DIVERSITY OF 
 
 
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 CHECK FOR UNBOUND 
 CIRCULATING COPY 
 
UNIVERSITY OF ILLINOIS 
 
 Agricultural Experiment Station 
 
 BULLETIN No. 259 
 
 THE CULTIVATION OF CORN 
 
 Weed Control vs. Moisture Conservation 
 
 BY D. C. WIMER AND M. B. HARLAND 
 
 URBANA, ILLINOIS, MARCH, 1925 
 
SUMMARY 
 
 The principal object and greatest value of corn cultivation 
 on Brown Silt Loam is the destruction of weeds. Weedy corn 
 probably suffers more from a lack of nutrients than from a 
 moisture deficiency in this climate. Since cultivation is the 
 only practical method of controlling weeds, the depth and 
 frequency of corn cultivation should be determined by their 
 growth. The growth of weeds should be prevented in so far 
 as possible by shallow rather than by deep cultivation. 
 
 Deep cultivation of corn may result in root injury and 
 decreased yields in comparison with shallow cultivation. The 
 effect of excessive and deep cultivation seems comparable to 
 that of actual root pruning. Proper cultivation should kill 
 the weeds with minimum injury to the corn roots; obviously, 
 this is more easily accomplished when the weeds are small. 
 
 The need for cultivation seems to be no greater in dry 
 than in wet years; it may, in fact, be less. However, on 
 heavy soils which check badly, cultivation may be necessary 
 in order to fill the large cracks and thus stop the direct loss 
 of moisture from the deeper strata. 
 
 The data and brief discussions presented in this bulletin 
 are intended to be of assistance in developing the principles 
 underlying the successful cultivation of corn and are not in- 
 tended as recommendations of specific methods or particu- 
 lar implements. 
 
 (This Bulletin is a revision of No. 181. Soil Moist- 
 ure and Tillage for Corn, issued in 1915. See note, 
 page 196.) 
 
THE CULTIVATION OF CORN 
 
 Weed Control vs. Moisture Conservation 
 
 By D. C. WIMER, Assistant Chief in Soil Physics, and M. B. HARLAND, First 
 Assistant in Soil Physics 
 
 The cultivation of corn is clearly for the purpose of making a more 
 satisfactory crop yield possible. The specific reasons why cultivation 
 helps to achieve this result are not so obvious. Several explanations 
 have been offered; one, a common assumption, has been that the mulch 
 formed by cultivating the soil results in the conservation of moisture. 
 There seems to be no evidence to justify this conclusion; instead, it is 
 now generally recognized that the drier the season, the less need for 
 cultivation. Even in arid and semiarid regions where the evaporation 
 rate is high, cultivation apparently results in little or no conservation of 
 moisture. The killing of weeds, however, appears to have been proved 
 the most important object of cultivation; except on very heavy soils 
 which check badly, it seems that cultivation ordinarily is necessary only 
 for the control of weed growth. 
 
 A dry crust is probably just as effective in checking the movement of 
 water vapor from the deeper layers of moist soil to the open air as is a 
 dry, granular mulch. If the conditions are such that this dry top layer 
 forms promptly, then it is clear that cultivation is not needed as an aid 
 to its formation. If it does not form promptly, then cultivation will 
 assist in its formation by increasing temporarily the rate of evaporation. 
 Fig. 1 perhaps gives a clearer idea of the way in which a dry top layer 
 of soil affects evaporation than can be given by discussion. 
 
 Under field conditions, the upward movement of capillary water is 
 very slow as soon as the saturated condition of the soil in early spring 
 is past. A dry top layer then forms readily because the amount of 
 water evaporated from the surface exceeds the amount brought up by 
 capillary rise, and loss by evaporation is thus decreased. 
 
 From the above it would seem that conservation of moisture is not 
 a reason for cultivating corn except possibly in case of soils which crack 
 badly. This conclusion is strengthened by the fact that early in the 
 growth period the corn roots become so completely distributed between 
 the rows that they intercept any moisture which may be brought up by 
 capillary action. Thus there is little chance of the moisture reaching the 
 surface and evaporating. 
 
