THE UNIVERSITY OF ILLINOIS LIBRARY 630.7 wo. 34-9-362 , T3— Jl (o t> T3 ^f Response of Illinois Soils to SyBttWbf Soil Treatment yjSliVtriv)! By F. C. BAUER UNIVERSITY OF ILLINOIS AGRICULTURAL EXPERIMENT STATION BULLETIN 362 CONTENTS PAGEI INTRODUCTION 437; PART I. COMPARISON OF ILLINOIS SOILS IN THEIR RESPONSE TO SOIL TREATMENT 442 Variations in Natural Productiveness of Illinois Soils 442 Manure Alone Effective on Most Soils 444 Value of Crop Residues Dependent on Successful Growth of Legumes.. 446 1 Limestone Effective When Used With Manure 449 Limestone Influence More Striking in Absence of Manure 451 Rock Phosphate With Manure and Limestone Gives Variable Results . . 456 Rock Phosphate More Effective in Grain Systems 459 High Variability in Rock Phosphate Response a Complex Problem 461 Potassium Response Better on Light-Colored Soils 466. Light-Colored Soils Show Greater Response to Soil Treatment 470 Soil Treatment Tends to Reduce Fertility Inequalities 472 Total Level of Crop Production the Important Consideration 472,1 Soil Treatments Change in Their Effectiveness 474 i PART II. MANAGEMENT PRACTICES FOR ILLINOIS SOILS 476' Dark Soils With Heavy, Noncalcareous Subsoils 476 I Dark Soils With Heavy, Calcareous Subsoils 480 Dark Soils With Noncalcareous Subsoils 482 Dark Soils With Open, Noncalcareous Subsoils 484 Dark Soils With Impervious, Noncalcareous Subsoils 488 , Gray Soils With Impervious, Noncalcareous Subsoils 491 Yellow Soils With Noncalcareous Subsoils 499 Brownish Yellow Soils With Open, Noncalcareous Subsoils 500. Sandy Loams and Sands 504 Hilly Land 506 PART III. IMPORTANT GUIDING PRINCIPLES IN SOIL MANAGE- MENT 508 Soils Constantly Changed by Natural Forces 508- How Farm Practices Influence Soil Productivity 509 SUMMARY 512 APPENDIX 514a Urbana, Illinois December, 1930 Publications in the Bulletin series report the results of investigations made or sponsored by the Experiment Station Response of Illinois Soils to Systems of Soil Treatment By F. C. Bauer, Chief, Soil Experiment Fields INTRODUCTION »~^r "7"ARIATI0N in crop-producing power is an outstanding char- A / acteristic of soils. Not only are variations evident among soils v in different locations but they are to be found also on the same soil in different seasons. Frequently they are quite marked, assuming with some soils a gradual downward trend, with others a gradual trend upward. Knowledge of the causes of these natural variations and of the means of controlling them obviously becomes of fundamental im- portance in the successful management of farm lands. Indeed the best use of such lands will depend to a large extent on the knowledge that farmers possess concerning their soils and the effects of the crop- ping and treatment practices they use. Broadly speaking, farmers are interested in the simplest management practices that will give them the most profitable yields. Twenty-Eight Experiment Fields Furnish Data for Study For many years the Illinois Agricultural Experiment Station, thru survey, chemical investigation, and field culture experiments, has sought to obtain useful agricultural information about the soils of the state. The various types of soil are being carefully classified, mapped, and inventoried, and a number of the more extensive ones, varying widely in productiveness, are being studied with respect to their re- sponse to different systems of soil treatment and management. This bulletin brings together, in summarized form, certain results obtained from twenty-eight experiment fields that are located on representative types of Illinois soils and have been under investigation for periods ranging from fifteen to twenty-six years. For purposes of simplifying the discussion, this bulletin is divided | into three parts. Part I is primarily a comparison of different Illinois soils with respect to their susceptibility to improvement for crop pur- poses. Part II is primarily a study of the merits of different systems [l. of soil treatment when applied to soils of similar characteristics. While I a farmer is interested in knowing what may be expected from different kinds of soils, he is more interested in knowing what can be expected from different systems of soil treatment that he might use on his own farm. The discussion' in Part II is therefore presented from this point 437 438 Bulletin No. 362 [December, of view, specific suggestions being made as to the best management for each type of soil. In Part III certain broad principles concerning soils and their improvement are discussed, the long-time experiments on the famous Morrow plots on the campus of the University of Illi- nois being used to illustrate the points made. Eight Systems of Soil Management In the investigational work carried out on the twenty-eight fields discussed herein, eight rather definite systems of soil treatment and management have been given special attention. An outline of these systems is shown below: Plot Treatment No. symbols 1 2 M ML MLrP 7 RL 8 RLrP 9 RLrPK 10 Description No treatment. All crop growth is removed. Manure. Animal manure, with accompanying litter, is ap- plied in proportion to the weight of crops removed during the previous rotation, and is plowed down for the corn crop. Manure, limestone. Crushed limestone is applied initially at the rate of 4 tons an acre, and thereafter once during the rotation, at the annual rate of 1,000 pounds an acre on the plowed soil. The application is usually made just ahead of wheat seeding. In the experiments here reported no lime- stone has been applied since 1923. Manure, limestone, rock phosphate. The rock phosphate ap- plied once during the rotation at the annual rate of 500 pounds an acre is plowed under for the wheat crop. Ap- plications cease when a total of 4 tons has been applied. No treatment. All crop growth is removed. Crop residues. Chiefly cornstalks, green manure, sweet clover, second crop of clover, and legume chaff and residues after the removal of the seed, are plowed under at conven- ient times during the rotation. Until recent years oats and wheat straw were also returned. Crop residues, limestone. See above. Crop residues, limestone, rock phosphate. See above. Crop residues, limestone, rock phosphate, kainit. Kainit, a potash salt, is applied once during the rotation at the annual rate of 200 pounds an acre in connection with the rock phosphate. During recent years this amount has been applied twice during the rotation, one-half for corn and one-half for wheat. No treatment. All crop growth is removed. Ten individual plots, it will be noted, have been devoted to these experiments. Seven of these plots have received various kinds of soil treatment and three have been left untreated to serve as checks. Of 1930] Response of Illinois Soils to Soil Treatment 439 the seven treated plots three have received animal manure in accord- ance with good livestock farming practices, and four have received the various crop residues that were grown upon them. The manure plots represent systems of farming in which the chief source of income is from livestock products and the other plots systems of farming where the chief source of income is from the sale of grain. Definite crop rotations have been practiced in connection with these systems of soil treatment. The plots are so arranged that it has been possible to grow each crop in the rotation each year. Altho the cropping program has varied somewhat, a four-year rotation consisting of wheat, corn, oats, and clover has been used on a number of the fields. This rotation permits the growing of sweet clover in the wheat for use as a green manure for the corn crop following, a practice of value in grain systems of farming where no animal manure is avail- able. Widely Varying Soil Conditions Represented A diversity of soil conditions and soil types are represented by the Illinois soil experiment fields. The soil types, while showing more or less variation among the different fields, can be classified into groups with certain similar characteristics. The following outline indicates their general grouping, and the accompanying map (Fig. 1) shows the location of these soil groups and of the soil experiment fields over the state. The numbers coincide with group-numbers on the map. 1 1. Dark soils with heavy, noncalcareous subsoils Semimature soils Bloomington, McLean county Sidell, Vermilion county Young soils Aledo, Mercer county LaMoille, Bureau county Minonk, Woodford county 2. Dark soils with heavy, calcareous subsoils Young soils (influenced by sedimentation) Hartsburg, Logan county Young soils (erosion continually exposes the compact little-weathered subsoil) Joliet, Will county 3. Dark soils with noncalcareous subsoils Semimature soils Urbana, Champaign county Young soils Kewanee, Henry county J Thi3 work of mapping and classifying these soils has been done under (ho direction of Dr. R. S. Smith, in charge of the Illinois Soil Survey. 440 Bulletin No. 362 [December] 4. Dark soils with open, noncalcareous subsoils Semimature soils Dixon, Lee county Mt. Morris, Ogle county Young soils (influenced by sedimentation) McNabb, Putnam county 5. Dark soils with impervious, noncalcareous subsoils Semimature soils Carthage, Hancock county Clayton, Adams county Lebanon, St. Clair county Mature soils Carlinville, Macoupin county 7. Gray soils with impervious noncalcareous subsoils Old soils (moderately well drained) Ewing, Franklin county Oblong, Crawford county Old soils (poorly drained, slick spots numerous) Newton, Jasper county Odin, Marion county Raleigh, Saline county Toledo, Cumberland county Old soils (very poorly drained, slick spots numerous) Sparta, Randolph county 8. Yellow soils with noncalcareous subsoils Mature soils Enfield, White county Unionville, Massac county West Salem, Edwards county 9. Brownish yellow soils with open noncalcareous subsoils Semimature soils (much sedimentation and erosion) Springvalley, Bureau county 11. Brownish yellow soils with calcareous subsoils Young soils Antioch, Lake county 14. Sandy loams and sands Mature soils Palestine, Crawford county Semimature soils Oquawka, Henderson county 16. Hilly land Mature soils Elizabethtown, Hardin county Of the thirty-one fields listed above, all except those at Antioch, Bloomington, and Palestine, are considered in this bulletin. A complete chemical analysis of the soils upon which the experi- ment fields have been established probably would not contribute a great deal to an understanding of the results obtained. A knowledge, however, of the total content of nitrogen and phosphorus, the relative amounts of readily available phosphorus, and the reaction will be of some interest. Such data will be found in Table 30 in the Appendix. EEUu«„.. *,<„„,„ I v Fia. 1.