University of Illinois 
 
 Library at 
 
 Urbana-Champaign 
 ACES 
 
 yw*?,*^ 
 
UNIVERSITY OF ILLINOIS 
 
 Agricultural Experiment Station 
 
 BULLETIN No. 125 
 
 THIRTY YEARS OF CROP ROTATIONS 
 ON THE COMMON PRAIRIE SOIL OF ILLINOIS 
 
 BY CYRIL, G. HOPKINS, J. E. READHIMER 
 AND WM. G. ECKHARDT 
 
 UKBANA, ILLINOIS, MAY, 1908 
 
SUMMARY OF BULLETIN No. 125 
 
 1. Authentic records show that our oldest soil experiment fields were 
 established at the University of Illinois in 1879. Page 327 
 
 2. Under one system of farming- the yield of corn has decreased from 
 70 bushels to 27 bushels per acre within thirty years; while under another 
 system the yield of corn has increased to 96 bushels per acre as an average . 
 
 Page 324 
 
 3. The fertility of the soil can be maintained, or even increased,, by a 
 proper system of grain farming with legumes in rotation. Page 325 
 
 4. A good system of live stock farming, which may or may not be 
 more profitable than grain farming, will also maintain the fertility of the 
 soil. Page 326 
 
 5. Farm manure has given a net profit in the first three crops of $1.30 
 per ton, or of $7.80 an acre when six tons have been applied. Page 341 
 
 6. As an average of 18 tests, covering three years, with a rotation of 
 corn, oats, and clover, the use of 75 pounds of phosphorus has produced in- 
 creases in crop yields worth $12.39. Page 342 
 
 7. L/arger crop yields have been secured (and phosphorus has been 
 nearly twice as effective) in a three-year rotation of corn, oats, and clover, 
 than in a two-year rotation of corn and oats. Page 346 
 
 8. While phosphorus is commonly the element that first limits the yields 
 of crops on our common soils, nitrogen is lost from the soil so much more 
 rapidly under poor systems of farming that nitrogen soon becomes the limit- 
 ing element, after which phosphorus alone has no power to increase the crop 
 yields. Page 353 
 
 9. This bulletin will be sent free of charge to anyone interested in 
 Illinois agriculture, upon request to E. Davenport, Director Agricultural Ex- 
 periment Station, Urbana, Illinois, and if so requested, the name of the 
 applicant will be placed upon the permanent mailing list of the. Experiment 
 Station, so that all subsequent bulletins will be sent to him as they are 
 issued. 
 
THIRTY YEARS OF CROP U ROTATIONS ON 
 THE COMMON PRAIRIE SOIL OF ILLINOIS 
 
 BY CYRIL, G. HOPKINS, CHIEF IN AGRONOMY AND CHEMISTRY, 
 J. E. READHIMER, SUPERINTENDENT OF SOIL EXPERIMENT FIELDS, AND 
 
 WM. G. ECKHARDT, ASSISTANT IN Soil, FERTILITY 
 
 Near the end of thirty years an average yield of 96 bushels of 
 corn per acre on one field, and an average yield of 27 bushels of 
 corn per acre on another field, must be accepted as the results of 
 different systems of farming on land that was similar and uniform 
 at the beginning. These results have been obtained in the heart 
 of the corn belt and on typical Illinois prairie land, representing the 
 most extensive and the most important type of soil in the state, 
 land whose present market value ranges from $150 to $200 per 
 acre, a value that may change rapidly in Illinois, as it has already 
 changed in the older states. 
 
 The 96 bushels is the average yield per acre for the years 1905, 
 1906, and 1907, in one system of farming; and the 27 bushels is 
 the average yield for the same years in another system of farming 
 on land originally the same. Between these extremes other results 
 have been obtained from several other systems of farming. 
 
 It is the purpose of this bulletin to report, especially to Illinois 
 landowners and farmers, the valuable data that have been secured 
 in these investigations. The results from these experiment fields 
 are now beginning to influence the agricultural practice of the 
 state, and they are destined to be of inestimable value to the com- 
 monwealth. Before discussing the details of the work, a compre- 
 hensive summary of the effects of the different systems of farming 
 will be considered. 
 
 SYSTEMS OF FARMING 
 
 In Table i are given three-year averages of the yields of corn 
 secured in recent years, including 1907, which is the 29th year of 
 the oldest experiments and the i3th year of a newer and more ex- 
 tensive series of experiments with crop rotations and soil treatment 
 with special reference to two markedly different systems of farm- 
 
 323 
 
324 
 
 BULLETIN No. 125. 
 
 [May, 
 
 ing, of which one is termed grain farming and the other live stock 
 farming. (Some preliminary cropping and other variations from 
 the systems indicated are reported in the detailed discussion and 
 tabular statements in the following pages.) The crops in the 3Oth 
 year of the older experiments may be seen by visiting these fields 
 during the season of 1908. 
 
 TABLE 1. LATEST CORN YIELDS PROM THE UNIVERSITY off ILLINOIS EX- 
 PERIMENT FIELD AT URBANA: TYPICAL CORN BELT PRAIRIE SOIL 
 (Three-year averages: Bushels per acre) 
 
 Crop 
 years. 
 
 Crop system. 
 
 13-year 
 experiments. 
 
 29-year 
 experiments. 
 
 1905 -6 -7 
 
 Corn every year. .' 
 
 35 bu. 
 
 27 bu. 
 
 1903 -5 -7 
 
 
 62 " 
 
 46 " 
 
 1901,-4,-7 
 
 Corn, oats, clover 
 
 66 " 
 
 58 " 
 
 Average of Three Corn Crops in Corn-Oats-Clover Rotation: 
 13-Year Experiments 
 
 Crop 
 years. 
 
 
 Special treatment. 
 
 Grain 
 farming- 
 (with legumes*) . 
 
 Live stock 
 farming- 
 (with manuref). 
 
 1905 -6 -7 
 
 None. 
 
 
 d't lin 
 
 81 bu 
 
 1905 -6 -7 
 
 Lime. 
 
 
 72 " 
 
 85 " 
 
 1905, -6, -7 
 
 Lime, 
 
 phosphorus 
 
 90 " 
 
 93 " 
 
 1905, -6,-7 
 
 Lime, 
 
 phosphorus, potassium. . . 
 
 94 " 
 
 96 " 
 
 *Legume catch crops and crop residues. 
 
 fManure applied in proportion to previous crop yields. 
 
 As an average of the last three years where corn has been 
 grown every year the yield has been 27 bushels in the 29-year ex- 
 periments and 35 bushels in the 1 3-year experiments. The lesson 
 of these experiments is that 12 years of cropping where corn fol- 
 lows corn every year reduces the yield from more than 70 bushels 
 to 35 bushels per acre, after which the decrease is much less rapid, 
 amounting to only 8 bushels reduction during the next 16 years. 
 Undoubtedly the rapid reduction during the first 12 years of con- 
 tinuous corn growing is due in large part to the destruction of the 
 more active decaying organic matter, resulting ultimately in insuf- 
 ficient liberation of plant food within the feeding range of the 
 corn roots. In addition to this, the development of corn insects in 
 soil on which their favorite crop is grown every year is sometimes 
 an important factor in reducing the yield. 
 
 Where corn is followed by oats in a two-year rotation the av- 
 erage yield of the last three crops of corn is 46 bushels in the 29- 
 
1908.] THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 325 
 
 
 
 year experiments, whereas in the 1 3-year experiments the average 
 yield for the same three years is 62 bushels of corn per acre. In 
 this case the destruction of humus is less rapid, and the develop- 
 ment of the corn insects is discouraged by changing to oats every 
 other year, so that the decrease in yield is less marked during the 
 early years, although the reduction continues persistently with 
 passing years. During the first n years the yield decreased from 
 more than 70 bushels to 62 bushels, and during the next 16 years 
 a further reduction of 16 bushels has occurred. 
 
 With the three-year rotation corn is grown for one year, fol- 
 lowed by oats with clover seeding the second year, and clover alone 
 the third year. During the first 10 years under this system the 
 yield of corn has decreased from more than 70 bushels to 66, and 
 during the next 16 years the yield has further decreased to 58 bush- 
 els, the average reduction being only one-half bushel a year. In 
 this system the most marked reduction in crop yields has not yet 
 appeared, although it must be expected in the future because the 
 clover crop is already beginning to fail on the oldest field even in 
 seasons when clover succeeds well on newer land under the same 
 crop rotation. When clover fails we substitute cowpeas for that 
 year on that field, which thus provides a legume crop and preserves 
 the three-year rotation. Further time is required to determine 
 how much the cowpeas will help to lessen the rate of decrease in 
 yield of corn and oats. 
 
 GRAIN FARMING 
 
 In the lower part of Table I (third column) are recorded the 
 average yields of corn for the last three years in a system of grain 
 farming, in a three-year rotation of corn, oats, and clover. This 
 system when fully under way provides that the corn shall be husked 
 and the stalks disked down in preparation for the seeding of oats 
 and clover the second year. In harvesting the oats as much straw 
 as possible is left in the stubble, which may be mowed later in the 
 summer to prevent the seeding of the clover or weeds. In the 
 spring of the third year the clover is mowed once or twice be- 
 fore the usual haying time and left lying on the land. The seed 
 crop, if successful, is harvested with a hay buncher attached to the 
 mower or in any other way to avoid raking, and afterward the 
 threshed clover straw is returned to the land, all of this accumu- 
 lated organic matter to be plowed under for the following corn 
 crop, which begins the next rotation. In addition to this, catch 
 crops of annual legumes, such as cowpeas, may be seeded in the 
 corn at the time of the last cultivation and disked in the next spring 
 
326 BULLETIN No. 125. [May, 
 
 
 
 with the corn stalks. If biennial or perennial legumes are used as 
 catch crops, the corn ground may be plowed for oats. 
 
 The corn yields reported for this system in Table I were se- 
 cured where the system was not fully under way, the legume catch 
 crops being the only organic matter returned to the soil, aside from 
 the residues necessarily left from the corn-oats-clover rotation. By 
 using three different fields for this rotation, every crop may be 
 grown every year, and the yields of corn reported are true three- 
 year averages. 
 
 With no special soil treatment aside from the use of legume 
 catch crops, the yield of corn for 1905, 1906, and 1907 averaged 
 69 bushels. Where the equivalent of ^ ton per acre of ground 
 limestone was applied five years ago the corn has yielded 72 bush- 
 els per acre ; and, with phosphorus added for six years at the rate 
 per annum of 25 pounds per acre of the element phosphorus (in 
 200 pounds of steamed bone meal) the average yield of corn has 
 been 90 bushels per acre for the last three years. The yearly addi- 
 tion of 42 pounds of potassium in 100 pounds of potassium sulfate 
 has further increased the yield to 94 bushels. 
 
 The cost per ton delivered is about $2 for the limestone, $25 
 for the steamed bone meal, and $50 for the potassium sulfate. 
 
 LIVE STOCK FARMING 
 
 Under the heading "Live Stock Farming" in Table i are re- 
 corded the average yields of corn secured during the last three 
 years where farm manure has been applied to the clover ground 
 to be plowed under for corn. The plan of this system is to remove 
 all crops from the land as usually harvested, including the corn and 
 stover, oats and straw, and both first and second crops of clover. 
 The amounts of manure applied to the different plots are deter- 
 mined by the crop yields secured during the previous rotation. 
 While the system of cropping followed during the past 13 years on 
 these plots, and on those just described under "grain farming," has 
 been approximately equivalent to a three-year rotation of corn, 
 oats, and clover, the applications of manure have been made only 
 for the three years, 1905, 1906, and 1907. If the average yields 
 are decreasing on plots that receive only the amounts of manure 
 that can be produced in practice from the crops grown, then the 
 applications of manure must also be reduced on such land ; where- 
 as if the crop yields are increasing where both manure and phos- 
 phorus are applied, then the applications of manure for such plots 
 may be increased in direct proportion. 
 
iooS.] THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 327 
 
 Where manure alone has been used in this rotation the corn has 
 averaged 81 bushels per acre for the last three years; with lime 
 added the average is 85 bushels; with lime and phosphorus the 
 manured land has averaged 93 bushels of corn, and this was in- 
 creased to 96 bushels by adding potassium. 
 
 While potassium has usually made some increase in crop yields 
 on these fields it has not nearly paid its cost. The most profitable 
 yields are the 9O-bushel average in the grain farming or the 93- 
 bushel average in the live stock system. The effect of limestone has 
 not yet been sufficiently uniform to recommend its use on this soil, 
 but marked profit has resulted from the addition of phosphorus, 
 which is applied in sufficient amount actually to enrich the land and 
 not as a stimulant. 
 
 HISTORY OF THE OLD EXPERIMENT FIELD 
 
 It appears that the oldest soil experiment field in the United 
 States with an authentic record of its origin and with a present 
 continuation of the experiments originally inaugurated is on the 
 campus of the University of Illinois, or rather it is surrounded by 
 the University campus. In the biennial report for 1879 and 1880, 
 on page 232, and under date of March 10, 1880, is the following: 
 
 "The Farm Committee then submitted the following report: 
 To the Hon. Board of Trustees of the Illinois Industrial University: 
 
 "Your committee beg- leave to submit the following recommendations 
 from the Professor of Agriculture, in regard to experiments for the coming 
 season: 
 
 "Fifth The formal commencement of what is designed to be a long con- 
 tinued experiment to show the effect of rotation of crops, contrasted with 
 continuous corn growing with and without manuring, and also the effect 
 of clover and grass in a rotation. A commencement was made last year, 
 and we are fortunate in having a piece of land more than usually well adapted 
 for such a test. 
 
 "The report was approved, and its recommendation concurred in." 
 
 Thus, these oldest rotation experiments, begun, according to 
 the official records, by Professor George E. Morrow, in 1879, wMl 
 complete a record of thirty years in 1908. 
 
 In Bulletin No. 13 of the Illinois Agricultural Experiment Sta- 
 tion, published in 1901 and signed by Professor Morrow, the state- 
 ment is made that from the beginning of these experiments plot 
 No. 3 had "been in corn continuously," that plot No. 4 had been 
 "in corn and oats alternately," and that plot No. 5 had "had this 
 rotation: Corn, 2 years; oats, I year; meadow (clover, timothy, 
 or both) 3 years." The records also state that these plots had re- 
 ceived "no manure or commercial fertilizers of any kind." 
 
328 
 
 BULLETIN No. 125. 
 
 [May, 
 
 
 k 
 
 
 ^ 
 
 
 j 
 
 * 
 
 z 
 
 z' 
 
 s:' 
 
 X 
 
 Z 
 
 
 
 N. 
 
 X 
 
 O 
 
 
 PLATE 1. DIAGRAM (DRAWN TO SCALE) OF THE URBANA SOIL EXPERIMENT FIELDS, SHOWING THE OLD FIELD SOUTH OF THE 
 OBSERVATORY, AND ALSO THE SEVEN SERIES OF TEN PLOTS EACH LYING EAST OF MATHEWS AVENUE. 
 
 The photographs shown on the opposite page were both taken from the same point. The lower view looking southwest shows the 
 oldest plots on the right and series 100 on the left, with Mathews avenue between and farm buildings in the background. The upper 
 vie.w looking southeast shows plainly series 200 to 600, with series 700 and the University forestry in the background. 
 Note the plot labels (shown in full for series 400), also the oats harvesting in progress on series 500. 
 None means no soil treatment (except the regular crop system); Le means grain farming with legumes (including catch crops) 
 and crop residues returned to the land; M means farm manure; L means limestone; /'means phosphorus; A' means potassium (kalium) 
 >and A^ means commercial nitrogen; $x means five times the standard applications. 
 
 i 
 
 7 
 
 z 
 
 Z 
 
 z 
 
 _J 
 O 
 
 1 
 
 ^ 
 
 1 
 
 _/ 
 
 ITl 
 g 
 
 J 
 
 J 
 
 J 
 
 
 j 
 
 M 
 
 3 
 
 u 
 
 f 
 
 1 
 
 0) 
 
 in 
 
 Z 
 
 
 
 
 
 
 _J 
 1 
 
 i 
 
 ^0 
 
 _J 
 i 
 
 _! 
 
