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OF THE 
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 -NON CIRCULATING 
 
 CHECK FOR UNBOUND 
 CIRCULATING COPY 
 
UNIVlKSMTUf 
 
 Agricultural Experiment Station 
 
 BULLETIN No. 181 
 
 BY J. G. MOSIEE AND A. F. GUSTAFSON 
 
 URBANA, ILLINOIS, APRIL, 1915 
 
SUMMARY OF BULLETIN No. 181 
 
 I. A deep, well-prepared seed bed is essential for aeration, proper root devel- 
 opment, and conservation of moisture. It gave a gain of 14.5 bushels ($7.25 at 
 50 cents) per acre over no seed bed. (Table 6.) 
 
 1 2. Killing weeds is the most important factor in cultivating corn on brown 
 silt loam. No weeds gave an increase over weeds of 38.6 bushels of corn, a gain 
 of $19.30 per acre. (Table 6.) 
 
 ^ 3. Weeds reduce the yield of corn more by robbing it of plant food and light 
 than by depriving it of moisture. Irrigation on a weed plot gave an increase of 
 only 3.8 bushels. (Table 6.) 
 
 ' 4. As an average of sixteen tests in eight years, killing weeds without cul- 
 tivation produced a gain of 17.1 percent, or 6.7 bushels per acre, over ordinary cul- 
 tivation. (Table 6.) 
 
 5. Three-fourths of the corn roots are in the plowed soil, and as plants de- 
 velop no unnecessary roots, any injury to them results in a lower yield. Four-inch 
 pruning six inches from the hill reduced the yield 16.9 bushels. (Table 4.) 
 
 6. The cultivated soil, especially in periods of drouth, is too loose and dry 
 for proper root development, consequently the plant is deprived of the food which 
 it contains. 
 
 7. After the roots are well distributed thru the soil, little moisture can es- 
 cape, even from uncultivated land. (Table 9.) 
 
 8. On gray silt loam on tight clay in southern Illinois, as a three-year aver- 
 age, preparation of seed bed gave an increase of 21.5 bushels; killing weeds by 
 scraping with a hoe gave a gain of 21 bushels over allowing them to grow; and 
 fertilization gave an increase of 14.2 bushels. Ordinary shallow cultivation gave 
 a yield of 31.2 bushels per acre, while killing weeds without stirring the surface 
 gave 31.5 bushels. (Table 12.) 
 
 9. The proper type of cultivation is deep enough to kill the weeds but shal- 
 low enough to reduce root injury to the minimum. On Illinois soils a good seed 
 bed, killing weeds, and soil enrichment are the important factors in growing corn. 
 
 10. Cultivation is beneficial for aeration of heavy soils, clays and clay loams. 
 (Table 14.) 
 
 II. Cultivation raises soil temperature early in the season and lowers it later. 
 (Table 11.) 
 
 12. Subsoiling on gray silt loam on tight clay at Odin caused a decrease of" 
 2.7 bushels per acre. (Table 15.) 
 
 13. Results of deep-tilling tests so far conducted by this experiment station 
 do not warrant recommending the purchase and use of deep-tilling machines in 
 this state. 
 
SOIL MOISTURE AND TILLAGE FOR CORN 
 
 BY J. G. MOSIEE, CHIEF IN SOIL PHYSICS, AND 
 A. F. GUSTAFSON, ASSOCIATE IN SOIL PHYSICS 
 
 The common impression among farmers and most agricultural 
 writers is that cultivation of corn is necessary as a means for con- 
 serving moisture. While this may be true to a large extent in sub- 
 humid and semiarid regions, yet in humid sections this purpose in 
 the cultivation of corn is a very secondary object. 
 
 The reader is asked to note and to keep in mind that it is not the 
 purpose of the authors of this bulletin to recommend specific methods 
 or implements to be used in the cultivation of corn, but to develop 
 principles that should be observed in order to secure the best results. 
 The investigations reported were conducted to discover why corn is 
 cultivated, and no one should assume that we advocate for practical 
 farming the substitution of hand labor for horse power, but only 
 that principles should guide practice toward the greatest profits. 
 