— Map or Illinois Showinq Soil Groups and Location or Experiment Fields 440 Bulletin No. 362 [December, 4. Dark soils with open, noncalcareous subsoils Bl m( gr< ho an soi 1930] Response of Illinois Soils to Soil Treatment 441 Plan Followed in Summarizing Field Results Crop-yield data extending over many years are difficult to sum- marize. A mere averaging of yields fails to bring to light many points of interest and importance; for instance, whether yields are increasing or decreasing and whether the soil is becoming improved or impov- erished. It is therefore necessary to consider yields by individual years and rotation periods as well as by averages over longer periods. A second difficulty in dealing with crop-yield data is the lack of a satisfactory common denominator in which to express yields of dif- ferent crops, so that comparisons of the productiveness of different soils and the effectiveness of different soil treatments can be made. While money values for this purpose have their disadvantages, since prices not only are constantly changing but vary greatly in different localities and since, furthermore, costs on one farm may be far different from those on a neighboring farm, yet they supply the only practical basis for making comparisons. Money values therefore are used thruout this publication, but with the understanding that they indi- cate only approximations and are not to be taken as literally appli- cable at any time or at any place. The following prices were used in figuring all crop values. They represent approximately the average Illinois prices on farms on De- cember 1, as reported by the federal government, for the five-year period ending in 1927. Corn $ .70 a bushel Oats 40 a bushel Wheat 1.25 a bushel Soybeans 1 25 a bushel Sweet-clover seed 6.00 a bushel Hay 12.50 a ton Seed cotton 05 a pound Rye 90 a bushel Where net returns are used they are regarded as the difference be- tween the value of the crop increases and the approximate cost of ap- plying the fertilizer materials. This plan does not recognize the cost of harvesting the crop increases, interest on the fertilizer investment, and certain other factors, all of which should be considered in a strict accounting of the results obtained from the different fertilizer ma- terials. In these experiments, however, comparison of systems of soil treatment is of more interest than comparison of individual fer- tilizers, since the farm as a whole is kept in mind and certain inci- dental benefits accruing from the various systems of soil treatment are therefore not evaluated. Straws, for example, are not considered ex- cept as they enter into the production of manure, and pasturing bene- fits are not taken into account. Such factors as these tend, it is true, to offset some of the cost factors, but since the absolute value of a 442 Bulletin No. 362 [December, system of soil treatment can never be satisfactorily determined, a detailed accounting of all the factors involved does not seem essential. Price and cost figures, representing general average conditions, would therefore appear to serve present purposes. Where the figures are out of line with personal experience, the person desiring to make use of them is in the best position to make the proper adjustments. In estimating net returns, the following values have been used, which in general may be taken to represent the average cost of getting these fertilizer materials on the land during recent years: Manure $ .75 a ton Crop residues 75 an acre Limestone 3.00 a ton Rock Phosphate 15.00 a ton Kainit 25.00 a ton PART I. COMPARISON OF ILLINOIS SOILS IN THEIR RESPONSE TO SOIL TREATMENT Variations in Natural Productiveness of Illinois Soils That the natural productiveness of Illinois soils varies strikingly is evident from the crop yields obtained from the untreated land — the check plots — of the soil experiment fields. The data from these plots are presented in Table 1 and graphically shown in Fig. 2, where the fields are grouped as dark-colored soils, light-colored soils, and sand soils, and arranged in the order of their natural productiveness. Inspection of these data reveals some interesting facts. No two fields, it will be noted, gave similar results, tho in some cases the vari- ation was not great. The most fertile field, as indicated by the results for the last rotation, was nearly ten times as productive as the least fertile field. In general the dark-colored soils were four to five times as productive as the light-colored soils; the one sandy field occupies an intermediate position. It will also be noted that there was con- siderable variation within the soil groups. Among the dark-colored soils the field at Joliet during the last rotation was only about one- half as productive as the field at McNabb. Similarly, the least pro- ductive field in the light-colored group was only about one-third as productive as the best field. Comparison of the positions of these fields in their respective groups with the chemical analyses given in Table 30, Appendix, shows that in general the most-productive fields tend to contain the highest percentages of nitrogen and phosphorus. There are, however, some striking exceptions. The McNabb field, which ranks first in crop pro- duction, occupies a middle position with respect to the nitrogen and 1930] Response of Illinois Soils to Soil Treatment 443 Table 1. — Results From Untreated Land on 28 Illinois Experiment Fields (Average annual acre-yields and values for periods ending in 1927) Location of field First crop year Years in rota- tion Average yields of all major grain crops, all complete rotations Gross value for all crops All rotations Corn Oats Wheat Last rotation Dark-colored soils * 1907 1910 1910 1910 1911 1915 1915 1910 19111 1912 1910 1911 1910 1910 1911 1914 1912 1913 1911 1912 1910 1902 1910 1912 1912 1917 1916 1915 4 4 4 4 4 4 4 4 5 5 4 4 4 4 4 6 4 4 4 4 4 4 4 4 5 4 4 6 bu. 70.4 56.6 46.3 49.3 51.6 54.2 39.0 43.7 51.2 41.0 39.6 35.9 25.6 30.3 35.2 31.8 43.7 21.2 17.9 16.3 9.8 16.2 19.8 11.9 17.8 13.2 13.5 12.8 15.5 19.2 bu. 62.6 58.4 63.0 57.4 46.2 60.0 47.0 54.6 52.8 45.5 50.9 33.3 28.3 32.2 37.8 57.3 49.2 15.8 14.7 (1561b.*) 5.43 10.9 7.23 10.4 10.9 9.3 2.73 5.13 12.0 10.2* bu. 32.9 30.3 34.0 32.4 28.4 30.9 34.7 23.3 26.6 25.2 20.5 20.0 26.2 17.9 16.9 22.5 26.4 7.9 8.3 6.2 .7 5.5 8.1 2.6 5.8 4.3 4.8 4.8 5.4 9.8 $36.65 32.24 33.36 31.60 31.83 29.22 29.09 26.60 29.84 24.61 23.53 21.94 22.02 18.34 20.85 20.29 27.00 9.30 6.92 8.68 5.05 6.60 9.59 6.36 6.66 6.27 5.14 6.13 6.97 8.89 $38.31 34.08 LaMoille 33.61 32.74 30.98 30.22 29.56 Mt. Morris 25.44 Urbana 25.37 Sidell 24.64 Dixon 23.94 22.21 20.94 20.53 20.21 19.54 Average 27.02 Light-colored soils Oblong 10.45 Toledo 7.11 6.96 6.51 6.09 Odin 5.72 5.59 Enfield 5.05 5.04 4.36 3.90 Average 6.07 Sand soils Oquawka 11.55 Originally established 189£ place of oats. 'Seed cotton instead of oats. 'Soybeans in place of oats. .5 "5 c a. e S .o Light-Colored Soils: Will Not Grow Any Clover Without Limestone 3 5" Sand Soils Will Grow Some Clover Without LimestofK Fig. 4. — Value of Crop Increases Resulting From Use of Crop Residues The more highly productive soils were made still more productive by the plowing under of crop residues without further soil treatment. The moderately productive and less productive soils did not give very marked responses to this system of soil treatment. The differences between the crop increases during the last rotation and those of all complete rotations should also be noted. In the first division of the dark-colored soils the results for the last rotation were much better than for all complete rotations. The advantage in terms of money value averaged more than $1.50 an acre a year. In the second division of the dark-colored soils there was little difference be- tween the two periods, only three fields giving better results for the last rotation. In the light-colored group there was but little difference between the two periods and whatever advantage there was appears to be with the last rotation. Thus crop residues alone have a soil-improvement value, tho there is great variation in response to them. Where sweet clover will grow, rather marked effects from residues may be expected even on highly productive soils. Where legumes grow indifferently or not at all, the 1930] Response of Illinois Soils to Soil Treatment 449 results are not very striking. Some benefit, however, was obtained on every field, a fact which indicates that non-legume crop residues have some soil-improvement value, tho when unaccompanied by any other soil-treatment practices the effect is not marked. If, however, some- thing can be done to encourage the growth of sweet clover, red clover, and other such legumes, the crop-residues system of soil improvement may be quite effective. Limestone Effective When Used With Manure Limestone applied in addition to farm manure has a very much greater effect on crop yields on the light-colored soils than on the Table 4. — Effect of Limestone When Used in Addition to Manure on 26 Illinois Experiment Fields (Average annual acre-yields and values of increases for periods ending in 1927) First crop year Years in rota- tion Average increases in major grain crops, all Gross value for all crops Location of field complete rotations All rota- tions Last Corn Oats Wheat rota- tion Dark-colored soils 19111 1910 1911 1910 1910 1911 1914 1910 1910 1912 1911 1915 1915 1910 1910 1910 1913 1912 1910 1912 1912 1917 1916 1911 1912 1915 5 4 4 4 4 4 6 4 4 5 4 4 4 4 4 4 4 4 4 4 4 4 4 4 5 6 bu. 5.5 8.7 7.0 5.1 7.3 8.7 5.9 4.1 4.5 2.4 6.2 4.0 3.7 .7 .3 4.9 17.0 11.6 13.4 14.6 9.1 11.2 15.5 10.0 8.5 2.8 10.4 9.4 bu. 3.8 6.3 4.3 3.5 4.7 5.6 .9 3.0 3.3 - .4 5.8 .7 2.7 - .9 - .8 2.8 13.3 10.8 9.2 9.1 3.92 7.5 2.12 6.72 (180 lbJ) 2.1 8.7 10.25 bu. 6.9 6.6 3.7 6.1 3.2 3.1 3.9 .3 3.6 -1.9 4.8 - .1 2.2 .6 -1.9 2.7 15.2 10.0 11.0 13.1 8.0 6.9 5.8 8.8 6.2 3.6 8.9 5.1 $4.96 6.51 3.55 3.38 3.61 3.47 2.66 1.98 2.86 .83 3.42 .98 .91 - .04 - .60 2.57 10.94 7.71 7.86 10.01 7.04 6.92 8.99 7.99 6.51 2.69 7.63 6.72 $9.07 8.75 7.40 6.77 6.64 4.73 4.13 4.07 4.07 Sidell 3.79 3.33 1.66 1.37 .40 — .73 4.36 Light-colored soils 17.75 Toledo 14.23 Enfield 13.72 11.79 11.74 11.09 10.59 8.91 8.50 West Salem* 4.89 11.32 Sand soils Oquawka 9.94 Originally established in 1895. Soybeans in place of oats. 3 Seed cotton in place of oats. «Check plots received by mistake 4 tons limestone when field was established. 