 1 
 
 i 
 
 1 
 
 ft 
 O 
 
 vO 
 
 _J 
 1 
 
 
 
 "; 
 
 a 
 
 B 
 
 c 
 
 1 
 8 
 
 10 
 
 
 
 J. 
 o 
 
 8 
 
 &. 
 _J 
 
 i 
 
 8 
 
 5O9- AVL.P.fV 1 
 
 1 
 
 
 
 
 
 6 
 
 oi 
 1 
 
 s 
 
 < 
 
 i 
 
 J 
 
 
 O 
 
 1 
 
 o 
 
 CL 
 
 C 
 
 i 
 
 o 
 
 J 
 
 i 
 
 409-A\.L.PK. 
 
 CL 
 
 
 1 
 O 
 
 
 
 I 
 
 _j 
 A 
 
 i 
 
 8 
 
 O 
 
 c 
 
 i 
 
 'ft: 
 
 i 
 
 i 
 o 
 
 u 
 
 _J 
 1 
 
 
 
 (0 
 
 309-M.L.PK. 1 
 
 ft.; 
 
 1 
 O 
 
 
 
 I 
 i 
 6 
 
 li 
 
 i 
 
 i 
 
 J 
 
 0" 
 1 
 
 <N 
 
 c 
 
 8 
 
 _j 
 
 ft, 
 
 l_l 
 
 C 
 
 i 
 
 o 
 
 CM 
 
 & 
 
 &>' 
 
 _J 
 
 
 
 (NJ 
 
 I 
 
 C 
 
 X 
 
 1 
 o 
 
 Csj 
 
 
 
 
 
 5 
 
 V 
 
 1 
 cs 
 
 
 s; 
 
 8 
 
 j 
 
 _J 
 C 
 
 o 
 
 
 
 * 
 
 r 
 
 
 i 
 
 vC 
 
 o 
 
 C 
 
 i 
 o 
 
 <c 
 c 
 
 c 
 
 'd 
 
 o 
 
 C 
 
 <o 
 i 
 o 
 
 
 .^v 4iW 
 
 JjLj 
 
 III fl! ill 
 
 
 u 
 
 1 
 
 1 
 
 z; 
 
 1 
 
 z. 
 1 
 
 z 
 
 1 
 
 1 
 
 _J 
 
 O 
 
 .JO. 
 
 
 
 
 
 
THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 329 
 
330 BULLETIN No. 125. [May, 
 
 The Illinois Agricultural Experiment Station was established 
 in 1888 and in the reports made by Professor Morrow and his as- 
 sistants relating to these experiments and published in Experiment 
 Station bulletins from 1888 to 1894 there is no record of crop yields 
 previous to 1888. Whether it was considered sufficient during the 
 first nine years to maintain the crop systems and wait for marked 
 differences to develop before beginning to take exact crop yields, 
 or whether the funds provided were inadequate to meet the ex- 
 pense of securing these complete records, is not stated. Certainly 
 the most important thing is the record that the crop systems were 
 maintained during those early years. 
 
 Since 1888 these crop systems for the three plots mentioned 
 have been essentially maintained, with the modification on Plot 
 No. 5 during the later years of adopting the more simple rotation 
 of corn, oats, and clover, one year each. From the recorded state- 
 ments and the existing knowledge it is safe to say that all crops 
 have been removed, including the grain, hay, straw, and corn fod- 
 der, from 1879 to the present time. 
 
 Originally these plots were one-half acre each in size, being 
 5 rods wide (north and south) by 16 rods long (east and west), 
 but in 1904, because of the enlargement of the University campus, 
 it became necessary to reduce the length to 9 rods, in the central 
 part of the original plots. At the same time one-half rod division 
 strips were established between the plots, also a one-fourth rod cul- 
 tivated or cropped protecting border around the plotted area, and 
 each of the three plots was also divided in four quarters by half- 
 rod division strips through the center in both directions. Thus 
 from each of the original plots we have four plots of one-twentieth 
 acre each. In each case the two plots on the north are continued 
 as a duplicate test of the original system, without the use of manure 
 or commercial fertilizers, while the two plots on the south are 
 cropped the same, but they are now being improved by such ap- 
 plications of farm manure as can easily be made from the crops 
 grown, by the use of legume catch crops, applications of ground 
 limestone to correct possible soil acidity, and by the use of phos- 
 phorus, applied for each year in the rotation in 200 pounds of 
 steamed bone meal or in 600 pounds of rock phosphate per acre. 
 
 The original plot numbers are retained, the untreated north 
 part being known as 3N, 4N, and 5N ; and the treated south part 
 as 38, 48, and 58, respectively; and to each of these may be added 
 W or E to designate the west or east half. Thus plots 3NW and 
 3NE are the untreated duplicate plots on which the thirtieth crop 
 of continuous corn is to be grown in 1908; and, while plots 3SW 
 
I90S.] 
 
 THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 331 
 
 and 3SE are treated as above described, they, too, are still kept in 
 corn every year. Corresponding to these are the divisions of the 
 corn and oats plot (No. 4) and of the corn-oats-clover plot 
 (No. 5), which are continually cropped by the respective rotations, 
 the duplicate plots in the north half receiving- no further treatment, 
 while the south half is manured and fertilized. 
 
 In Table 2 are recorded the yields of these old plots for the 
 last twenty years, from 1888 to 1907, including since 1904, for 
 each rotation system, the average of the untreated duplicates and of 
 the treated parts. 
 
 TABLE 2. CROP YIELDS PER ACRE PROM THE OLDEST PERMANENT EXPERI- 
 MENT PLOTS: URBANA SOIL EXPERIMENT FIELD 
 
 Years. 
 
 Soil treatment 
 applied. 
 
 Plot No. 3 
 
 Plot No. 4. 
 
 Plot No. 5. 
 
 Corn 
 every 
 year. 
 
 Two-year 
 rotation. 
 
 Three-year 
 rotation. 
 
 Corn 
 bu. 
 
 Corn 
 bu. 
 
 Oats 
 bu. 
 
 Corn 
 bu. 
 
 Oats 
 bu. 
 
 Clover 
 tons. 
 
 1879-87 
 1888 
 1889 
 1890 
 1891 
 1892 
 1893 
 1894 
 
 None 
 
 
 
 
 
 
 
 None 
 
 54.3 
 43.2 
 48.7 
 28.6 
 33.1 
 21.7 
 34.8 
 
 49.5 
 
 54.3 
 33.2 
 
 29.6 
 
 37.4 
 
 37.2 
 
 57.2 
 
 67.6 
 34.1 
 
 48.6 
 65.1 
 
 4.04 
 1.51 
 1.46 
 
 None 
 
 None 
 
 None 
 
 None 
 
 None 
 
 None 
 
 
 1895 
 1896 
 1897 
 1898 
 1899 
 1900 
 
 None 
 
 42.2 
 62.3 
 40.1 
 18.1 
 50.1 
 48.0 
 
 41.6 
 47.0 
 44.4 
 
 34.5 
 41.5 
 
 53.5 
 
 22.2 
 
 
 None 
 
 None 
 
 
 None 
 
 
 None 
 
 
 None 
 
 
 1901 
 1902 
 1903 
 
 None 
 
 23.7 
 60.2 
 26.0 
 
 33.7 
 35.9 
 
 56.3 
 
 34.3 
 
 54.6 
 
 1.11 
 
 None 
 
 None 
 
 
 1904 
 1904 
 
 N. % None 
 
 21.5 
 17.1 
 
 
 17.5 
 
 25.3 
 
 55.3 
 
 72.7 
 
 
 
 a i/ j Legume,*Mannre,** \ 
 /2 \ Lime, Phosphorus** J 
 
 1905 
 1905 
 
 N.^ None 
 
 24.8 
 31.4 
 
 50.0 
 44.9 
 
 
 
 42.3 
 50.6 
 
 
 c i/ ( Legume, Manure, ) 
 2 ( Lime, Phosphorus f 
 
 1906 
 1906 
 
 N.K None . 
 
 27.1 
 35.8 
 
 
 34.7 
 
 52.5 
 
 
 
 1.43f 
 1.74f 
 
 g y j Legume, Manure, } 
 ' /2 \ Lime, Phosphorus \ 
 
 1907 
 1907 
 
 N.J None 
 
 29.0 
 
 48.7 
 
 47.8 
 87.6 
 
 
 80.5 
 93.6 
 
 
 
 g y j Legume, Manure, ) 
 2 | Lime, Phosphorus \ 
 
 *L,egume catch crops first grown in 1904 to benefit 1905 crops. 
 **Manure and phosphorus first applied to plot 5S for 1904 crop, but to 
 plots 3S and 4S for 1905 crop. fCowpea hay; the clover failed. 
 
332 
 
 BULLETIN No. 125. 
 
 [May, 
 
 PLATE 3. THE 2QTH CROP OF CONTINUOUS CORN WITH NO MANURE OR FERTILIZ- 
 ERS: PLOT 3 (UNTREATED HALF), URBANA SOIL EXPERIMENT FIELD, 1907: 
 YIELD 29.0 BUSHELS PER ACRE. 
 
 These old plots lie west of Mathews avenue and immediately 
 south of the astronomical observatory, which is near the Agricul- 
 tural Building. These plots, as well as the newer series of plots 
 described more fully in the following pages, were all tile-drained 
 in 1904, every plot having a 4-inch tile on one side, laid in the half- 
 rod division strip. 
 
 Seasonal influences are so great that no very satisfactory com- 
 parison can be made between different years for the sake of de- 
 termining the effect of the different systems upon the productive 
 power of the soil, and the thorough under drainage provided for in 
 1904 must be expected to markedly increase the crop yields in sub- 
 sequent seasons of excessive rainfall, such as 1907, for example, as 
 compared with previous years. Thus, on the continuous corn plot 
 the yield was 18.1 bushels in 1898 and 60.2 bushels four years later, 
 in 1902, and the largest recorded corn yield in the corn-oats-clover 
 
THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 333 
 
 PLATE 4. THE 2QTH CROP IN CORN, OATS, AND CLOVER ROTATION: PLOT 5 
 (TREATED HALF), URBANA SOIL EXPERIMENT FIELD, 1907: YIELD 93.6 BUSH- 
 ELS PER ACRE. 
 
 rotation was 80.5 bushels in the wet season of 1907, the land hav- 
 ing been well tile-drained in 1904. 
 
 A fair comparison between different systems can usually be 
 made in the same years, and the change in productive power under 
 any system can best be ascertained by comparing the results from 
 the older experiments with those from the newer experiments, as 
 shown in Table i, when the effect of sixteen years' cropping can be 
 noted. It will be seen from the following tabular statements that 
 every plot in the newer experiments produced more than 75 bushels 
 of corn per acre in 1896 and that the average in 1897 was about 
 70 bushels. Upon these facts is based the assumption that all of 
 the older plots originally produced 70 bushels or more per acre. 
 
 It is apparent that the legume catch crops (chiefly cowpeas) 
 seeded in the corn decrease the yield for the first year at least, as 
 
334 BULLETIN No. 125. [May, 
 
 shown in 1904 on plot 3 and, even in spite of the light manuring, 
 on plot 4 in 1905. 
 
 The general effect of the system of soil improvement adopted 
 for the south half of each of these old plots is already very marked, 
 an increase of 40 bushels of corn per acre being secured in 1907 from 
 the treatment on plot 4, where the most marked effect is to be ex- 
 pected because no clover or other legumes had been grown previous 
 to 1904 in this rotation and the frequent change from corn to oats 
 has helped to avoid the development of corn insects. 
 
 For the separate effect of each individual kind of treatment, as 
 manure, lime, or phosphorus, reference must be made to the de- 
 tailed statements in the tables of data from the newer experiments 
 reported in the following pages. 
 
 THE NEWER SERIES OF SOIL EXPERIMENTS 
 
 On the opposite side of Mathews avenue and extending east- 
 ward to the University forestry plantation are seven series of 
 additional experiment fields, laid out in 1895 and brought under 
 definite systems of crop rotation and soil treatment since 1900. 
 
 During at least 16 years previous to 1895 this land was all in 
 pasture continuously, and it may perhaps be fair to assume that 
 the fertility of the soil was essentially maintained* during that 
 period, so that 16 years of crops harvested and removed may rep- 
 resent the difference between the old and new fields. 
 
 On the new field, series 100 lies immediately east of Mathews 
 avenue, with series 200 next east, and so on to series 700, which 
 is near the forestry. Each series is divided into 10 plots numbered 
 from north to south from i to 10. Thus, series 100 contains plots 
 101 to no; series 200 contains plots 201 to 210, etc., etc. The 
 individual plots are 2 by 8 rods, containing exactly one-tenth acre 
 each, aside from the cultivated, or cropped, protecting border about 
 one-fourth rod wide which completely surrounds every individual 
 plot. A higher degree of accuracy is made possible by having an 
 outside row of corn or strip of other crops surrounding each plot, 
 thus giving half-rodt division strips between the tenth-acre plots, 
 to prevent treatment applied to one plot from influencing the crop 
 yields on adjoining plots. 
 
 Three series, 100, 200, and 300, are being cropped in the three- 
 year rotation, corn, oats, and clover, in which every crop may be 
 
 *If the stock remain in the pasture day and night and receive a small 
 amount of grain, the fertility will be maintained, and with heavier feeding of 
 grain the fertility will be gradually increased ; but if the stock remain in the 
 pasture only during the day and receive no feed during the night, the fertility 
 of the land will be gradually reduced, especially in phosphorus. Abundance of 
 white clover in blue grass pastures will help to maintain the nitrogen. 
 
 fThese strips are exactly 8% meet in the old field but only 7^/3 feet in the 
 newer field. 
 
THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 335 
 
 represented every year. The next two series, 400 and 500, alter- 
 nate in the two-year rotation of corn and oats. On the two re- 
 maining series, 600 and 700, corn is grown every year in what is 
 termed a complete fertility test, containing duplicate plots treated 
 with commercial nitrogen, phosphorus, and potassium, these ele- 
 ments being applied singly and also in every possible combination 
 in uniform amount and form, and in addition a duplicate test is 
 made to determine the effect of lime, and another for "extra heavy" 
 treatment. 
 
 On the three series of plots in the three-year rotation, 100, 200, 
 and 300, and on the two series of plots in the two-year rotation, 
 400 and 500, no commercial nitrogen is applied, but the investiga- 
 tion is designed to furnish information concerning the value of 
 farm manure and legume crops and other crop residues in practical 
 systems of live stock farming and of grain farming. These sys- 
 tems are each practiced without additional treatment, and also with 
 the addition of lime, of lime and phosphorus, and of lime, phos- 
 phorus, and potassium. There is also in each of the five series one 
 plot (No. i) that receives no treatment (aside from the crop rota- 
 tion) and another plot (No. 10) that receives "extra heavy" treat- 
 ment by which it is hoped to remove the soil limit in crop produc- 
 tion. In other words, the treatment of plot 10 is designed to show 
 how large crops can be grown in Illinois with the rainfall and sun- 
 shine as the only limiting factors, all controllable factors being pro- 
 vided for, even at heavy expense. 
 
 Following is the general plan of soil treatment for the ten plots 
 in each of the five series, 100 to 500. 
 
 PLAN OF SOIL TREATMENT: SERIES 100 TO 500 
 
 Plot No. 
 
 Soil treatment. 
 
 9. 
 10. 
 
 None 
 
 L/egume (catch crops and crop residues) 
 
 Manure 
 
 L<egume, lime 
 
 Manure, lime 
 
 I^egume, lime, phosphorus 
 
 Manure, lime, phosphorus 
 
 Ivegume, lime, phosphorus, potassium 
 
 Manure, lime, phosphorus, potassium 
 
 I^egume, manure x 5, lime, phosphorus x 5 
 
 The lime was applied at the rate per acre of 250 pounds of air- 
 slacked in 1902 and 600 pounds of limestone in 1903. 
 
336 BULLETIN No. 125. [May, 
 
 The phosphorus has been applied at the rate per annum of 
 25 pounds of the element in 200 pounds of steamed bone meal since 
 1902, the present practice being to apply 600 pounds of bone meal to 
 the clover land to be plowed under for corn. Beginning with 1908 
 the west half of all plots receiving phosphorus will be treated with 
 rock phosphate, while the use of bone meal will be continued on 
 the east half. The potassium has been applied at the yearly rate of 
 42 pounds per acre in 100 pounds of potassium sulfate, usually in 
 connection with the bone meal, the steamed bone being run through 
 the grain box and the potassium salt through the fertilizer box of 
 an ordinary fertilizer drill. 
 
