adaptability to different crops, 
 
 2. Chemical composition, 
 
 3. Physical composition, 
 
 4. Mode of origin. 
 
 With reference to the crops to which they are adapted, 
 they are frequently classified into truck, grass, and in- 
 termediate soils. 
 
 (131) Truck Soils. Soils to be adapted to truck 
 crops are such as quickly become dry enough to work 
 after heavy rains. This is necessary because such crops 
 require transplanting and considerable work on the 
 land so that if the ground is not suitable much valuable 
 time is lost. Truck crops also require a soil that warms 
 readily. Soils of open texture permit the development 
 of the coarse rooted truck crops. Sandy soils have these 
 characteristics and are therefore best adapted to this 
 use. While they are not as fertile as other soils this 
 can be made good by the use of fertilizers which are 
 i datively less expensive than the labor involved in grow- 
 ing such crops. Moreover manure, available usually in 
 large quantities in the cities which form the market for 
 
102 NOTES ON SOILS. 
 
 the crop decomposes rapidly in these warm soils and be- 
 (( Hies available to the crop. .Many vegetables grow 
 more rapidly on these warm, highly fertilized soils than 
 they would on colder soils and are therefore of better 
 quality. 
 
 (132) Grass and Grain Soils. Grasses that are 
 used for pastui'e or for hay. grow throughoul the season, 
 and therefore draw especially heavily on the supply of 
 water in the soil. Moreover I lie roots of grasses are ex- 
 tremely tine enabling them to penetrate compact clay 
 soils and thereby take advantage of the large water- 
 holding capacity which these soils have. Heavy clay 
 soils are. therefore, often spoken of as grass and pasture 
 soils. This leaves the intermediate soils, such as loams, 
 which are adapted to other intermediate crops, such as 
 corn, and also some truck crops, and grain, but less well 
 to grasses. 
 
 (133) Chemical Composition. Chemical composi- 
 tion of soils influences the growth of crops in two ways: 
 
 1. By the presence of the necessary plant food. 
 
 2. By the presence, in certain cases, of injurious sub- 
 stances, e. g., the accumulation of soluble salts in alkali 
 soils. 
 
 Several classes of soils have therefore been character- 
 ized chiefly by peculiarities in composition. Among 
 these may be mentioned peat and muck soils, largely 
 composed of vegetable matter; recent glacial clays in a 
 limestone region, characterized by excess of lime car- 
 bonate in the subsoil ; black prairie soils, characterized 
 by considerable amounts of organic matter, though hav- 
 ing good drainage; and alkali soils, characterized by 
 large amounts of soluble salts which collect as a result 
 
CLASSIFICATION OF SOILS. 103 
 
 of weathering in a climate where the rainfall is too 
 small to cause their removal. 
 
 (134) Physical Composition. Recognizing the im- 
 portance of physical composition and its influence on 
 the operations of tillage, water-holding capacity, tem- 
 perature, and other factors influencing the growth of 
 crops, soils may be classified on the basis of their me- 
 chanical composition into as many subdivisions as de- 
 sirable. The following subdivisions are the ones most 
 commonly made : 
 
 1. Gravelly sand, 
 
 2. Fine sand, 
 
 3. Sandy loam, 
 
 4. Fine sandy loam, 
 
 6. Silt loam, 
 
 7. Clay loam, 
 
 5. Clay. 
 
 To these must be added from a purely physical point, 
 classes to include those having large amounts of organic 
 matter, such as peat, consisting largely of sphagnum 
 moss; and muck, in part sphagnum moss and in part 
 vegetable matter from grasses, all in process of decom- 
 position. 
 
 (135) Mode of Origin. Soils are in all cases the 
 results of the action of certain physical forces on rocks. 
 They may be classified on the basis of the agent chiefly 
 concerned in the formation of the soil from this rock 
 material. On this basis soils are classified into: 
 
 1. Wind blown or loess soils (see paragraph 28). 
 
 2. Residual, those formed in place by direct weather- 
 ing of the rock (see paragraph 25). 
 
104 NOTES ON SOILS. 
 
 .'!. Glacial (see paragraph 27). 
 
 4. Alluvial, transported soils deposited by water. 
 
 5. Colluvial, those formed by wash on side hills to- 
 gether with sliding which takes place in such locations. 
 
 While it is important to study the various factors 
 which influence the character of the soils, as indicated 
 in the above classification, it must still be recognized 
 that any practical classification to he used by the farmer 
 must he based primarily on the relation of the crop to 
 the soil and the kind of farming to which adapted and 
 so must include all of the factors above mentioned. 
 Such a classification would recognize types of soil each 
 characterized by a combination of physical and chemical 
 characters which give them a distinct uniformity and 
 a distinct relation to agricultural practice. No com- 
 plete classification of soils looked at from this stand- 
 point has been made, but some of the more important 
 types will be mentioned in a succeeding chapter to- 
 gether with their crop adaptations and special treat- 
 ment necessary to maintain them in a good state of 
 fertility. Before classifying soils on this basis, we must 
 examine the relation of the various important crops to 
 the soil and climate. This will be the subject of the 
 next chapter. 
 
CONDITIONS NEEDED BY VARIOUS CROPS. 105 
 
 CHAPTER XVI. 
 
 CONDITIONS OF CLIMATE AND SOILS NEEDED 
 BY VARIOUS CROPS. 
 
 There is nothing more essential to the success of the 
 farmer than a full knowledge of the conditions neces- 
 sary for the best growth of the various crops. Some of 
 these conditions he cannot modify but must adapt him- 
 self to, while others can be influenced by proper meth- 
 ods of cultivation. 
 
 The chief conditions over which the farmer has little 
 influence arc those of the climate and of the funda- 
 mental character of the soil. It is very important, 
 however, to know the relation between the climate and 
 soil and various farm crops in order to be able to select 
 those crops which are adapted to the climate and soil 
 of his locality. 
 
 (136) Relation of Character of Plant to Char- 
 acter of Soil. There is a great variation in soils in 
 their texture and fertility and there is also a great vari- 
 ation in plants in the character of their root systems, in 
 the length and time of their growing period, and in the 
 elements which they require from the soil. It is not 
 strange, therefore, that some plants are adapted to one 
 condition and some to another. 
 
 The character of the root system determines to a con- 
 siderable extent the texture of soil to which the plant 
 
106 NOTES ON SOILS. 
 
 is adapted. Coarse rooted plants and those producing 
 tubers require ;i somewhal open texture to permit of 
 their besl development. Others less coarse, such as 
 alfalfa and coin can grow in soils of medium texture, 
 while soils of very close texture can he [tenet rated with 
 ease only by fine roots such as those of the cereals and 
 grasses. 
 
 Some plants make a very large part of their growth 
 in a short period of time. Corn, for instance, in Wis- 
 consin, often makes nearly one-half its growth in a 
 month. In this case il is essential that there he a large 
 amount of available planl material ready during that 
 
 1 illie. 
 
 Some plants on account of the great length of their 
 roots are able to draw water from depths of soil beyond 
 the reach of other plants. Such is the case with alfalfa 
 and brome grass. 
 
 Leguminous plants are able to supply themselves 
 with nitrogen when tubercle forming bacteria are pre- 
 sent, Imt these bacteria do not develop rapidly in soils 
 which are acid. These plants also seem to require 
 larger amounts of lime than most crops (see table in 
 paragraph 10) and hence thrive unusually well on the 
 li ess soils of the Missouri and Mississippi valleys and 
 on the glacial till of the northern states where this con- 
 tains very large amounts of ground limestone. They 
 also do well on limestone soils where the thickness of 
 residual soil from which all lime has been removed is 
 not too greal 1<» permit the roots to get to the partially 
 undecomposed limestone. 
 
 The winter killing of plants is often dependent on 
 
< ( (NDITIONS NEEDED BY VARIOUS CROPS. 107 
 
 the character and condition of the soil. Clover is much 
 more apt to be killed in poorly drained soils and in 
 those of dose texture than in "well drained and open 
 textured soils on account of the heaving produced by the 
 freezing of the water in the soil. 
 
 (136a) Relation of Crop to Climate. The dis- 
 tribution and amount of rainfall in a given region also 
 exercises a very great influence on the kind of crops to 
 which it is adapted. Corn is especially adapted to the 
 Mississippi Valley not only on account of the fertility 
 oi the soil, but on account of the fact that the rainfall 
 of this region is greatest during the months of June and 
 July when corn is making its most rapid growth. 
 
 The grasses do best in a region having an even and 
 copious rainfall, such as that of the Atlantic Coast 
 states. 
 
 These and many other factors must be considered ill 
 determining the conditions necessary for the best devel- 
 opment of the various crops. Their systematic study 
 can best lie made in connection with the study of the 
 individual crops. 
 
 For convenience we may classify farm crops into 
 three classes; first, tilled crops; second, cereals; and 
 third, grasses and clovers. 
 
 Tilled Crops. 
 