 SHALLOW CULTIVATION PREFERABLE 
 
 Cultivation should always be as shallow as possible, altho deeper 
 stirring is less harmful at the first cultivation than later. For the highest 
 yields, cultivation should never be deep enough to injure the roots, for 
 such injury is likely to retard the development of the corn plant. 
 
 175 
 
176 
 
 BULLETIN No. 259 
 
 [March, 
 
 It must be remembered too, that the plowed stratum is the richest 
 in available plant nutrients, and that it is far more valuable as a feeding 
 ground for the corn roots than it is as a dry layer of soil functioning 
 as a mulch. 
 
 That good yields of corn cannot be produced in fields where weeds 
 are allowed to grow unmolested is clearly shown by results of experi- 
 
 EVAPORATION RATE DETERMINED BY 
 KATE OF CAPILLARY RISE. 
 
 EVAPORATION KATE DCTEKUWED BY RATt OF 
 PAS^ACC. OF WATER VAPOK THRU MYSO/L 
 
 
 
 
 
 
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 EVAPORATION OF SOIL MOISTURE 
 
 So long as the soil is moist entirely to the surface (A), evaporation is 
 free to go on; but just as soon as a dry layer forms (B and C), the 
 evaporating surface is lowered to the bottom of the dry soil and any 
 further loss must take place by movement of the water in the form of 
 vapor thru the dry soil. Since the movement of water in this way is 
 exceedingly slow, the loss of soil moisture is greatly lessened. 
 
 ments at this Station and by the experience of farmers. For instance, 
 with the same preparation of seed bed, only 7.4 bushels of corn per acre 
 were produced as a nine-year average where weeds were allowed to 
 grow, while 48.9 bushels were obtained where the weeds were kept 
 down without any cultivation. Keeping the weeds down was apparently 
 responsible for an increase of 41.5 bushels yearly. This is easy to under- 
 stand when we realize that weeds deprive the corn plant of moisture, 
 light, and nutrients, all of which are necessary for the growth of the 
 plant and seed. Of these factors, however, the lack of plant nutrients 
 probably makes the greatest difference. 
 
 On another plot weeds were allowed to grow, but the plot was irri- 
 gated so that the corn was not deprived of moisture, yet the increase 
 from irrigation as a five-year average was only 2.5 bushels an acre. 
 
1925] THE CULTIVATION OF CORN 177 
 
 Weeds are much better foragers than are most cultivated crops; as 
 has well been said, "It would be just as reasonable to expect a lamb to 
 thrive with a bunch of hogs as to expect corn to compete with weeds." 
 
 EARLY EXPERIMENTS AT URBANA 
 
 Morrow and Hunt began some experiments in 1888 to determine 
 the value of cultivation and its best depth and frequency; also the effect 
 of root pruning. These experiments were continued up to and including 
 1893 by Gardner, who concluded that "there seems to be no advantage 
 in cultivating more frequently than is necessary to destroy weeds and 
 keep the ground moderately porous; that shallow cultivation has never 
 failed to produce an increase in yield over that of deep cultivation"; and 
 that "root pruning has never failed to reduce the yield in a marked 
 degree." Table 1, reprinted from Bulletin 181 of this Station, gives a 
 partial summary of the results obtained in these early cultivation experi- 
 ments, and Table 2 shows the rainfall by months during the time the 
 experiments were in progress, with the exception of the year 1888, for 
 which the record is not complete. 
 
 Where the weeds were kept down by scraping with a hoe without 
 producing a mulch, the yield as a six-year average was 96.9 percent of 
 that for ordinary, shallow cultivation a difference of 2.1 bushels an 
 acre in favor of cultivation. Deep cultivation practiced four or five times 
 also gave a 96.9-percent yield, or 2.1 bushels less than shallow cultiva- 
 tion. As a five-year average, shallow cultivation practiced twelve to 
 fourteen times during the season gave a 103.6-percent yield, or an 
 increase of 2.5 bushels an acre over ordinary shallow cultivation, while 
 deep cultivation the same number of times gave a 91.7-percent yield, or 
 a decrease of 5.8 bushels an acre. Compared with twelve to fourteen 
 shallow cultivations, deep cultivation practiced twelve to fourteen times 
 resulted in a decrease of 8.3 bushels an acre. 
 