6 Rye in place of oata. dark-colored soils. On the light-colored soils the average value of the crop increases for limestone during the last rotation was $11.32 an acre annually; for the dark-colored group it was only $4.36 an acre. 450 Bulletin No. 362 [December, The crop-yield increases and money values showing the influence of limestone when used in addition to farm manure are shown in Table 4 and Fig. 5. Within each of the two groups of soil represented there is consider- able variation in response to limestone. In the dark-colored group Fig. 5. — Increases in Crop Values From Limestone Used in Addition to Manure The more-productive, dark-colored soils do not give so great a response to limestone when used with manure as do the more-mature light-colored soils, tho on a number of the dark-colored soils the returns have been very profitable. The need for limestone can be readily and simply determined by soil tests. The proper use of limestone is fundamental to the best management of most Illinois farm lands. during the last rotation the annual acre-values of the crop increases ranged from $9.07 to a loss of 73 cents an acre. In this group the naturally least-productive soils tended to give the greater response. The Joliet field, however, was an exception to this general observation. It has been the poorest field in natural productiveness and yet occupies a middle position with respect to the influence of limestone. In the 1930] Response of Illinois Soils to Soil Treatment 451 light-colored group, tho the level of response was very much higher, the tendency also has been for the least-productive fields to give the greater response. An exception is the Sparta field. This field, naturally the least fertile field of the group, did not give a very high response compared with most of the other fields in the group, tho the influence of limestone upon it was fairly good. (The West Salem field is proba- bly out of its proper order because of the error in applying limestone to the check plots when the field was established in 1912.) ^A comparison of the influence of the limestone in the short- and long-time periods will show that on most fields the crop increases were considerably greater during the last rotation than they were for the entire period. These differences were much larger in the light-colored and sandy groups than they were in the dark-colored group. The average difference between the value of the crop increases in the last rotation and during the long-time period was $1.79 an acre a year in the dark-colored group, $3.69 in the light-colored group, and $3.22 in the sandy group. These figures indicate that the effects of limestone are cumulative; that is to say, the use of limestone tends to make the soil increasingly more productive. Some fields in the dark-colored group did not show very much response to limestone. In fact, some fields revealed small losses. This lack of response appears to be directly related to the need of the soil for limestone, as will be noted by comparing the results obtained for the use of limestone on these fields with the reaction of the soil as given in Table 5. On the whole, the crop increases resulting from the application of limestone in addition to farm manure have been rather striking. For the most part these increases have been obtained from limestone used at the rate of approximately one-half ton an acre annually. Consider- ing the cost of the limestone applied, in relation to the value of the crop increases, it is apparent that on many fields the use of limestone has been highly profitable. Limestone Influence More Striking in Absence of Manure The results obtained from the use of limestone in addition to crop residues are brought together in Table 5 and Fig. 6. Here the crop increases have been somewhat similar to those obtained when lime- stone was used in addition to farm manure, except that the general level of results on the dark-colored soils is somewhat higher and on the light-colored soils somewhat lower. The reason for this is not entirely clear. It would appear that on the dark-colored soils the manure re- duced the need for limestone and on the light-colored soils limestone enhanced the value of the manure. This point will receive further dis- cussion in connection with another system of soil treatment (pages 466-470). 452 Bulletin No. 362 [December, Table 5. — Effect of Limestone When Used in Addition to Crop Residues on 27 Illinois Experiment Fields (Average annual acre-yields and values of increases for periods ending in 1927) Location of field First crop year Years in rota- tion Average increases in major grain crops, all complete rotations Gross value for all crops All rotations Corn Oats Wheat Last rotation Dark-colored soils 1910 1910 1911 1910 1911 19111 1910 1910 1912 1915 1914 1910 1911 1915 1910 1910 1913 1910 1912 1916 1917 1902 1912 1911 1912 1912 1915 4 4 4 4 4 5 4 4 5 4 6 4 4 4 4 4 4 4 4 4 4 4 4 4 4 5 6 bu. 11.3 11.5 10.6 7.7 10.0 11.5 7.3 6.5 2.7 8.2 4.3 3.4 3.5 2.0 2.1 6.8 14.0 7.7 16.7 13.1 9.0 17.3 4.5 6.1 15.3 7.6 2.4 11.4 15.5 bu. 19.7 9.7 10.5 8.0 9.5 5.2 5.4 3.8 3.9 2.7 2.0 1.2 -1.8 7.5 - .2 5.8 15.6 14.8 9.9 10.9 7.02 1.42 1.82 3.32 (103 lb.3) 5.7 5.5 10.4 12.25 bu. 6.5 7.2 3.8 7.0 7.8 4.8 2.3 3.2 .8 2.0 1.5 1.0 -2.6 .8 -3.2 2.8 15.7 12.2 10.1 10.5 10.2 5.5 8.5 6.6 8.0 8.0 3.4 9.0 3.6 86.80 6.11 4.79 5.95 5.25 4.94 2.95 2.80 2.02 2.45 2.80 1.37 - .47 1.60 - .80 3.24 10.24 7.58 8.96 7.46 8.13 9.20 5.53 5.26 6.73 6.29 2.59 7.09 7.55 $11.29 9.50 9.50 9.11 8.82 8.33 7.22 6.28 Sidell 5.51 4.76 3.58 LaMoille 2.08 1.65 .35 - .41 5.84 Light-colored soils 12.78 Toledo 12.46 10.76 Enfield 10.09 Sparta 10.05 9.91 Odin 8.94 8.62 7.49 7.44 West Salem< 5.37 9.45 Sand soils Oquawka 9.90 Originally established in 1895. 2 Soybeans in place of oats. 3 Seed cotton in place of oats. «Check plots received by mistake 4 tons of limestone when field was established. 6 Rye in place of oats. In general the influence of limestone without manure has been striking, and has been due to a considerable extent to the fact that thru its use sweet clover was made to grow luxuriantly on all fields, whereas it grew on but few fields without limestone. The sweet clover in turn was probably largely responsible for the crop increases ob- tained. These results point to the necessity of every farmer's de- termining whether his fields need limestone, and to the advantages to be gained by using limestone intelligently when it is needed. In considering the results obtained from the use of limestone on the Illinois experiment fields, questions arise as to whether it was used as efficiently as possible. From the original plan adopted for applying limestone, as outlined on page 438, it can be readily seen that in a comparatively short time the total application per acre would be quite large. In the light of information available at the time the fields were established, the procedure adopted seemed to be advisable. It was 1930] Response of Illinois Soils to Soil Treatment 453 based principally on the assumption that this rather liberal applica- tion would make good the losses of limestone that occur as a natural consequence of cropping and leaching. With the passing years, ques- tions began to arise as to whether so much limestone was necessary. If limestone was not lost so rapidly from the soil as had been sup- posed, then smaller applications or a less frequent use of it would be $5 $ SI I 5 •» k. — .— - o O 3 < Q Dark -Colored Soils Fig. 6. — Effect of Limestone Used in Addition to Crop Residues In general the dark-colored soils give better responses to limestone with crop residues than to limestone with manure (Fig. 5), and the light-colored soils better responses to limestone with manure than with crop residues. On sour soils lime- stone gives excellent results in both the manure and the crop residues systems of farming. even more profitable than the larger amounts called for in these sys- tems. Then there was also the question as to the advisability of ap- plying limestone at uniform and regular rates on all kinds of soils. The field results indicated that limestone was not profitable on some fields, probably because it was not needed. The application of lime- stone under such conditions was uneconomical. These questions raised still another relative to the influence of excessive quantities of lime- stone in the soil. If more limestone is applied to the soil than is needed, is the excess merely an unnecessary expense, or may it have a retarding influence on various soil processes related to crop produc- tion? In either case it would be better to leave limestone off land 454 Bulletin No. 362 [December, not in particular need of it. These and other questions have arisen in regard to the use of limestone. Some of these questions can be con- sidered in the light of present experiment-field results while others will need further investigation, both in the field and laboratory, be- fore they can be answered intelligently. A brief discussion of some , of these problems will not be out of place at this point. One of the important functions of limestone is to correct certain soil conditions that are adverse to the growth of many legume crops. The more important of these conditions may be covered by the term soil acidity. It is well known that soil acidity varies greatly among soil types, and also frequently among fields on the same farm and even in different parts of the same field. Thus such legumes as sweet clover, alfalfa, and others may grow well on some soil types, on some fields, or in parts of a particular field, and indifferently, or not at all in other places, according to the acidity of the soil. Since in the resi- dues system it is the legume crop properly utilized that has marked effects upon the crop-producing powers of soils, it would appear that the farmer's chief interest would be in maintaining his soil conditions in such a manner that the legumes will grow abundantly. And since the degree, or intensity, of soil acidity is more or less directly related to the ability of soils to grow various legumes successfully, it seems clear that the best plan is to use limestone in direct proportion to the intensity of the acidity of the soil. In other words, limestone should be applied only when it is needed to encourage the growth of legum- inous crops. Such a practice would in many cases do away with regu- lar applications of limestone. Since on many soils the initial applica- tion of limestone may be effective for longer periods than was antici- pated when the experiment fields were established, the investment in limestone could be reduced without interfering with the crop-producing power of the soil so far as soil acidity is concerned. Results obtained from the West Salem field are interesting in con- nection with this problem. When this field was established in 1912, four tons of limestone were applied by mistake to plots that were to receive no limestone. No additional limestone has ever been applied to these plots. Other plots have received limestone regularly in accord- ance with the original plan. Data from these plots will be found in Table 6. The influence of the single application of limestone, it will be seen from the first column of Table 