 All those crops which are planted in rows so as to 
 admit of tillage, such as corn, potatoes, tobacco, rape 
 and the root crops generally, have certain features in 
 
108 NOTES ON soll.s. 
 
 common. The chief one is thai of coarseness of root 
 system and size of stalk. The first causes them to be 
 adapted to somewhat open textured soils through which 
 the coarser roots may ramify, while the second makes 
 them adapted to intertillage because the plants finally 
 grow so large as to completely cover the ground with 
 foliage. The foliage is so extensive that it utilizes all 
 the lighl reaching the soil during the later growth of 
 crops, while still leaving space for tillage during the 
 earlier growth. Tilled crops all have the same season 
 of principal growth, which starts later than in the case 
 of the cereals and grasses, thus allowing nitrification to 
 produce the necessary supply of nitrates before the 
 time of greatest need. 
 
 (137) Corn. Corn has already become the greatest 
 crop produced in America and will undoubtedly grow 
 in importance for some time to come. It produces a 
 larger amount of grain and of fodder per acre and of a 
 kind which can be more easily handled than any other 
 cl op. 
 
 (138) Roots of the Corn Plant. The corn plant 
 develops two classes of roots. The primary roots, from 
 six to twenty in number, spread laterally in all direc- 
 tions and grow down in a direction which varies greatly 
 with the character of the soil. The secondary roots, 
 starting from the first and second nodes above ground, 
 blanch ont as braces to the soil and develop horizontally 
 comparatively near the surface. In a deep loam soil the 
 roots at six weeks from planting, when the plant is 
 about a foot and a hall' high, often meet between two 
 rows which are forty-two inches apart and extend to a 
 
CONDITIONS NEEDED BY VARIOUS CROPS. 109 
 
 depth of eighteen inches. When the com has reached 
 the height of three feet, the roots usually extend to a 
 depth of twenty-four inches and reach horizontally en- 
 tirely across the space between the rows. When the 
 corn comes into tassel, the roots are usually three feet 
 deep, and when ripe, four feet and over. After the 
 first month or five weeks, the soil is filled with roots 
 to within two and one-half to four inches of the surface 
 depending on the amount of moisture in it. 
 
 (139) Com on Clover Sod. The soil to which corn 
 is best adapted is a deep, fertile, somewhat open tex- 
 tured loam having a large water-holding capacity, but 
 a surface such that it becomes warm early. Corn is the 
 most vigorously growing plant which we commonly 
 raise and the one which takes the greatest amount of 
 material from the soil, particularly nitrogen and potash 
 This, together with the lateness of starting, permits the 
 use of stable manure, green manure or other organic, 
 forms such as dried blood which will be transformed 
 into available material for the growth of the crop as 
 will also the roots of a clover sod. It must not be for- 
 gotten, however, that the clover, while adding large 
 quantities of nitrogen to the soil takes away large 
 amounts of potash and phosphoric acid, which deficiency 
 must be made good either by stable manure or by arti- 
 ficial fertilizers to secure the best growth of the corn on 
 ground not containing large amounts of available pot- 
 ash and phosphate. 
 
 Where the available potash and phosphoric acid in 
 the soil is sufficient for both clover and corn, the benefit 
 of the clover sod to the corn is very great. The Cana- 
 dian Experiment Station report a yield of eight and a 
 
lid NOTES ON SOILS. 
 
 half t<ms of green fodder per acre more on a clover sod 
 than on ground which had grown grain the previous 
 year. This is a gain of forty per cent. 
 
 (140) Effect of Stable Manure on Corn. The 
 effect of stable manure is chiefly noticeable in the 
 earliest growth of the plant. Nine average hills of the 
 corn on the manured portion of a field which had previ- 
 ously grown several crops without fertilizer weighed 
 7)-A pounds, while that on the unmanured portion 
 weighed 2!) pounds July 29. Later during the season 
 the difference was not so great although of course the 
 manured portion produced a heavier crop than the un- 
 manured. the yield being 8,440 pounds of dry matter 
 per acre on the manured and 5,965 pounds on the un- 
 manured. Professor Latta of the Indiana Experiment 
 Station found that a single application of fifty tons of 
 fresh horse manure increased the yield an average of 
 ten and four-tenths bushels per acre per year for eleven 
 years, lie also found that an application of artificial 
 fertilizers containing more nitrogen, phosphoric acid 
 and potash than the crop took' from the soil gave a 
 yield of only four-fifths that of cow manure. Humus 
 .Mid sandy soils very frequently require potash for the 
 growth of corn, while clay soils are frequently bene- 
 fited by phosphoric acid. 
 
 (141) Potash for Corn on Marsh Soils. The 
 marsh soils of southern Wisconsin, of Indiana and Il- 
 linois practically always contain enough nitrogen and 
 phosphoric acid for the heaviest crops of corn, but are 
 lacking in available potash. It is often more econom- 
 ical, therefore, to use ;m artificial potash fertilizer rather 
 
CONDITIONS NEEDED BY VARIOUS CROPS. Ill 
 
 than stable manure on these soils, provided there is 
 other land on which the farmer can use the manure. 
 The potash can be applied either in the form of Kainite 
 at the rate of four to five hundred pounds per acre 
 spread broadcast before the last harrowing in prepar- 
 ing the seed bed or in the form of chloride or sulphate 
 at the rate of 75 to 100 pounds per acre applied with a 
 drill. Care must be taken that the salt is far enough 
 from the grain not to retard or prevent its germina- 
 tion. It should be three or four inches from the seed 
 and if the soil is quite dry it may be necessary to re- 
 duce the amount used to 50 pounds per acre. The 
 Kainite applied broadcast is perhaps as economical 
 where the ground is to be planted to corn two years 
 in succession, while the chloride or sulphate is prefer- 
 able for a single crop of corn since it is more readily 
 available when applied in the manner above described. 
 
 (142) Preparation of Soils for Corn. Deep plow- 
 ing is especially important in the preparation of clay 
 soils for corn and should as far as possible be done in 
 the fall. A thorough working with the disc harrow 
 in the spring followed by a planker or float where neces- 
 sary to break clods will then leave the ground in good 
 condition for planting. The discing is particularly ef- 
 fective in compacting the soil and produces a close con- 
 tact between the furrow slice and subsoil. The practice 
 of listing so generally followed in the Southwestern 
 states with marked success has no advantage over the 
 usual method followed in this section. 
 
 When the corn is planted early on account of favor- 
 able weather the planting should be deeper than when 
 
1 12 NOTES ON SOILS. 
 
 done Inter in the season. The planting should also bo- 
 deeper on Lighl than on heavy soils. 
 
 The rool system regulates itself to the depth of plant- 
 ing. The distance aparl of rows and of hills in the row 
 depends on both climate ;in<l soil. In the south where 
 the long warm season permits a very large growth 
 much wider planting is desirable than in the North. 
 
 (142) Cultivation of Corn. Frequent cultivation 
 is necessary but no rule as to the number of times of 
 cultivation can be made. .V light harrowing to kill 
 weeds and fine the surface after the corn is up two 
 inches is usually necessary. Cultivation should follow 
 every rain to destroy the crust which it produces; care 
 being taken to so time il as to develop the best tilth, 
 all possible work being done when the soil is in proper 
 condition. This cultivation Should, as far as possible, 
 be shallow so as to avoid cutting the roots which come 
 i lose to the surface. A mulch of three inches is as ef- 
 fective as one of greater depth, while the loss to the 
 corn by cutting of the roots which are growing in the 
 soil near the surface where nitrification is most rapid 
 may be serious. The results of a large number of ex- 
 periments show that deep cultivation reduces the yield 
 Prom three to five bushels per acre besides requiring 
 more labor than shallow cultivation. In a wet season 
 deeper cultivation may he necessary to cover weeds. 
 
 (143) Potatoes. The most desirable conditions for 
 potatoes arc very similar to those for corn. It is es- 
 pecially important that the soil he loose and not liable 
 to hake. The cracks in the soil permit access of the 
 sun's rays, thereby causing sunburn. On a. piece of 
 
CONDITIONS NEEDED BY VARIOUS CROPS. 113 
 
 moderately heavy clay soil, the amount of sunburn, in 
 one case, as a result of the baking of the ground was 
 found to be over 10 per cent. Clay loam soils contain- 
 ing sufficient humus to render them open textured for 
 the development of tubers, and to prevent baking, will 
 ordinarily give larger yields of potatoes than the more 
 sandy soils to which they are supposed to be best 
 adapted. 
 
 Thorough preparation of the ground is very impor- 
 tant. Deep fall plowing followed by shallow spring 
 plowing or discing, together with deep planting and 
 careful cultivation to keep a proper mulch and to pre- 
 vent loss of water, are the essentials for success. Flat 
 culture is preferable to the ridging system in general, 
 although in the event of a very wet season the ridged 
 ground may shed the water better. Potatoes are very 
 similar to corn in their demands on' the fertility of the 
 soil and are especially benefited by potash fertilizers. 
 Sulphate of potassium is said to produce a better qual- 
 ity than chloride. 
 
 (144) Tobacco. The texture of the tobacco leaf 
 depends on the rate of growth, on the amount of shad- 
 ing and on the amount of moisture in the atmosphere. 
 It is very important, therefore, that the soil should be so 
 rich as to cause very rapid growth of the crop and to 
 permit close planting which shades a large part of the 
 leaves. A heavy crop of tobacco uses large amounts of 
 water so that the soil should have a large water-holding 
 capacity and yet be dry enough on the surface to allow 
 it to warm up readily in the' spring. 
 