 KILLING OF WEEDS 
 
 The most important factor in the growth of a crop of corn on 
 fertile soil with a well-prepared seed bed in humid regions is the kill- 
 ing of weeds. With the same preparation of seed bed, corn produced, 
 as an eight-year average, 7.3 bushels per acre where the weeds were 
 allowed to grow, and 45.9 bushels where the weeds were kept down 
 without any cultivation. This gives an increase of 38.6 bushels, or 
 say $19.30 per acre, for keeping weeds down. Weeds deprive the 
 plant of moisture, light, and food, all of which are absolutely neces- 
 sary for the production of crops. Of these factors, however, the one 
 that has made the greatest difference is that of plant food. Corn has 
 been grow r n together with weeds, but irrigated so that it was not de- 
 prived of moisture, yet the increase from irrigation, as a four-year 
 average, was only 3.8 bushels per acre. Weeds are much better for- 
 agers than are most cultivated crops; and it would be just as rea- 
 sonable to expect a lamb to thrive with a bunch of hogs as to expect 
 corn to compete with weeds. 
 
 MOISTURE AND FOOD 
 
 If a soil is in good tilth and there are no weeds, little or no cul- 
 tivation is necessary. If it is in poor tilth with no weeds present, 
 some cultivation may be necessary for aeration. This is especially 
 
 565 
 
566 
 
 BULLETIN No. 181 
 
 [April, 
 
 true of heavy soils or those containing a large amount of clay. In 
 humid climates cultivation of corn is rarely necessary for the con- 
 servation of moisture if a good seed bed has been prepared. After 
 the corn has become twelve inches or more in height, the roots are 
 so completely distributed between the rows that it is difficult for 
 moisture to escape from the soil, for it is captured by the roots in its 
 upward progress. As an average of eight years' investigations, the 
 soil was found to contain no more moisture where the corn was cul- 
 tivated than where the weeds were destroyed without cultivation. 
 (See Table 9.) 
 
 Cultivation should be as shallow as possible at all times, altho 
 deeper stirring is permissible the first time than later. For the high- 
 est yield, cultivation should never be deep enough to injure the roots. 
 The purpose of the roots is to get plant food and moisture, and as 
 a general rule plants develop no more than are necessary for this pur- 
 pose. The injury of a few roots, therefore, may stunt the corn. It must 
 be remembered, too, that the plowed stratum is the richest part of the 
 soil, and that the roots will naturally develop where there is the largest 
 supply of plant food. Three-fourths of the roots of the corn plant are 
 developed in the plowed soil. For this reason deep plowing in both 
 fall and spring should be done to give a large feeding area. 
 
 CULTIVATION EXPERIMENTS IN OHIO 
 
 Experiments have been carried on at several stations to determine 
 how often and how deep corn should be cultivated. A few stations 
 have determined the effect of weeds on a crop of corn. The first 
 
 TABLE 1. KESULTS OF CORN CULTIVATION AT OHIO EXPERIMENT STATION, 
 
 COLUMBUS, OHIO* 
 (Yields in bushels per acre) 
 
 Kind of cultivation 
 
 1883 
 
 1884 
 
 1885 
 
 1886 
 
 1887 
 
 3-yr. 
 av. 
 
 Av. % of 
 No. 3 
 
 1. None, weeds allowed to 
 srrow . 
 
 21 7 
 
 14.5 
 
 6.4 
 
 13.5 
 
 .35 
 
 6 7 
 
 23.8 
 
 2 Surface 
 
 
 284 
 
 91 3 
 
 53.5 
 
 1340 
 
 52 7 
 
 994 
 
 3. Ordinary, 4 or 5 times. . . . 
 4. Ordinary, excessive num- 
 ber 
 
 49.8 
 
 29.4 
 
 82.4 
 88.3 
 
 56.0 
 55.2 
 
 20.00 
 21.30 
 
 52.8 
 54.9 
 
 100.0 
 104.0 
 
 5. Ordinary, three times, 2 
 days apart 
 
 
 
 895 
 
 44.7 
 
 18.90 
 
 51.0 
 
 96.5 
 
 6. Ordinary, three times, 4 
 
 
 
 78.1 
 
 47.0 
 
 20.40 
 
 48.5 
 
 91.8 
 
 7. Ordinary, three times, 8 
 <3ays apart 
 
 
 
 81.0 
 
 56.4 
 
 16.10 
 
 51.2 
 
 97.0 
 
 8. Ordinary, three times, 12 
 days apart 
 
 
 
 94.0 
 
 53.0 
 
 18.80 
 
 55.3 
 
 104.7 
 
 'Annual Eeports 2 to 6. 
 
 2 The yield from shallow cultivation is taken as the standard and represented 
 as 100 percent ; the relative yields from the other methods of cultivation are then 
 expressed in percentage of this, based upon all comparable yields. 
 