6, steadily increased thru the ninth year. From that time to the present, the crop increases from this single application have been declining. At the present time, after a period of seventeen years, the influence of this application has just about disappeared. From columns two and three it will be seen that repeated applica- tions did not show any marked superiority over the single application 1980] Response of Illinois Soils to Soil Treatment 455 until the tenth year. From the tenth year to date the crop increases from the regular applications have been steadily growing larger, altho as a matter of fact these plots have not received any limestone since 1923. The original plan of applying limestone was abandoned in 1923 and the plan adopted of making future applications only at such times as they might appear to be needed. These data indicate that on this Table 6. — Lasting Effect of a Single Application of Limestone and Compar- ison Between Effects of Single and Repeated Applications 1 (West Salem field 1912-1928) Year Value of crop increases resulting from a single application of lime- stone made in 191 1 1 Value of crop increases from repeated appli- cations of limestone over those from a single application made in 1911* Livestock system Grain system 1912 $- .31 1.14 1.23 1.43 1.85 2.66 3.39 3.86 3.89 2.76 2.76 2.82 2.60 1.72 .93 .54 .49 $- .21 - .07 - .07 - .41 - .25 - .01 .25 .86 1.06 .72 2.11 3.88 4.24 5.13 5.23 5.60 $ .03 1913 .20 1914 .04 1915 .12 1916 .22 1917 1918 .29 .53 1919 .81 1920 .55 1921 1.29 1922 1.86 1923 1.79 1924 3.71 1925 4.83 1926 5.79 1927 1928 5.90 6.84 !No limestone applied since 1923. ^Prices used in figuring crop increases were as follows: conit 50 cents; oats, 30 cents; wheat, $1; soybeans, $1 a bushel and hay $10 a ton. field the second application might have been delayed until the seventh or eighth year without interfering with the influence of the limestone. At that time it is quite possible that a reduced application would have been as effective as the larger application. Such a possibility is indi- cated by data from other fields. Whether a larger initial application would have given larger crop increases and persisted longer in its ef- fects cannot be answered definitely. The larger responses that have been obtained in recent years suggest that a larger initial application might have given better results. When limestone is needed, it probably is just as uneconomic to make the initial application too small as it is to make it too large. For such a crop as sweet clover there is a critical point in the acidity of the soil above which the sweet clover will not grow. Consequently an application of limestone which fails to reduce the acidity below this point will either have no influence on the sweet-clover growth, or else it will produce a scattering growth for two or three years, after which failures will recur. On the other hand, a very slightly larger applica- tion may be sufficient to lower the acidity below the critical point so that there will be a maximum growth of sweet clover. This is illus- 456 Bulletin No. 362 [December, trated by results obtained at Springvalley, where four years' data are available in a rotation in which the corn increases were directly in- fluenced by the preceding growth of sweet clover. In these experiments one group of plots was treated with an initial application of limestone at the rate of 1 ton an acre and another group at the rate of 4 tons an acre. The results for the four crops are summarized in Table 7. They clearly indicate that the larger initial application was more effective. Table 7. — Influence of a Light and Heavy Initial Application of Limestone on Yields of Corn and Oats (Springvalley field 1924-1927) Treatment Corn 2 crops Oats 2 crops Annual acre-value of crops 1 bu. per acre 44.5 47.6 56.1 bu. per acre 51.8 48.7 51.9 $25.93 26.40 Rock phosphate, sweet clover, 4 tons of limestone 30.01 'Based on December 1 prices for crops on the farm. Another important fact indicated by a study of these and other field results is that limestone applied to the soil is not lost as rapidly as was formerly thought. With knowledge that has accumulated re- garding the varying nature of soils, it also seems clear that limestone need not be applied in regular and uniform amounts. It would there- fore seem that the expense for limestone can be reduced and the profits from its use increased by more judiciously arranged applications. The growth of clover is a fairly reliable index of the need of the soil for limestone. The use of such an indicator, however, is time- consuming and expensive. From the farmer's point of view, probably the most practical soil-acidity test now in use is the test devised by Comber in England which makes use of a solution of potassium thio- cyanate. Detailed instructions for applying this test have been brought together in Circular 346 of this Station. By following the plan there outlined, any farmer in Illinois can make an acidity map of his farm that will enable him to apply limestone to his fields with much greater assurance of profitable returns than he can have by guessing. Rock Phosphate With Manure and Limestone Gives Variable Results Rock phosphate applied in addition to manure and limestone has had a marked effect in increasing the crop-producing power of some soils and little effect on other soils. The crop increases and money values for rock phosphate used in this manner on the Illinois soil ex- periment fields are shown in Table 8 and Fig. 7. 19801 Response of Illinois Soils to Soil Treatment 457 Table 8. — Effect of Rock Phosphate When Used in Addition to Manure and Limestone on 27 Illinois Experiment Fields (Average annual acre-yields and values of increases for periods ending in 1927) First crop year Years in rota- tion Average increases in major grain crops, all Gross value for all crops Location of field complete rotations All rota- tions Last Corn Oats Wheat rota- tion Dark-colored soils 19111 1914 1915 1911 1907 1915 1910 1912 1910 1910 1911 1910 1910 1910 1910 1911 1917 1912 1912 1912 1912 1910 1916 1910 1911 1913 1915 5 6 4 4 4 4 4 5 4 4 4 4 4 4 4 4 4 4 5 4 4 4 4 4 4 4 6 bu. 1.5 2.8 1.3 5.8 4.5 4.6 2.5 1.1 .5 1.2 -1.0 -1.9 - .4 .2 -".8 1.4 4.9 1.2 2.6 1.8 1.7 1.3 1.8 .7 .6 - .4 1.6 - .6 bu. 5.2 4.1 - .8 2.9 3.3 7.1 1.8 1.6 - .5 .4 .7 - .6 .9 -2.0 - .8 - .6 1.4 1.63 .93 4.5 1.2 2.9 1.0 .13 1.4 (15lb.<) 1.8 2.1 -1.25 bu. 4.9 7.3 4.9 1.7 2.2 2.4 3.2 2.6 .5 1.7 2.5 1.5 1.4 .5 1.8 2.2 2.6 3.3 5.7 5.5 5.2 1.8 1.4 .7 3.4 3.6 1.5 3.2 .2 $6.47 3.99 1.44 1.79 2.88 2.03 2.31 1.87 .44 .84 .87 .27 .37 - .12 .48 1.08 1.69 4.73 2.70 2.03 2.50 1.26 1.17 .73 1.29 1.46 .68 1.86 .14 $7.11 6 00 3 49 3.10 McNabb* 2.35 1.77 1.25 Sidell 1.14 .82 77 .58 - .03 Mt. Morris — .14 LaMoille - .17 - .29 — .42 1.71 Light-colored soils 5.14 2.85 West Salem 2.39 2.24 Enfield 1.90 1.47 1.16 1.09 - .20 -1.49 1.65 Sand soils - .30 Originally established in 1895. 2 No limestone applied on this field. *Seed cotton in place of oats. 5 Rye in place of oats. 3 Soybeans in place of oats. The influence of rock phosphate has been more or less variable on both the dark- and light-colored soils, tho the average results in both groups are quite similar. The highest average annual acre-value of the crop increases for the last rotation was $7.11. Some fields, how- ever, gave no crop increases at all. A comparison of the results for the last rotation period with the results for all complete rotations shows varying differences. Among the dark-colored soils there were only a few fields that gave larger re- sponses during the last rotation; the other fields gave larger responses for the long-time period. A similar situation exists in the light-colored group but is not quite so striking there. Apparently rock phosphate gave better results in the earlier years than in recent years or the manure applications have tended to meet the phosphorus needs of the soils and hence have lessened the need for applications of phosphate. Other complications which will be mentioned later might also have entered into the situation. 458 Bulletin No. 362 [December, W lAII Complete Dotations rfaifc . ^^ 2 *. 2 1 s 2 % t c = £ 9 ■" 3 ■§ ° « — J !g s fc. .5 -g Js i2 o s: 60 23 67 70 11 .96 .51 1.87 .77 .62 1.66 2.47 5.96 3.86 2.88 3.34 1.92 1.37 1.89 2.00 1.79 1.14 .41 2.47 .02 Last rota- tion $10.79 10.26 5.21 4.53 3.14 3.05 2.91 2. 2. 2. 2. 2. 1 8.74 4.95 3.48 3.48 2.72 2.54 2.51 2.51 1.06 1.53 .24 3.27 .10 Originally established in 1895. l No limestone applied on the McNabb field. 3 Soy beans in place of oats. *Seed cotton in place of oats. 5 Bone meal used in place of rock phosphate on Odin field. 8 Rye in place of oats. 460 Bulletin No. 362 [December, limestone or with manure and limestone, was their marked variation. The highest average annual acre-value of the crop increases was $10.79 and the lowest an apparent loss of 10 cents. The differences in the response to rock phosphate between the last rotation and the average of all complete rotations were greater in the residues system than in the manure system. This was true for prac- tically all fields in both groups of soil altho in some cases the differ- ences were not very great. The general average in the dark-colored group was 40 percent higher in the last rotation than in the long-time period and in the light-colored group it was more than 30 percent higher. In both the manure and residues systems the crop increases result- ing from the use of rock phosphate do not reveal any definite relation- ships to the natural productiveness of the various fields. In the dark- colored group the fields giving the largest crop increases are found among the highly productive, the moderately productive, and the least productive fields. The Joliet field, naturally the least productive in this group, and a field which has not shown any marked response to the other systems of soil treatment, stands in the front rank of the fields showing response to rock phosphate. On the other hand, the Kewanee field, standing fairly high in natural productiveness, is also found among the fields giving the best responses to rock phosphate. Relationships of the same sort exist among the fields in the light- colored group. A study of the varying responses of these fields to rock phosphate and the total phosphorus content of the soils (Table 12, page 463) does not show any striking relationships. In the dark-colored group there is a tendency for the fields having the lowest phosphorus con- tents to be among those giving the best responses. There are, however, a number of exceptions. The Springvalley and Lebanon fields, for instance, which have low phosphorus contents, have given but little response to phosphate. In the light-colored group the Elizabethtown field, which has the highest phosphorus content, has