 8 
 
114 NOTES ON SOILS. 
 
 This crop is a very heavy feeder on nitrogen and es- 
 pecially on potash. It therefore does exceptionally 
 well on a good clover sod. It would be better to prac- 
 tice a short rotation with clover than to grow tobacco 
 continually on the same ground. Manure is often bet- 
 ter applied as a top dressing and disked in than plowed 
 under. 
 
 It is bad policy to use all the manure produced on 
 the farm on the tobacco land and allow the remainder 
 to be exhausted. It would be better to use some pot- 
 ash and phosphate fertilizers on clover sod for tobacco 
 and use part of the manure at least for other crops. 
 
 (145) Effect of Heavy Manuring on Tobacco 
 Soils. The common practice of using excessively large 
 applications of manure on tobacco land results in an 
 enormous loss of phosphoric acid from fields so treated. 
 Keeent results obtained at the Wisconsin Station (see 
 Research Bulletin No. 2, Wis. Exp. Sta.) from a study 
 of 16 tobacco fields, whose average cropping period was 
 4j3 years, 30 years of that time to tobacco, show an aver- 
 age loss of over 3,000 pounds of phosphoric acid per 
 acre surface eight inches, above thai taken by the to- 
 bacco and other crops. On the average five times as 
 much phosphoric acid had been added in the manure as 
 was removed by the crops. This enormous wastage of 
 one of the fertilizing constituents which we are forced 
 to buy when it becomes deficient should be avoided by 
 spreading the manure over larger areas, and by rotat- 
 ing the tobacco with clover and other crops. How great 
 the less of nitrogen and potash is under the present 
 system is now being studied at the Wisconsin Station. 
 
CONDITIONS NEEDED BY VARIOUS CROPS. 115 
 
 (146) Tobacco Soils. The soils which give the 
 finest quality of leaf have a certain combination of 
 characteristics. They are usually very fine sandy loams 
 occurring in valleys in such a situation that the water 
 moves to the lower layer from the slopes while the sur- 
 face dries off so as to be warm. The protection of the 
 hills also doubtless increases the humidity of the at- 
 mosphere. In some cases these soils are derived from a 
 shale which produces a soil of good texture and contains 
 relatively large amounts of potash. Many soils which 
 have the proper texture and situation are lacking in 
 sufficient potash for the best tobacco production and 
 should be fertilized with potash fertilizers ; sulphate be- 
 ing preferable to chloride. Thorough cultivation is im- 
 portant, but should not be so late as to stimulate a late 
 growth of the plant which prevents it from ripening 
 properly. 
 
 (147) Sugar Beets. The sugar beet is best 
 adapted to the latitude of Wisconsin, probably because 
 of the greater amount of light during its growing period 
 and of cool nights during its ripening period than far- 
 ther south. The amount of sugar probably averages 
 three or four per cent higher in beets grown on the 
 fortieth parallel than in those grown on the thirty- 
 eighth. The greater amount of sunshine of arid regions 
 increases still more the per cent of sugar. 
 
 Sugar beets do best on rather distinct clay loam soils, 
 although with proper fertilizers they may do well on 
 more distinctly humus or sandy soils. Contrary to a 
 somewhat general opinion, there is no injury to the 
 quality of beet produced by the use of stable manure 
 
116 NOTES ON SOILS. 
 
 as Ims been proven by the New York Experiment Sta- 
 tion. At that ]>l;ice manure was found to give better 
 results in point of yield and quality of beet than any 
 combination ol' eommereial fertilizers. The roots of 
 the sugar beet do not come so near the surface as those 
 of potatoes according to Ten Eyck and hence permit 
 of deeper cultivation where this is desirable, although 
 a depth of three inches is ordinarily sufficient. 
 
 The sugar beet requires very fertile soil and does 
 well on good clover sod manured. They also do well 
 following tobacco which has been heavily manured. 
 
 (148) Rape. Rape is an exceptionally strong 
 feeder requiring large amounts of nitrates and hence 
 does best in a soil very rich in humus. It should grow 
 rapidly so as to be tender and rich in proteids. When 
 used for a soiling crop it is therefore very desirable to 
 prepare the ground thoroughly and manure it heavily 
 so as to get a heavy, thick growth of tender leaves. 
 Its cultivation should be similar to that for potatoes 
 and when the leaves are cut off for fodder, should be 
 cultivated at once to stimulate a new growth. On suf- 
 ficiently fertile soil or one manured, it is an excellent 
 catch crop, growing rapidly during the latter part of 
 July and August when the moisture is sufficient. It 
 also endures dry weather after being well rooted. 
 
 Cereals and Flax. 
 
 All grain crops, in the main, are alike in their essen- 
 tial requirements from the soil and in their effect on it, 
 although they differ among themselves, in many minor 
 respects. They are adapted to finer soils in general 
 
CONDITIONS NEEDED BY VARIOUS CROPS. 117 
 
 than those on which the tilled crops do best, chiefly on 
 account of their fine root system. They start growing 
 early in the spring and hence require a store of avail- 
 able material at that time for the most rapid growth. 
 This is particularly true in reference to nitrates and 
 cereals, therefore, do best on soil which has been culti- 
 vated the previous year and has therefore accumulated 
 nitrates. As a rule they require a relatively large 
 amount of available phosphate. 
 
 (149) Oats. Oats are particularly well suited to 
 the northern part of the country as is shown by the fact 
 that a bushel of northern grown oats frequently weighs 
 as high as forty pounds, while a bushel of southern 
 grown oats frequently weighs only twenty pounds. The 
 oat is a strong feeder and adapted to a very large vari- 
 ety of soils. The danger of lodging, however, makes it 
 less desirable for use on heavily manured ground which 
 has raised corn the preceding year, than rye, the strong 
 stalk of which prevents lodging. This danger of lodg- 
 ing makes it desirable to use less seed on rich soil; two 
 bushels per acre often being better than a larger amount. 
 
 (150) Rye. Rye, on account of the fact that it is 
 sown in the fall, and therefore starts early in the spring 
 is available for use on very light sandy soils which are 
 liable to be too dry for other crops later in the season, 
 although for its best development a more fertile soil is 
 required. 
 
 (151) Wheat. Wheat makes its best growth on 
 deep clay loam soils containing considerable humus. 
 The large yields secured formerly in this and adjoining 
 states were probably due to the large amounts of humus 
 
118 NOTES ON SOILS. 
 
 in the virgin soils which has since been reduced by crop- 
 ping. While Large yields are produced in the northern 
 regions of our own country ;md in Canada, experiment 
 has shown thai wheal grown farther south, in Kentucky 
 and Tennessee, is richer in protein than that grown far- 
 ther north. 
 
 (152) Buckwheat. Buckwheat probably takes less 
 of the mineral elements from the soil than any other 
 cereal. It does well on very light, poor soil, provided 
 the moisture is sufficient. It is also well adapted to 
 wild marsh lands because of the lateness with which it 
 may he planted, thus allowing these lands to dry. 
 
 (153) Flax. Flax is particularly adapted to the 
 open prairie loam soils, rich in humus and under proper 
 conditions is a very profitable crop. While its require- 
 ment in the way of fertility is not as great as that of 
 other grain, it cannot be grown on the same ground in 
 successive years, unless treated to prevent a fungus 
 disease. This fungus usually disappears in the course 
 of five to eight years, when another crop may be grown. 
 That flax does not reduce the fertility of soils as much 
 as other grains is shown by the fact that crops do bet- 
 ter following flax than following most of the other 
 grains. 
 
 Grasses. 
 
 (154) Soils for the Grasses. There is probably 
 a wider range in the adaptation of grasses to different 
 soils and climates than of any other group of cultivated 
 plants. Some are adapted to very moist ground and are 
 not injured by water standing on them for some time, 
 but often require these conditions to make their best 
 
CONDITIONS NEEDED BY VARIOUS CROPS. 119 
 
 growth; others again are especially adapted by their 
 structure and habit for growing on extremely dry soil 
 and are quickly killed by an excess of moisture. A few 
 do well on either dry or wet soils. It is, therefore, es- 
 pecially necessary to select varieties of grass carefully 
 with reference to the conditions under which they are 
 to be grown. In general the grasses are suited to a 
 much finer clay soil than other crops, although some of 
 them grow better on deep humus soils than on clay. 
 
 (155) Preparation of the Soil for Grasses. In 
 raising the grass crops nothing is more important than 
 the securing of a strong vigorous growth at the very 
 start. To do this it is essential that the seed bed be 
 clean and very thoroughly prepared; much more care 
 being necessary than in preparing ground for most 
 other crops. "While it is desirable that the soil be deep, 
 it is particularly important that it be in the best tilth 
 and thoroughly fined. To promote rapid growth from 
 the start it is necessary that there be sufficient available 
 fertility and moisture. The best condition as regards 
 fertility can usually be produced by applying a moder- 
 ately heavy dressing of well rotted manure to ground 
 from which an early crop of cereals such as rye or 
 barley has been taken; plowing it shallow and thor- 
 oughly discing it, then harrowing it during the follow- 
 ing four weeks at such times as will produce the best 
 effect on texture and then sowing grass in the early 
 autumn. This plan, however, would frequently fail on 
 account of lack of sufficient moisture in the fall in which 
 case it would be necessary to wait until the early spring 
 of the following year before sowing the grass. 
 