 The six series, 100 to 600, were laid out in the spring of 1895 
 by Dean Eugene Davenport, who came to the University in January 
 of that year. It was necessary to break the old pasture sod in the 
 spring, and, as might be expected, the corn crop for that year was 
 poor. Series 700 was broken later in 1895 and all plots were 
 cropped in corn in 1896 and 1897, in order that any marked differ- 
 ences in the soil might be noted. 
 
 From 1897 to 1900, Professor P. G. Holden was in charge of 
 the work reported in this bulletin. Series 100 to 300 were cropped 
 somewhat irregularly, oats, cowpeas, and clover being the principal 
 crops grown, with some catch crops one year on certain plots, as 
 shown in the following tables, and series 400 to 700 were cropped 
 in corn every year. 
 
 The definite crop rotations were begun in 1901 and the appli- 
 cations of lime, phosphorus, and potassium have been made as 
 stated above and as shown in the tables. The growing of legume 
 catch crops was begun in 1901 for the benefit of the succeeding 
 crops, and a comparison of plots 2, 4, 6, and 8 with plots 3, 5, 7, 
 and 9 will show what effect was produced by these catch crops dur- 
 ing the three years, 1902, 1903, and 1904. 
 
 Beginning with 1905, manure has been applied as indicated in 
 the tables, which will afford, when the results for 1908 and 1909 
 become available, a comparison between manure and legume catch 
 crops for three years on each series. The standard applications of 
 manure are the same weights of average fresh farm manure (con- 
 taining about 25 percent of dry matter) as the weights of air-dry 
 produce secured from the same plots during the previous rotation. 
 This allows about one-third of the produce to be sold and also al- 
 lows a loss of 20 percent of the manure possible to be produced 
 from the remaining two-thirds. On plot 10 about five times as 
 much manure and phosphorus are applied as on the other plots, but 
 this "extra heavy" treatment was begun in 1906, only lime, phos- 
 phorus, and potassium having been applied in previous years. 
 
1908.] 
 
 THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 337 
 
 o 
 
 ro n in 
 
 W 00 
 
 t> * 
 
 Ha 
 
 U 3 
 
 gx'w 
 
 ON ON ^ 
 
 
 
 S g 
 
 3 
 
 S *'S 
 
 CO <O C^ 
 
 ON 
 
 00 
 
 rH 
 
 vo M oo 
 
 CO O vo 
 rH 
 
 N rH 
 
 .5 aS 
 
 (J 0) Rj 
 
 la 
 
 >o o n 
 
 oo 10 
 
 "t O< ID 
 
 ^SjS 
 
 ^ 2 
 
 rXrX 
 
 rH rH N 
 
 cot- 
 
 ON 
 & 
 
 a 
 
 CO ON ON 
 
 10 oo 
 
 CO * 
 
 ga 
 Pll 
 
 ON 
 t>- M 1> 
 
 Sg 
 
 i> C a 
 
 J^ <u o.H 
 P a x cc 
 
 ON 
 
 O ON rH 
 
 S 
 
 1-4 
 
 * fO VO 
 
 rO O VO 
 
 T-t 
 
 N rH 
 
 .^ CL, * 
 j tfl rt 
 '^ O -t- 1 
 
 1 a 
 
 o. a 
 
 ON ON r^ 
 
 oo * 
 
 CL, to 
 d ^ <e "i 
 "^ O "S 
 * J= S, 
 
 f^rX 
 
 t> rH fS) 
 
 00 CO 
 
 I 
 
 9S 
 
 VO t> * 
 
 N l> 
 t- f} 
 
 !fl 
 
 S 
 a 8-2 
 
 rj *d 
 00 5 <U 
 
 OB 
 
 58 
 
 a2.5 
 
 ONrnS 
 
 I- 
 
 ro 
 
 rH 
 
 * M 00 
 rO ON vo 
 
 Cq rH 
 
 H|| 
 
 > S TT 
 
 ^ && 
 
 Ma 
 
 Wri 
 
 > O -M 
 
 M J3 
 
 eu a 
 
 ss; M 
 
 >0 
 
 ^C 
 
 </> 
 
 t- 
 
 rH VO ON 
 
 N rH 
 
 VC Tfr 
 
 OB 
 
 n 
 h 
 o> o 
 
 6j3 
 
 ON 
 O ro t> 
 
 i 
 
 V U< 
 
 ^8- 
 
 rH 1C M 
 
 rH 
 
 rO 
 
 rH 
 
 t- * ON 
 
 CO ON VO 
 
 ^ rH 
 
 -! 
 
 ^1 
 a 
 
 fe^^ 
 
 c 8 a- 
 
 Cd UH 1C 
 ^ O 
 
 X 
 a 
 
 SoS^ 
 
 VC 
 
 O 
 
 ^ 
 
 VO 
 
 rH 1C GO 
 
 * 10 
 
 MS fO 
 
 tfl 
 <D 2 
 
 Is* 
 
 %-a 
 10 5 D 
 
 I/! 
 
 5 
 
 ls 
 
 Q 
 rO >O 00 
 
 rt 
 
 rH 
 
 rH ON VO 
 
 rO ON vo 
 
 M rH . 
 
 i.fe& 
 
 a"J 
 a 
 
 ^ .2 '3 
 
 nn !j ra 
 
 6^ 
 
 |l f 
 
 H X 
 
 a 
 
 M M rH 
 
 oo ON 
 
 ri 
 
 ^ 
 
 
 rO ON iO 
 
 00 VO 
 M * 
 
 0) 
 
 s 
 
 00 
 rH fO M 
 
 |. 
 
 S a 
 
 
 ^f 
 
 rO 
 
 
 
 rH 
 
 VO t- 
 rO ON VO 
 
 M rH 
 
 *vH 
 
 J 
 
 Si 
 
 | - 
 
 a 
 
 ON rH rH 
 t- t- 
 
 iO 
 UO 
 * 
 
 S 
 
 rO CO VO 
 
 rH VO 
 CO iO 
 
 0) 
 
 a 
 
 s 
 
 ) "O 
 
 rH 5 0) 
 
 <u 
 
 
 
 ? a 
 
 53 
 
 00 ON CO 
 
 8 
 
 1-1 
 
 VO * VO 
 M ON vo 
 
 M rH 
 
 bc-S 
 
 D "" 
 
 _' ."- 
 
 3*2 
 
 00 g MH 
 
 M 
 
 h4 
 
 rHVO 
 I>1> 
 
 S 
 
 s 
 
 t> 00 iO 
 
 rH 1C 
 
 O vo 
 
 
 
 i 
 
 C1 
 
 ON r<5 M 
 
 K 
 
 3 
 
 iO 
 
 CO rj-t- 
 
 rO 
 
 oo 
 
 rH 
 
 >O ON t- 
 
 M 00 VO 
 
 M rH 
 
 S5 
 
 O rH 
 
 OOiO 
 
 S 
 
 S 
 
 rl ro rH 
 
 cot- 
 
 i^ 
 S 
 
 a 
 
 rHio vo 
 
 S3 
 
 V 
 
 S 
 
 a 
 
 * 
 O ^j 
 fsj (U 4> 
 
 OJ 
 
 a 
 
 3 
 
 rH 
 CO rH 00 
 
 c^ 
 I- 
 
 rH 
 
 O\ ON 00 
 oj co vo 
 
 M rH 
 
 be 
 
 
 a 
 
 ^-a 
 
 00 6^ 
 
 bo 
 
 0) 
 
 h4 
 
 rf> ro 
 t- t- 
 
 CO 
 
 * 
 ^f 
 
 
 O ON 
 
 C4t>- 
 rO N 
 
 <u 
 
 i 
 
 ro 
 rO^O Tt 
 
 0) 
 
 a 
 
 rH 
 O\ * ON 
 
 CO 
 Cl 
 
 O 
 1-1 
 
 O t> ON 
 
 co oo vo 
 
 M rH 
 
 o 
 
 * 
 
 cot- 
 
 1> * 
 
 o 
 
 fc 
 
 vo rO 
 1> vo 
 
 oo 
 % 
 
 
 
 
 a 
 3 
 bo 
 
 
 
 bo 
 
 
 <fi 
 
 ^ 
 
 o 
 
 to 
 
 -4-1 
 
 
 
 
 
 323 
 
 & & ,0 
 c" s? c~ 
 
 ;-'_ 
 
 O 
 
 uoo 
 
 iO VO t- 
 
 ON ON ON 
 
 oo oo co 
 
 . . y 
 
 : ' - "S 
 
 ? 
 o5g 
 $>:*;to 
 
 !H <U IU 4) 
 
 n > > S 
 ,2 O-H 
 
 5-00" 
 
 00 ON O rH 
 
 ON ON O O 
 00 CO ON O\ 
 
 i Partial soil 
 1902 -1 treatment 
 ( be 
 
 0) 
 
 p 
 O 
 
 2*- 
 
 - fc 
 
 fl to" & 
 
 fe^o 
 
 uoo 
 
 M ro TJ- 
 
 p o o 
 
 ON ON ON 
 
 {Complete soil 
 treatment 
 be 
 
 !fl 
 
 a 
 
 il* 5 
 
 X3^ v ; 
 C tfl > 
 
 S^o 
 OOO 
 
 iO vp t- 
 
 ON ON ON 
 
 O 
 E 
 
 o 
 
 0) 
 
 1 
 
 tfl 
 
 cd 
 
 M-i 
 
 O 
 
 a 
 2 
 
 "rt 
 > 
 
 
 
 a 
 
 
 '5 
 
 S . S . 
 
 it 
 
 (A 
 
 a 
 
 N t> 
 
 ON 
 
 o 
 
 ^ 
 
 
 fk 
 
 1 
 
 a 
 
 
 3 
 
 ^ (^ 
 
 
 
 '* 
 
 VO >O 
 
 X 
 
 
 a 
 
 <St- 
 
 -t 
 
 "o 
 
 
 
 
 CM 
 
 
 (X) 
 
 c 
 
 o 
 
 I- O 
 
 ON >O 
 
 t- 
 
 rl- 
 
 OH 
 
 ot- 
 
 ro' 
 
 to 
 
 rH 
 
 
 
 
 S 
 
 
 rH 
 
 
 m 
 
 
 
 
 * o 
 
 VO iO 
 
 rH 
 
 a 
 
 fO t- 
 
 '0 
 
 to 
 
 
 
 O 
 
 ^ 
 
 
 
 
 
 V 
 
 . 
 
 ?s 
 7 
 
 T 
 
 4) 
 
 a 
 
 o o 
 
 o 
 r) 
 
 3 
 
 rH 
 
 rH 
 
 b 
 
 P 
 
 O O 
 
 VO CO 
 
 O 
 00 
 
 rt 
 
 ON rH 
 
 l " 
 
 I 
 
 VO Q 
 
 
 ^ 
 
 he 
 
 
 
 
 V 
 
 
 
 -* 
 
 w 
 
 
 
 
 a 
 
 : i ; 
 
 o 
 
 H * J 
 
 j3 
 
 ^ ! a 
 
 3 
 
 ?.g 2 
 
 d 
 
 rt 
 
 ^ rt 
 
 \O D rO 
 
 f-> 
 
 O r^ JH 
 
 .0 
 
 rH "U 
 
 -M 
 
 n 
 
 JH ^H 
 
 4) 
 
 a 
 
 n HM (0 
 ^ C 
 
 "rt 
 
 l2 '(3 
 
 4> 
 
 bi 
 
 kl 
 
 H 
 
 O tfl -t- 1 
 W O 4) 
 
338 
 
 BULLETIN No. 125. 
 
 o 
 
 r-i re co 
 
 re ON 
 
 r/l 
 
 3 C 
 
 W> 5 
 
 D 0.2 
 fl J3 ) 
 
 ON * 
 r-l rH VO rH 
 
 vo 
 
 S * " 
 
 S a S 
 
 
 
 S 
 
 f>l 
 
 ON t^ ON 
 
 r-l ^ VO 
 
 vo re 
 
 * re 
 
 .5 CU M 
 
 tf) rt 
 Mo-'-' 
 
 Is. 
 
 rH ci f>i rN 
 
 00 >* 
 
 &3 J 
 
 " c'- g- 
 
 J ^ 
 
 S * 
 
 [> vo 
 
 ,? 
 w 
 
 S 
 
 1>VO M 
 
 rH fN 
 
 0! 
 
 SS 
 
 <u o 3 
 
 C J3 '5 
 
 N ON ON o 
 
 2 S| 
 
 )-c O 3 
 
 3 <U X -^ 
 
 VO CO 
 
 VO 
 M 
 
 M 
 
 ret^ O 
 
 rH ON1> 
 
 re I> 
 
 <* re 
 
 ,2 O* o? 
 
 -t M rt 
 M o*; 
 
 ta 
 
 rH VO 'O fN 
 CO * 
 
 G CX t 
 |3j2 
 
 J3 
 
 ac^ 
 
 VO ro 
 00 * 
 
 re 
 '0 
 
 v. 
 
 GO 
 
 * r-l re 
 
 ON rj- 
 
 S 2g 
 
 8-S 
 
 n-* 08 
 
 
 
 2| 
 
 .-i Ji X 'S 
 
 00 rO 
 
 r-l 
 
 VC 
 
 ?5 
 
 r-l r-l rH 
 r-l OM> 
 
 VO CO 
 
 TJ- re 
 
 ^3 
 
 a li 
 
 rHt^ Q fN 
 
 oo vT5 
 
 &j g.a 
 &3g| 
 
 J && 
 
 vo VO 
 
 CO * 
 
 re 
 
 >o 
 tf> 
 
 
 
 rH VO VO 
 
 t^ VO fN 
 
 rH ON I> 
 
 *a9^ 
 
 rt vo oo 
 fkj vo re 
 
 L/ime 
 phosphorus 
 
 VO re 
 rH 00 re 00 
 
 rH rH O rH 
 00 vo 
 
 Manure 
 lime 
 phosphorus 
 
 * * 
 I> * 
 
 oo * 
 
 1 3 
 
 r\ 
 
 'O 
 
 <f! 
 
 8 
 
 fM 
 
 re O M 
 
 VO ON 1O 
 rH ON l^ 
 
 * 
 
 EG 
 
 rt 
 
 a ^^. 
 
 t* vo re 
 > ^~ <* 
 
 o 
 
 o 
 
 Leg-ume 
 lime 
 phosphorus 
 
 l>- re 
 
 rH VO re CO 
 
 ^S8S^ 
 
 a) 
 
 S 2 
 
 is* 
 
 5>S a 
 fag 
 
 H X 
 
 a 
 
 <l rC 
 
 TflO 
 
 00 f 
 
 X 
 
 l> 
 
 I 1 
 
 ffi 
 
 /.. 
 
 vo 
 
 re * ON 
 
 * 
 
 IONO 
 
 <L) 
 
 8 
 
 re r-t 
 
 O O O 00 
 
 0) 
 
 *8 
 
 CD 
 
 vO 00 
 
 1^ 
 
 f>l 
 
 M 00 M 
 
 rH ON t^ 
 
 ivo'rn' 
 5** 
 
 v4 
 
 a 
 
 r-l re vo 
 
 1> Tf 
 
 *a 
 X : 
 
 r*3 1^ 
 I> re 
 
 $ 
 
 /- 
 
 + 
 
 8 
 
 VO rH fN 
 
 ^ *" re' 
 
 rH ON I> 
 
 t 
 
 IJret- 
 
 Ovo' ON* 
 ^^re 
 
 Legume 
 lime 
 
 rH 1> 
 
 O * * CO 
 
 r-l i-l 00 
 t- "* 
 
 V 
 
 8 ^ 
 
 3 S 
 bc* M 
 <u 
 a 
 
 VO vo 
 
 t^ vo 
 
 vo re 
 
 OQ 
 
 r) 
 
 Tt 
 
 S 
 
 S 
 
 l> 00 O 
 
 rH re 
 
 <u 
 
 a 
 
 fM t> 
 
 O O VC I> 
 
 V 
 
 h 
 
 3 
 
 * re 
 
 
 
 
 
 ON VO f>1 
 
 N coi> 
 
 vo re 
 
 fc 
 
 -g$ 
 
 8 
 
 ri 
 
 a 
 
 O vo 
 t^ re 
 
 00 
 
 re 
 '/? 
 