 These decreased yields from deep cultivation seem comparable to 
 the results secured from actual root pruning in another portion of the 
 same experiment. A frame twelve inches square was placed over the hill 
 and a knife run around the outside to a depth of four inches, thus cut- 
 ting the roots to that depth. Where shallow cultivation was practiced, 
 this pruning resulted in a decrease of 13.2 bushels an acre as an average 
 of six years, but where the weeds were removed by scraping with a hoe 
 instead of by shallow cultivation, the yield was diminished 16.9 bushels 
 an acre as an average of four years. 
 
178 
 
 BULLETIN No. 259 
 
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1925] THE CULTIVATION OF CORN 179 
 
 LATER EXPERIMENTS AT URBANA 
 
 The results obtained by Morrow and Hunt were contrary to popu- 
 lar belief and seemed so remarkable that in 1906 and 1907 a series of 
 experiments was begun to test them and at the same time to obtain 
 information on some other features such as the damage resulting from 
 allowing weeds to grow and the value of seed-bed preparation, irriga- 
 tion, and fertilizer treatment. 
 
 The results of these experiments, as given in Table 3, represent the 
 averages of first and second-year corn; the individual yields are reported 
 in Table 4 for the convenience of those who may care to make a more 
 thoro study of the data. Table 5 gives the rainfall during the time, 
 covered by the experiments. 
 
 The soil on which these experiments were conducted is Brown Silt 
 Loam, an upland prairie soil formed from loess overlying the drift of 
 the early Wisconsin glaciation. This soil is fairly representative of the 
 gently undulating areas of the corn belt in Illinois. The field had been 
 under cultivation for fifty years or more, but during that time no ferti- 
 lizer had been applied, with the possible exception of barnyard manure. 
 
 A four-year rotation of corn, corn, oats, and clover was practiced. 
 The cornstalks and both crops of clover were removed. In 1912 and 
 1914 soybeans were grown because of the failure of clover. The cultivat- 
 ing was done with the three-shovel cultivator till 1912, and after that 
 the surface cultivator was 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 
 the time when corn should have been making its greatest growth and 
 needed a large supply oi moisture. It will be noted that in 1911 during 
 June only .82 inch of rain fell, and during July .62 inch; while in 1913 
 in May only .56 inch fell; in June, 1.67 inches; 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 6 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 by the furrow method of irrigation, individual appli- 
 cations being approximately equal to one inch of rainfall. After it was 
 absorbed and the soil had become sufficiently dry, the furrows were 
 partly filled with loose soil to prevent an excessive loss by evaporation. 
 The yields for 1913 were diminished by the extreme heat during the 
 time when pollination was taking place. A storm on July 16, 1914, 
 damaged the corn on all plots to some extent, but particularly where 
 the growth was rank, as on the fertilized and irrigated plots. 
 
180 
 
 BULLETIN No. 259 
 
 [March, 
 
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19251 
 
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 BULLETIN No. 259 
 
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1925] THE CULTIVATION OF CORN 183 
 
 CULTIVATION NEEDS No GREATER IN DRY YEARS 
 
 The statement has frequently been made that the drier the season, 
 the greater the need of cultivation. However, this has never been proved 
 by experimental results where the yield of the crop produced has been 
 taken as the standard of measurement. There is, on the other hand, 
 
 AVERAGE RAINFALL 
 
 
 AVERAGE RAINFALL 
 
 1907 1908 1909 1910 1911 1912 1913 1914 1915 
 SECOND YEAR CORN 
 
 AVERAGE RAINFALL 
 
 I 
 
 1907 1906 1909 13/0 1911 19/2 1913 
 
 AVERAGE. OF FIRST AND SECOND YEAR CORN 
 
 FIG. 2. THE NECESSITY OF CULTIVATION AS INFLUENCED BY RAINFALL 
 
 This diagram constructed from the data given in Tables 3, 4, and 6, shows 
 the comparative yields on the "scraped" and "cultivated" plots in relation to the 
 total rainfall from April 1 to August 31. There seems to be little or no evidence 
 of greater cultivation need in seasons of limited rainfall. 
 