1915] 
 
 SOIL MOISTURE AND TILLAGE FOR CORN 
 
 567 
 
 to carry on experiments along this line was Ohio, at Columbus, be- 
 fore the station was removed to Wooster. Table 1 gives the results. 
 Little was gained by a large number of cultivations. Comparing 
 the average yields of 1885-1887, we find 54.9 bushels for excessive 
 cultivation as against 52.8 bushels for four ordinary cultivations, or 
 an increase of 2.1 bushels. The effect of weeds on the crop as shown 
 in these results was very striking. Where the weeds were allowed 
 to grow, 8.7 bushels of corn per acre were produced, as a four-year 
 average, but where the weeds were kept down by surface cultivation 
 the yield was 46.6 bushels, or 37.9 bushels increase. 
 
 MISSOURI EXPERIMENTS 
 
 Table 2 gives the results from some experiments on tillage at the 
 Missouri Station. 
 
 TABLE 2. RESULTS OF CORN CULTIVATION AT MISSOURI EXPERIMENT STATION 1 
 (Yields in bushels per acre) 
 
 Kind of cultivation 
 
 1889 
 
 1890 
 
 Av. 
 
 Av. % of 
 No. 2 
 
 1 None scraped with hoe 
 
 82.0 
 
 45.7 
 
 63.8 
 
 95.3 
 
 2 Shallow, 4 times 
 
 80.1 
 
 53.8 
 
 66.9 
 
 100.0 
 
 3. Deep, 4 times 
 
 65.8 
 
 41.2 
 
 53.5 
 
 80.0 
 
 
 
 
 
 
 'Bulletin 14. 
 
 Without cultivation, but with the weeds kept down by scraping 
 with a hoe, the average yield for the two years was 63.8 bushels per 
 acre, while for shallow cultivation the yield was 66.9 bushels, or 3.1 
 bushels increase. Deep cultivation, compared with shallow, shows a 
 loss of 13.4 bushels per acre. 
 
 INDIANA EXPERIMENTS 
 
 Table 3 gives the results from experiments at the Indiana Station 
 in which cultivations at different depths were compared. 
 
 TABLE 3. RESULTS OF CORN CULTIVATION AT INDIANA EXPERIMENT STATION* 
 (Yields in bushels per acre) 
 
 Depth of cultivation 
 
 1888 
 
 1889 
 
 1890 
 
 1891 
 
 2-yr. 
 av. 
 
 4-yr. 
 av. 
 
 One inch deep 
 
 60.7 
 
 
 
 56.6 
 
 58 7 
 
 
 Two inches deep 
 Three inches deen. . 
 
 64.3 
 64.6 
 
 45.5 
 41.8 
 
 46.7 
 46.4 
 
 57.6 
 50.2 
 
 61.0 
 57.4 
 
 53.5 
 50.8 
 
 'Bulletin 39. 
 
 EARLY EXPERIMENTS IN ILLINOIS 
 
 Professor G. E. Morrow, of the University of Illinois, began some 
 experiments in 1888 to determine the value of cultivation and its best 
 
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1015] SOIL MOISTURE AND TILLAGE FOR CORN 569 
 
 depth and frequency ; also the effect of root pruning. Table 4 gives 
 his results, while Table 5 gives the rainfall by months during the 
 time the experiments were in progress, with the exception of the year 
 1888, for which the record was not complete. 
 
 Where the weeds were kept down by scraping with a hoe without 
 producing a mulch, the yield, as a seven-year average, was 97.6 per- 
 cent of that for ordinary, shallow cultivation, or a difference of 1.7 
 bushels per acre in favor of cultivation. Deep cultivation, four or 
 five times, gave 96.9 percent, or 2.2 bushels less than shallow cultiva- 
 tion. Shallow cultivation twelve to fourteen times during the season 
 gave 103.6 percent, or an increase of 2.5 bushels per acre, while deep 
 cultivation the same number of times gave 91.7 percent, or a decrease 
 of 5.8 bushels per acre. Compared with twelve to fourteen shallow 
 cultivations, deep cultivation twelve to fourteen times gave 8.3 bushels 
 decrease per acre. 
 
 Another experiment carried on at the same time was the pruning 
 of the roots of corn at a distance of about six inches from the hill. 
 This was accomplished by placing a frame twelve inches square over 
 the hill and running a knife around the outside to a depth of four 
 inches, thus cutting the roots to that depth. Where shallow cultiva- 
 tion was practiced, this pruning resulted in a decrease of 12.5 bushels 
 per acre, but where the weeds were removed by scraping with a hoe 
 instead of by shallow cultivation, the yield was diminished 16.9 bush- 
 els per acre. 
 