 M 
 
 vo co r- 
 
 M re 
 
 4) 
 
 s 
 
 pi 
 
 fH r-l 
 O 00 fN CO 
 
 <u 
 
 S 
 
 VO 00 
 
 S 
 
 fN 
 
 O rH ON' 
 re ON VO 
 
 t^ CO 
 vo re 
 
 he 
 a> 
 4 
 
 rH VO N 
 1> LO 
 
 bn 
 
 0) 
 
 a 
 
 vo ci 
 
 vo re 
 
 n 
 3 
 
 
 re t^ ON 
 
 ON ON 
 
 0) 
 
 re Tt- 
 
 O CO VO 00 
 
 0) 
 
 O M 
 
 91 
 i- 
 
 r^ 
 
 fXl X vo 
 
 rH re 
 vo re 
 
 
 
 
 
 r-i fN vo 
 
 J> "* 
 
 o 
 
 g 
 
 1> l> 
 
 VO M 
 
 r-l 
 S 
 
 
 
 
 c 
 
 
 a 
 
 3 
 
 
 r/l 
 
 
 333 
 .0.0.0 
 
 a c c 
 
 rj^ 
 
 '- '- 
 O 
 V O 
 1) <U 
 We VH 
 
 0033 
 
 .,,0,0 
 tc to wT tfl 
 
 'artial soil 
 treatment 
 begt 
 
 en 
 
 I a 
 Plf- 
 
 (X, -' - V 
 JT C t > 
 
 omplete soil 
 treatment 
 beg 
 
 3 3 
 
 J= 
 
 G uT 
 
 2- 
 O 
 
 O 
 
 1) 
 
 <u 
 
 IN 
 
 J= 
 
 *-> 
 (0 
 RJ 
 
 O 
 
 
 
 "o 
 
 S 
 
 o o o 
 
 aao 
 
 vo OI> 
 
 ON ON ON 
 
 oo oo oo 
 
 rt ri rt rt 
 OOOO 
 
 00 ON O rH 
 ON ON O O 
 00 00 ON ON 
 
 rH 
 
 8 
 
 ON 
 
 o o 13 J2 
 oooo 
 
 rN re <* vo 
 
 SN ON ON ON 
 
 U 
 
 O rt 
 
 oo 
 
 <+- 
 
 O 
 
 0) 
 
 2 
 "rt 
 > 
 
 
 
 
 
 1 
 
 ON O 
 vo vo 
 
 r-l 
 
 9< 
 
 
 >n 
 
 j,J 
 
 vc' 
 
 
 nj 
 
 #* 
 
 | 
 
 
 O 
 
 
 
 
 S 
 
 
 
 
 3 
 
 re O 
 00 vo 
 
 C 
 
 
 l/l 
 
 
 
 
 1 
 
 T^ !> 
 
 VO 
 
 
 "S 
 
 <& 
 
 
 
 a) 
 
 3 
 
 O 
 
 go 
 
 C 
 
 M 
 
 a 
 
 M t^ 
 
 10 
 
 a 
 
 
 rH 
 
 
 Ui 
 
 
 
 
 
 a 
 
 JC 
 
 
 
 en 
 
 4-> 
 
 CO 
 
 3 
 
 
 
 X 
 u 
 
 a 
 
 O 
 
 O O 
 vo <O 
 
 
 
 0) 
 
 a 
 
 
 o 
 
 ,& 
 
 *J 
 
 b 
 
 m 
 
 r-l 
 
 Wi 
 
 iU 
 
 Hi 
 
 
 
 a 
 c 
 
 
 
 
 3 
 
 1> 
 
 B 
 
 00 O 
 ON vo 
 
 00 
 
 -1- 
 
 a 
 
 V 
 
 & 
 
 3 
 
 rH r-l 
 
 
 j3 
 
 
 m 
 
 
 a 
 
 
 
 
 ^ 
 
 s 
 
 4- O 
 * vo 
 
 8 
 
 3 
 
 cd 
 
 
 
 
 rO 
 
 3 
 
 rH rH 
 
 
 2g 
 
 a rH 
 
 lanure 
 
 M O 
 t^ M 
 
 Vo'rH 
 
 VO 
 
 1.S 
 
 rt -d 
 
 &l 
 
 .2) 
 
 
 
 
 2^ 
 
 D 
 
 
 
 o M 
 
 S 
 
 3 
 
 S8 
 
 VO 
 
 X^ 
 
 U Wi 
 
 be 
 
 
 
 s* 
 
 V 
 
 
 
 O 0) 
 
 J 
 
 
 
 
 sS 
 
 
 
 
 l>t 
 
 
 
 
 to * 
 
 
 
 
 (J CU 
 
 
 
 
 > p 
 
 LJ U 
 
 
 
 
 i 
 
 C 
 
 .2 
 
 v> 
 
 Wi 
 
 
 c js a 
 
 *j O O 
 
 rt-J* 5 
 
 O TO O 
 
 S 
 -o 
 
 ri 
 
 vo W 
 
 f. 
 
 0- 
 
 
 O - 
 
 Wi o 
 > JJ fc 
 
 B* 
 
 -M 
 
 C 
 
 S 
 
 7-1 <u 
 
 (fi Wi 
 
 C X 
 
 o 
 
 re 
 
 c 
 z 
 
 <t g. ^ 
 
 |_^1 
 l^s 
 
 ccHfa 
 
 13 
 
 <u 
 
 ~ 
 H 
 
 t/3 **-! 
 (C 4-> 
 
 O cfl 
 U O 
 
 "a 
 be 
 
 t! 
 
 # -T--M- 
 
 
 OO 
 
 <5 
 
 
1908.} 
 
 THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 339 
 
 o 
 
 
 VO 
 
 > 
 
 3 g 
 V O 3 
 
 P -c '35 
 
 ON ON 
 C-l vc 'O vo ON 
 
 >O 
 
 v * "C 
 
 S D 1> 2 
 
 o 
 
 * 
 
 I-H 
 
 rO 
 
 ro 00 M 
 rO ON 1> 
 
 <O 
 IO 
 
 .5 0.$ 
 ^oJ5 
 
 .C 
 
 ao. 
 
 vo ro TH 10 r-( 
 
 VO ON1> 
 
 ?>pl 
 
 3~! 
 a s - 
 
 oo 
 
 i-H 
 
 T-l 
 
 n 
 
 l^ 
 
 M 
 
 3 
 
 l> O\ * 
 
 VO 
 
 a 
 
 2 S 
 
 4J O 3 
 
 S-C '35 
 
 ro M 
 
 00 vo 00 O ON 
 
 Efl 
 
 e 
 
 U .. O 3 
 
 rt <U S .-1 
 
 i-H 
 
 o 
 
 00 
 
 ti 
 
 rO OM> 
 
 VO 
 lO 
 
 J o3 
 
 > X J 
 t 1 O -M 
 
 ^ 2 
 
 0.0. 
 
 vo rO * <O rH 
 vo ON t> 
 
 aj*i 
 
 51^ o-2 
 
 fl & 2 
 
 P. Oc 
 
 rO 
 
 TH 
 
 i-H 
 
 0^ 
 M 
 
 00 
 
 * TH rj- 
 
 
 
 eo 
 
 2 6 
 
 8 a; 0.5 
 3 n ** to 
 
 * iO 
 
 t 
 
 i.M 
 
 vo 
 
 -t- 
 ri 
 
 8 
 
 TH O VO 
 ro O l> 
 TH 
 
 
 
 he C O. at 
 
 w^gj 
 
 a = S 
 o<o. 
 
 t> rO O "* .H 
 
 VO ONt^ 
 
 I'll 
 j ii 
 
 i 1 
 1-1 
 1-1 
 
 8 
 
 
 
 t^ 
 
 <* n ro 
 
 >o 
 
 H 
 
 3 
 
 c 
 
 <u o 
 c 
 
 oo ci 
 
 iH 00 'O 00 VO 
 
 
 
 V S 
 
 S S* 
 
 TH 
 
 k 
 
 -t- 
 
 ro 
 
 i-H IO t^ 
 
 ro OM> 
 
 s 
 
 .a o, 
 Ug 
 
 A 
 
 a. 
 
 3 M ^S^ 
 
 c E a 
 
 rt ^ te 
 
 ^ J 
 
 O. 
 
 O 
 
 i-H 
 i-H 
 
 VC 
 ^C 
 
 <f:- 
 
 VO 
 
 ON O VO 
 
 
 
 at 
 
 e 
 
 is* 
 
 * TH 
 
 00 ON ON Tf t^ 
 
 M 
 
 2 
 6 2 
 
 >r 
 
 I- 
 
 -t 
 
 ro 
 
 M t^ >O 
 
 rO OM> 
 
 * 
 
 10 
 
 P- 
 
 M J3 
 
 O. 
 
 M M * * tH 
 
 vo ON r> 
 
 flf 
 
 H X 
 
 O. 
 
 3 
 ,-H 
 
 vo 
 
 
 
 ffj 
 
 iO 
 
 VO * rO 
 
 * 
 
 
 
 s 
 
 ro vo 
 
 oo vo ri o IH 
 
 D 
 
 t-i m 
 3 g 
 
 TH 
 
 
 
 ro 
 
 00 ON 00 
 rO O> I> 
 
 * 
 
 UJ 
 
 rt 
 
 ri d ON o TH 
 
 VO 00 1> 
 
 Bj r5 
 S 
 
 I-H 
 
 O 
 
 1-H 
 
 ON 
 'O 
 <f: 
 
 * 
 
 ON OM 
 
 I> 
 
 0> 
 
 S <u 
 3 S 
 
 T}- vo 
 
 Tf Tt l^ Tf ON 
 
 V 
 
 S o 
 
 !l! Q 
 
 -1- 
 
 LO 
 
 "t 
 
 ro 
 
 M M ro 
 
 rO OM> 
 
 S 
 
 &S3 
 
 <u 
 
 a 
 
 00 CN ro * 
 
 iO 00 VO 
 
 gj 
 
 0) ^H 
 
 h4 
 
 1^ 
 
 oo 
 
 ri 
 'O 
 
 M 
 
 ro 
 
 ON fH vo 
 
 oo 
 
 V 
 
 a 
 
 -4- vo H vo 00 
 
 u 
 u 
 
 3 
 
 * 
 
 -t 
 
 ON 
 
 ro 
 
 V0>0 t^ 
 
 C) 00 O 
 
 * 
 
 
 
 * 
 
 ro rxo >o 
 
 lO I> iO 
 
 M 
 
 S 
 
 00 
 00 
 
 ON 
 't 
 > 
 
 M 
 
 ON CM CT\ 
 
 * 
 
 0) 
 
 S 
 
 3 
 
 O vo 
 ro iO M O l> 
 
 <u 
 
 e 
 
 3 
 
 00 
 
 ON 
 O 
 
 S 
 
 M CO ON 
 
 ro 00 O 
 
 * 
 * 
 
 ho 
 
 0) 
 
 ,4 
 
 * ci *" o" 
 
 lO 1> >O 
 
 > 
 D 
 a 
 
 IO 
 
 t^ 
 
 ro 
 't 
 
 
 
 
 over- 
 
 VO 
 
 o 
 
 00 TH 
 * rO O TH GO 
 
 V 
 
 10 
 
 i i 
 
 rO 
 
 O 
 ro 
 
 O ON * 
 ro 00 VO 
 
 ro 
 <* 
 
 
 
 g 
 
 rO <M <O ON 
 
 10 I> Tj- 
 
 o 
 
 % 
 
 g 
 
 
 
 i 
 
 
 
 o -d 
 
 * 
 
 ej 
 
 
 c 
 
 
 
 O 
 K 
 
 "o 
 
 s 
 
 333 
 42 ,0 J2 
 
 c~ s" c 
 
 _ _ u 
 O O O 
 
 OQO 
 
 1C vo t^ 
 
 ON ON ON 
 X 00 CO 
 
 1898 Cowpeas, (no recor 
 1899 Oats, (no record) . 
 1900 Cowpeas, (no recor 
 1901 Corn, bu 
 
 ( Partial soil 
 1902 treatment 
 ( begu 
 
 at 
 
 52 
 O c 
 
 o 
 
 SH- 3 s - 1 - 1 
 
 fe' -' ' 
 T > c M" > 
 
 rt 5 o rt o 
 OOOOO 
 
 fN ro * 10 vo 
 
 O O O> O O 
 ON ON ON ON ON 
 
 ( Complete soil 
 1907 -j treatment 
 f begi 
 
 3 
 ,C 
 
 
 
 r o 
 
 i 
 
 T I 
 
 a 
 
 
 LI 
 
 
 
 u 
 o 
 Lj 
 
 J3 
 to 
 
 3 
 
 o 
 o 
 _n 
 
 "rt 
 > 
 
 
 
 
 
 4-* < 
 
 rt M 
 
 _C 
 
 
 
 
 
 5 v 
 
 
 
 
 
 Ja 
 
 
 
 
 
 "O T-J 
 
 
 
 
 
 rt ri 
 
 
 
 
 
 o P 
 
 
 
 
 
 O * 
 
 
 g 
 
 
 
 at 
 
 
 3 
 
 00 
 
 o 
 
 Q) O 
 
 
 Potassi 
 
 * vo 
 
 TH 
 
 1 
 
 1 = 
 
 ^ ri 
 O. n 
 o 5 
 
 i^ O p t 
 
 
 
 
 
 0^0 
 
 
 a 
 
 
 
 
 
 :assiu 
 
 t- vo 
 
 rO 
 I- 
 
 -t 
 1 
 
 > (U 
 ^O 3 C 
 
 Tj 
 
 
 o 
 
 ^ 
 
 1 
 
 ZC W ^ 
 
 
 DH 
 
 
 
 S c 
 
 
 to 
 
 3 
 
 
 
 -j- O< u 
 o 
 
 
 O 
 
 TH O 
 
 VO vo 
 
 ON 
 X 
 
 . rt fe. 
 
 
 O. 
 
 VO t> 
 
 
 S 
 
 c 
 
 CO 
 
 O 
 
 
 
 8 ^ 
 
 .2 
 
 S 
 
 
 
 o> o *CL, 
 
 .~ti 
 
 at 
 
 
 
 5 a; t^ 
 
 2 
 
 3 
 
 
 
 MH .t3 *^ 
 
 3 
 
 O 
 
 SO 
 VO 
 
 10 
 
 S3 S 
 
 x 
 
 0. 
 
 (M 
 
 TH 
 
 10 
 
 .2 a, n 
 
 o 
 
 O 
 
 
 
 rH *"^ 
 
 ri 
 
 
 
 
 S "^ 'O 
 
 <U 
 
 CU 
 
 
 
 43 >. U 
 
 1 
 
 o 
 
 4H 
 
 0) 
 
 S 
 
 TH O 
 
 ON vo 
 
 ? 
 
 '1 a^ 
 
 " 0) <U 
 
 -M 3 X 
 
 c 
 
 0) 
 
 s 
 
 D 
 
 -" 
 
 ON TH 
 
 oo 
 
 | g .S 
 
 
 
 
 
 x o t: 
 
 "ri 
 
 -t-J 
 
 0> 
 
 vo O 
 
 1 C 
 
 - fe 
 
 Cfl 
 
 a 
 
 00 vo 
 
 
 "rt 'O 5o 
 
 'ri 
 
 a 
 
 00 r-i 
 
 ^ 
 
 g ri rt 
 
 'o 
 
 
 t& 
 
 
 S >s "^ 
 
 n 
 ri 
 
 <u 
 
 M-H-+ 
 
 ^^ 
 
 a II 
 
 s 
 
 3 
 
 t- O 
 
 t> VO 
 
 TH 
 
 
 Izj 
 
 a 
 
 
 
 rti ^ *^^ 
 
 hH 
 
 ri 
 
 ri 
 
 ri 
 
 'O o >% 
 
 
 ^ 
 
 w 
 
 
 ty ^ ,O 
 
 
 <u 
 
 1 
 
 M O 
 
 t** ^P 
 
 n 
 
 "S "3 
 
 
 he 
 
 TH rH 
 
 ri 
 
 n ^ 
 
 
 a> 
 
 T 
 
 1 
 
 j_j O o 
 
 ^ O nH 
 
 
 
 
 
 t 2 ^3 
 t> ri ^ 
 
 
 
 
 
 o " 
 
 
 
 
 
 O< D 
 
 
 
 
 
 
 
 
 
 
 Ui ^ Ui 
 
 
 
 
 
 M ri 
 
 
 j. 
 