184 
 
 BULLETIN No. 259 
 
 [March, 
 
 some evidence which tends to discredit, if not to disprove, this teaching. 
 It may be noted from the accompanying diagram (Fig. 2) that dur- 
 ing the four years when the rainfall was below the nine-year average, 
 cultivation gave an increased yield but once. This increase 14.8 
 
 FIG. 3. DECREASED GROWTH RESULTED WHERE PLOWING AND PREPARATION OF SEED 
 
 BED WERE OMITTED 
 
 On this plot (No. 1, photographed in 1911) the weeds were kept down by scraping 
 with a hoe, but the ground had not been plowed nor a seed bed prepared. Compare 
 with Fig. 4. 
 
 bushels an acre in the first-year corn in 1910 is insignificant when com- 
 pared with the total decrease in the first- and second-year corn in 
 1910, 11 and 1913, 14, which amounted to 58.8 bushels. The net de- 
 crease as a result of cultivation on the two plots during the four years 
 when the rainfall was deficient in the growing period, was 44 bushels an 
 acre. An average decrease of 5.5 bushels of corn to an acre would 
 hardly warrant any recommendations for more cultivation in dry 
 seasons. 
 
 TREATMENT OF PLOTS 
 
 Plot 1 (Fig. 3) was plowed for the oats crop only; that is, but once 
 in each rotation. The vegetation, such as clover or corn stubs, was 
 removed and the corn planted with a hoe. The weeds were kept down 
 
1925] 
 
 THE CULTIVATION OF CORN 
 
 185 
 
 by scraping with a sharp hoe so as to produce practically no mulch, and 
 this was done only as often as necessary to kill the young weeds. 
 
 Plot 2 (Fig. 4) was plowed in the spring about 6 inches deep for 
 corn; a good seed bed was prepared before planting the corn, but no 
 
 FIG. 4. BETTER GROWTH RESULTED FROM PLOWING AND PREPARATION OF SEED BED 
 
 On this plot (No. 2, photographed in 1911) the ground was plowed, a seed bed 
 prepared, and the weeds kept down by scraping with a hoe. 
 
 cultivation was given after planting. The weeds were kept down in the 
 same way as on Plot 1. 
 
 Plot 3S (Plot 3 until 1911) (Fig. 5) was plowed in the spring and 
 a good seed bed prepared, but after planting the corn, 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 (Fig. 6) was treated the same as Plot 2 except that the corn 
 was given three shallow cultivations with the three-shovel cultivator 
 previous to 1912 and with the surface cultivator after that time. Any 
 weeds that escaped the cultivator were pulled or cut out with a hoe. 
 
 Plot 5 (Fig. 7) was treated the same as Plot 4 except that the crop 
 was irrigated whenever it seemed necessary. 
 
186 
 
 BULLETIN No. 259 
 
 [March, 
 
 Plot 6 (Fig. 8) was treated similarly to Plot 5 except that 2 tons 
 of rock phosphate and 80 tons of manure per acre were applied once in 
 each rotation before the second crop of corn. 
 
 DISCUSSION OF RESULTS 
 
 In Table 3, the yield of the cultivated plot, No. 4, is taken as the 
 standard for computing the relative yields shown in the last three 
 columns. On Plot 1, without plowing or the preparation of a seed bed 
 in any way the average yield for nine years was 35.2 bushels an acre, 
 or 81.3 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 
 and the weeds kept down, the percentage yield was 112.9; while the 
 average actual yield for the nine years was 48.9 bushels, or an increase 
 of 13.7 bushels an acre over Plot 1. This increase presumably repre- 
 sents the value of seed-bed preparation. The lowest yield on Plot 2 
 was 33 bushels in 1908 and the highest, 75.5 bushels in 1912. At the 
 time these results were secured it seemed scarcely possible that so high 
 
 FIG. 5. UNMOLESTED WEED GROWTH BADLY STUNTED THE GROWTH OF CORN 
 
 This plot (No. 3S, photographed in 1911) was undisturbed after planting. In spite 
 of previous plowing and seed-bed preparation, the resultant growth of corn was very 
 poor and the yields appreciably lower than might be expected from the growth shown. 
 
1925] 
 
 THE CULTIVATION OF CORN 
 
 187 
 
 a yield could be produced without cultivation. It will be noticed that 
 Plot 2, uncultivated, gave larger yields four out of the nine years than 
 Plot 5, the cultivated and irrigated plot, and that the average for Plot 2 
 was 5.6 bushels larger than for the standard cultivated plot, No. 4. 
 