given the best response to phosphates. The Odin and Toledo fields, which have low phosphorus contents, have been low in response to phosphate. Some relationships of interest are brought out by comparing the responses of these fields to phosphate applications with their contents of readily available phosphorus as reported in Table 30, Appendix. All fields having an abundance of available phosphate have given little or no response to the applied phosphate. The fields having moderate amounts of available phosphate have been more or less indifferent in their response. But the fields low in available phosphate appear, with but few exceptions, to have been directly and indirectly benefited by the application of phosphate. All the fields that have given high re- sponse to phosphate applications are in this low available-phosphorus 1930] Response of Illinois Soils to Soil Treatment 461 group. The other fields in this group, altho not giving a good response to phosphate alone, have given good response to combined appli- cations of phosphate and potash, the Dixon and Mt. Morris fields being the only exceptions to this general observation. It would thus appear that a number of fields low in available phosphorus were, from the standpoint of the crops grown, more deficient in potash, and that before the phosphates could give response the potash deficiency would have to be corrected. High Variability in Rock Phosphate Response a Complex Problem Not only has the response of the Illinois soil experiment fields to applications of rock phosphate been exceedingly variable, some fields giving excellent responses and others very meager or no response at all, but on the whole, the increases have not been as large as those ob- tained from such fertilizer materials as manure, legumes, and lime- stone. The fact that phosphate has not given equally good results on all the Illinois experiment fields has led to considerable speculation. A number of explanations have been advanced, the more frequent of which may be listed as follows: 1. Rock phosphate cannot be an effective carrier of phosphorus when applied to soils that have received liberal or excessive applica- tions of limestone, as has been the case on the Illinois soil experiment fields. 2. Rock phosphate is an ineffective carrier of phosphorus. 3. The methods of application were incorrect. 4. Phosphates of the proper degree of fineness were not used. 5. The use of deep-rooted legumes delays the need for applied phosphates. 6. Many Illinois soils are not yet in need of a phosphatic fertilizer to increase their crop-producing powers, or else other nutrient ma- terials are more deficient and must first be supplied before phosphorus can be of value. These and other explanations have been suggested as the possible reasons why some Illinois soils have responded and some have not more definitely responded to rock phosphate. Because of the interest in them a brief discussion of some of the data now available may be worth while at this point. 1. 7s rock phosphate an effective carrier of phosphorus when ap- plied to soils that have received liberal or excessive applications of limestone f In both the manure and residues systems rock phosphate, in the present investigations, was always applied in addition to the organic manures and limestone. The limestone was applied in quantities which soon built up comparatively large reserves in the soil, a point that has already been discussed from the standpoint of limestone economy. 462 Bulletin No. 362 [December, After 8% to 10 tons of limestone an acre had been applied to most fields, the applications were discontinued and the plan adopted of making future applications only when they appeared to be needed. Since applications of limestone always accompanied the applica- tions of rock phosphate, the question arose as to whether or not this use of limestone had been an interfering factor. On a number of fields the crop increases resulting from rock phosphate were better in earlier years than in recent years. Those fields giving the better responses were usually fields on which, for one reason or another, the limestone had not yet been applied in the largest amounts. Supplementary ex- periments on the Illinois fields also indicated that the use of limestone with rock phosphate might tend to reduce the efficiency of the phos- phate. In order to throw more light on this question, soil treatments on a number of fields were modified to include a comparison of crop re- sponses for phosphate on both limed and unlimed fields. On the Aledo field in 1916 experiments were established with four carriers of phos- phate — bone phosphate, superphosphate, rock phosphate, and basic slag. All were applied with and without limestone. The limestone was applied at the rate of 6 tons an acre. The value of the crop increases for the phosphates during the last rotation (1925-1928) are recorded in Table 10. Table 10. — Average Annual Acre- Value of Crop Increases From the Use of Phosphates With and Without Limestone (Aledo field 1925-1928) Phosphorus carrier Bone phosphate Superphosphate Basic slag Rock phosphate Value when used without limestone $11.11 9.73 9.37 8.93 Value when used with limestone $9.36 7.61 8.15 3.94 Decrease when used with limestone $1.75 2.12 1.22 4.99 Experiments were also established in 1922 on the Kewanee field to determine the relative response of rock and superphosphate applied with and without limestone. The total amount of limerlone applied in these experiments was 8 tons an acre. The rock phosphate was applied at the annual rate of 400 pounds an acre, and the superphos- phate at the rate of 200 pounds an acre. The crop yields and values for the last rotation are shown in Table 11. More extensive experiments were initiated on five experiment fields in 1924. Original plots were divided into halves and additional treat- ments applied to one of the halves. These experiments will give in- formation, not only concerning the influence of limestone on the avail- 1930] Response of Illinois Soils to Soil Treatment Table 11. — Average Annual Acre- Yields and Values for Phosphates Used With and Without Limestone (Kewanee field 1925-1928) Phosphorus carrier Accompanying treatment Wheat Corn Oats Clover Average annual acre-value Difference due to limestone Rock phosphate Superphosphate Rock phosphate Superphosphate Crop residues Crop residues Crop residues Limestone . . . Crop residues Limestone. . . bu. 45.4 45.0 39 .'4 46 .*9 bu. 75.4 74.1 73!2 77^6 bu. 82.1 80.5 74i8 11.2 (0718 2.21 2.13 2!65 2* ii $41.67 40.91 38!2i 42."5i $-3] 46 +ii66 ability of rock phosphate, but also relative to the effectiveness of other carriers of phosphorus and different methods of application. Altho these experiments have been under way for only five years, a brief summary of them at this time will be of interest in order to show what direction the results are taking (Table 12). The data from all five experiment fields indicate that the use of limestone with rock phosphate may have a retarding influence on the availability of the phosphate. They further indicate that the presence Table 12. — Average Annual Acre- Values of Crop Increases for Rock Phos- phate, Superphosphate, and Bone Phosphate When Applied in Various Combinations With Limestone (Five experiment fields 1925-1928) Phosphate treatment Rock phosphate No limestone No limestone Light limestone 1 . . . Heavy limestone 1 ' 2 . No limestone Rock phosphate. Superphosphate 3 . Heavy limestone 1 Rook phosphate 2 . Superphosphate. . Bone phosphate. . Rock phosphate applied to plowed soil before wheat and corn since 1924, compared with residual rock phosphate plowed down for wheat in previous years. . . . Heavy limestone 1 Heavy limestone 1 . treat- ment M R RL RL RL RL ML ML RL Harts- burg Dixon Aledo Raleigh Toledo Relative response to limestone Very slight $1.72 3.33 2.02 2.37 3.33 6.06 2.37 4.09 .21 .90 .25 Medium $1.13 2.78 3.72 2.40 2.78 2.88 2.40 2.61 • .38 1.17 .35 Medium high $1.02 2.26 4.43 2.49 2.26 2.76 2.49 1.47 1.43 - .63 .60 High $2.28 3.97 4.04 3.55 3.97 2.92 3.55 2.80 2.61 2.35 .55 Very high $4.07 2.79 3.36 .26 2.79 1.03 .26 1.83 .99 1.67 2.02 !Heavy limestone applications range from 8 to 10 tons an acre; light applications, from 2 to 4 tons an acre. 'Old phosphate plots; all others new in 1924. 8 Figures include combined effects of super- phosphate and crop residues. 464 Bulletin No. 362 [December, of some soil acidity may increase the efficiency of the phosphate. The Hartsburg field, giving only a very slight response to limestone, re- sponded best to rock phosphate when no limestone was applied. On all the other fields where limestone produced better responses, the rock phosphate was more effective when applied with light applications of limestone. In no case did the rock phosphate give its best responses where heavy applications of limestone were made. These results, altho not showing large crop increases, appear to be in harmony with chemical reasoning. The need of limestone on very sour soils to increase the availability of phosphorus has long been em- phasized. On such soils the iron and alumnium compounds present tend to react with the phosphorus and convert it into rather insoluble forms, which are not considered to be very highly available for plant use. The presence of limestone on such soils tends to keep the phos- phorus in forms which are more readily available to crop plants. Thus in very sour soils the presence of limestone may have a desirable influence on the phosphates naturally present or on those applied to it. On the other hand, the excessive use of limestone may affect ad- versely the availability of phosphates. There are several forms of calcium phosphate that vary considerably in solubility and hence in availability. Rock phosphate has most of its phosphorus in the form of tricalcium phosphate, a form that is less soluble than some others. When acted upon by acids, it loses some of its calcium, which is con- verted into the calcium salts of those acids. When one-third of the calcium is removed, the phosphate becomes dicalcium phosphate, and when two-thirds is removed it becomes monocalcium phosphate. The more calcium the phosphate loses, the more soluble and available it becomes. Hence if limestone, a calcium compound, is present in ex- cessive amounts, it tends to prevent the loss of calcium from the phos- phate, and thus interferes with its effectiveness. In view of the chemical changes thru which rock phosphate goes in becoming available to crop plants, the disposition of the calcium that must be removed from it is a factor of some importance. If it cannot be removed, then phosphate rock is likely to be of little value. The more efficiently the calcium is disposed of, the greater will be the benefits from the phosphate, provided, of