J 20 NOTES ON SOILS. 
 
 When sown in the fall it may be sown with rye and 
 in the spring with a light seeding of barley or of oats; 
 the barley being preferable. The nurse crop should be 
 cut rather high so as to leave the stubble for the pro- 
 ted inn of the grass. 
 
 Timothy makes its best growth on clay loam but also 
 dues well on very moist soil if not covered by w'ater 
 until too late in the spring. Brome grass does well in 
 regions subject to drought on account of its very 
 strong deep root system. It also seems to be adapted 
 to marsh lands where it produces a finer hay than tim- 
 othy. 
 
 Clovers. 
 
 (156) Soil Treatment for Clover. The clovers 
 are especially valuable both for use as hay and for add- 
 ing nitrogen to the soil. They are especially adapted to 
 loam and clay loam soils containing an abundance of 
 lime and hence grow exceedingly well on the loess soils 
 of the Missouri and Mississippi rivers and on the glacial 
 soils of the northern part of the country. AA T here the 
 soil is not well supplied with lime this should be added 
 at the rate of twenty to thirty bushels per acre the fall 
 preceding the sowing of the clover (see paragraphs 58- 
 60). 
 
 "While clover has the power of using nitrogen from 
 the air it requires larger amounts of the other elements 
 than most crops and will make a better start on fertile 
 soils containing considerable nitrates as well as the 
 other elements. Better success will therefore be at- 
 tained in sowing it on ground which has been man- 
 ured for the crop preceding. When' sown with a nurse 
 
CONDITIONS NEEDED BY VARIOUS CROPS. 121 
 
 crop, as is desirable on soils which are at all weedy, 
 the nurse crop should be light and one which is cut 
 off early; hence the advantage of barley over oats ok 
 wheat. When oats are used it is usually desirable to 
 sow not more than a bushel and a half to two bushels 
 of grain or else to cut it early for hay, thus leaving more 
 moisture for the clover. 
 
122 NOTES ON SOILS. 
 
 CHAPTER XVII. 
 ROTATION OF CROPS. 
 
 (157) Advantages of Rotation. Among the ad- 
 vantages gained by raising several crops rather than a 
 single one are, first, it distributes labor through the 
 season or year; second, it lessens the danger of a com- 
 plete failure due to unfavorable conditions for the single 
 crop, and third, it allows of a rotation of crops. A 
 rotation of crops is desirable because, first, it tends to 
 improve the texture of most soils; second, allows man- 
 ure to be applied to that crop which can make the best 
 use of it at the time of application, while others are 
 benefited by the fertility following its complete decom- 
 position in the soil; third, it distributes the draft on the 
 fertility of the soil and fourth, it tends to destroy dis- 
 eases to which individual plants are subject. In spite 
 of the fact, therefore, that there are some disadvantages 
 in rotation such as that it sometimes requires the growth 
 of a crop on a field to which it is not best adapted and 
 sometimes does not give the most convenient placing of 
 crops for the work of raising them; yet it is on the 
 whole very desirable in general farming. 
 
 (158) Some effects of Rotation. In the raising 
 of grain it is found that continuous cropping of a soil 
 develops a very poor texture, probably the result of the 
 
ROTATION OP CROPS. 123 
 
 thorough drying which these crops produce. This un- 
 favorable condition of texture is very largely remedied 
 by raising a tilled crop such as corn or potatoes on the 
 soil. A very striking illustration of the increase in the 
 yield of grain due to interrupting continuous crops with 
 corn, is reported from the experiment station of North 
 Dakota. On a very uniform piece of ground wheat was 
 grown for five years preceding 1899. That year wheat 
 was grown on one plot, corn on a second, potatoes on a 
 third and the fourth was summer-fallowed, being culti- 
 vated and kept free from the weeds. The following year 
 wheat was sown. on all of these plots with result that the 
 yield on the ground winch had grown wheat contin- 
 ually was 7.1 bushels per acre; on the plot which grew 
 corn the year previous the yield was 25.1 bushels; on 
 the one which grew potatoes, 24.3 bushels; and on the 
 summer-fallowed plot, 29 bushels per acre. While this 
 influence is doubtless greater in that state than it would 
 be here under different conditions of soil and moisture, 
 there is no cpiestion about its importance throughout 
 this region. 
 
 The application of stable manure is very desirable 
 in raising corn and potatoes, while when used on grain 
 ground directly there is danger of rank growth, caus- 
 ing lodging and incomplete filling of grain. The grain 
 however, is very much benefited by the application of 
 manure to the tilled crop the previous year. 
 
 A considerable part of our prairie region is not well 
 adapted to permanent pasture grasses and better pas- 
 tures are secured for a year or two following a crop 
 of hay or clover and timothy; these grasses being sown 
 
12-1 NOTES ON SOILS. 
 
 with one of the grains as a nurse crop. Many crops 
 are subjed to diseases and insect enemies which be- 
 come worse with successive crops on the same ground. 
 Among these may be mentioned the corn root worm in 
 corn, the Hessian fly in wheal ;md the fungus disease 
 of flax. A rotation of crops is very helpful in destroy- 
 ing these. 
 
 (159) Systems of Rotation. The basis of many 
 systems of rotation is a three-fold division of, first, tilled 
 crops, second, grain or cereal, and third, grass crops. 
 The number of crops of each of these three kinds in- 
 troduced into the rotation depends chiefly on the rela- 
 tive amount of each kind which the farmer wishes to 
 raise. If it is desired to plant one-third of cultivated 
 land to corn, one-third to grain and one-third to hay 
 then a three year system would be developed. The 
 use of the hay ground for pasture the following year 
 would make it a four year rotation. If, however, twice 
 as much ground is to be planted to one of these three 
 classes, than to another, then this class must occupy 
 the ground two years in succession. So in some of the 
 northern states a five year system is developed consist- 
 ing of first, corn; second, barley or wheat; third, a 
 second grain crop such as oats or rye with which clover 
 or timothy are sown ; fourth, hay ; and fifth, hay and 
 pasture. An excellent short system adapted to farm- 
 ing without stock raising consists of first, clover, sec- 
 ond, potatoes, and third, winter wheat. This is often 
 profitable in the vicinity of towns where manure can 
 be procured and where the clover can be readily sold 
 at a good price after having added nitrogen to the soil. 
 
SANDY SOILS AND THEIR MANAGEMENT. 125 
 
 CHAPTER XVIII. 
 
 TYPE? OF SANDY SOILS AND THEIR MANAGE- 
 MENT. 
 
 (160) Types of Sandy Soils. The term "sandy 
 soils*' may be used to cover a considerable range of 
 variation in physical texture, including every thing 
 from coarse, wind blown sands to comparatively fine 
 sandy loams. It also includes considerable variation in 
 the amount of organic matter. They may be roughly 
 subdivided into three classes : 
 
 1. Coarse sandy soils, 
 
 2. Sandy loam soils, 
 
 3. Black sandy loams. 
 
 Coarse Sandy Soils. 
 
 (161) Management of Coarse Sandy Soils. 
 Coarse sand soils are seriously deficient in many of the 
 important factors which go to produce fertility. The 
 water-holding capacity is frequently the limiting one, 
 but they are also deficient in nitrogen on account of the 
 readiness with which any vegetable matter which they 
 may contain is oxidized and lost. They are also ex- 
 tremely low in potash and even in phosphoric acid. In- 
 deed it is practically necessary for one operating on 
 such soils to make the soil. They are also difficult to 
 
126 NOTES ON SOILS. 
 
 manage od account of the readiness with which the sand 
 is blown by the wind. 
 
 Such soils, however, have some advantage in the 
 readiness with which they warm up in the spring and 
 after rains. The treatments especially called for on 
 such soils are : 
 
 i. Protection from wind, 
 
 2. Increase of humus and nitrogen, 
 
 3. Addition of essential mineral elements, 
 
 4. Cultivation to conserve moisture. 
 
 (162) Protection from Wind. It frequently hap- 
 pens that wind storms, especially of spring and early 
 summer, blow these sands with such force as to cut crops 
 entirely to the ground. Corn after reaching a height 
 of two or three feet frequently has its leaves stripped 
 from the stalk, and tomatoes that have been trans- 
 planted three or four weeks may be so entirely destroyed 
 that one would scarcely think that the field had ever 
 been planted. This destruction by the wind can be 
 lessened by leaving strips of Jack pine and other native 
 vegetation between comparatively narrow strips of cul- 
 tivated lands. Such wind breaks should be two or three 
 rods wide and should be left along roads and fences, 
 and at frequent intervals across the larger fields. This 
 protection, while helpful, is not complete and should 
 be supplemented by so arranging the cultivated crops 
 that those which are sown in the fall and soon cover the 
 ground in the spring, as rye, alternate with corn and 
 other crops planted later in the season. By arranging 
 Lands in narrow strips of not more than six or eight 
 rods wide in this way, great protection can be given. 
 