 The treatment on Plot 3 was for the purpose of determining the 
 effect of weeds on the corn crop. It will be noticed that the average 
 yield of Plot 3S was only 17.1 percent of that of the cultivated plot; 
 however, the actual yields varied from to 16 bushels. The results on. 
 this plot 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 effect was quite 
 noticeable both on the corn and the weeds, but as an average of five 
 years the yield of corn was increased only 2.5 bushels an acre. It must 
 therefore appear that the injury done by weeds is not due so much to 
 the moisture they take out of the soil as to some other cause or causes. 
 
 FIG. 6. WEED CONTROL BY MEANS OF MODERATE CULTIVATION INSURED 
 A MORE SATISFACTORY GROWTH 
 
 This plot (No. 4, photographed in 1911) was plowed, a seed bed prepared, and the 
 corn cultivated three times. Compare with Figs. 4 and 5. 
 
188 
 
 BULLETIN No. 259 
 
 [March, 
 
 It would be well to compare very carefully Plot 4 with Plots 2 
 and 5. Plot 2, uncultivated, produced 5.6 bushels more corn per acre 
 than Plot 4 with standard cultivation; but the fact should be empha- 
 
 FIG. 7. IRRIGATION GAVE A SOMEWHAT INCREASED GROWTH 
 
 Irrigation on this plot (No. 5, photographed in 1911) in addition to plowing, seed- 
 bed preparation, and cultivation, gave better growth but not an economic increase 
 in yield. 
 
 sized that to obtain such a result the weeds must be kept down. Plot 5, 
 cultivated and supplied with all the moisture that was necessary, pro- 
 duced as an average of nine years only 1.3 bushels more than the 
 uncultivated, unirrigated plot where weeds were kept down. Irrigation 
 gave an increase every year but two. These exceptions were in 1912 
 and 1915, when only a small amount of water was used. There is no 
 doubt that the one irrigation in 1912, 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 fertilizer treatment for Plot 6 was accidentally omitted for the 
 1909 crop of second-year corn; for this reason, the yield for that year, 
 as given in Table 3, is for first-year corn only, and is not included in the 
 averages. In 1914 a storm damaged the crop badly, especially on the 
 fertilized plot, where the growth was particularly heavy. The increase 
 
1925] 
 
 THE CULTIVATION OF CORN 
 
 189 
 
 for fertilization as an average of eight years was 18.3 bushels an acre, 
 as shown by comparing the yields on Plots 5 and 6 (Table 3). It should 
 be noted that the fertilized plot received an excessive amount of manure 
 
 FIG. 8. FERTILIZATION PRODUCED GREATER GROWTH OF CORN 
 
 This plot (No. 6, photographed in 1911) was plowed, prepared, cultivated, and 
 irrigated in a way similar to Plot 7, but in addition received liberal applications of rock 
 phosphate and manure. The fertilizer treatment, however, was so excessive that the 
 increased yield does not represent an economic gain. 
 
 and rock phosphate, and that the increased yield on this plot is no indi- 
 cation of the value of rational fertilizer treatment on this soil. 
 
 The fact that the uncultivated corn produced so well in comparison 
 with the cultivated, also with the cultivated and irrigated, shows that 
 cultivation for conservation of moisture is decidedly a secondary con- 
 sideration in this climate on Brown Silt Loam. On Plot 2 the crop 
 could use all the plowed soil as a feeding ground, while on Plots 4, 5, 
 and 6 probably half the plowed soil was so disturbed by cultivation 
 that the roots of the corn were either injured or could not develop in 
 the stirred portion because of its dry, loose character. This was espe- 
 cially true on Plot 4 during dry seasons. As a result, the nutrients in 
 the stirred soil were of little benefit to the crop; the logical conclusion is 
 that the cultivated soil is of much greater value for the plant nutrients 
 it contains than for the moisture it may conserve. 
 
190 
 
 BULLETIN No. 259 
 
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1925~\ THE CULTIVATION OF CORN 191 
 
 EXPERIMENTS IN SOUTHERN ILLINOIS 
 
 A series of experiments was conducted at the Fairfield experiment 
 field in Wayne county, on Gray Silt Loam On Tight Clay, the common 
 prairie soil of southern Illinois, to ascertain the relative value of cultiva- 
 tion and thoro seed-bed preparation on that type of soil. 
 