 LATER EXPERIMENTS AT URBANA, ILLINOIS 
 
 The results obtained by Professor Morrow seemed so remarkable 
 that in 1906 and 1907 a series of experiments was begun to demon- 
 strate them, and at the same time to obtain data on some other fea- 
 tures; namely, the damage by weeds, the value of a seed bed, the 
 effect of cultivation on moisture and temperature, and the value of 
 irrigation and the addition of plant food in abundance. The results 
 of these experiments are given in Table 6. Table 7 gives the rainfall 
 during the time covered by the experiments. 
 
 The soil on which these experiments have been conducted is a 
 brown silt loam, the ordinary corn-belt soil. The field had been under 
 cultivation for fifty years or more, but during this time no fertilizer 
 had been applied, with the possible exception of farmyard manure. 
 
 A four-year rotation of corn, corn, oats, and clover has been prac- 
 ticed. The corn stalks and both crops of clover have been removed. 
 In 1912 and 1914 soybeans were grown because of the failure of clover. 
 The cultivating was done with the three-shovel cultivator till 1912 ; 
 and since then the surface cultivator has been used. 
 
 While the total rainfall of 1911 and 1913 appears to be approxi- 
 mately normal, yet in both these years there were dry periods during 
 
570 
 
 BULLETIN No. 181 
 
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1915} 
 
 SOIL MOISTURE AND TILLAGE FOR CORN 
 
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572 
 
 BULLETIN No. 181 
 
 [April, 
 
 the time when corn should have been making its greatest growth and 
 needed a large supply of moisture. It will be noted that in 1911 dur- 
 ing June .82 inch of rain fell, and during July .62 inch, while in 
 1913 in May .56 inch fell, in June 1.67, in July 1.52, and in August 
 1.44 inches. The year 1913 was the driest during the growing time 
 for corn since the rainfall record has been kept at the University. 
 
 Table 8 gives the amount of water applied to the irrigated plots 
 for each year of the experiment, and also the rainfall from April 1 
 to August 31. 
 
 It will be seen that the largest amount of water, 16.91 inches, was 
 applied during 1911, and the next largest, 12.85 inches, in 1913. The 
 water was applied in amounts equal to about an inch of rainfall, by 
 the furrow method of irrigation. After it was absorbed and the soil 
 had become sufficiently dry, the furrows- were partly filled with loose 
 soil to prevent any excessive loss by evaporation. The yields for 1913 
 were diminished by the extreme heat during the time when pollina- 
 tion was taking place. A storm on July 16, 1914, damaged the corn 
 on all plots to some extent, but especially where the growth was rank, 
 as on the fertilized and irrigated plots. 
 
 FIG. 1. PLOT 1: GROUND NOT PLOWED, No SEED BED PREPARED, WEEDS KEPT 
 DOWN BY SCRAPING WITH A HOE. YIELD, 25.5 BUSHELS (1911) 
 
1915] 
 
 SOIL MOISTURE AND TILLAGE FOB CORN 
 
 573 
 
 TREATMENT OF PLOTS 
 
 Plot 1 was plowed but once during a rotation, and that for 
 oats. The vegetation, such as clover or old corn stubs, was 
 removed and the corn planted with a hoe. The weeds were 
 kept down by scraping with a sharp hoe so as to produce prac- 
 tically no mulch, and this was done only as often as necessary 
 to kill the young weeds. 
 
 Plot 2 was plowed in the spring about 6 inches deep for 
 corn ; a good seed bed was prepared before planting the corn, 
 but no cultivation was given. The weeds were kept down in 
 the same way as on Plot 1. 
 
 Plot 3S (Plot 3 until 1910) was plowed in the spring and 
 a good seed bed prepared, but after planting time the weeds 
 were allowed to grow. 
 
 Plot 3N was plowed and a seed bed prepared ; weeds were 
 allowed to grow as in 3S, but the plot was irrigated as often 
 as necessary to keep the soil in a moist condition. 
 
 Plot 4 was treated like Plot 2, except that the corn was 
 cultivated shallow three times with the three-shovel cultiva- 
 
 FIG. 2. PLOT 2: GROUND PLOWED, SEED BED PREPARED, WEEDS KEPT DOWN BY 
 SCRAPING WITH A HOE. YIELD, 39.8 BUSHELS (1911) 
 
574 
 
 BULLETIN No. 181 
 
 [April, 
 
 tor previous to 1912, and with the surface cultivator since 
 then. Any weeds that escaped the cultivator were pulled or 
 cut out with a hoe. 
 