SANDY SOILS AND THEIR MANAGEMENT. 127 
 
 (163) Increase of Humus and Nitrogen. On ac- 
 count of the great water-holding capacity of humus it is 
 extremely important to increase this material in sandy 
 soils as much as possible. Where such soils are com- 
 paratively flat and not too high above ground water 
 their humus can probably be increased somewhat by 
 careful management. The turning under of green man- 
 uring crops, or letting the land lie in clover and grasses 
 for two and three years without cutting, will doubtless 
 increase the humus to some extent. It must be recog- 
 nized, however, that the conditions are entirely- unfavor- 
 able to the development of humus, and that only by the 
 greatest care can this be accomplished. The supply 
 of nitrogen for cultivated crops should as far as possi- 
 ble be gained by fixation through legumes, but it must 
 be recognized that the nitrogen fixed in one crop of 
 legumes is exhausted quickly in the succeeding year 
 when under cultivation. The nitrogen left by the le- 
 gumes is largely consumed by the first crop, so that 
 short rotations are necessary. Except under unusual 
 conditions of origin, such as an arid climate, or where 
 affected by glacial action, or by the presence of lime- 
 stone rock, sandy soils are as a rule acid and for the 
 growth of medium red clover, alfalfa, and some other 
 legumes, treatment with ground limestone or marl or 
 other lime carbonate is necessary to secure good results. 
 (See paragraphs 59 and 60.) Some other legumes, 
 such as serradella, yellow lupine, and alsike clover are 
 less affected by acidity and may be used to advantage 
 where the lime treatment is omitted (See paragraph 
 .56). 
 
128 NOTES ON SOILS. 
 
 (164) Addition of Essential Mineral Elements. 
 The addition of potash and phosphoric acid may be in 
 the form of barnyard manure or commercial fertilizers. 
 .Manure used on such lands should ordinarily be well 
 retted in order to avoid the drying- effect of material 
 used in bedding, but, of course, special care is necessary 
 in this composting to prevent loss of the soluble mate- 
 rial as indicated in paragraph 126. The commercial 
 fertilizers muriate and sulphate of potash, or wood 
 ashes where available, should be used as indicated in 
 paragraph 88. Phosphoric acid may he applied in the 
 form of floats if thoroughly incorporated with manure 
 or applied on a good green manuring crop or clover 
 sod, but under other conditions acid phosphate should 
 be used. 
 
 (165) Cultivation to Conserve Moisture. No 
 other soils require as much care in their cultivation to 
 conserve moisture as do the sands. Constant cultiva- 
 tion during a dry season to prevent the firming of such 
 soils will thereby greatly lessen evaporation and mater- 
 ially increase the crop. 
 
 (166) Crops for Sandy Soils. On account of the 
 Low water-holding capacity of these soils they are adap- 
 ted especially to those crops which have relatively low 
 water requirements, such as the grains, especially rye, 
 which being seeded in the fall is in condition to begin 
 growth immediately in the spring. Beans and buck- 
 wheat are well adapted to sandy soils. On account of 
 the readiness with which they can be worked such crops 
 as potatoes, strawberries and other truck crops can be 
 profitably grown on these soils when sufficient care is 
 taken to have these crops go onto the land after a good 
 
SANDY SOILS AND THEIR MANAGEMENT. 129 
 
 green manuring crop or on a good clover sod, the or- 
 ganic matter of which will retain a good supply of mois- 
 ture for at least one year. 
 
 Sandy Loams. 
 
 (167) Management of Sandy Loams. Sandy 
 loam soils vary all the way from distinct sandy soils to 
 silt loams and clay loams. The lighter phases have the 
 same general characteristics of those of the distinctly 
 sandy soils though to a less marked extent and their 
 management is therefore very much easier. These soils 
 on account of considerably larger water-holding capac- 
 ity, although still low enough to permit them to be- 
 come warm readily are exceptionally well adapted to a 
 considerable range of crops, especially truck and small 
 fruit. Many soils of this general class have a very 
 high value on account of their natural adaptation to 
 these crops. Their management is similar to that of 
 the sandy soils. 
 
 Black Sandy Loams. 
 
 (168) Management of Black Sandy Loams. 
 
 There are considerable areas of black sandy loam soils 
 which have been formed by the gradual drying up of 
 marshes having a sandy subsoil. This leaves a sandy soil 
 with a large amount of black humus. Such soils are bet- 
 ter than the distinctly sandy soils not having much hu- 
 mus, in that they possess a good water-holding capacity. 
 However, their fertility is often not much greater than 
 sandy soils since this black humus may be of an acid 
 character and contains relatively little mineral matter 
 9 
 
130 NOTES ON SOILS. 
 
 and moreover oxidizes slowly when present in consid- 
 erable amounts,. Its oxidation after cultivation will 
 usually yield a fair supply of nitrogen to growing 
 crops, but such soils are ap1 to be deficient in both pot- 
 ash and phosphate, and require either barnyard manure 
 or commercial fertilizers to supply this deficiency. 
 They are apt also to be quite highly acid and for the 
 growth of clover or alfalfa would require lime treat- 
 ment. This class of soils, while better adapted than the 
 coarse sandy soils to such crops as corn and potatoes 
 and other crops requiring large amounts of water, are 
 not so well adapted for growing vegetables as are the 
 fine sandy loams above mentioned. 
 
CLAY SOILS OP HUMID REGIONS. 131 
 
 CHAPTER XIX. 
 
 TYPES AND MANAGEMENT OF CLAY SOILS OF 
 HUMID REGIONS. 
 
 (169) General Character of Clay Soils. Clay 
 soils vary in texture from fine sandy loams to heavy 
 clays. As a class they are more subject to erosion than 
 are sandy soils and the influence of topography is there- 
 fore much greater. Their water-holding capacity is so 
 great .that drainage is an important factor. On account 
 of their good water-holding capacity it is less difficult 
 to maintain humus and therefore nitrogen than in the 
 case of the sandy soils. Clays have a much larger 
 amount of available potash, but the supply of phos- 
 phoric acid is frequently too small to balance the other 
 conditions so that these soils need phosphate treatment. 
 Three types of clay soils will be mentioned, each of 
 which has some distinct characteristics. 
 
 Heavy Clay Soils. 
 
 (170) Occurrence. There are considerable areas 
 of very heavy clay soils in the northern part of the 
 country, most of which were formed either in lakes 
 which existed during the glacial period or in former 
 extensions of present lakes. The heavy red clays of 
 the Lake Superior and Green Bay area and the heavy 
 
132 NOTES ON SOILS. 
 
 clays of the Red River Valley may be filed as illustra- 
 tions. 
 
 (171) Drainage. From their mode of origin such 
 clay lands are frequently so level as to have poor sur- 
 t'aee drainage and, on account of their extreme fineness, 
 also lack underdrainage. Drainage is. therefore, the all 
 important treatment required for their improvement. 
 This may be either surface or underdrainage. By the 
 Laying out of fields on such soil in narrow plow lands, 
 the dead fin-rows of which are deepened and either re- 
 tained permanently or at least two years out of three 
 in the same place, and these dead furrows connected 
 with end ditches;, great improvement in surface drain- 
 age may be effected. 
 
 Underdrainage by tile constitutes a permanent im- 
 provement of such soils of the greatest possible value. 
 It greatly lessens the care which is necessary to effect 
 surface drainage, and on many flat clay soils, is much 
 more effective than surface drainage can be. It is often 
 supposed that such tenacious clays cannot be tile drained, 
 because it is thought that the water cannot move hor- 
 izontally through them. As a matter of fact most of 
 these line clay soils usually check and crack to a con- 
 siderable extent, on drying out during a dry season and 
 if umlerd rained by tile, water falling will pass out quite 
 readily through the checks and cracks so that these are 
 retained and the physical condition improves from year 
 lc year. It has been demonstrated repeatedly by prac- 
 ical experience that the heaviest of these clays can be 
 successfully tile drained. 
 
CLAY SOILS OF HUMID REGIONS. 133 
 
 (172) Tilth of Heavy Clay Lands. Heavy clay 
 lands when plowed in the fall and allowed to lie in the 
 rough furrow will be found to greatly improve in tex- 
 ture, provided sufficient care is taken not to cultivate 
 them when so wet that puddling would result. Such 
 treatment will improve tenacious clays, so that, while 
 at the beginning of their cultivation their working 
 costs at least double the labor for ordinary clay loam 
 soils, they can be so improved that the labor involved is 
 comparatively little greater than that on much lighter 
 soils. The thick roots of such plants as clover and al- 
 falfa by their rapid decomposition greatly aid in the 
 development of good tilth on such soils. The use of 
 coarse manure is also beneficial in this respect. It has 
 been the practice in older countries to apply lime to 
 such soils for the purpose of improving their tilth. This 
 effect it undoubtedly has. but it may also cause, the 
 burning out of the organic matter), which frequently 
 exists in very small quantities in such soils, so that its 
 use for this purpose is questionable. At least two tons 
 of quick lime per acre are necessary to effect a notice- 
 able improvement in the tilth. 
 