course, that the soil is lack- ing in available phosphorus. There are several ways in which the calcium compounds derived from rock phosphate may be disposed of. The acids that originally re- acted with the phosphate may unite with the calcium and thus remove it from the field of action. The existence of some soil acidity may therefore be highly desirable from the standpoint of the effectiveness of rock phosphate. Also, large quantities of calcium are required by such plants as alfalfa, red clover, and sweet clover. If such crops are grown in rotation on land receiving rock phosphate, more value may 1930] Response of Illinois Soils to Soil Treatment 465 be obtained from the phosphate than if only such crops as corn and oats are grown, which have a smaller calcium requirement. In addi- tion, on some soils drainage may be an important factor in removing the excess calcium and thus in permitting a better utilization of the phosphate. Other factors of equal or greater importance than these may also affect the disposal of calcium. In this connection it may be well to point out that the calcium from rock phosphate cannot be considered except to a limited extent as a substitute for limestone in growing clovers. The quantities of calcium that could be derived from rock phosphate would be insufficient and too slowly available on most soils that are too sour to grow clovers. Soil reaction would thus appear to be a matter of more or less im- portance in connection with the use of rock phosphate. Where the acidity is too great, unfavorable results may be obtained because of the conversion of the phosphates to iron and aluminum phosphate. If the soil is too alkaline, as would be the case where limestone is used excessively, then the reactions making the phosphate available would be retarded. Apparently the proper reaction should tend toward acidity rather than alkalinity. No definite information is available, however, as to the optimum range for this acidity. It is quite possible that it would vary more or less for the different soil types. Until these matters are better understood, the farmer must rely on present knowledge to guide his practices. One point clearly empha- sized by these experiments with rock phosphate is the need for the judicious use of limestone; that is, its use only where the soil shows definite need for it. Farmers will be on safe ground if they will base their limestone applications on a soil-testing program similar to that outlined in Illinois Circular 346, using limestone only on those fields or parts of fields where the test shows that it is deficient. 2. 7s rock phosphate an effective carrier of phosphorus? The data in Table 12, contrasting rock phosphate and superphosphate, altho not strictly comparable, do not reveal any striking differences between these two phosphorus carriers. Both carriers appear to have been influenced by heavy applications of limestone. Bone meal used in addition to manure and limestone has not been so effective as the other carriers used with crop residues and limestone. 3. Are the best methods used for applying rock phosphate? Experi- ments testing different methods of applying rock phosphate are not very extensive. Applications of rock phosphate mixed with the soil before the corn and wheat were planted and seeded have not proved any more successful in increasing crop yields than the method original- ly used (Table 12). More extensive experiments have recently been established in connection with this problem and will be of value in the course of several years. 4. What degree of grinding is best? Experiments relating to the 466 Bulletin No. 362 [December, effectiveness of various degrees of fineness of rock phosphate have only recently been established. The data thus far obtained are too meager to present in connection with this question. Theoretically, however, fine grinding of phosphate rock should be of considerable value. 5. Do deep-rooted legumes delay the need for applied phosphates? The contention that the use of deep-rooted legumes such as sweet clover, alfalfa, and red clover for soil-improvement purposes may delay the need for applied phosphate, is based on the fact that legume crops in general have rather strong feeding powers for phosphates, especially calcium phosphate, and that these legumes are able to get from the subsoils phosphorus not ordinarily available to other crops. If these deep-rooted legumes are grown extensively, they may take up considerable phosphorus which later becomes available for other crops. In this event, applied phosphates would be in competition with subsoil phosphates until such a time as the subsoil phosphates might become exhausted beyond the point of competition. Since many soils contain considerable phosphorus within the reach of legume roots, the need for replenishing surface soils with phosphates may vary con- siderably depending on whether or not deep-rooted legumes are grown regularly on them. Altho this influence of deep-rooted legumes appears possible, there is not yet sufficient data at hand to indicate how important it may be. Since on some soils deep-rooted legumes are markedly benefited by the application of phosphates, it is apparent that the problem is some- what complex. Investigations are now in progress on this matter. 6. Are some Illinois soils sufficiently supplied with available phos- phorus? This is an important question concerning which it has been difficult to obtain positive information because of lack of practical methods for studying it. A field method has recently been devised at this Station (Illinois Bulletin 337) which gives evidence of being use- ful in connection with such studies. The test has been applied to the soil of various Illinois experiment fields, and the results, summarized in Table 30 of the Appendix, indicate that one of the important factors in the lack of striking positive returns for phosphates on some fields is the absence of any special need for a phosphate fertilizer or else a greater deficiency in some other nutrient material, such as potash, which must be supplied before phosphates can become effective. The proposed test provides a new field method for studying this problem, and when used in connection with well-planned field experiments may throw considerable light on the complex phosphate question. Potassium Response Better on Light-Colored Soils Potassium, applied chiefly in the form of kainit, and in addition to crop residues, limestone, and rock phosphate, increased the value 1930] Response of Illinois Soils to Soil Treatment 467 of the crop yields on the light-colored soils $5.07 an acre annually, as an average of the last rotation on eleven Illinois soil experiment fields, and only $1.86 on the dark-colored soils of fifteen other fields. On the sandy soil of the Oquawka field the increase was worth only 41 cents. The highest value was realized on the Ewing field, $8.57, and the lowest, a loss of nearly $1.50 an acre, on the Minonk field. (Table 13 and Fig. 9). Table 13. — Effect of Kainit (Potash) When Used in Addition to Crop Resi- dues, Limestone, and Rock Phosphate, on 27 Illinois Experiment Fields (Average annual acre-yields and values of increases for periods ending in 1927) First crop year Years in rota- tion Average increases in major grain crops, all complete rotations Gross value for all crops Location of field All rota- tions Last Corn Oats Wheat rota- tion Dark-colored soils 1911 1912 1910 1911 1910 1910 1914 1915 1910 1915 1911* 1910 1911 1910 1910 1910 1912 1913 1911 1902 1912 1912 1910 1912 1916 1917 1915 4 5 4 4 4 4 6 4 4 4 5 4 4 4 4 4 4 4 4 4 4 4 4 5 4 4 6 bu. 3.0 1.7 4.5 4.1 4.3 4.9 4.8 6.2 3.5 3.5 2.7 1.4 -1.6 - .4 -2.4 2.7 14.6 4.5 1.2 4.4 13.4 4.7 7.7 6.8 6.8 5.5 - .9 5.5 2.0 bu. .5 2.1 - .4 .9 2.3 5.2 1.4 -1.0 - .5 1.9 .6 .3 - .6 -1.4 .1 .8 5.2 1.03 4.3 (192 lb.«) 3.7» 2.3 .5 .5 3.8 .83 1.23 2.8 1.86 bu. 4.6 1.0 1.0 1.8 - .4 - .3 3.4 -2.2 .9 .3 -2.1 .2 - .9 -1.0 -1.0 .5 6.7 3.1 4.2 1.8 2.2 .9 1.1 3.4 3.9 1.2 1.1 2.7 - .6 $1.73 2.29 .90 2.08 .21 1.51 2.37 .05 1.09 1.19 .22 .68 - .34 - .55 - .96 .88 5.42 3.03 3.81 3.93 5.10 1.92 2.21 2.49 3.38 2.36 .95 2.95 .54 $4.75 Sidell 4.10 3.95 3.50 3.25 3.06 2.59 1.74 1.08 1.06 .93 .23 - .89 - .92 -1.44 1.86 Light-colored soils 8.57 6.56 Toledo 6.39 Unionville 5.32 Odin» 5.61 Enfield 5.11 4.97 4.20 4.05 3.88 1.68 5.07 Sand soils Oquawka .41 Originally established in 1895. ^Potassium sulfate in place of kainit. 4 Seed cotton in place of oats. B Rye in place of oats. 3 Soybeans in place of oats. Thus the use of potassium in the manner indicated has had con- siderable influence on some of the experiment fields and little or no influence on others. On most fields the response during the last rotation was considerably greater than it was for the entire period. This was not true, however, for those fields with dark-colored soils that gave but little or no response. Of those fields that gave negative responses, the decrease in crop response in the last rotation was greater than the 468 Bulletin No. 362 [December, decrease for the whole period, thus suggesting that there may be an actual detrimental effect from kainit. It is evident that the use of potassium in systems of soil treatment needs careful consideration. Altho the potassium content of Illinois soils in general is fairly large, it seems quite clear that the use of potassium has produced some positive crop increases on a number of the Illinois soil experiment fields. In general, the less-productive fields Fig. 9. — Increases in Crop Values From Kainit (Potash) Used in Addition to Crop Residues, Limestone, and Rock Phosphate The light-colored, more mature soils give strikingly greater responses to po- tassium fertilizers than do the dark-colored, less mature soils. Most fields in the light-colored group give a profitable response to this fertilizer. In the dark- colored group only the more mature soils tend to give such responses. Livestock systems without potassium fertilizers give about the same kind of crop yields as grain systems with potassium fertilizers; which fact indicates that where there is plenty of manure, potassium fertilizers may not be needed. have tended to give the largest responses, tho some of the more- productive fields have also given rather marked responses. Just why the responses to the potash salts on many fields have been so positive is not entirely clear. It was thought at one time that po- tassium in its relation to soil fertility was a matter of liberating the supply in the soil rather than of adding to the soil. If this is true, then crop increases from potassium should decline with the continued practice of good systems of farming rather than increase, as they have been doing on many fields. Also if the problem is merely one of liber- ation, it would seem that the crop-residues system employed would be ideal for such liberation. Evidently there are other factors involved than liberation. 