 0) 
 
 
 JS "0 - 15 
 
 
 .2 
 
 r*> * 
 
 
 -H -2 c 
 
 
 'S 
 
 at 
 
 j 
 
 2 S & 
 
 E * 
 
 
 T3 
 
 ri 
 
 "Vg 
 
 c" 
 
 Li 
 
 
 
 >> 
 
 4= 
 
 ij 
 
 
 ro 
 
 3 -C .S 
 he a) > 
 (1) n ri 
 
 
 "a 
 
 <L> 
 
 /: V-i 
 
 C JS 
 
 
 
 "0 CO 
 
 
 a 
 
 'ri ^ 
 
 S 
 
 S3 ri 
 
 
 ri 
 
 <+H 
 
 'ri 
 
 * 3 3 
 
 
 (L> 
 LI 
 
 H 
 
 M +J 
 O to 
 
 O 
 
 1 
 
 o *o 
 
 0> 
 
 iH 3 
 
340 
 
 BULLETIN No. 125. 
 
 PLATE 5. CORN AFTER CLOVER WITH NO SPECIAL SOIL TREATMENT: PLOT 301, 
 URBANA SOIL EXPERIMENT FIELD, 1907: YIELD 80.5 BUSHELS PER ACRE. 
 
 The complete grain system is first put under way for the 1908 
 corn crop, the equivalent of the clover grown in 1907 having been 
 returned to the legume plots (102, 104, 106, and 108) to be plowed 
 under for corn. The corn stalks will be disked down when seeding 
 to oats and clover in the spring, and the effect of this on a subse- 
 quent crop of corn on series 300 cannot be seen till 1913. Thus, 
 while much valuable information has already been secured from 
 these fields, as shown in this bulletin and in Circular 96 (published 
 in 1905), it should be kept in mind that the full effect of these sys- 
 tems of soil improvement will not be seen for several years. 
 
 THREE- YEAR ROTATION 
 
 In Tables 3, 4, and 5 are reported in detail the crop yields from 
 series 100, 200, and 300, for the 13 years from 1895 to 1907. 
 
1908.] 
 
 THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 341 
 
 PLATE 6. CORN AFTER CLOVER WITH LEGUME-LIME-PHOSPHORUS TREATMENT 
 (GRAIN FARMING) : PLOT 306, URBANA SOIL EXPERIMENT FIELD, 1907 : 
 YIELD 104.6 BUSHELS PER ACRE. 
 
 With few exceptions all yields of grain and hay are recorded 
 in the tables, and a financial statement is also given at the bottom 
 of each table showing the effect of each addition in the soil treat- 
 ment during the last three years, on each series of plots, counting 
 corn at 35 cents a bushel, oats at 25 cents, and hay at $6 a ton. 
 
 It will be seen that but little effect has been produced by sowing 
 legume catch crops in the corn in the three-year rotation, where 
 corn is followed by oats and clover. From 1902 to 1905-6-7, the 
 legume catch crops produced but little benefit on other crops, as 
 shown by comparing plots 2, 4, 6, and 8 with plots 3, 5, 7, and 9, 
 except on the oat crop in 1904 and 1905. 
 
 The effect of the farm manure on each of the three crops is 
 shown only in Table 3 (series 100), the manure on series 200 and 
 300' having benefited only two crops and one crop, respectively. Six 
 tons of manure per acre on series 100 have produced increases in 
 
342 BULLETIN No. 125. [May, 
 
 the three crops amounting to $9.60 per acre, or to $1.60 per ton 
 of manure applied, leaving a profit of $1.30 a ton for the manure 
 of the farm if it can be hauled and spread for 30 cents a ton. Of 
 still greater interest will be the effect on the next three crops of the 
 second application of manure ; (made for the 1908 corn crop on 
 series 100), including any possible residual effect carried over from 
 the previous application. 
 
 Aside from the legume and manure, there is a duplicate test 
 for each addition, and the effect is determined independent of the 
 check plot (No. i). Thus the effect of lime is determined by com- 
 paring plots 4 and 5, not with plot I, but with plots 2 and 3; and 
 the effect of phosphorus is determined by comparing plots 6 and 7 
 with plots 4 and 5, respectively. 
 
 On five plots out of six lime has shown some increase, and on 
 three plots it has paid more than 50 cents per acre per annum, 
 which is more than sufficient to pay for the applications actually 
 made to these plots, but the results vary so greatly with the differ- 
 ent crops and seasons that safe conclusions cannot be drawn until 
 further data are secured. The apparently marked effects on plots 
 304 and 305 are evidently due in part at least to original soil dif- 
 ferences,* indicated in the early records for those plots, as compared 
 with 302 and 303. 
 
 Aside from farm manure the only well established benefit is 
 derived from the application of phosphorus, which has produced a 
 marked increase on every plot and in five cases out of six has much 
 
 *The large amount of data accumulated and reported in the preceding and 
 following pages concerning these plots previous to the beginning of soil treat- 
 ment has suggested, of course, that even small natural soil differences could be 
 detected in the early yields secured under similar conditions of cropping, so that 
 corrections might be made for such natural variations when considering subse- 
 quent yields as affected by soil treatment A careful study of all the results 
 shows, however, that it is very unsafe to try to make any such corrections. That 
 plot A has produced larger yields than plot B for two or three years does not 
 prove that it will continue to do so. In fact, under normal conditions, this relation 
 may be reversed. The larger crops from plot A remove more plant food, and 
 the later crops may be smaller in consequence ; whereas, if smaller crops are 
 removed from plot B in the early years, the yields may be larger than on plot 
 A in subsequent years. 
 
 Several illustrations of this have actually occurred in these experiments. 
 Thus for the three years, 1895 to 1897, plot 406 produced, as an average, 5 bush- 
 els more corn per acre than plot 506, but as an average of the next three years 
 plot 506 produced 2.9 bushels more corn per acre than plot 406. Likewise, a 
 decision based upon the first three years would hold the natural productiveness 
 of plot 407 to be 3.8 bushels higher than plot 507, but the records of the next 
 three years would reverse the decision because for those years plot 407 was not 
 3.8 bushels better but 3.1 bushels poorer than plot 507, as an average. The aver- 
 age yield for the entire six years differs by less than half a bushel for these 
 two plots. (See also the last page of this bulletin.) 
 
 Because of these facts it seems unsafe to try to make any corrections or 
 to use "corrected" results. The data actually secured are correctly reported 
 and if there is reason to believe that any results are untrustworthy they may be 
 discarded. 
 
THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 343 
 
 more than paid for its cost even in 200 pounds per annum of 
 steamed bone meal, in which more phosphorus is applied than is 
 removed from the soil in the crops grown. This, of course, gives 
 promise of some residual effect in subsequent years, more especially 
 for clover, because the land is growing richer year by year in phos- 
 phorus and because clover should not be limited in yield by lack of 
 nitrogen, while corn or oats may be, no matter how much phos- 
 phorus is supplied. 
 
 The very marked effect of phosphorus upon the yield of clover 
 during the last three years, averaging more than 75 percent in- 
 crease, is especially significant, and constitutes probably the most 
 valuable information furnished from these particular experiment 
 fields. 
 
 The addition of potassium has produced . some increase on most 
 plots, but never sufficient to pay for even one-half its 'cost. The 
 effect of potassium indicates the need of more decaying organic 
 matter, which has power to liberate sufficient potassium from the 
 immense total supply in the soil. (Soil samples 59 to 421, whose 
 analyses are reported on page 270 of Bulletin 123 were collected in 
 1901 from series 100 to 700, respectively, and samples 467 to 472 
 from plot 3 of the old experiment field.) 
 
 TWO-YEAR ROTATION 
 
 In Tables 6 and 7 are given data from the two-year rotation of 
 corn and oats on series 400 and 500. 
 
 It will be seen that corn was grown for six years on series 400 
 and 500 before the two-year rotation was begun. The subsequent 
 substitution of oats for corn in alternate years lessens the liability to 
 insect injury and somewhat reduces the draft upon the soil, so that 
 larger corn yields are likely to be secured for a few years than 
 were produced near the close of the six years of continuous corn, 
 even with no increase in the annually available fertility. 
 
 The legume catch crops, as cowpeas seeded in the corn at the 
 last cultivation or clover seeded with the oats, have produced but 
 little effect, and this effect has been a decrease as often as an in- 
 crease in the regular crops. Plot i is apparently slightly better land 
 than plots 2 and 3, as indicated by the crop yields secured previous 
 to the beginning of soil treatment; but a comparison of plots 2, 
 4, 6, and 8 with plots 3, 5, 7, and 9, from 1902 to 1904-5 shows 
 only a small average benefit on the oats. On the other hand, the 
 legume treatment produced noticeably larger yields of corn in 1907 
 than were obtained from the plots to which light applications of 
 farm manure had been applied. 
 
 As a rule lime has produced some increase, but as an average 
 it amounts to but little more than cost. 
 
344 
 
 BULLETIN No. 125. 
 
 [May, 
 
 
 
 CO rH vo 
 
 VO VO ON 1/3 
 
 3s 
 il 
 
 C J3 aj 
 
 N O r-( 
 
 rt 
 
 eg 
 
 o> o 2 
 s3 j: 'S 
 
 H 
 -1 
 
 O I> vo 
 
 -1- 
 
 rH 
 
 -* 
 
 CM 00 VO 
 CN ON*^ 
 
 vo vo vo t^ 
 
 VO *O vo CO 
 
 .5 0U i 
 
 > i/i rt 
 
 *l 
 
 a o, 
 
 vo vo ON 
 vo <* CO 
 
 .5 OH > 
 ag| 
 
 U& 
 
 t^ 00 vo 
 
 vo vo ON 
 
 00 
 
 ?, 
 
 
 
 * * CO 
 
 VO rH rH t> 
 
 SS 
 S.2 
 
 P -C 
 
 vo ON vo 
 
 la 
 Bl 
 
 rH 
 
 9 
 
 vo 
 
 -* 
 
 rH Q M 
 
 CN o t^ 
 
 O vo * * 
 1C VO vo cO 
 
 S CU X 
 
 i4 g * 
 P 
 
 VO 00 vo 
 ^C * CO 
 
 C w G- ) 
 
 -| 
 s -H& 
 
 * 00 rH 
 l> voi> 
 
 ON 
 
 
 
 95 
 
 t^ rH N 
 
 N O * ON 
 
 8 ^ 
 
 1151 
 
 J* 
 
 * _ 
 S 21 
 Ig^-a 
 
 O 00 rH 
 
 -t 
 
 rH 
 
 
 N ON VO 
 
 i> rN d N 
 
 cO vo VO CO 
 
 SJe-a 
 
 ^ te jS 
 
 ^ is. 
 
 5 ^ 
 
 Cu 
 
 M * 
 
 VO * 
 
 Mfl 
 
 ^ !& 
 
 a CM * 
 
 VO VO 00 
 
 10 
 
 s 
 
 
 
 t^ rH CO 
 
 l> TH> ON 
 
 
 
 3 
 V O 
 
 S-c 
 
 z 
 
 vo 00 
 
 
 
 3 
 
 0) VH 
 1- <u 
 
 3 cj: 
 
 * rH VO 
 
 a\ 
 i^ 
 
 
 O CM> 
 
 d ON oo ON 
 
 vo vc vo CM 
 
 .5 OH 
 
 Sjj 
 
 a 
 
 n M 
 
 VO * 
 
 s.S o, 
 
 n) ~ ) 
 fcrt O 
 
 S ,c 
 
 P< 
 
 rH CO 00 
 
 1^ vo vo 
 
 ON 
 
 rO 
 
 M 
 
 1 
 
 rH 00 1> 
 
 t^ ON IO 
 CO OM> 
 
 rH CO O rH 
 /} vo vo cO 
 
 Legume 
 lime 
 phosphorus. 
 
 * 
 
 H ( 
 
 l^ <O 
 
 VO vo 
 
 Legume 
 lime 
 phosphorus 
 
 O rH VO 
 
 oo * 'i- 
 
 VOI^ 00 
 
 * 
 
 rH 
 
 oo' 
 
 
 
 
 
 ON vo O 
 
 ON ON1> O 
 
 
 
 a 
 
 r-l O 00 
 
 <u 
 
 w 
 
 3 1) 
 
 O rH VO 
 
 g 
 
 5 
 
 $S 
 
 VO rH vo VO 
 vo vo vo cO 
 
 .^ 
 
 h4 
 
 N 00 VO 
 VC * CO 
 
 91 
 
 S^ 
 
 cN CO vo 
 
 l> vo VO 
 
 9 
 
 
 O 00 1> 
 
 fN O ON cM 
 
 e 
 
 6 aj 
 3 S 
 
 M r-t VO 
 
 u 
 
 I, 
 
 3 - 
 
 rH t> ON 
 
 Tf 
 
 r) 
 
 _ 
 
 o ON -H 
 
 CO 00 > 
 
 iO * co iO 
 
 iO vo VO CO 
 
 bog 
 
 JF 
 
 rH UJ ON 
 VO * CO 
 
 || 
 
 328S 
 
 rH 
 
 
 8 
 
 r-t VO 00 
 
 ON ON O iH 
 
 V 
 
 8 
 
 VO N rH 
 
 V 
 
 h 
 
 3 
 
 * vo rf 
 
 1^ 
 
 VO 
 
 
 I>1> 00 
 
 n oo vo 
 
 IO rH VO CO 
 
 VO vo i/> CO 
 
 ^ 
 
 ON O Tf- 
 vo vo CO 
 
 i 
 
 S 
 
 ON t^ ON 
 vo vo vo 
 
 oo 
 |g 
 
 
 -fr CO O 
 
 VO t^ O vo 
 
 V 
 
 i 
 
 3 
 
 vo ON * 
 
 o> 
 
 ON * ON 
 
 fe 
 
 _ 
 
 rH VO t> 
 
 CO 00 VO 
 
 CO 00 J> * 
 vo iO vo CO 
 
 So 
 u 
 
 I> C<1 00 
 
 vo * CO 
 
 ho 
 
 V 
 HJ 
 
 fN rf ON 
 
 VO vo vo 
 
 g 
 
 rH 
 
 * CN CM 
 
 rH O 1> ON 
 
 <u 
 
 
 
 00 O 
 
 0) 
 
 C 
 
 *r> * 
 
 -M- 
 
 iO 
 X 
 
 <t 
 
 tH 00 ON 
 CO OC 
 
 vo CO ON 00 
 vo VO vo CO 
 
 
 
 
 
 M t^ vo 
 vo -f CO 
 
 o 
 
 
 
 ON ON 00 
 vo vo vo 
 
 OC' 
 rO 
 
 ; 
 
 
 
 
 * 
 
 
 C 
 
 
 05 
 
 
 : ' : 
 
 : i : i 
 
 d 
 
 -M 3 
 
 ^ C tc 
 
 
 3 
 ^3 -M be 
 
 O C 0) 
 
 
 0. 
 O 
 
 
 . . 
 
 . . . . 
 
 '8 c^ 
 
 [fl C " 
 
 
 gfl 
 
 fl) -*- 1 
 
 
 o 
 
 t- 
 
 
 333 
 .0,0,0 
 
 3333 
 
 XI X3 > & 
 
 '4 
 
 333 
 ,0.0,0 
 
 ^J rt 
 Pug 
 
 E i 
 
 3 3 g 
 
 XI > J3 
 
 *J 
 
 -*-> 
 
 CO 
 
 
 C C C 
 
 a c a n 
 
 n) 
 
 CC C 0) 
 
 o 
 
 CMC" 
 
 rf 
 
 o 
 
 fc 
 
 -*-> 
 
 o 
 
 s 
 
 O O O 
 
 000 
 
 IT) VO I> 
 
 ON ON ON 
 00 00 00 
 
 O O 
 
 OOOO 
 
 00 ON O r-i 
 
 CN ON Q Q 
 00 00 ON ON 
 
 CH 
 
 M 
 
 g 
 
 rt o rt 
 
 ooo 
 
 n co * 
 
 ON ON ON 
 
 O 
 
 vo 
 
 O 
 
 ON 
 
 O rt O 
 OOO 
 
 iO vo t> 
 
 ON ON ON 
 
 H- 
 
 o 
 
 CJ 
 _3 
 
 "(3 
 
 > 
 
 
 
 
 5 
 
 
 3 
 
 
 
 
 
 '3 
 
 
 Cl 
 
 
 U) 
 
 ' vo 
 
 VO 
 
 
 o 
 
 1 
 
 
 
 PH 
 
 
 
 sium 
 
 SS 
 
 8 
 
 
 0) 
 
 rt 
 
 CO vo 
 ? 
 