 (173) Fertilizer Requirements. Ais above 
 stated, these soils are apt to be deficient in nitrogen and 
 phosphate. Nitrogen should be supplied by the growth 
 of clover or other legume and the phosphate can be 
 most cheaply supplied in the form of floats, though 
 where little organic matter is present and no manure 
 available acid phosphate should be used instead. (See 
 Paragraph 84.) Peat, which is frequently available 
 in the vicinity of both clay and sandy soils, contains in 
 a partially dry condition two or three times the amount 
 
1 34 NOTES ON SOILS. 
 
 of nitrogen contained in barnyard manures, and while 
 il becomes available slowly its application at the rate 
 of 20 to 30 loads to the acre is very effective in add- 
 ing nil rogen to such soils. 
 
 (174) Crops for Clay Soils. The large water- 
 holding capacity of such soils renders them particularly 
 adapted to grasses. bu1 they are also well adapted to 
 grains such as wheat and barley. Heavy clay -oils are 
 ap1 to he comparatively cold and are consequently less 
 well adapted to corn. When kept in good tilth fair 
 yields of rool crops can he obtained, though this soil is 
 not especially adapted to such crops. 
 
 Exhausted Clay Loam Soils. 
 
 (175) Management of Exhausted Clay Loams. 
 Large areas of the central and eastern states consist ot 
 clay loam soils which have been under crop from two to 
 five generations, largely in grain, with comparatively 
 little regard to maintaining their fertility. Soils which 
 have this history are characterized by low organic mat- 
 ter, much acidity, and lack of available phosphates, and 
 require treatment accordingly. The acidity must be 
 corrected by the use of lime or lime carbonate, as in- 
 dicated in paragraphs 58 to 60, in order to permit the 
 growth of good nitrogen fixing legumes which will add 
 Hie necessary nitrogen for other crops. Since these 
 lands are ,-is a rule adapted to dairying or the raising 
 of other classes of live stock, manure should be avail- 
 able, winch, when supplemented with floats or rock 
 phosphate, as indicated in paragraph 84. will add the 
 necessary phosphate. The use of green manuring crops 
 
CLAY SOILS OF HUMID REGIONS. 135 
 
 and of pasture in rotation will increase the humus sup- 
 ply. This treatment is important not only for its in- 
 fluence on fertility,, but also for its tendency to retard 
 erosion to which these soils are particularly subject. 
 
 Rough Clay Lands and Erosion. 
 
 (176) Management to Lessen Erosion. Large 
 tracts of clay soils along our rivers and their tribu- 
 taries are so steep that they constitute a distinct type 
 of agricultural lands. The cropping of such lands by 
 cultivated crops greatly increases the tendency to ero- 
 sion, which is the greatest difficulty met with in the 
 management of these soils. Such lands are therefore 
 best fitted for grazing purposes. It is especially im- 
 portant in the selection of farms in such regions that 
 care be taken to have the farm include some sufficiently 
 level land to permit of eonsiderable cultivation, as veil 
 as considerable rough land which must be used as pas- 
 ture. It is frequently possible to take off one crop of 
 corn every fourth or fifth year without serious injury 
 since the newly broken sod is very much less liable to 
 wash than the soil after the sod is rotted. 
 
 The withdrawal of water from side hills through dead 
 furrows or shallow ditches leading to the main ravines, 
 which can be kept well grassed greatly retards the ero- 
 sion by lessening the amount of water going over the 
 surface. Dead furrows used for this purpose should 
 have a low gradient. This system of contour plowing 
 will greatly lessen erosion of lands having less steep 
 slopes, although kept in cultivated crops a large portion 
 of the time. 
 
336 NOTES ON SOILS. 
 
 CHAPTER XX. 
 
 MARSH SOILS. 
 
 (177) Characteristics of Marsh Soils. Marsh 
 soils have been formed by the drying up and filling in 
 of hikes and marshes to such an extent as to permit 
 their drainage and cultivation. They are characterized 
 
 by an excess of organic matter and a deficiency of the 
 miner;i I elements. These soils may have either a clay 
 or sand subsoil and vary greatly in depth. An im- 
 portant distinction may be made between marsh soils 
 which are acid and those which are neutral. 
 
 Acid Marsh Soils. 
 
 The excess of organic matter in marshes develops 
 acidity and causes, when not neutralized by lime, a 
 distinctly acid soil. Such soils exist in regions of gran- 
 itic and other crystalline rocks and of sandstone. They 
 include practically all of the marshes of central and 
 northern Wisconsin and large areas of Minnesota and 
 Michigan and other states. These soils are usually 
 Largely formed of sphagnum moss producing a peat and 
 varying in depth from a few inches to 12 or even 15 
 feet. They are extremely light in weight, a cubic foot 
 of dry peai weighing but 15 pounds as compared with 
 70 pounds for a cubic foot of an ordinary clay loam soil. 
 
MARSH SOILS. 137 
 
 (178) • Nitrogen and Acidity of Peat Soils. The 
 excess of nitrogen in peat soils usually makes it unnec- 
 essary to grow legumes for the purpose of increasing 
 nitrogen. It is therefore unnecessary to neutralize their 
 acidity as in the case of sandy or clay soils. Indeed the 
 acidity is frequently so concentrated that the amount of 
 lime which would be necessary to neutralize it would 
 make the expense prohibitive. It occasionally happens, 
 however, that such soils are so cold that nitrification 
 docs not take place readily and under such conditions 
 a nitrogen fertilizer may be used. This is true of con- 
 siderable areas of peat lands in Europe, but has met 
 with by the writers to a very slight extent in this coun- 
 try. 
 
 (179) Phosphate and Potash. Acid marsh soils, 
 in common with acid soils generally, are deficient in 
 available phosphates. Indeed this deficiency is more 
 striking in the case of peat lands than of most other 
 soils. In many cases without the addition of a phos- 
 phate fertilizer in some form, the yields are unprofitably 
 small. On account of the abundance of organic matter 
 and the acidity in such soils raw rock phosphate can be 
 used to advantage to supply this element. Half a ton 
 to the acre for the first treatment and 300 to 400 pounds 
 every third or fourth year thereafter will be sufficient 
 to supply the phosphorus for the growth of good crops. 
 These soils are usually very deficient in potash, and this 
 may be supplied in the form of wood ashes, of which 
 30 to 40 bushels per acre is a good treatment, or of 
 muriate or sulphate of potash, of which 100 to 150 
 pounds to the acre every year is sufficient. 
 
138 NOTES ON SOILS. 
 
 (180) Crops for Acid Marsh Soils. These lands 
 in the colder sections of the country are more subject to 
 frosts than upland and for this reason they are not well 
 adapted to corn and potatoes, for which they would 
 otherwise be well suited. The Leading crop on such 
 hinds should be the hay grasses, of which timothy and 
 alsike clover are perhaps the best. When given the 
 above mentioned treatment with phosphate and potash 
 fertilizers, such soils should yield from two to two and 
 one-half tons of excellent bay annually. Rape, millet, 
 and buckwheat are oilier crops well adapted to such 
 hinds. 
 
 Neutral Marsh Soils. 
 
 (181) Characteristics of Neutral Marsh Soils. 
 Within the region covered by glaciers during the glacial 
 period and where underlaid by limestone rocks, the sur- 
 face soils have usually been thoroughly mixed with 
 ground limestone from the rock below. This lime car- 
 bonate is being dissolved out gradually by percolating 
 waters and carried to the marshes, so that the acidity, 
 produced by the decomposition of vegetable matter is 
 neutralized. As a rule, therefore, the marshes of such 
 regions as the southeastern portion of Wisconsin are 
 not acid. They differ in this respect from the central 
 and northern part of the state. The subsoil is most 
 commonly clay. These soils, therefore, ordinarily ni- 
 trify more rapidly than the acid marsh soils, and seldom 
 show need of phosphate fertilizers. They are,, however, 
 often deficient in potash. 
 
 (182) Neutral Marsh Soils and Potash. The 
 only diffieultv met with in regard to the fertility of the 
 
MARSH SOILS. 
 
 139 
 
 neutral marsh soils is their deficiency in potash. On 
 drained marsh soils of this type, patches varying from 
 a few square rods to many acres develop, on which corn 
 or other crops turn yellow at a very early stage in their 
 growth and therefore fail to mature. This, where the 
 drainage is good, is practically always an indication of 
 lack of potash, and the addition of a potash fertilizer 
 alone will enable this soil to produce heavy yields. From 
 100 to 150 pounds of sulphate or muriate of potash on 
 such soils will frequently he found to be as effective as a 
 fair application of barnyard manure. Where the muck 
 or peat is not too deep, say from 12 to 16 inches, its cul- 
 tivation during a period of years will cause it to settle, 
 so that deep plowing and the roots of crops will reach 
 the clayey subsoil. This subsoil contains an abundance 
 of potash, so that the deficiency in this element which 
 exists at first often disappears, and special potash treat- 
 ment becomes unnecessary. Of course continued culti- 
 vation will require a general fertilizer such as barnyard 
 manure. 
 
 (183) Crops for Neutral Marsh Soils. These 
 soils are adapted to the same crops as acid marsh soils, 
 but when so situated that frost is not .troublesome are 
 especially adapted to corn. If well fertilized with pot- 
 ash, cabbages can be successfully grown on the neutral 
 marsh soils. 
 