1930] Response of Illinois Soils to Soil Treatment 469 It has long been known that alkali soils, characterized frequently by a high carbonate content, respond markedly to potassium fertilizers, even tho the natural potassium content of the soil may be fairly high. The alkali condition appears to reduce the solubility and availability of the soil potassium. Experiments under controlled conditions (in Tennessee and elsewhere) have indicated that the amount of potas- sium leached from soils can be reduced by applying various kinds of limestone. These facts suggest that the responses obtained from the kainit may be related to the large amounts of limestone applied to most of the soil experiment fields. In the early history of these fields, the limestone no doubt materially assisted in growing larger crops, chiefly thru encouraging the growth of the legumes. Because of the larger crops, the supply of readily available potassium in the soil was reduced. As the total amounts of limestone applied to the soil in- creased, conditions were set up which tended to prevent the formation of readily available potassium. Hence as time went on, the crop plants encountered more and more difficulty in getting the potassium they needed for normal growth. Under such conditions the application of potassium would be expected to have gradually increasing effects on crop yields. The field results obtained from the use of kainit support such reasoning. The Ewing field has given some striking results for kainit (Table 14). An examination of the corn yields obtained during the first and Table 14. — Average Acre-Yields of Corn During First and Last Rotation Periods (Ewing field 1925-1928) Soil treatment None Crop residues Crop residues, limestone Crop residues, limestone, rock phosphate Crop residues, limestone, rock phosphate, kainit First rotation 1910-1913 Corn Last rotation 1925-1928 Corn bu. 21.6 22.7 36.4 34.6 38.0 bu. 10.3 13.1 25.5 28.2 54.7 last rotations will be of interest in connection with this discussion. During the first rotation there was but little variation in the yield of corn on all three plots to which limestone had been applied. The last rotation, compared with the first, showed an appreciable reduction in the yield of corn on all these plots except the one on which kainit had been used in addition to limestone. Here there was a very marked increase in the yield of corn. Apparently the availability of soil po- tassium may be retarded by the presence of excessive amounts of lime- stone. If this is true, we have still another reason for limiting lime- 470 Bulletin No. 362 [December, stone applications to amounts actually needed. While there is no ques- tion concerning the importance and value of limestone on the sour soils of the state, and nothing should be allowed to interfere with the proper use of this material on such soils, these experiment field results would seem to indicate that an overzealous use of limestone may, under some conditions, be a handicap instead of an advantage. The need for potash fertilizers on peaty soils has been widely recog- nized, but the need of upland soils in general for potash fertilizers is not so clearly understood. The crop increases obtained for potassium may not be entirely related to the excessive use of limestone, as indi- cated by the data presented. Other factors may also be involved, such as conditions peculiar to certain soil types. The fact that in the experi- mental work referred to above the potash carrier was always used in connection with other soil treatment materials may in part account for the responses obtained. Sweet-clover, for instance, has been an im- portant factor in the residues system of farming in which the potash salts have been used. The continued growing and plowing down of this crop alters considerably the nitrogen relationships of soils. In time these relationships, in connection with the associated biological transformations, may create unbalanced conditions which would tend to make it difficult for the crop plants to get all the potassium they should have for normal growth. Thus the continued growing of sweet clover may in time create a need for potash on some soils. This prob- lem is now being investigated and evidence is at hand that such re- lationships with sweet clover may exist. The excellent results obtained from the application of manure on those fields that have given good re- sponse to potash salts may have been due in part to the potassium contained in the manure. Thus experiment-field data indicate that potassium has a more important place in the soil-treatment systems on some types of soil than was anticipated when these experiments were established. Light-Colored Soils Show Greater Response to Soil Treatment On a percentage basis increases in crop yields resulting from the practice of the various systems of soil treatment were on the average from six to seven times greater on the light-colored soils than on the dark-colored soils. This difference, however, was due not to the fact that actual crop increases on the light-colored soils were larger than those on the dark-colored soils (tho this was true in the case of several soil-treatment systems), but to the fact that the yields on the un- treated land were very much smaller on the light-colored soils. In general, increases in crop yields ranged from around 100 percent to nothing on the dark-colored soils and from around 450 percent to 150 percent on the light-colored soils. The sand field at Oquawka occu- pies an intermediate position between the light- and dark-colored 1930] Response of Illinois Soils to Soil Treatment 471 All Complete Potations iMMm IMrfUAMZLJA t J I o <3 h E 1 \S> o -v -c O I— llJ c* Light-Colored Soils o Soils Fig. 12. — Soil Treatments Reduce Natural Differences in Productivity The value of the crop yields from untreated plots on the above fields was shown in Fig. 2. Here are represented the crop values from the most-productive plot on each field under the livestock system. It is evident that some of the light-colored soils offer good opportunities for profitable crop production when good systems of soil treatment are practiced, tho the dark-colored soils, in general, are superior. All Complete Rotations Last Rotation Only I ■ n t I I 21 21 21 21 21 21 21 21 21 21 21 21 21 II SI 21 21 21 2.1 21 21 21 21 II 21 II 21 21 21 21 21 21 21 21 21 21 21 21 21 Sill SI 21 21 21 21 21 21 21 21 21 211 21 H 21 21 21 21 21 21 21 21 21 21 21 21 21 211 21 21 21 21 21 21 21 21 21 21 211 2 S 3 £ °: S S g < 3 O *: 3T Dark - Colored Soils 5 1 t J -§ 2 * S .2 2 5 J £ £ Lighb-Colored Soils c x. O to Fig. 13, -Productive Levels of Light- and Dark-Colored Soils Under Grain Systems of Farming The same general facts are to be observed here as in Fig. 12; namely, that differences in productivity between the light- and the dark-colored soils are reduced by proper soil treatments, and that while both grain and livestock sys- tems can be used effectively on many Illinois soils, it is difficult on other soils to raise the productive level to a point that is economically profitable. 474 Bulletin No. 362 [December, family. At Aledo the total gross acre-income from this system of soil treatment was $46.91, or three times as much as at Sparta. Another comparison will be of interest in this connection. At Sparta the annual gross acre-value of the crops grown on untreated land was $3.90 during the last rotation; at the Ewing field it was $5.59. Neither field could be said to be naturally very productive. The manure-limestone treatment gave good crop increases on both fields. At Sparta the average acre-value of the crops grown during the last rotation was raised to $15.61 a year. At Ewing it was raised to $27.82, or to a level nearly twice as high as at Sparta. The Ewing field is much more responsive than the Sparta field, and it is readily seen that the opportunities for profitable crop production under condi- tions similar to those at Ewing would be very much greater than under conditions similar to those at Sparta. The total level of production is thus seen to be an important point in considering the practical aspects of systems of soil treatment. Soil Treatments Change in Their Effectiveness A study by rotation periods of the systems of soil treatment that have given the highest net returns reveals the fact that the most effec- Table 15. — Systems of Soil Treatment Giving Largest Net Acre-Returns in Livestock Farming Rotation periods 1 Location Last ending in 1927 Next to last Second to last Third to last Fourth to last Dark-colored soils ML ML ML ML ML ML MLrP ML M ML M ML ML ML MLrP MLrP ML ML ML ML ML ML ML ML ML ML M ML ML ML ML ML ML ML M ML M ML M M MLrP MLrP ML ML ML ML ML ML ML ML ML ML M ML ML ML ML ML ML M M ML None ML None None ML ML ML ML ML ML ML ML ML ML None ML ML M M M ML m" ML None M None MLrP None ML ML ML ML ML ML Mt. Morris Sidell Light-colored soils Enfield M Toledo West Salem Sand soils Oquawka iFour-year rotations practiced on all fields except Joliet, Sidell, Newton, and West Salem. 1930] Response of Illinois Soils to Soil Treatment 475 Table 16. — Systems of Soil Treatment Giving Largest Net Acre-Returns in Grain Farming Rotation periods 1 Location Last end- ing in 1927 Next to last Second to last Third to last Fourth to last Fifth to last Dark-colored soils RL RL RLrPK RLrPK RL RL RLrPK RLrP RL RL R RL RLrPK R RLrP RLrP RLrPK RLrPK RLrPK RLrPK RL RLrPK RL RLrPK RLrPK RLrPK RL R RL RL RL RL R RLrP RL RL RL R RL RL R RL RL RL RLrPK RLrPK RL RLbPK RL RL RL RL RL RL RL RL RL RL RL R RL R R RL R RL None RL RLrP rl" RL RLrPK RLrP RL RL RL RL RL RL None R RL RL RL R R R*" RL R None None RLrP* rl'" RL RL RL RL RL R L " RL None RLbPK LaMoille Mt. Morris Sidell Light-colored soils Enfield Odin RLbPK West Salem Sand soils Oquawka !Four-year rotations practiced on all fields except Joliet, Sidell, Newton, and West Salem. tive system for any particular field may change from time to time. A system of soil treatment that produces the best results during one ro- tation period may not be the best system during a succeeding period. The system of soil treatment that has given the largest annual net acre-returns in both livestock and grain systems of farming on each of the soil experiment fields in each rotation period is shown in Tables 15 and 16. A study of these tables shows that every system of soil treatment employed on these fields has at one time or another, on one field or another, been the most effective system used. In general the simplest systems predominated in effectiveness during the early peri- ods, but during succeeding rotations the more-complicated systems tended to become more effective. Also, the more-fertile fields tended to respond to the simpler systems for longer periods than the less-fertile fields. The continued cropping of soil, by reducing its productiveness, evi- dently increases its need for more comprehensive systems of soil treat- ment; not only do more plant- food elements need to be supplied, but they need to be supplied in different quantities. These are facts that every farmer who desires to make the best use of his lands should recognize. 