 Plot 5 was treated the same as Plot 4, except that the crop 
 was irrigated whenever it was deemed necessary. 
 
 Plot 6 was treated similarly to Plot 5, except that 2 tons 
 of rock phosphate and 80 tons of manure per acre were ap- 
 plied once in each rotation before the second crop of corn. 
 
 In Table 6, the yield of the cultivated plot, No. 4, is taken as the 
 standard for computing the relative yields shown in the last column. 
 On Plot 1, without plowing or the preparation of a seed bed in any 
 way, the average yield for eight years was 31.4 bushels per acre, or 
 80.1 percent of that of the standard cultivated plot, No. 4. In com- 
 parison with this, on Plot 2, where a good seed bed had been prepared 
 arid the weeds kept down, the percentage of yield was 117.1, while 
 the average actual yield for the eight years was 45.9 bushels, or an 
 increase of 14.5 bushels per acre over Plot 1. This represents the 
 value of the seed bed. The lowest yield of Plot 2 was 33 bushels in 
 1908 and the highest, 75.5 bushels in 1912. It would seem scarcely 
 possible that such a yield as this could be produced without cultiva- 
 
 FIG. 3. PLOT 3: GROUND PLOWED, SEED BED PREPARED, WEEDS ALLOWED TO GROW. 
 YIELD, .8 BUSHEL (1911) 
 
1915} 
 
 SOIL MOISTURE AND TILLAGE FOR CORN 
 
 575 
 
 tion; yet this yield was the highest obtained from any plot except 
 the fertilized one, and was 10.3 bushels larger than that produced by 
 cultivation. It will be noticed that Plot 2, uncultivated, gave larger 
 yields three out of the eight years than Plot 5, the cultivated and 
 irrigated plot, and that the average was 6.7 bushels larger than for 
 the standard cultivated plot, No. 4. 
 
 On Plot 3, it was the intention to see what would be the effect of 
 weeds on the corn crop. It will be noticed that the average yield here 
 is only 18.6 percent of that of the cultivated plot, but the actual yields 
 varied from to 16 bushels. The results of Plot 3S certainly make it 
 very evident that corn cannot thrive with weeds. 
 
 In order to determine whether it was a lack of moisture that pro- 
 duced the low yields where weeds and corn were grown together, 
 Plot 3 was divided in 1911, and the north half was irrigated often 
 enough to keep the soil abundantly supplied with moisture. The ef- 
 fect was quite noticeable both on the corn and the weeds, but as an 
 average of four years the yield was increased only 3.3 bushels per acre. 
 It must therefore appear that the injury done by weeds is not largely 
 due to the moisture that they take out of the soil, but to some other 
 cause or causes. 
 
 FIG. 4. PLOT 4: GROUND PLOWED, SEED BED PREPARED, CULTIVATED THREE TIMES. 
 YIELD, 34.5 BUSHELS (1911) 
 
576 
 
 BULLETIN No. 181 
 
 [April, 
 
 It would be well to compare very carefully Plot 4 with Plots 2 
 and 5. Plot 2, uncultivated, produced 6.7 bushels more corn per acre 
 than Plot 4 with standard cultivation; but the fact should be em- 
 phasized that to obtain such a result requires that the weeds be kept 
 down. Plot 5, cultivated and supplied with all the moisture that 
 was necessary, produced, as an average of eight years, only 1.8 bush- 
 els more than the uncultivated, unirrigated plot where weeds were 
 kept down. Irrigation gave an increase every year but one. This 
 exception was in 1912, when only a small amount of water was used. 
 There is no doubt that one irrigation, which was followed within a 
 few hours by a heavy rain, did no good and even may have damaged 
 the crop to some extent. 
 
 The fertilized plot, No. 6, gave a large increase, the average yield 
 being 74.5 percent above that from standard cultivation. For two 
 years, 1908 and 1909, this plot was not fertilized; hence the yields 
 for these years have been omitted in the table. In 1914, because of 
 the heavy growth, the crop was badly damaged by a storm. The 
 average yield for the seven years was 75.3 bushels per acre, or 174.5 
 percent of the yield from the standard cultivated plot for the same 
 years. 
 