140 NOTES ON SOILS. 
 
 APPENDIX. 
 
 Experiment Station- Bulletins Relating to Soils 
 and Soil Treatment. 
 
 The following list, although very incomplete, includes 
 some of the more important experiment station litera- 
 ture available in bulletin form, bearing directly upon 
 the subject of Soils. Earlier bulletins, and material 
 published in the various Annual Reports can be con- 
 sulted at the Agricultural Library. AVisconsin students 
 will find that bulletins issued by the Illinois, Iowa, Ohio, 
 Minnesota, and Wisconsin Stations bear more directly 
 upon AVisconsin conditions than those from other sta- 
 tions. 
 
 NORTH CENTRAL. 
 
 Illinois. 
 
 Bulletin No. 99 — Soil Treatment for the Lower Illinois 
 Glaciation. (Hopkins.) 
 
 Bulletin No. 115 — Soil Improvement for the Worn Hill Lands 
 of Illinois. (Hopkins.) 
 
 Bulletin No. 123 — The Fertility in Illinois Soils. (Hopkins.) 
 
 Bulletin No. 125 — Thirty Years of Crop Rotations on the 
 Common Prairie Soil of Illinois. (Hop- 
 kins.) 
 
 Circular No. 82 — Physical Improvement of Soils. (J. G. 
 Mosier.) 
 
APPENDIX. 
 
 141 
 
 Circular No. 110 — Ground Limestone for Acid Soils. (Hop- 
 kins. ) 
 
 Circular No. 116— Phosphorus and Humus in Relation to Il- 
 linois Soils. (Hopkins.) 
 
 Circular No. 127— Rock Phosphate or Acid Phosphate. (Hop- 
 kins. ) 
 
 (A. H. 
 
 Iowa. 
 
 Bulletin No. 1 — Extension Division — Farm Manures. 
 
 Snyder.) 
 
 Bulletin No. 82— The Principal Soil Areas of Iowa. (Steven- 
 son et al.) 
 Bulletin No. 95— The Maintenance of Fertility with Special 
 
 Reference to the Missouri Loess. 
 
 (Stevenson, et al.) 
 Bulletin No. 78 — Drainage Conditions in Iowa. (Stevenson 
 
 and Christie.) 
 Bulletin No. 98 — Clover Growing on the Loess and Till Soils 
 
 of Southern Iowa. (Stevenson and 
 
 Watson.) 
 
 Wisconsin. 
 
 Research Bui. No. 2- 
 
 the Phosphate Con- 
 (Whitson and Stod- 
 
 Bulletin 
 Bulletin 
 
 Bulletin 
 
 Bulletin 
 Bulletin 
 Bulletin 
 Bulletin 
 Circular 
 23d and 
 
 -Factors Influencing 
 tent of Soils 
 dart.) 
 
 No. 138— Land Drainage. (Whitson and Jones.) 
 
 No. 85— Development and Distribution of Nitrates 
 and Other Soluble Salts in Cultivated 
 Soils. (King and Whitson.) 
 
 No. 93— Development and Distribution of Nitrates 
 in Cultivated Soils. (King and Whit- 
 son.) 
 
 No. 139— Principles and Maintenance of Soil Fertil- 
 ity. (Whitson and Stoddart.) 
 
 No. 146— Drainage Conditions of Wisconsin. (Whit- 
 son and Jones.) 
 
 No. 147— Report on Northern Sub-Station Work 
 (E. J. Delwiche.) 
 
 No. 174— The Conservation of Phosphates on Wiscon- 
 , r, sin Farms - (Whitson and Stoddart.) 
 
 No. 6— Synopsis of Wisconsin Drainage Laws 
 (E. R. Jones.) 
 
 24th Annual Reports— Articles on Nitrogen Content 
 of Soils as Affected by Methods of 
 Farming. (Whitson. Stoddart, Mc- 
 Leod.) 
 
142 
 
 NOTES ON SOILS. 
 
 Bulletin No. 159- 
 Bulletin No. 182- 
 
 Oiiio. 
 
 Bulletin No. 150 — Ohio Soil Studies I, (Chemical and Me- 
 chanical Analysis of the Soils Under 
 Experiment). (Selby and Ames.) 
 -The .Maintenance of Fertility (Liming the 
 Soil). (Thorne.) 
 I — The Maintenance of Fertility (Field Ex- 
 periments with Fertilizers on Cereal 
 Crops and Potatoes. Results for Thir- 
 teen Years). (Thorne.) 
 Bulletin No. 183 — The Maintenance of Fertility, Production, 
 Reinforcement, and Value of Manure. 
 (Thorne.) 
 
 Maintenance of Fertility (Thorne) 
 (Statistical Data (1894-1906 inclusive). 
 -Field Experiments with Fertilizers and 
 Manures on Tobacco, Corn, Wheat, and 
 Clover in the Miami Valley. (Thorne.) 
 Circular No. 79 — How to Determine the Fertilizer Require- 
 ments of Ohio Soils. (Thorne.) 
 
 Bulletin No. 184—1 
 Bulletin No. 206- 
 
 MlNXESOTA. 
 
 Bulletin No. 70 — Influence of Wheat Farming Upon Soil 
 
 Fertility. (Harry Snyder.) 
 Bulletin No. 89 — Soil Investigations: 
 
 1. The Influence of Crop Rotations and 
 
 Use of Farm Manures upon the 
 Humus Content and Fertility of 
 Soils. 
 
 2. The Water-Soluble Plant Food of 
 
 Soils. 
 
 3. The Production of Humus in Soils. 
 
 (Harry Snyder.) 
 Bulletin No. 94 — Soil Investigations. (Snyder.) 
 
 Part 2. Loss of Nitrogen from Soils. 
 Bulletin No. 109 — The Rotation of Crops. (Hays, Boss, & 
 
 Wilson.) 
 
 EASTERN. 
 
 Rhode Island. 
 
 Bulletin No. 90 — Top Dressing Grass Lands. (Wheeler and 
 
 Adams.) 
 Bulletin No. 96 — Influence of Lime upon Plant Growth. 
 
 (Wheeler.) 
 
APPENDIX. 143 
 
 Bulletin Xo: 114— A Comparison of Nine Different Phosphates 
 upon limed and unlimed Land with 
 Several Varieties of Plants. (Wheeler 
 and Adams.) 
 
 Vermont. 
 The following Vermont Bulletins are the "special feature" 
 articles contained in the Annual fertilizer bulletins of the 
 Vermont Station. 
 Bulletin No. 130— Soil Biology in its Relation to Fertilization 
 
 (J. L. Hills, et al.) 
 Bulletin No. 135— Soil Deterioration and Soil Humus (J I 
 
 Hills, et al.) 
 Bulletin No. 143— Soil Physiography. (J. L. Hills, et al.) 
 
 Pennsylvania. 
 Bulletin No. 90— Soil Fertility. (Thomas F. Hunt.) 
 
 Maryland. 
 Bulletin No. 66— Lime— Sources, and Relation to Agricul- 
 _, , ture. (H. J. Patterson.) 
 
 Bulletin No. 70— Chemical Composition of Maryland Soils 
 
 (Veitch.) 
 Bulletin No. 110— Investigations on Liming of Soils. (H. J. 
 
 Patterson. ) 
 
 New York (Cornell Sta.). 
 Bulletin No. 254— Drainage in New York. (E O Fipnin ) 
 Bulletin No. 264— Experiments in the Growth of Clover on 
 
 Farms where it once grew, but now 
 
 fails. (G. F. Warren.) 
 
 WESTERN. 
 
 California. 
 Bulletin No. 128— Nature, Value, and Utilization of Alkali 
 Lands. (Hilgard.) 
 
 Colorado. 
 Bulletins Nos. 46, 58, 65, 72— A Soil Studv (in four parts) 
 
 (W. P. Headden.) 
 Bulletin No. 99— How can we maintain the Fertility of our 
 
 Colorado Soils? (W. P. Headden.) 
 
1 I [ NOTES ON SOILS. 
 
 Washington. 
 
 Bulletin No. 85— Washington Soils. (R. W. Thatcher.) 
 
 Utah. 
 
 Bulletin No. 100 — Arid Farming Investigations. (W. M. 
 
 Jardine. ) 
 Bulletin No. 104 — The Storage of Winter Precipitation in 
 
 Soils. (J. A. Widtsoe.) 
 
 New Mexico. 
 
 Bulletin No. 61 — Dry Farming in New Mexico. (J. J. Ver- 
 non. ) 
 
 Oregon. 
 Bulletin No. 90— Acid Soils. (A. L. Knisely.) 
 
 Wyoming. 
 Bulletin No. 80 — Dry Farming in Wyoming. (J. D. Towar.) 
 
 Montana. 
 
 Bulletin No. 74 — Dry Farming Investigations in Montana. 
 (Atkinson and Nelson.) 
 
 South Dakota. 
 Bulletin No. 54 — Subsoiling. (N. E. Hansen.) 
 
 SOUTHERN. 
 
 Texas. 
 
 Bulletin No. 99 — Composition and Properties of Some Texas 
 Soils. (G. S. Fraps.) 
 
 Florida. 
 Bulletin No. 93— Acid Soils. (A. W. Blair and E. J. Macy.) 
 