 00 
 
 . 
 
 O 
 
 
 
 13 
 
 rH 
 
 
 S 
 
 
 
 E 
 
 X 
 
 
 O 
 
 3 
 
 
 a 
 
 V* 
 
 o 
 
 S8 
 
 
 
 V 
 
 > 
 
 a 
 
 ' vo 
 
 -t 
 
 o 
 
 XI 
 
 o 
 
 ^ 
 
 
 nl 
 
 
 
 
 fe 'O 
 
 ON D 
 
 3 
 
 
 rH .JH 
 
 C ^ 
 
 Q 
 
 ~> Q 
 
 
 
 - >s 
 
 a 
 
 VO vo 
 
 ^ 
 
 tiS 
 
 c S 
 
 o 
 
 
 
 
 *s >% 
 
 
 
 c qn 
 
 DH 
 
 
 ? 
 
 
 
 (0 u> 
 
 V 
 
 Mg 
 
 X 
 
 M 
 
 . . 
 
 
 3 (0 
 
 3 
 
 ^^ 
 
 
 C c 
 
 
 
 
 
 g J3 
 
 & 
 
 
 
 
 
 
 ^ o c 
 
 1 
 
 'l^ 
 
 r 
 
 C A rt 
 ^-C 
 
 3 
 
 ^^ 
 
 C) 
 
 S-T3 * 
 
 o 5 fe 
 
 
 
 o nJ ? 
 
 D 
 
 
 (U 4> 1) 
 
 3 
 
 ooo 
 
 rH CM 
 
 X 
 CO 
 
 -sl 
 
 C 
 1 
 
 ^^ 
 
 rH 
 
 fl M-t 
 
 .S^S 
 
 n3 S * 
 
 
 
 fl) *>^ 4^ 
 
 a 
 
 3 
 be 
 
 ^^ 
 
 X 
 
 VV r^t "^ 
 
 -o > g 
 
 <u rt o 
 
 **: 
 
 D 
 
 ^^ 
 
 
 "S rt "" 
 
 ^J 
 
 1 
 
 
 >- h > 
 
 
 ' 
 
 tr; "S *rl 
 
 
 
 *^ KS V 
 
 28 
 
 
 
 "U T^ ^ 
 
 
 
 ^ rH- 
 
 
 
 |o ? 
 
 O i_i 
 
 | 
 
 t : 2 
 
 f*% * rt 
 
 "- ) ^ 
 
 B C.O 
 
 <U^ 
 
 1^ 
 
 S 
 -o 
 
 rt 
 
 vo f3 
 
 S^U 
 
 u-S-c 
 
 Xi 
 
 "c 
 o> 
 
 rH ^ O 
 
 B-o g 
 
 ^1x1 
 ^*^H 
 
 s 
 
 bC O "I 
 ,j~ w 
 
 * * ++ 
 
 "rt 
 
 tfl -l-> 
 
 
 
 O * H- 1 
 
 
 ^ 
 
 w o <u 
 
 
 H 
 
 00 .? 
 
 
1908.] 
 
 THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 345 
 
 o 
 
 ON OM- 
 
 VO I> ON 00 
 
 3s 
 
 ' *" 
 0) 3 
 fl J3 'S 
 
 rO 00 rH M 
 
 gX M 
 
 a <y ~ 
 
 ON * 
 
 S 
 
 to 
 
 c<) vo o 
 
 C<1 & vo 
 
 CO 00 CO 00 
 * vo iO * 
 
 S OH t/J 
 
 ^45 
 |l 
 
 iO rq t^ M 
 
 VO vo to * 
 
 illi 
 
 J fi i 
 
 * * 
 vo * 
 
 ro 
 fO 
 ^ 
 
 
 
 O ON to 
 
 t^O rHO 
 
 3 
 
 2S 
 
 V o S 
 
 843*3 
 
 O rH O NO 
 
 I 6 
 
 V-i ^3 
 
 a g^' S 
 
 VO VO 
 
 rH 
 
 to 
 
 
 * to CO 
 N ONF- 
 
 O O CO M 
 * l> VO LO 
 
 rj P_ i 
 4 tfi rt 
 O -M 
 
 S 
 aa 
 
 O C^rO VO 
 
 I> VO vo LO 
 
 ^43 ^! 
 
 S o o 
 
 It* 
 
 3% 
 
 S 
 
 <f: 
 
 s 
 
 <t vo N 
 
 * Tj- rH O 
 
 * rt 
 
 El 
 
 t-i r( 
 
 S v o.2 
 
 * 00 VO M 
 
 s 
 
 <U VH 2 
 
 1 g-sl 
 
 tO rH 
 
 00 
 
 rH 
 
 05 
 
 cO M O 
 N ON I> 
 
 O O rH CO 
 T- t> vo LO 
 
 &.i^i 
 
 ^"o^ 
 
 >-l ~ O 
 
 a^ 
 
 00 00 rO rH 
 VO vo -O vo 
 
 M.S Ja rt 
 
 1) ^H o -M 
 
 a *. 
 
 00 ON 
 LO ro 
 
 S 
 
 
 cO ON <* 
 
 rH rH ON CO 
 
 to 
 
 3 
 
 gg 
 
 8-fl 
 
 M ri M CO 
 
 09 
 
 hi 
 
 00 CO 
 
 0^ 
 
 
 
 3 
 
 * 00 * 
 fN ONl> 
 
 00 rH O 00 
 iO t> vo VO 
 
 .t3 a, 
 
 a 
 
 A 
 
 a 
 
 vo f3 rO rO 
 
 VO I> vo vo 
 
 ail 
 * ! 
 
 a 
 
 rH rH 
 vO * 
 
 rH 
 rO 
 
 ^ 
 
 * 
 
 vo CO t> 
 
 t> O f) vo 
 
 N 
 
 S 2 
 
 2- 
 
 vo <* vo * 
 
 
 
 2 
 l 
 
 CO 00 
 
 VO 
 CO 
 
 
 oo * * 
 
 fN ONI> 
 
 vo vo *f) to 
 
 S.fe| 
 
 J^^ 
 
 a 
 
 rH rO rH Tj- 
 
 vo VO I> vo 
 
 bcG O- 
 
 ^^o 
 
 M X 
 
 a 
 
 CO 00 
 VO CO 
 
 1-1 
 ro 
 
 <y> 
 
 v? 
 
 rH O <* 
 
 rHOrJ-M- 
 
 D 
 
 S 
 
 M rH ON rH 
 
 u 
 
 gfi 
 
 00 00 
 
 S 
 
 i/) 
 
 ON vo N 
 M ONt^ 
 
 if) vo iO LO 
 
 ^4 
 
 l> M 00 00 
 10 10 * LO 
 
 nj;3 
 
 S 
 
 l> CO 
 O CO 
 
 S 
 
 
 -t ON * 
 
 I> rO -t O\ 
 
 u 
 
 S 
 
 3 S 
 
 vo ON O 00 
 
 0) 
 
 Ba; 
 ? S 
 
 ON rH 
 
 ON 
 
 CO 
 
 3 
 
 t^vo l- 
 
 Cl 00 VO 
 
 rH rH rH If) 
 If) VO IO * 
 
 hc^ 
 
 a> ^ 
 
 a 
 
 * VO VO M 
 iO * * LO 
 
 M.H 
 
 OJ ^ 
 
 a 
 
 00 ON 
 
 Tf N 
 
 S 
 <f) 
 
 CO 
 
 rf C3 CO 
 
 * O\ * 00 
 
 0) 
 
 rO M M vo 
 
 <u 
 
 S 
 
 CO t> 
 
 5 
 
 
 
 ON VO 00 
 M 00 VO 
 
 Tt- rH rH * 
 10 VO IO * 
 
 fe 
 
 IO CO VO rH 
 iO * * to 
 
 cd 
 S 
 
 * ON 
 
 LO M 
 
 VO 
 n 
 
 7 
 
 g 
 
 * rH 1> 
 
 O O rH O 
 
 0) 
 
 a 
 
 T|- M vo vo 
 
 0) 
 
 a 
 
 3 
 
 ONTf 
 
 w 
 10 
 
 
 r-( 00 ON 
 rO 00 VO 
 
 t> M * VO 
 iO VO iO * 
 
 be 
 
 0) 
 
 h4 
 
 00 ro M to 
 iO * iO iO 
 
 bo 
 U 
 
 u 
 
 rH ON 
 
 LO CJ 
 
 LO 
 
 n 
 
 ff: 
 
 l-H 
 
 O VO vo 
 
 IO OM>iO 
 
 D 
 
 n 
 
 VO to OtO 
 
 ID 
 
 i 
 
 CO * 
 
 * 
 
 LO 
 
 LO 
 
 t^ oo ON 
 
 CO 00 VO 
 
 ON ^J" oo 00 
 to voi/) * 
 
 Z 
 
 I> M ON M 
 iO * to <O 
 
 K 
 
 oo oo 
 
 LO fN 
 
 t^ 
 
 M 
 fj 
 
 
 
 
 ^ C bo 
 
 ! i i I 
 
 a 
 
 "3-M 3 
 
 O e bfl 
 f r, ?r 
 
 
 r. 
 
 a 
 
 O 
 
 
 3 3 3 
 .0 X! JD 
 
 3 s 3 a 
 
 .0 ^2 X) > 
 
 r< <U jf 
 O rt X 
 
 H<Q 
 
 .IS 
 
 -2 v< 
 
 3 g 3 S 
 Xl^ ,0,0 
 
 o> S- 
 
 sl 
 ll 
 
 ^ 3 
 
 a ,3 
 
 
 
 ^ 
 
 tfl 
 
 
 CSC 
 
 G n" c" 
 
 cd 
 
 Q to" fl tc 
 
 
 
 fl" ta 
 
 ^ 
 
 6 
 g. 
 
 "o 
 
 s 
 
 O O O 
 
 OOO 
 
 tO VO I> 
 
 0*1 ON ON 
 
 oo oo oo 
 
 o o o s 
 OUOO 
 
 00 ON Q rH 
 00 00 O^ ON 
 
 CH 
 
 | 
 
 O cd o rt 
 OOOO 
 
 n to * *o 
 
 ^ c^ ^ ^ 
 
 O 
 
 o rt 
 OO 
 
 vot^ 
 
 3\ o^ 
 
 H 
 
 
 V 
 
 3 
 
 i5 
 
 > 
 
 
 
 
 
 
 Potassium 
 
 to o 
 n- q 
 
 iO to 
 
 f 
 
 to 
 
 rt- 
 
 
 1 
 
 
 Potassium 
 
 00 Q 
 VO O 
 
 T 
 
 CO 
 
 1 
 
 c 
 
 
 
 Phosphorus 
 
 88 
 
 COLO 
 
 c 
 
 1-1 
 
 1 
 
 "o 
 ri 
 
 0) 
 
 Phosphorus 
 
 t^ Q 
 
 S 
 
 o 
 
 HH 
 
 "s 
 6 
 
 J 
 
 LO O 
 
 (N O 
 
 M rH 
 
 LO 
 
 M 
 
 "S 
 
 CC 
 
 'o 
 
 a 
 
 3 
 
 T 
 
 rO 
 Cl 
 
 U 
 
 3 
 
 s 
 
 Manure 
 
 00 O 
 rH rH 
 
 T 
 
 ri 
 
 
 Legume 
 
 88 
 
 ro 
 1 
 
 
 
 
 
 
 a 
 
 o 
 
 -5 
 o 
 
 ri 
 
 "S 
 
 <u 
 
 "S 
 
 H 
 
 Gross gains 1906-7;2 yrs. 
 Cost for two years 
 
 to 
 
 
 c 
 
 V 
 
346 BULLETIN No. 125. [May, 
 
 Phosphorus has nearly always produced an appreciable increase 
 on both corn and oats, and as an average of twenty-two tests, cov- 
 ering the six years, the value of the increase is greater than the 
 cost of the phosphorus in steamed bone meal, and the amount of 
 phosphorus applied (25 pounds per acre for each year) is nearly 
 twice as much as removed in the cropsj so that the soil is being en- 
 riched quite rapidly in phosphorus. 
 
 It must be understood, however, that phosphorus alone cannot 
 make the soil highly productive, because the nitrogen limit is but 
 little higher than the limit due to phosphorus, and the yields cannot 
 be very high unless ample provision is made for both elements. 
 The three-year rotation makes better provision for nitrogen, and 
 in consquence the crop yields are not only larger but the phos- 
 phorus also becomes more effective. 
 
 Thus, as an average of the last three years, plot 4 (without 
 phosphorus) has produced 63 bushels of corn per acre, in the two- 
 year rotation, and 72 bushels in the three-year rotation, while plot 6 
 (with phosphorus) has averaged 72 bushels per acre in the two- 
 year rotation, and 90 bushels in the three-year rotation. In other 
 words, phosphorus has made an average increase of 18 bushels per 
 acre in the three-year rotation, but only 9 bushels in the two-year 
 rotation. Smaller but nearly proportionate differences have been 
 made as an average of all tests with corn and oats during the last 
 three years, larger yields having been secured in the three-year ro- 
 tation and the difference between that and the two-year rotation 
 being still greater where phosphorus is applied to both. 
 
 As an average of all tests during the past three years the value 
 of the crops on plots 6 and 7 has been about one dollar an acre a 
 year greater for the three-year rotation than for the two-year ro- 
 tation, counting corn at 35 cents a bushel, oats at 25 cents, and 
 clover hay at $6 a ton. At higher prices the difference in favor of 
 the three-year rotation would be still greater. Furthermore some 
 clover seed has been secured in the three-year rotation, but we have 
 begun to try to save clover seed only recently and have as yet too 
 little data on that crop to justify further discussion of it. 
 
 Potassium has actually reduced the yield as an average of all 
 tests in the two-year rotation during the entire period of six years, 
 the average decrease amounting to 2 bushels of corn and 4 bushels 
 of oats per acre, aside from the total loss of the cost of the potas- 
 sium applied. 
 
 CONTINUOUS CORN IN COMPLETE FERTILITY EXPERIMENTS 
 
 In Tables 8 and 9 are reported the corn yields from series 600 
 and 700, where experiments are in progress which include the use 
 of commercial nitrogen, phosphorus, and potassium, singly and in 
 
1908.] THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 347 
 
 all combinations. In all tests there are duplicate plots with the 
 same kind of treatment. Besides this two plots remain untreated 
 (601 and 602), two are treated with lime only (603 and 604), and 
 two plots are now being given "extra heavy" treatment, including 
 farm manure. 
 
 Corn is grown every year in these complete fertility experi- 
 ments, a part of the investigation being to ascertain how much of 
 the rapid decrease in yield resulting from continuous corn growing 
 is due to insect injuries and how much is due to other causes, such 
 as depletion of decaying organic matter and lack of available plant 
 food. In other words, the experiments on series 600 and 700 are 
 designed, not to demonstrate any good system of farming, but 
 rather to secure definite information concerning insect injuries, 
 plant food requirements, and possible injurious effects of too much 
 corn-growing on the same land, as contrasted with a good crop 
 rotation such as is practiced on series 100, 200, and 300. 
 
 Plots 60 1 and 602 serve as duplicate check plots on which corn 
 is grown every year with good preparation of the land and with 
 good cultivation of the crop, but the entire crop is harvested and 
 removed, and no manure or fertilizer is returned. (See Table 8). 
 
 On plots 603 and 604 a duplicate test is made to determine the 
 effect of applying lime, and on the other six plots in the 600 series 
 are duplicate tests with each of the three elements, nitrogen, phos- 
 phorus, and potassium, the effect of each element being determined 
 by comparing the results obtained with the yields of plots 603 and 
 604. 
 
 On the 700 series (Table 9) a duplicate test is made of every 
 possible pair of elements and of all three elements together (plots 
 707 and 708), and "extra heavy" treatment is applied to the last 
 two plots (709 and 710). 
 