 FIG. 5. PLOT 5: GROUND PLOWED AND SEED BED PREPARED, CULTIVATED THREE 
 TIMES, IRRIGATED (16.91 INCHES APPLIED). YIELD, 55 BUSHELS (1911) 
 
1015] 
 
 SOIL MOISTURE AND TILLAGE FOR CORN 
 
 577 
 
 The fact that the uncultivated corn produced so well in comparison 
 with the cultivated and with the cultivated and irrigated, shows that 
 cultivation for conservation of moisture is a very secondary consid- 
 eration in this climate on brown silt loam, the common prairie soil of 
 the corn belt. On Plot 2 the crop was enabled to use all the plowed 
 soil as a feeding ground, while on Plots 4, 5, and 6 almost half the 
 plowed soil was disturbed by cultivation, so that the roots of the corn 
 were either injured or could not develop in that stratum because of 
 its dry, loose character. This was especially true on Plot 4 during 
 dry seasons. As a result, the plant food in the stirred soil was of 
 little benefit to the crop ; and the conclusion that must be drawn is 
 that the cultivated soil is of much greater value for the plant food 
 that it contains than for the conservation of moisture. In semiarid 
 or subhumid regions this probably would not be true. 
 
 A study of the moisture content of the plots at Urbana was made 
 from samples taken to a depth of 40 inches from four different plots. 
 The samples were taken in the spring immediately after the plowing 
 was done and once each week until the corn was mature. Table 9 
 gives the results in percentage of total moisture. 
 
 FIG. 6. PLOT 6 : GROUND PLOWED, SEED BED PREPARED, CULTIVATED THREE TIMES, 
 
 IRRIGATED (16.91 INCHES APPLIED), HEAVILY FERTILIZED. YIELD, 77.3 
 
 BUSHELS (1911) 
 
BULLETIN No. 181 
 
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1915] SOIL MOISTURE AND TILLAGE FOR CORN 579 
 
 From the averages given in the table, it will be seen that the sur- 
 face stratum of the unplowed plot, No. 1, had the lowest moisture 
 content, but the difference among the plots was slight, the average 
 being only 1.0 percent higher in the plowed, uncultivated plot, No. 2, 
 .5 percent higher in the weed plot, No. 3S, and .7 percent higher in 
 No. 4, cultivated. The weed plot, both in 1911 and in 1913, showed a 
 lower moisture content than the other plots less even than the un- 
 plowed one. 
 
 Probably a better idea of the moisture content of the soil can be 
 obtained from Table 10, which gives the lowest moisture content 
 found in the surface soil during the season. 
 
 The moisture content as given includes both hygroscopic and 
 capillary moisture. The wilting coefficient of this type of soil, i.e., 
 the point at which the plant wilts permanently, or where the plant 
 has used all of the available water, is about 9.3 percent. The amount 
 of available water in the soil at any time is the difference between 
 the actual amount present and the wilting coefficient. From the 
 above it will be seen that but little available moisture was in the soil 
 at certain times in 1911, 1913, and 1914. 
 
 The temperatures at a depth of 2 and 4 inches have been deter- 
 mined once each week during the last five years on Plot 1, unplowed, 
 and on Plot 4, plowed and cultivated. The temperatures were taken 
 three times a day, at 9 a. m. and at 1 :45 and 4 :45 p.m., from plow- 
 ing time till the corn was mature. Table 11 gives the averages of 
 these determinations. 
 
 The general effect of tillage, as an average for the season, was to 
 lower the temperature from .3 to 12.4 degrees. A single exception 
 was the average temperature taken at 9 a.m. for the two-inch depth 
 in 1909, which was the same for both the plowed and the unplowed 
 soil. The average differences in temperature between the plowed and 
 the unplowed plots for the two-inch depth were 1.7 degrees at 9 a.m., 
 
 4.7 at 1 :45 p.m., and 3.9 at 4 :45 p.m. The average differences for 
 the four-inch depth were 1.3 degrees at 9 a.m., 2.2 at 1 :45 p.m., and 
 
 1.8 at 4:45 p.m. 
 
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 the tendency is for it to become warmer than the plowed and culti- 
 vated soil, and the result is that during June, July, August, and Sep- 
 tember the relative temperature of the unplo.wed, uncultivated soil is 
 higher from one to twelve degrees. 
 
580 
 
 BULLETIN No. 181 
 
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582 
 
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1915] SOIL MOISTURE AND TILLAGE FOR CORN 583 
 
 A series of experiments was conducted at the Fairfield field in 
 Wayne county, on the gray silt loam on tight clay, the common prairie 
 soil of southern Illinois, to determine the relative value of cultivation 
 on that type of soil. The results are given in Table 12, while Table 
 13 shows the monthly rainfall during the time of the experiments. 
 