 Mississippi. 
 
 Bulletin No. 108 — On Prevention of Erosion, etc. (C. T. 
 Ames.) 
 
 Kentucky. 
 Bulletin No. 126— Soils. (Peter and Averitt.) 
 
INDEX. 
 
 Absorption of water by seed, 1. 
 
 Acidulated bone, 64. 
 
 Acid Phosphate, 64. 
 
 Acid soils, marsh, 136; prevalence of, 42; treatment for, 45. 
 
 Acidity 42, and availability of phosphate, 59; effects on dif- 
 ferent plants, 44; harmful effects of, 43; origin of, 43; test 
 for, 42. 
 
 Aeration, 50; effect on formation of humus, 33. 
 
 Agencies in soil formation, 20. 
 
 Alkali soils, 22. 
 
 Availability of phosphates, 59. 
 
 Availability of potash, 65. 
 
 Beets, sugar, 115; manure on, 115; soil for, 115. 
 Bone, Acidulated, 64. 
 Bone meal, raw, 63; steamed, 63. 
 Buckwheat, 118. 
 
 Capacity of soil for water, 75. 
 
 Capillary rise of water, 81. 
 
 Capillary water, amount, 76. 
 
 Cereals, soils for, 116. 
 
 Chemical requirements of crops, 12. 
 
 Classification of soils, 101. 
 
 Clay, definition of, 69; flocculation of, 73. 
 
 Clays, heavy, 131; crops for, 134; drainage, 132; fertilizers 
 for, 133; erosion of, 135; improvement of tilth, 133; oc- 
 currence, 131. 
 
 Clay loams, management, 134. 
 
 Clays, rough, erosion, 135. 
 
 Climate, relation to crop, 107. 
 
 Clover, soil treatment for, 120. 
 
 Corn, 108; cultivation of, 112; on clover sod, 109; manure on, 
 110; on marshes, 110; roots of, 108. 
 
 Crops, 107; for acid marsh soils, 138; chemical requirements 
 of, 12; for green manuring, 40; for heavy clay soils, 134; 
 for neutral marsh soils, 139; rotation of, 122. 
 10 
 
146 INDEX. 
 
 Cultivation, objects of, 90. 
 Cycle of nitrogen, 48. 
 
 Denitrification, 74. • 
 
 Distribution of elements in plants, 9. 
 Drainage, advantages of, 81; of heavy clay soils, 132. 
 Dried blood, 56. 
 
 Early soils, 128. 
 Erosion of clays, 135, 
 
 Fallowing, effect on nitrification, 52. 
 
 Fertilizers, nitrogen, 56; phosphate, 62, 63, 64; potash, 66. 
 
 Fertility, factors influencing, 27, 28, 29; limiting factors, 
 
 29-31; revolving fund of, 26. 
 Flax, 118. 
 Floats, 64. 
 
 Flocculation of clay, 73. 
 Fruition, conditions influencing, 17. 
 
 Germination, conditions necessary, 1. 
 Glacial soils, 22. 
 Grass and grain soils, 102. 
 Grass soils, 118; preparation of, 119. 
 Green manuring, 40. 
 .Ground limestone, 45. 
 Ground water, 80. 
 
 Growth, 1; conditions for, 4; rate of, 16; relation to light, 14; 
 relation to soil, 18. 
 
 Heavy clays (See clays, heavy) 
 
 Humus, 32; composition. 32; effect on temperature, 37; effect 
 on texture, 37, 73; effect on soil organisms, 38; function, 
 35; loss of, 38; maintenance of, 39-41; origin, 24; plant 
 food in, 35; water-holding capacity of, 36. 
 
 Hydroscopic moisture, 75. 
 
 Inoculation of soil, 54. 
 
 Kaolin, 20. 
 
 Leaching of lime, 28. 
 Leaching of nitrogen, 55. 
 Legumes, nitrogen fixation by, 52, 53. 
 Legumes on sandy soils, 127. 
 Light, relation to plant growth, 14. 
 Lime, application of, 45. 
 
INDEX. 147 
 
 Limestone,- ground, 45. 
 
 Lime refuse, 46. 
 
 Limiting factors in fertility, 29. 
 
 Loams, clay, 134. 
 
 Loams, sandy. 129. 
 
 Lodging, 17. 
 
 Loess, 24. 
 
 Management of soils, 125; of heavy clay soils, 131; of rough 
 clay lands, 135; of acid marsh soils, 137; of neutral marsh 
 soils, 138; of coarse sandy soils, 125; of sandy loams, 129; 
 of black sandy loams, 129. 
 
 Manure, 95; amount produced by live stock, 96; application, 
 99; care of, 98; composition of fresh, 96; composition of 
 liquid and solid. 97; litter, 98; lasting effect of, 100; 
 manure on corn; 110; re-inforcement of, 99; value of, 
 factors influencing, 95. 
 
 Marl, 46. 
 
 Marsh soils, 136; acid, 136; character, 136; need of phosphate 
 and potash, 137; neutral, 138; nitrogen in, 137. 
 
 Mechanical composition, 68; and texture, 71. 
 
 Mineral plant food in humus, 35. 
 
 Moisture of soil, availability to plants, 77. 
 
 Movements of soil water, 79. 
 
 Nitrates, close use by plants, 51. 
 
 Nitrification, influenced by, 49; aeration, 50; character of 
 humus, 51; moisture, 50; reaction of soil, 51; tempera- 
 ture, 50. 
 
 Nitrogen, 47; amount in soil, 47; cycle of, 48; fertilizers, 56; 
 removal from soil, 55; in humus, 35; kinds of in soil, 47. 
 
 Nitrogen, fixation, 52; amount of, 53; conditions favoring, 
 53. 
 
 Neutral marsh soils, 138. 
 
 Oats, 117. 
 
 Organic matter, decomposition, 34. 87. 
 Origin of soil material, 19. 
 Oxidation of vegetable matter. 33. 
 
 Oxygen, relation to germination, 3; to nitrification. 50; to 
 denitriflcation, 55. 
 
 Percolation and seepage, 80. 
 
 Phosphorus, function in plants, 10. 
 
 Phosphorus in soils, 58; amount, 58; availability of, 59: main- 
 tenance of, 62; occurrence of, 58; relation to method of 
 farming, 60; soils deficient in, 59. 
 
148 INDEX. 
 
 Phosphate fertilizers, 62. 
 
 Plant, character of in relation to character of soil, in:,. 
 
 Plant food in humus, 35. 
 
 Plant food removed by crops (Table) 8 
 
 Potash, function in plants, 10. 
 
 Potash in soils, 65; amount. 65; availability, 6T>; loss of, 66. 
 
 Potash fertilizers, 66; for corn on marsh soils, 110. 
 
 Potatoes, 112. 
 
 Rape, 116. 
 Raw bone meal, 63. 
 Residual soils, 20. 
 Rock phosphate, 64. 
 Rocks forming soils, 19. 
 Roots of corn, 10S. 
 Roots and texture, 74. 
 
 Rotation of crops, 122; advantages of, 122; effects of, 122; sys- 
 tems of, 124. 
 Rye, 117. 
 
 Sand, definition, 69; effect on mechanical composition, 70, 
 
 72. 
 Salts, influence of on germination, 3; amount taken up by 
 
 plants, 5, 7. 
 Sandy loams, management, 129. 
 Sandy soils, 125; acidity of, 127; conservation of moisture in, 
 
 128; crops for, 128; legumes on, 127; management of 
 
 125; maintenance of humus and nitrogen in, .127; types 
 
 of, 125. 
 Seepage, 80. 
 
 Slope of land, effect on temperature, S6 
 Soil grains, area of surface per pound, 71. 
 Soil, origin, 19; classification of, 101. 
 Steamed bone meal, 63. 
 Subsoil, 24. 
 Sugar beets, 115. 
 
 Temperature for germination, 2. 
 
 Temperature, relation to growth, 16. 
 
 Temperature of soils, S3; influenced by amount of water, 
 
 84; character of soil, 84; organic matter, 87; roughness 
 
 of surface, 85. 
 Texture, 71; effect of cultivation on, 74, 90; of humus on, 73; 
 
 of freezing and thawing on, 74; of water, 72; relation 
 
 to roots, 74; relation to soil solutions, 73; relation to 
 
 tilth, 71. 
 Tillage, objects of, 90. 
 
INDEX. 149 
 
 Tobacco, 113. 
 
 Tobacco soils, 115; effect of heavy manuring on, 114. 
 
 Translocation of material in plant, 17. 
 
 Transpiration current, 13. 
 
 Transpiration, rate of, 13. 
 
 Truck soils, 101. 
 
 Ventilation of soils, SS; necessity for, 88; agencies causing, 
 
 88; excessive, 89. 
 Variation, 6; in fertilizing constituents at different stages of 
 
 growth, 6; in composition during growth, 9. 
 
 Water, absorption by seed, 1. 
 
 Water in soil. 76; availability to plants, 77; capillary, 76; 
 
 cultivation to increase. 77; kinds of, 75; movements of, 
 
 79; removal of, 81. 
 Water used by plants, 13, 14. 
 Wheat, 117. 
 Wind breaks, 126.