 It will be seen that no treatment was applied to any of the plots 
 previous to 1901. From 1901 to 1905 nitrogen was applied at the 
 rate of 100 pounds per acre a year. That is less than the nitrogen 
 contained in a 7O-bushel crop of corn. It soon became apparent, 
 however, that that amount was not sufficient to meet the nitrogen 
 requirements of the crops actually grown and that the crop yields 
 on certain nitrogen plots were decreasing because of insufficient 
 nitrogen, consequently, beginning with 1906, the annual applica- 
 tion was increased to 250 pounds per acre of the element nitrogen. 
 This provides sufficient nitrogen for a hundred-bushel crop of corn 
 and allows for a loss in drainage water of 40 percent of the nitro- 
 gen applied, a loss which is no greater than commonly occurs where 
 commercial nitrogen is used. 
 
348 
 
 BULLETIN No. 125. 
 
 [May, 
 
 
 
 Ovo * 
 
 LO vor- 
 
 V 
 
 - v> 
 
 VO VO 00 " r-t 
 
 a 
 
 * .2 
 
 i- 10 
 
 00 ON 
 
 VO 
 
 O VO W 
 co OMr^ 
 
 rO CO CO 
 
 vo vo vo 
 
 Jl 
 
 3 42 
 
 
 
 PH 
 
 vo vo vo O I> 
 rO vo -* vo * 
 
 1 s 
 
 ^ ^ 
 
 PH 
 
 oo t> 
 
 rO rO 
 
 ON 
 
 TH <! rO 
 
 ON r-l O 
 
 s 
 
 0) 
 
 I>l> ON TH 00 
 
 S 
 
 .3 
 
 rO rO 
 
 s 
 
 t^~ ri ON 
 
 M ON VO 
 
 rO ON * 
 LO vo vo 
 
 1 8 
 
 a 3 
 
 OH 
 
 M * M ^ N 
 
 rO vo * rO * 
 
 3 
 
 4 ri 
 
 3 
 
 a 
 
 * cq 
 rO CO 
 
 oo 
 
 TH VO r-( 
 
 VO *!> 
 
 go 
 
 3 
 
 c 
 
 
 
 fl X 
 
 O CO N 00 ** 
 
 
 
 3 
 L 
 
 w 2 
 
 eJ3 
 
 ON O 
 
 vo 
 
 t- TH VO 
 
 cNJ ON VO 
 
 N 00 O 
 Tf vo vo 
 
 "> tfl 
 
 H 
 
 X 
 
 a 
 
 S ro n vo l> 
 
 r*J VO iO * f<5 
 
 a 
 i 
 >4 o 
 x 
 (X 
 
 T- rq 
 *rO 
 
 
 
 O O TH 
 
 ON ON vo 
 
 <n 
 3 
 C 
 a> o 
 SJQ 
 
 VO O O^ ON ON 
 
 : 
 
 2 
 S 
 
 TH CO 
 
 s 
 
 O Tj- TH 
 
 co ONI> 
 
 00 TH VO 
 
 * vo vo 
 
 .- OH 
 
 a 8 
 ^ 
 
 PH 
 
 r<3 ci >! VO O 
 rO VO * vo * 
 
 PH 
 "1 tfl 
 
 ^ J 
 
 a 
 
 I> vo 
 
 * CO 
 
 
 CO M ON 
 
 N r<5 * 
 
 1 
 
 ON 00 VO O\ VO 
 
 c 
 
 si 
 
 VO TH 
 
 
 * co co 
 
 CO ON l^- 
 
 cr\ vo o 
 10 vc vo 
 
 S o 
 
 a| 
 
 a 
 
 rO *!> M 00 
 
 rO 10 * vo * 
 
 3.1 
 
 a 
 
 <t Tj- 
 
 vo vo 
 
 V2 
 
 O VO * 
 
 OM> ro 
 
 a 
 
 a^ 
 
 O\ ON VO * O 
 
 a 
 <u s 
 
 60C 
 Q 
 
 THO 
 
 Co 
 
 N Tt- M 
 
 CO ON I> 
 
 LO Tt O 
 
 10 vo vo 
 
 .5 2 
 >-].t: 
 a 
 
 Ovo vo ON 00 
 e<) if) tt -*t <* 
 
 "1 Ul 
 
 t-J.t! 
 
 9 
 
 M M 
 
 vo vo 
 
 
 VO vo rf 
 
 M O\ * 
 
 ID 
 
 s 
 
 a CO vo TH fO 
 
 V 
 
 S 
 
 * TH 
 
 
 CO CO TH 
 M COI> 
 
 Tj- VO VO 
 
 4 
 
 r<5 * rO ON vo 
 ro vo * -<!- rt 
 
 a 
 
 M l> 
 
 * 
 
 23 
 
 VO 00 O 
 
 t> O * 
 
 e 
 
 
 
 ON vo ON M vo 
 
 m 
 
 S 
 
 00 TH 
 
 vo 
 
 O rH 1> 
 
 CO 00 VO 
 
 N Ot> 
 iO VO vo 
 
 H 
 HJ 
 
 TH M TH VO TH 
 
 rO vo * Tj- * 
 
 5 
 
 CO1> 
 CO rO 
 
 
 VO vo CO 
 
 1> rO J> 
 
 V 
 
 a 
 
 ON M (S O CO 
 
 V 
 
 c 
 
 00 VO 
 
 i 
 
 CJ 00 VO 
 
 8VO rO 
 vo LO 
 
 o 
 fe 
 
 VO r-t M VO CO 
 M vo * rO rO 
 
 1 
 
 CO CO 
 
 
 VO 00 W 
 
 i> o <y\ 
 
 0) 
 
 a 
 
 VO 00 ON VO * 
 
 <u 
 
 c 
 
 O VO 
 
 s 
 
 M 00 VO 
 
 M rH VO 
 vo VO vo 
 
 o 
 
 K 
 
 ON TH TH TJ- rO 
 CJ vo xfr -* * 
 
 o 
 K 
 
 l> O 
 
 CO * 
 
 
 
 
 a 
 
 3 
 t! bo 
 S 0) 
 
 
 d 
 
 M.& 
 
 C 4) 
 
 ^ JJ- 
 
 
 
 3 3 3 
 ,0,0,0 
 
 3 3 3 
 J3 JO X5 
 
 s* 
 
 O rt 
 
 (A <U 
 
 oJ ** 
 
 M 
 
 -!- 
 
 33333 
 
 o S 
 
 tn +3 
 
 3 
 
 2^ 
 "a 
 g 
 
 3 3 
 
 J0^2 
 
 
 a c a 
 
 c a c 
 
 
 
 C C C C G 
 
 
 
 C C 
 
 | 
 
 "o 
 
 s 
 
 000 
 
 OOO 
 LO vc t> 
 
 ON ON ON 
 
 00 00 CO 
 
 000 
 
 ooo 
 
 ^^8 
 
 co oo o\ 
 
 PL) 
 
 TH 
 
 c? 
 
 O O O O O 
 
 OOOOO 
 
 TH f<) CO T(- VO 
 
 ON CN wN ON ON 
 
 O 
 
 
 
 ou 
 
 O t^* 
 
 s * G\ 
 
 
 3 
 
 
 
 - 
 tfl 
 
 CO VO M 00 
 
 
 S 
 
 co' * 10 
 
 
 "o 
 
 
 
 S 
 
 
 
 .5 
 
 
 
 
 VO VO ON X 
 
 
 to 
 
 TH C 1 ~t~ 
 
 
 ri 
 
 1 I 
 
 
 "o 
 
 1 1 
 
 
 iorus 
 
 *) it-lf) r* 
 
 
 a 
 
 vo'vo CO vo 
 
 to 
 
 
 
 1 
 
 'v 
 
 m 
 
 3 
 JO 
 
 aj 
 
 3 
 
 O 
 
 VO ^t CO 00 
 
 
 
 
 VO 1> VO TH 
 
 c~ 
 LI 
 
 <n 
 
 
 
 1 
 
 
 
 
 
 
 
 c 
 
 
 
 .2 
 
 {H 
 
 
 ii 
 
 be 
 
 TH l> ON O 
 
 
 
 O 
 
 CN VO CO I> 
 
 9 
 
 .t{ 
 
 
 o 
 
 ^ 
 
 
 rt 
 
 C 
 
 
 V 
 
 0) 
 
 
 o 
 
 bo 
 
 O 
 
 M vo * ON 
 
 MH 
 
 E 
 
 rH rj- f\l rj- 
 
 ', 
 
 C 
 
 V 
 
 a 
 
 T- 
 
 t> M CO vo 
 
 ;/) 
 
 ^ 
 
 
 t_> 
 
 ft) 
 
 
 3 
 
 a 
 
 M vo M VO 
 
 0) 
 
 "i 
 
 CO * CO N 
 
 be 
 
 M 
 
 
 i 
 
 
 
 1 
 
 
 
 
 
 
 
 -S 
 
 
 
 nj 
 
 rHC^L^ 
 
 
 JO 
 
 TH TH rH ^ 
 
 
 "c 
 
 <U 1) 0) . 
 
 tfl (fl tfl Q 
 
 
 <u 
 
 rt rd rt u^ 
 
 
 a 
 
 D 0) 4> 
 
 
 "rt 
 
 w 
 
 O O O tfl 
 
 .5.5.5 S 
 
 "* u 
 
 
 H 
 
 > > > w 
 
7905.] 
 
 THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 349 
 
 
 
 rr 10 
 
 10 VO rH 
 
 
 
 |si 
 
 sP*i 
 
 iO >O tf) TH 10 
 
 VO 
 
 * ^ 
 
 <u 
 
 P 
 
 00 O 
 
 I> 
 
 8K 
 
 1> CM iO 
 
 VC VO iO 
 
 2g-E3 
 2|I 
 
 00 O TH M rO 
 rO t >O 00 VO 
 
 3 J 
 
 C "S. 
 re S 
 
 "o. 
 
 ON 10 
 t^ VO 
 
 g 
 
 Mt~ 
 
 t> 1> CO 
 
 g6 
 
 ^ 
 
 M"S 
 
 Ml> VO VO 
 
 >o 
 
 * ?," 
 8,g 
 
 ON 00 
 
 f^ 
 
 VO M 
 t- CO 
 
 O VO iO 
 
 2^^ 
 
 S4S 
 
 \i VO O:00 O 
 rO >O iO 1> O 
 
 i 
 
 re-r; g 
 C -- 
 
 ON t^ 
 
 
 
 iO CO 
 
 VO O vo 
 
 05 
 
 2 S 
 
 a> J o 3 
 fl ^X'S 
 
 M mo * 10 
 
 i 
 
 cgfi 
 
 1) W 2 
 
 P s?*"3 
 
 O >O 
 
 
 
 t> VO 
 
 t^J>- 
 
 oo r-i r> 
 
 VO VO >O 
 
 J?&2 
 S|fjS 
 
 ex o 
 e. 
 
 VD ON Tj- O\ t*- 
 rO VO iO l> iO 
 
 .52^" 
 >} 
 
 G ta 
 
 1> W 
 
 I> VO 
 
 t: 
 
 lOl^ 
 
 VO TH TH 
 
 M 
 
 S 
 
 4J 0.3 
 
 c OC.G S 
 
 iOI> VO TJ- iO 
 
 tc 
 
 s|l 
 1 1^1 
 
 CO CO 
 
 t^ 
 
 n oo 
 oo i> 
 
 VO CO 00 
 1- VO >O 
 
 E P CU at 
 ^ 
 
 a x g 
 p,a 
 
 TH ON VO r-1 00 
 
 * o 10 oo >o 
 
 .S 8 ft 
 
 ^i! tc re 
 
 " 5 o -a 
 
 ex 2 
 a^ 
 
 GO O 
 l> vo 
 
 s 
 
 rH TH 
 
 00 TH CO 
 
 3g 
 
 il 
 
 SJ3 3 
 
 O\iO * *O TJ- 
 
 to 
 
 3 g 
 
 ^ 5 
 
 D O 3 
 S iB*S 
 
 O O 
 
 1> 
 
 vd O\ 
 00 J> 
 
 >O ON O 
 iO VO 
 
 - *1 
 
 a js 
 
 It 
 
 O ON O O M 
 
 5. o 10 1> 10 
 
 .5 g.S 
 
 > 3 
 
 II 
 
 ON N 
 
 10 Tj- 
 
 y? 
 
 -t 00 
 
 rH xj- ON 
 
 P |J 
 
 ON * * VO CO 
 
 1 11 
 
 TH O 
 
 ti 
 
 ON t^ 
 
 oo i> 
 
 CO *O VO 
 
 3 ?-3 
 ^ is. 
 
 M rO t> ON ON 
 
 13 11 
 
 * IO 
 
 iO CO 
 
 * 
 
 CO VO 
 
 iO t> ON 
 
 n 
 
 0)0) = 
 
 a 'i 
 
 00 fO * TH TH 
 
 ID o> a 
 a be - 
 " o S 
 
 CO Oi 
 
 ti 
 
 * ON 
 ooi^ 
 
 o o n 
 
 CO VO VO 
 
 i4.-b -| 
 
 _a 
 
 C3 ON -* ri ro 
 rt iO >O l> VO 
 
 38 5 
 
 " .ti E. 
 'a 
 
 Sg 
 
 3 
 
 oo ON 
 
 O * rH 
 
 S3 
 4 <U S 
 
 a 
 
 TJ-IO O * ON 
 
 a) i 
 S^ 'i 
 
 iO ON 
 
 
 iH -<t 
 001^ 
 
 00 O M 
 * VO NO 
 
 j 2 J 
 
 M-B g_ 
 
 *c 
 
 rO TH -* (^ rO 
 
 * vo iO t^ \o 
 
 3.1 t 
 
 a 
 
 TH 00 
 l^ vo 
 
 8 
 
 If, Tf 
 
 CO * 
 00 1> 
 
 fO ON ON 
 rH C<1 Th 
 
 vo vo 10 
 
 a M 
 
 c 5 B 
 
 P ^^g 
 S o-S. 
 
 ^.^J 
 
 c ~ 
 
 00 rO 00 <* 00 
 
 00 1^ <O 00 00 
 rO vo to I> iO 
 
 a 
 
 0) l> S 
 
 n bc 
 .5 o-g. 
 
 > IH 35 
 
 MM 
 
 a 
 
 ON CO 
 
 CO * 
 t^ vo 
 
 fH 
 
 g 
 
 OMO 
 
 CN o 
 ooi^ 
 
 00 * O 
 
 2S 
 
 Lime 
 nitrogen 
 phosphorus 
 
 iO ro TH t^ TJ- 
 
 iO M TJ- ro O 
 
 rO vo >O t> O 
 
 a 
 
 (0 4) g 
 
 a bo fe 
 
 *" r^ FJ=: 
 
 2|1 
 
 C **" 
 
 TJ-IO 
 
 CO CO 
 t>. VO 
 
 
 
 
 ^- 
 
 . 
 
 s- 
 
 
 
 
 
 
 O a; hC 
 1C ,-. 0) 
 
 
 :!l 
 
 
 
 3 3 
 .0 > 
 
 3^3 
 
 X2 ^3 J2 
 
 -3-- 
 
 .5 re 
 
 4-1 <U 
 
 S 3333 
 X) ,0 XJ ^3 XI 
 
 *! 2 
 tl 
 
 SH 0) 
 
 3' 3* 
 Xi -Q 
 
 
 C C 
 
 c a n 
 
 rt "*"" 
 
 c c a n fl 
 
 S -b 
 
 C C 
 
 1 
 
 -4-> 
 O 
 
 S 
 
 
 
 OO 
 
 VOt^ 
 ON ON 
 CO 00 
 i-l rH 
 
 o o o 
 
 ooo 
 
 50 ON O 
 OS ON O 
 30 OO ON 
 rH rH rH 
 
 PH 
 
 rH 
 g 
 
 TH 
 
 o o o o o 
 UOOUO 
 
 r-l N r5 * >O 
 
 ON ON ON ON ON 
 
 rH TH rH TH rH 
 
 
 
 rH 
 
 O 
 
 OO 
 
 ot^ 
 o p 
 
 ON ON 
 rH TH 
 
 4- 
 
 
 10 D 
 
 O W 
 
 4) 
 
 
 vo ro 
 
 j3 
 
 
 
 2 X 
 
 re 
 
 1 5^ ro rn 
 
 
 9 
 
 CN V V 
 
 QH -4-> 
 
 JH 
 
 n 
 
 
 IH to 
 O 3 
 
 -g 
 
 
 il 
 
 I 
 
 -*0N 
 
 p 5 
 
 "re 
 
 N iO Cjj I> 
 
 re "S 
 
 *u 
 
 ^^ ' 
 
 o> ra 
 
 IH 
 
 
 f 
 
 6 
 
 3 
 
 
 > o 
 
 Potassi 
 
 TH TH TH 
 
 I I 
 
 . Q 
 
 1 ' 
 
 | 
 
 
 O ^, 
 
 H 
 
 to 
 
 VO O 00 * 
 
 ^2 'o 
 
 re 
 
 n-^THTH 
 
 o <u 
 
 
 
 
 OH 
 
 04 
 
 
 O r- 
 
 MH ^~* 
 
 
 
 0> J3 
 
 
 
 * ." 
 