 Comparing Plots 1 and 2, we find that a good seed bed, as prepared 
 on Plot 2, increased the yield by 215 percent on this type of soil, 
 while on the brow,n silt loam treated similarly at the University, it 
 gave an increase of 46.2 percent. Expressed in actual yield, the in- 
 crease at Fairfield was 12.9 bushels, and at Urbana 14.5. The yields as 
 given in the table show a benefit of only .2 bushel from cultivation 
 after the seed bed was prepared. Taking the average of the first three 
 years, it will be seen that the uncultivated plot gave an actual increase 
 of .3 bushel over the cultivated. The fertilized gave an increase of 58.1 
 percent over the standard cultivated. 
 
 EXPERIMENTS IN MANY STATES 
 
 Bulletin 257 of the United States Bureau of Plant Industry gives 
 data recently obtained on many different soils in twenty-eight states. 
 It seems unfortunate that the types of soil were not described more 
 fully in the bulletin, as some important distinctions in regard to soils 
 might be deduced. In six years' experiments with corn, from 1905 
 to 1911, representing 112 tests, the average yield from uncultivated 
 plots of various types of soil expressed in percentage of similar cul- 
 tivated plots was 99.8 percent. This figure indicates that cultivation 
 has but little value in growing a crop of corn, provided the weeds are 
 kept down in some other way. It shows that the principal value of 
 cultivation lies in the killing of weeds and not in the aeration of the 
 soil or the conservation of moisture. We find that in subhumid or 
 semiarid sections the average yield from the uncultivated land was 
 
 TABLE 14. CORN YIELDS OP UNCULTIVATED PLOTS EXPRESSED IN PERCENTAGE OP 
 THE YIELDS OF CULTIVATED PLOTS FOR DIFFERENT GROUPS OF SOIL TYPES 1 
 
 (Average of six years' experiments, 1905-1911 ) 2 
 
 Groups of soil types 
 
 Average percent 
 
 Clays 
 
 92.6 
 
 Clay loams 
 
 94.5 
 
 Silt loams 
 
 102.4 
 
 Sandy loams 
 
 105.7 
 
 Average of groups 
 
 98.8 
 
 
 
 'Data taken from U. S. Bur. Plant Indus. Bui. 257. 
 
 2 This includes only the data from soils which could be classified. 
 
584 
 
 BULLETIN No. 181 
 
 [April, 
 
 85.9 percent of that from the cultivated. This shows a greater neces- 
 sity for cultivation in such regions than in humid ones. The results 
 obtained from some of the different types of soil experimented with 
 are reported in Table 14. 
 
 It will be noticed that the value of cultivation diminishes as the 
 coarseness of the soil increases. This is what would be expected, con- 
 sidered theoretically. The fine-grained soils, such as clays and clay 
 loams, are naturally somewhat poorly aerated, and for these culti- 
 vation would be of value for aeration. In the coarser soils, the silt 
 loams and sandy loams, aeration is naturally better and hence culti- 
 vation is not so beneficial. 
 
 SUBSOILING 
 
 Investigations to determine the value- of subsoiling in preparation 
 for corn on gray silt loam on tight clay, the common prairie soil of 
 the lower Illinois glaciation, have been carried on for eight years at 
 the Odin field, in southern Illinois. Table 15 gives the results of 
 these experiments. The form of plow used, shown by Fig. 7, consists 
 of a shoe that runs in the bottom of the furrow made by the ordinary 
 mold-board plow, loosening the soil but not throwing it upon the 
 surface. 
 
 FIG. 7. SUBSOIL PLOW. FOLLOWS ORDINARY PLOW AND LOOSENS THE SOIL IN THE 
 BOTTOM OF THE FURROW 
 
 It will be seen that with every soil treatment there was an almost 
 uniform decrease in yield for subsoiling. The general average for 
 eight years shows a decrease of 2.7 bushels per acre. The alleged 
 
1915} 
 
 SOIL MOISTURE AND TILLAGE FOR CORN 
 
 585 
 
 benefit of subsoiling is the increasing of the water capacity of soils and 
 of their ability to retain water during dry seasons. Yet in 1913 and 
 1914, both of which were very dry seasons, this method, as a general 
 average, gave only the very slight increases of .5 and .7 bushel respec- 
 tively. The subsoil was loosened by the plow, but ran together as soon 
 as it was wet and became approximately as it was before. The experi- 
 ments as a whole show that subsoiling on this type of soil not only does 
 not pay, but is a losing operation, for in order to pay for the extra 
 work involved in subsoiling, at least a three-bushel increase would be 
 necessary. 
 