 This experiment in general was similar to the one begun at Urbana 
 in 1907 except that irrigation was not practiced. The plots, twelve in 
 number and one-tenth of an acre in size, were arranged in two series, 
 one of which was cropped to corn in 1908 when the experiment was 
 started. According to the records, the 1908 corn yields are unreliable, 
 due to damage by livestock, and are therefore omitted. No corn was 
 grown on either series in the years 1909 and 1910. The original four- 
 year rotation of corn, cowpeas, wheat, and clover was changed in 1912 
 to a two-year rotation of corn and soybeans. The tillage and fertilizer 
 treatments of the individual plots are explained in Table 7. Table 8 
 shows the monthly rainfall during the years for which the corn yields 
 are reported. 
 
 The value of seed-bed preparation is shown by comparing the corn 
 yields on Plot 1, which received no preparation, with those on Plot 2, 
 which was thoroly prepared prior to planting. This comparison shows 
 that on Gray Silt Loam On Tight Clay, seed-bed preparation trebled the 
 yield. On Brown Silt Loam at Urbana it resulted in an increase of 
 almost 40 percent. Expressed in actual yield, the increase at Fairfield 
 was 12.9 bushels an acre, and at Urbana, 13.7 bushels. 
 
 Where the seed bed had been prepared, cultivation resulted in an 
 apparent decrease of 2.6 bushels an acre, as a four-year average (com- 
 pare Plots 2 and 4). For the first two years the decrease was 5.8 bushels 
 an acre a year. 
 
 The fertilized plot, No. 5, yielded 64.3 percent more than the 
 standard cultivated plot, No. 4, an increase of 10.8 bushels an acre 
 yearly. This, however, does not represent a profitable gain because of 
 the cost of the excessive fertilizer treatment. 
 
 The Fairfield results, while failing to indicate the relative merits 
 of scraping compared with ordinary cultivation, show rather clearly 
 the necessity of seed-bed preparation on this type of soil. However, 
 the limited amount of data furnished by the present experiment does 
 not warrant the drawing of any definite conclusions. 
 
 RECENT EXPERIMENTS AT URBANA 
 
 The most recent experiments on corn cultivation at this Station 
 were conducted from 1916 to 1921 inclusive, on the Roland farm, 
 Urbana, which is now a part of the Stadium field. The purpose of this 
 series of experiments was to study the effect upon corn yield of weeds 
 growing unmolested; of surface scraping to eradicate weeds without 
 the formation of a mulch; and of shallow cultivation with blade or 
 
192 BULLETIN No. 259 [March, 
 
 shovel cultivator. These studies were made on both fertilized and un- 
 fertilized plots, arranged in four series of six plots each. The size of 
 the individual plots was y 6 -^ of an acre. 
 
 The soil on which these experiments were conducted is the 
 morainal Brown Silt Loam, the same type of soil used for the series of 
 cultivation experiments in progress from 1907 to 1915. A four-year 
 rotation of corn, corn, oats, and sweet clover was practiced, with soy- 
 beans as a substitute crop when the clover failed in 1916, 1917, and 
 1919. All cornstalks and residues were removed from those plots 
 which received no treatments of manure, rock phosphate, or limestone. 
 All corn plots were disked, plowed, prepared, and planted in the same 
 manner. 
 
 TREATMENT OF PLOTS 
 
 On Plots 1 and 2 the weeds were allowed to grow. On Plots 3 and 
 4 the weeds were kept down by scraping with a sharp hoe without 
 forming a mulch. On Plots 5 and 6 the corn was given three or four 
 shallow cultivations, a blade cultivator being used on the north half 
 and a 3-shovel cultivator on the south half of the plots. The average 
 depth of the cultivations was about 1 to 1% inches for "blades" and 
 2 to 3 inches for "shovels." 
 
 With reference to the fertility treatments, Plots 1, 3, and 5 served 
 as checks in that they received no residues, manure, phosphate, or 
 limestone. Plots 2, 4, and 6 received manure in proportion to the crops 
 produced, also 1 ton of rock phosphate and 2 tons of limestone per 
 acre once in a rotation. Manure, equal in weight to all corn (grain), 
 oats (grain and straw), and clover (hay and seed) removed from each 
 plot, was returned to that plot in the spring preceding second-year 
 corn. Applications of phosphate and limestone were made in the fall 
 or early winter previous to the 1916 and 1920 crops. 
 