 
 
 D X 
 
 jj; 
 
 
 *-" fe 
 
 4 s 
 
 
 O p 
 
 
 
 S a 
 
 
 
 .2 
 
 
 
 ^ <u 
 
 1 
 
 
 <! *o 
 
 * 
 
 
 i I 
 
 
 
 v PI 
 
 
 
 o _a 
 
 
 
 Cy ^j 
 
 * 
 * 
 
 
 80< 
 3 { 
 
 
 
 t^ O -M 
 
 -t 
 
 1 
 
 TH * 00 00 
 
 p "Si 
 
 
 t> vo >o o 
 
 * a 
 
 
 
 -= 
 
 TH fH TH 
 
 5 a 
 
 &. 
 
 
 2-5 
 
 * 
 
 
 a g x 
 
 E) 
 
 co *o ^fr ON 
 
 < -> 
 
 s 
 
 CO VO 'O H 
 
 ^ 
 
 
 
 
 Nl 
 
 .S ^2 a, 
 
 TH^ ' 
 
 
 O O O o 
 
 js a 
 
 
 .v. increase 1? 
 .v. increase 1* 
 .v. increase 11 
 icrease for 19 
 
 re 3 
 
 fe * ^> 
 
 > ~ 
 
 ^ to 
 d .M 
 C o 
 
 
 <\ << <^ I_H 
 
 re a 
 
350 
 
 BULLETIN No. 125. 
 
 [May, 
 
 In 1901 the nitrogen was applied in sodium nitrate, but since 
 that year dried blood has been used as the nitrogen fertilizer. It 
 is well to keep in mind that while nitrogen can be secured with 
 profit from the inexhaustible supply of the air by means of clover 
 and other legume crops, it costs at least 15 cents a pound in com- 
 mercial form. The 250 pounds of nitrogen now being applied each 
 year to all nitrogen plots on series 600 and 700 costs at least $37.50 
 per acre a year. 
 
 It should be understood that the growing of clover produces 
 several effects on the land and upon subsequent yields of other 
 crops, only one of whch is due to the nitrogen secured from the 
 air. In fact the chief effect of clover in increasing the yield of a 
 subsequent crop of corn is not due to the nitrogen secured from 
 bie air, but rather to the liberation of phosphorus by the decay of 
 the clover residues in the soil. The physical improvement of the 
 soil and subsoil are also important factors in some cases. 
 
 PLATE 7. CORN EVERY YEAR WITH NO MANURE OR FERTILIZERS : PLOT 602, UR- 
 BANA SOIL EXPERIMENT FIELD, 1907 : YIELD 34.6 BUSHELS PER ACRE. 
 
1908.] 
 
 THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 351 
 
 But to determine the need and the effect of nitrogen itself we 
 must apply nitrogen in some form and dried blood is the most sat- 
 isfactory form to use. Sodium nitrate and ammonium sulfate are 
 also common concentrated nitrogen fertilizers but they are soluble 
 salts which may produce marked indirect effects, not infrequently 
 of greater consequence than the effect due to the nitrogen itself. 
 
 Phosphorus has been applied in steamed bone meal at the rate 
 of 25 pounds of the element per acre per annum, the requirement 
 of a hundred-bushel crop of corn being 23 pounds, and the annual 
 loss in drainage water being about i pound per acre. The annual 
 cost of the bone meal is $2.50 per acre. 
 
 Potassium is applied at the rate of 42 pounds per acre a year in 
 100 pounds of potassium sulfate, also at a cost of $2.50. A hun- 
 dred-bushel crop of corn contains 19 pounds of potassium in the 
 grain and 52 pounds in the stalks. The application made is not 
 
 PLATE 8. CORN EVERY YEAR WITH "EXTRA HEAVY" SOIL TREATMENT : PLOT 
 709, URBANA SOIL EXPERIMENT FIELD, 1907: YIELD 71.8 BUSHELS PER ACRE. 
 
352 BULLETIN No. 125. [May, 
 
 sufficient for the entire crop, but the natural supply of potassium in 
 the soil is so exceedingly large that it is both unnecessary and un- 
 profitable to return the potassium removed from the land in any 
 ordinary systems of farming. 
 
 On plots 709 and 710, beginning in 1906, the application of 
 phosphorus was increased to five times the standard amount, and 
 the application of manure was begun, using about five times as 
 much manure as could easily be made from the crops grown, or 
 20 tons per acre each year. The addition of commercial potassium 
 was discontinued on both plots and commercial nitrogen was also 
 discontinued on 710, but is still used on plot 709, at the rate of 
 250 pounds per acre each year since 1906. 
 
 The plots on series 600 and 700 are not quite so uniform in 
 character and in natural productive power as on series 100 to 500, 
 but since being tile-drained in 1904 the natural differences are re- 
 duced. It may be seen that in 1896, for example, plots 703 to 706 
 were among the best yielding plots, while in the season of 1898 
 those four plots produced markedly smaller yields than the other 
 plots in the series. This is explained in the foot note to Table 9. 
 
 One other natural condition should be understood: A slight 
 ridge crosses series 600 and 700, the crest passing through plots 
 606 and 607 and through 708. The lowest plots in the 600 series 
 are the end plots, 60 1 and 610, while in the 700 series the lowest 
 parts are plot 710 and the depression that covers part of plots 703, 
 704, 705, and 706. Because of the continuous cropping with a 
 cultivated crop these two series are continuously exposed to sur- 
 face washing, and there is some tendency for surface wash to be 
 deposited on 601, 610, and 710 and to a less extent on the four plots 
 affected by the depression mentioned. There is also a slight ten- 
 dency for the dried blood applied to plots 605 and 606 to be carried 
 north to plot 604 and south to 607. 
 
 Because of these facts the most trustworthy data are secured 
 from plots 602, 603, 605, 606, 608, and 609 and from plots 701, 
 702, 707, 708, and 709, and this is recognized in making the sum- 
 mary given in the lower part of Tables 8 and 9. 
 
 EFFECT OF LIME. The effect of lime on the yield of corn is 
 chiefly due to the fact that calcium carbonate (limestone) encour- 
 ages nitrification and the consequent liberation of the nitrogen and 
 to a less extent of the phosphorus contained in the natural humus 
 of the soil. This is best seen by comparing plots 603 and 602. 
 The summary shows an increase from lime of 3.2 bushels in 1901-2, 
 rising to 4.5 bushels in 1903-4, and falling to 2.5 bushels in 1907. 
 Plot 604 shows larger effects, but the possible washing of dried 
 blood from the adjoining plot may account for this difference. 
 
THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 
 
 Plot 709 compared with the average of 707 and 708 shows an 
 average increase of 2 bushels per acre from lime from 1901 to 1905. 
 
 From all of the investigations thus far conducted on the com- 
 mon brown silt loam prairie soils of the Illinois corn belt, it is 
 evident that the time is near for most of this soil, and already here 
 for some of it, when ground limestone must be applied to give the 
 most profitable results in crop yields. These soils were not rich in 
 lime in the beginning, and lime is constantly being lost from the 
 soil, both in crops removed and in the drainage waters, which per- 
 colate through the soils and when collected in surface wells are al- 
 ways recognized as "hard" waters because of the lime contained 
 in them. 
 
 EFFECT OF NITROGEN AND PHOSPHORUS. The effect of nitro- 
 gen is determined* by comparing plots 605 and 606 with plot 603. 
 These results are summarized in the lower part of Table 8. They 
 show but very little effect from nitrogen in 1901-2, the average in- 
 crease being about i l / 2 bushels. This was raised to about 5^ bush- 
 els in 1903-4 to 13 bushels in 1905-6 and to 16 bushels in 1907. It 
 is noteworthy, however, that this increasing difference is not due 
 to an actual increase in yield on the nitrogen plots, but rather to a 
 decrease in the yield of the plots not receiving nitrogen, so far as 
 we can judge. 
 
 By comparing plots 608 and 603 we have the most trustworthy 
 data as to the effect of phosphorus with no addition of nitrogen or 
 potassium. This shows an average increase of 5.4 bushels during 
 the four years, 1901 to 1904, chiefly produced during the second 
 and third years. The gain was 3.5 bushels for 1905-6; while the 
 effect in 1907 was a loss of 5.1 bushels. The somewhat higher 
 yields on plot 607 may be due to dried blood washed over from 606. 
 
 In comparison with nitrogen, it will be seen that at the begin- 
 ning of soil treatment in 1901 phosphorus was clearly the limiting 
 element and produced a greater effect than nitrogen during the first 
 four years, after which the effect of phosphorus soon decreased un- 
 til it produced smaller yields than the untreated plots, while the ef- 
 fect of nitrogen has been nearly to maintain the actual crop yields, 
 with increasing differences above the untreated land. 
 
 The lesson taught by these experiments is that on our ordinary 
 corn belt prairie soils phosphorus is the most deficient element of 
 plant food, because of which nitrogen applied alone produces little 
 or no increase in crops ; but in continuous corn growing the supply 
 of nitrogen is so rapidly depleted by removal in crops and in drain- 
 age waters that within a few years nitrogen itself becomes the most 
 
 *Plot 605 is probably the more trustworthy of the two nitrogen plots be- 
 cause of possible wash from 607 to a part of 606. 
 
354 BULLETIN No. 125. [May, 
 
 deficient element, after which phosphorus alone has no power to 
 increase the crop yields. 
 
 Thus on plots 605 and 606, more than 60 bushels were grown 
 in 1900, and, although nitrogen has been applied every year since, 
 that yield has not been equaled; whereas on plots 607 and 608 
 phosphorus actually increased the yields for two or three years.* 
 After that time the yields have been nearly maintained on the nitro- 
 gen plots but have steadily decreased on the phosphorus plots, ni- 
 trogen having become the limiting element. 
 
 If, now, we first restore the nitrogen so as to remove the nitro- 
 gen limit to crop yields, then phosphorus should again have power 
 to increase the yield above that produced by nitrogen on plots 605 
 and 606, which averaged 53 bushels for 1906 and 1907. This has 
 been done on plots 701 and 702, where both nitrogen and phos- 
 phorus have been applied and where the average yield for 1906 and 
 1907 has been 69 bushels per acre. This is 16 bushels higher than 
 on the nitrogen plots (605 and 606) and 30 bushels higher than 
 on the phosphorus plot (608). 
 
 This is shown in greater detail in the summary in the lower 
 part of Table 9. The effect of nitrogen and phosphorus above that 
 of phosphorus alone was 3.3 bushels in> 1901-2, 16.5 bushels in 
 1903-4, 25.4 bushels in 1905-6, and 31.9 bushels in 1907; where- 
 as, the effect of phosphorus applied in addition to nitrogen was 7. i 
 bushels the first two years, about 16 bushels the next four years, 
 but only 10.8 bushels in 1907. Here again the apparent gain for 
 nitrogen is not due to increasing yields on plots 701 and 702, which 
 as a matter of fact were about the same in 1904-5 as they were in 
 1906-7, but the difference is due rather to the actual decrease on 
 the phosphorus plot (608) where nitrogen has become the limit- 
 ing element. 
 
 It is very apparent that nitrogen alone cannot increase the yield 
 of corn on this soil, and that the increase from phosphorus alone 
 is very temporary, but that both nitrogen and phosphorus together 
 have power to produce a decided increase. This is in harmony 
 with the marked benefit of phosphorus on clover, which has power 
 to secure nitrogen from the air when the soil nitrogen becomes de- 
 ficient, as shown in the three-year rotation (Tables 3, 4, and 5). 
 
 EFFECT OF POTASSIUM. The effect of potassium can be ascer- 
 tained by comparing plot 609 with plot 603, also by comparing 707 
 and 708 with the average of 701 and 702. Under the most favor- 
 able conditions, with both nitrogen and phosphorus present, the 
 addition of potassium produced an average increase of 3 bushels in 
 
 *The year 1901 must be overlooked because of the drouth. 
 
/90<S.] THIRTY YEARS OF CROP ROTATIONS IN ILLINOIS. 355 
 
 1901-2, but this has steadily grown less and amounted to nothing 
 in 1907. 
 
 FURTHER OBSERVATIONS. Tables 8 and 9 afford other inter- 
 esting comparisons and valuable information. For example, plot 
 602 produced 86.5 bushels and plot 709 produced 5.6.2 bushels of 
 corn per acre in 1896, but in 1906 (ten years later) plot 602 (un- 
 treated) produced only 30.8 bushels, while plot 709 (treated) pro- 
 duced 92.9 bushels per acre. In other words, the yield of plot 709 
 was increased by 16 bushels while the yield of plot 602 decreased 
 by 55 bushels per acre in eleven years. 
 
 With liberal supplies of available plant food large crops have 
 been grown with corn every year in spite of insect injuries, which 
 have been very noticeable on the continuous corn plots, especially 
 the injuries from the corn root worm which cause the corn to fall 
 or to be blown over easily on all continuous corn plots, while the 
 corn on the rotated plots stands up well. 
 
 An interesting and suggestive relationship appears between the 
 comparable plots in the 600 and 700 series. Plots 2, 7, 8, and 9 
 in the two series lie end-to-end and for reasons previously explained 
 they are considered trustworthy and comparable plots. 
 
 Corn was grown on the 600 series in 1895 while the 700 series 
 was not cropped. Besides the small crop of 1895, the yields in 
 1896 were greater on the 600 than on the 700 series, so that by 
 the end of 1896 the four plots mentioned had produced as an aver- 
 age 39.4 bushels more corn per acre on the 600 series than on the 
 700 series. 
 
 But during the next four years, from 1897 to 1900, previous to 
 the beginning of soil treatment, the 700 series yielded more every 
 year, the average difference amounting to 35.9 bushels per acre 
 during the four years. In other words, the average difference of 
 39.4 bushels in favor of series 600 at the end of 1896 had been re- 
 duced to only 3.5 bushels at the close of 1900, every one of the four 
 plots having produced more corn every year on the 700 than on 
 the 600 series, the excess amounting to 3 bushels even in 1900, thus 
 indicating that the remaining difference of 3.5 bushels would have 
 been wiped out in perhaps t\vo more years. 
 
 The point suggested by these data is, that there is a relationship 
 between the plant food to be made available and the crops possible 
 to be produced. The land that was not cropped in 1895 grew 
 enough larger crops from 1897 to 1900 so that the five crops on 
 series 700 practically equaled the six crops on the 600 series. In 
 other words, the plant food removed in the 1895 crop apparently 
 
356 BULLETIN No. 125. [May, 1908.} 
 
 reduced proportionately the productive power of the soil for sub- 
 sequent crops. 
 
 The production of these comparatively large crops in the early 
 years is principally due to the rapid liberation of plant food from 
 the decay of .fresh organic matter accumulated in the roots and 
 other residues of clover and grasses and animal droppings during 
 the previous years of pasturing; but the lesson that is so well 
 brought out in this comparison between the 600 and 700 series 
 during the first few years is a true prophesy of a more important 
 lesson which applies to the future years, to-wit : 
 
 Certain essential elements of plant food (nitrogen and phos- 
 phorus) are present in limited quantities in the common Illinois 
 corn belt soil, and every crop removed with no adequate return 
 reduces to that extent the power of that soil to produce future crops. 
 
 NOTE. For further information concerning farm manure, effect of crop 
 rotations, sources of plant food materials, methods of application, comparative 
 value of natural rock phosphate, etc., Illinois readers are referred to Circular 
 108, "Illinois Soils in Relation to Systems of Permanent Agriculture," and 
 Circular 116, "Phosphorus and Humus in Relation to Illinois Soils." 
 
ir^^ M *;& ! 
 
 r UW >\ v -T . r ^Bt ^ -r\ /^**-ai..k/ /IK.^ ^-