 NOTE. Until recently the amounts of limestone and crop residues on the Odin 
 field were too small to provide for the adequate liberation of potassium ; but where 
 larger supplies of limestone and organic matter are provided the addition of potas- 
 sium salts produces but little effect, as will be seen from the results of the Fairfield 
 experiments reported in Bulletin 123, and in the Appendix of county soil reports. 
 
 TABLE 15. CORN YIELDS IN TILLAGE EXPERIMENTS ON GRAY SILT LOAM ON TIGHT 
 
 CLAY, ODIN FIELD* 
 
 (Bushels per acre as an average of two plots) 
 
 Soil treatment 
 
 1907 
 
 1908 
 
 1909 
 
 1910 
 
 1911 
 
 1912 
 
 1913 
 
 1914 
 
 8-yr. 
 av. 
 
 Not Subsoiled 
 
 None 
 
 44.4 
 
 35.5 
 
 29.3 
 
 28.8 
 
 16.8 
 
 26.1 
 
 25 
 
 43 
 
 235 
 
 Residues 
 
 50.1 
 
 33 ft 
 
 30.4 
 
 32.8 
 
 19.0 
 
 39.6 2 
 
 3 9 
 
 3 3 
 
 265 
 
 Residues, lime 
 
 473 
 
 35.5 
 
 ft9ft 
 
 40.3 
 
 24.7 
 
 48.6 
 
 4.1 
 
 2.1 
 
 28.9 
 
 Residues, lime, phosphorus 
 
 47.0 
 
 39.9 
 
 38.9 
 
 38.7 
 
 22.8 
 
 494 
 
 6 1 
 
 2 
 
 30 6 
 
 Residues, lime, phosphorus, potas. 
 
 70.1 
 
 76.1 
 
 64.0 
 
 79.8 
 
 35.7 
 
 65.4 3 
 
 10.1 
 
 3.1 
 
 50.5 
 
 Average . 
 
 51,8 
 
 44,0 
 
 38.3 
 
 44,1 
 
 ft38 
 
 45.8 
 
 53 
 
 ft9 
 
 3ft 
 
 Subsoiled 
 
 None 
 
 37.6 
 
 32.5 
 
 24.1 
 
 22.5 
 
 133 
 
 31 7 
 
 3 2 
 
 4 
 
 21 1 
 
 Residues 
 
 43.2 
 
 26.4 
 
 27.2 
 
 35.1 
 
 19.9 
 
 24.0 2 
 
 3 6 
 
 43 
 
 22 9 
 
 Residues, lime 
 
 473 
 
 34.9 
 
 28.5 
 
 37.5 
 
 22.7 
 
 47.5 
 
 4 1 
 
 24 
 
 28 1 
 
 Residues, lime, phosphorus 
 
 44.4 
 
 45.9 
 
 37.6 
 
 39.8 
 
 19 9 
 
 28 1 
 
 79 
 
 2 5 
 
 28 3 
 
 Residues, lime, phosphorus, potas. 
 
 59.4 
 
 60.3 
 
 60.4 
 
 85.6 
 
 40.4 
 
 48.5 2 
 
 10.1 
 
 5.0 
 
 46.2 
 
 Average 
 
 46.3 
 
 40.0 
 
 35.5 
 
 44.1 
 
 23.2 
 
 35.9 
 
 5.8 
 
 3.6 
 
 29.3 
 
 'The east half Q| each plot of each series was subsoiled as follows: Series 
 400 in 1907, Series 300 in 1908, Series 200 in 1909, Series 100 in 1910, and so on 
 in regular succession. 
 
 2 Yields from single plots, as the corn in two plots in 1912 was badly damaged 
 by water. 
 
 DEEP TILLING 
 
 Farmers are frequently urged to purchase a machine for plowing 
 to a depth of 12 to 15 inches. There is little doubt that under certain 
 conditions of soil and climate such plowing would be beneficial; but 
 the results obtained by the Experiment Station in this state with the 
 deep-tilling machine on the common prairie soil of the corn belt do 
 
586 BULLETIN No. 181 [April, 
 
 not warrant recommending its purchase. Experiments have been 
 started also on gray silt loam on tight clay, in southern Illinois, to 
 determine the comparative value of ordinary plowing, subsoiling, deep 
 tilling (plowing 12 to 15 inches deep), and dynamiting the subsoil. 
 Only one year's results have been secured, and no conclusions are as 
 yet justified. 
 
MVERSITYOFILLINOIS-URBANA 
 
 C001 
 
 166-181 1914-15 
 
 ' 
 
 3011201*28436 
 
 >*"** 
 
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