 DISCUSSION OF RESULTS 
 
 A careful study of the data in Tables 9, 10, and 11, reporting 
 yields and rainfall, fails to show any definite relation, similar to that 
 illustrated in Fig. 2, between the total rainfall during the growing 
 period and the cultivation needs of corn in seasons of deficient rainfall. 
 
 In Table 9 the yield of the shovel-cultivated plot is taken as 100 
 percent, or the standard for computing the relative yields of the other 
 plots. It should be noted that since the actual yields of the standard 
 plots (the cultivated plots Nos. SS and 6S), are widely different, the 
 percentage values for the yield of corn on the unfertilized plots are not 
 directly comparable with those of the fertilized plots. 
 
 The corn yields, as shown by the six-year averages, were always 
 higher on the fertilized than on the corresponding unfertilized plots. 
 The fertility treatment gave an apparent increase of 4.6 bushels of 
 
1925} 
 
 THE CULTIVATION OF CORN 
 
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194 
 
 BULLETIN No. 259 
 
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196 BULLETIN No. 259 
 
 corn per acre on the weed plot, No. 2; 2.3 bushels on the scraped plot, 
 No. 4; 5.1 bushels on the "blade" cultivated plot, No. 6N; and 8.4 
 bushels on the "shovel" cultivated plot, No. 6S. These increases are 
 probably too small to show an economic gain for the fertilization used. 
 
 The removal of weeds by scraping with a hoe instead of by culti- 
 vation increased the yield 46.3 bushels an acre on the unfertilized 
 plot, No. 3, and 44 bushels on the fertilized plot, No. 4. The average 
 yields of the unfertilized plots that were scraped and cultivated (Plots 
 3 and 5) show no significant differences, thus indicating that the great- 
 est value of cultivation with either blades or shovels was to eradicate 
 weeds. 
 
 When fertilized, the cultivated plots produced an average of 2.5 
 to 3.9 bushels an acre more than the scraped plots. While no great 
 importance can be attached to these small differences, they might sug- 
 gest the possibility that the corn plant, when grown on a heavily 
 fertilized soil, is less dependent upon the natural fertility of the surface 
 soil or perhaps has greater power of recovery from root injury caused 
 by cultivation. 
 
 NOTE 
 
 This bulletin includes material published in Bulletin 181 of this Station (1915) 
 entitled "Soil Moisture and Tillage for Corn," by J. G. Mosier and A. F. Gustafson. 
 Its purpose is to bring the discussion on corn cultivation up to date and to include 
 the final results, the work on this problem now having been discontinued. 
 
 The experimental work on corn cultivation at the Illinois Station, as herein 
 reported, falls into three periods: first, early experiments at Urbana begun in 1888 by 
 Morrow and Hunt and terminated in 1893; second, later experiments begun at Urbana 
 in 1906 and at Fairfield in 1908 by Mosier and terminated in 1915; third, experiments 
 begun in 1915 on the Roland farm, Urbana, by Mosier and Gustafson, and terminated 
 in 1922 because of the location of the Memorial Stadium on this field. 
 
 The data secured during the first period of experimentation are reprinted from 
 Bulletin 181; the data obtained in the second period have been corrected, completed, and 
 rearranged in part; while the data secured since Bulletin 181 was published, or for the 
 third period, are presented for the first time. It should be explained that the soil tem- 
 perature and moisture data found in Bulletin 181 are omitted because subsequent work 
 has shown them to be of questionable value; the number of determinations of temper- 
 ature and moisture in the individual plots was insufficient to give reliable averages. 
 
 This material represents the contributions of a number of present and former mem- 
 bers of the Agronomy Department. Special recognition should be given the late Pro- 
 fessor J. G. Mosier and Professor A. F. Gustafson, mentioned above, Mr. F. A. 
 Fisher, now Farm Adviser of Wabash county, and Dr. R. S. Smith, Associate Chief 
 in Soil Physics. 
 

UNIVERSITY OF ILLINOIS-URBANA