476 Bulletin No. 362 [December, PART II. MANAGEMENT PRACTICES FOR ILLINOIS SOILS In the preceding pages data have been presented that bring out the manner in which Illinois soils vary in response to applications of different fertilizer materials. While such information is essential to a clear understanding of fertility problems, the comparisons made do not answer the questions of individual farmers as to the practical procedure to follow in planning comprehensive systems of manage- ment for a given kind of soil. It is these questions that the second part of this bulletin attempts to cover. Here, in terms of crop yields and money values, the relative effectiveness of different systems of management for each of the principal groups of Illinois soils is shown, and in addition specific recommendations are given that will indicate for each group the steps to be taken in establishing effective and eco- nomic systems of treatment and management. The map between pages 440 and 441 furnishes a general guide to the location of the various soil groups over the state. Farmers who are in doubt as to how their soils classify may get assistance by consulting their farm adviser or by writing the Experiment Station. Dark Soils With Heavy, Noncalcareous Subsoils (Group l) The soils of Group 1 occur in the central and west-central parts of the state. They occupy flat-lying upland on which the surface drainage is poor, tho they underdrain satisfactorily. They are relatively heavy, particularly in the subsoil, dark brown or black in the surface, and are rich, productive soils. Alkali spots are not uncommon, tho the con- centration of alkali is not sufficiently high but that the condition can be readily corrected. The experiment fields coming within this group may be classified into two subdivisions: semimature soils and young soils, represented by the fields at Sidell, Aledo, LaMoille, and Minonk (Table 17). These fields, with the exception of Sidell, are young soils and are among the naturally most productive soils in the state. Being natural- ly productive, these fields have not given any marked response to any system of soil treatment employed on them, altho some of the simpler treatment combinations have given profitable increases. There are in- dications that in time other combinations of soil treatment may be used with profit. The more important responses on this group of fields have been 'The descriptive material concerning the various soil groups was prepared by Dr. R. S. Smith, in charge of the Illinois Soil Survey. 1980] Response of Illinois Soils to Soil Treatment 477 m hJ HH o rl) pq P m 93 P O W S 3 u J < * 03 O a> ft ^ oj * > > n-S c3 w 03 a (fl H c 2 a u 03 -g CO 03 Ifu £ « *8 3 « "5 > >> ja •fl a a 8f.i >> d a> o3 Sg o o o a o CD a 3 H •a > ■ss T3 in tj T ^ o 00 3 a 03 02 03 CO a a> 3 o3 f 8 3 •9 >< 43 a a s] H o3 a o> o .2 8 ■t»COCN .NNOffl ■«(ON •»-!< COCOCOCOCNCSKNCSICNICN CD <-• O "* CO 3 CO ^ t- 0 »-• ^ i-i "° C r-< r-l .-H . . ■* CO ■* O CO CO •* O O Ji © i-l © CN iiO m CD O — i . COCOCMCOCMCNCNCOCOCM COOO'tfOOOCOCNCO'tfCM CO»D©©cDCM©©cOTi< a. a. a. ©^gj§ ©####©" ©S3 CM© 0> O a) a > o o h £w ■ o©co • cm ■* © <* ■HiOiO .^^t>.>o • CO oo >o • cm od co t>I •COCMCO -COOCNCO^ rt.l>.CO»-l >t»t^r-(t,t.^lT».© OOCDt-OSNCOO^-lTjIOS a aa alalaiai© 478 Bulletin No. 362 [December, s £ 1 rr fa Q ■7; pa P oq 00 p w 2 < CD u -5 -J > fe -1 o a fc as Of] £ IS 73 P> w o u a H £ 3 CO a 3 o M 53 5 pj 5 > Q a P Ooo 12 5! •*CO •■«l*r)0")0 00 OJ 00 00 * CO >C - IN»H(NHlOO!CN ' oo oo a> io in io t»' co d (fa oSSSdrttfrtPSd o TftCN tN<35 ©,« OQ o h £co OZ "«t<<-ieN -OOCD^rH CN CO t^ • ' (N CO CO • c©"5»0 • cooooo COTj«^»Ct^00505GOCO COCOCOCOCNCOCNCNCNCN C0»0b-O^.tOC0t*CNCN CiO'-i'-'©00>G7>t"»>C 1-HCNlNCNCNCNrH^-I^Ht-l 00'-"0>0 *O00r-OiCOiOiOTjt~-*iOO IOCOCOCO>OCOCOCOCO»0 iMOtfUOO' :^3 I- Ih .J 1-3 1-3 o'SSSotftfrttfd 1930] Response of Illinois Soils to Soil Treatment 479 obtained from organic manures used either in the form of farm manure or crop residues. This is not true, however, in the case of the Sidell field, the behavior of which seems to be somewhat out of line with the rest of the fields in this group. The behavior of the Sidell field may be due in part to lack of uniformity, studies during recent years in- dicating that the soil, instead of being of a single type as was once thought, actually consists of several types, a fact that complicates the interpretation of results. On the Aledo field the application of farm manure alone has been the most important soil-improvement practice, and each succeeding rotation has been characterized by better results from the use of this material than the rotation preceding. During the last rotation lime- stone used in addition to manure and in addition to crop residues has given very good crop increases, showing that in time, under the influ- ence of cultivation, soils of this character may come to need limestone for best results. At LaMoille both farm manure and crop residues have given in- creased yields in all rotation periods, the increases during the last ro- tation being decidedly striking. The field at Minonk has been especial- ly responsive to the crop-residues system, each succeeding rotation giving larger crop increases than the preceding one. During the last two rotations farm manure has given good crop increases, tho this treatment has not been nearly so effective as the crop-residues treat- ment. With certain exceptions on the Sidell field, none of the other soil- improvement practices have thus far been of any consequence. At Sidell during the last rotation limestone was of some importance, and, rather strangely, the most effective treatment during this period was the one making use of crop residues, limestone, rock phosphate, and kainit. Suggestions for management — 1. Altho soils coming within this group are naturally highly pro- ductive and give opportunity for profitable cropping, it will be wise to plan a systematic rotation that includes the liberal use of such legume crops as alfalfa, sweet clover, and red clover. A larger propor- tion of corn can be successfully included in rotations for these soils than for other soils in the state. 2. Crop residues should be plowed down. Especial use should be made of sweet clover as a green manure. When alfalfa and red clover are grown, the last growth should be plowed down for the corn crop following. 3. Where livestock are fed, the manure should be carefully con- served and used for soil improvement. 4. From time to time the soil should be tested for acidity. Many 480 Bulletin No. 362 [December, soils in this group will grow good sweet clover without limestone, but continued cultivation is likely to bring about acid conditions and hence the need for limestone. Dark Soils With Heavy, Calcareous Subsoils (Group 2) Soils in this group occur in the north-central part of the state on both flat and rolling areas. The higher areas have a less dark-colored surface soil and are somewhat less productive than the lower areas which are well underdrained. They are characterized by a dark- colored surface soil and a rather heavy subsoil which contains sufficient limestone within a depth of 40 inches to effervesce with acid. The most easily observed difference between Group 1 and Group 2 is the absence of limestone to a depth of 40 inches in Group 1 and its pres- ence in Group 2. There are two fields that represent this group of soils, one at Harts- burg in Logan county and one at Joliet in Will county (Table 18) . Because of the differences in the processes that have operated to form them, these two young soils have given quite different responses to the systems of soil treatment employed upon them. The Hartsburg field being influenced by sedimentation is naturally much more pro- ductive than the Joliet field, which has been influenced by erosion. The Hartsburg field is similar in its responses to the fields which have non- calcareous subsoils, while the Joliet field is in a class by itself with respect to response to treatment. At Hartsburg both farm manure and crop residues have been prof- itable thruout the entire history of the field and have shown little dif- ference in effectiveness. Limestone applied in addition to farm manure has tended to be of value, but when used in addition to crop residues has not thus far produced results of much importance. The Joliet field has been responsive to several systems of soil treat- ment. Farm manure has produced good results, each succeeding rota- tion having given strikingly larger crop increases than the preceding rotation. The crop-residues system without further treatment has not been very effective, probably because of lack of sufficient minerals in the soil. Limestone used in addition to both manure and crop residues has resulted in crop increases, but the response has not been marked. Rock phosphate has been an important factor in the crop increases ob- tained in both the manure and the residues systems. Potash thus far has not been of much importance, but there are "some indications that in time it may be of some value, especially in connection with the growing of legumes. Suggestions for management — 1. For soil types corresponding to that on the Hartsburg field the 1930] Response of Illinois Soils to Soil Treatment 481 03 CD "sl §"8 c3 a CO c MO o r-l05 ^2 C w c3 ft CD O » ft > o On £co "2 CON- HMtOOOSNHiO eo t» t> i-H OS CO 00 lO •* CD O £ T)««ifflHMNTl*Oi-i(N eoeoeoT^cococcTtn-tfco l(M(NCN* 00 ■* Tt< CO i . Tt* O CN ■* b- CO 00 00 C CN Tfl lO CO CO iO CO CO CD CO <0 M 2J IN© CI'"' o 00 tN «! P o s 5 < CO CP » > o a H K BQ f m 53 hJ S OS H o fl « o> ci P. J3 u £<° i GO a a; CO 1" 2 2 NK5N .1 cn © cn • titOmOHHNrtlN . •* OS O 00 «# CO -t co OS 3 iO iO CN »-i >0 CO OS © CN *° CN CN CO ■* oi CN CN r* >*' e-s lOeoo-^io s_ COCOtOOCDi-H-HlOTft 3 .-Jj-J^J,.;^ t-4i-41Q|> rf> WV -' W "-' V -'CN CN CN CN Eh t*- io ^h os o h os t- o ■w t» <-< 00 CN t- T* 00 © OS S i-H CN CN CO --< 1-5 r-I IN <-< . CO <* CO CN CO O 00 GO b- .3 d OS CO t-h CO 00 CN CN © CNCNCO-tfCNCNCO"*'* . 00 CN © CN 00 »0 t>. OS »0 CN ■* OS ■.*< CN ■* OS CO CO J5 i-HNt^OS^O—it^Os' »C CO CO CO iO iO CD CO CO ©SSS©PhPhPhPh© 55 OSCN-* Tf CNOS CNTt*©-* . •COCOlO • co-^co • -4J s • tOOeo -lOiOOO • o •CNC0t> • CNCO00 • 8 o •■*rtO -COCNCOOS • •C00»0 -OSt^OSOS • d •COOCO • lOOH . o Tt<-HCOrHCNCO COCOTP-^cOCOCOrfTHCN 5 W ©CN CDCNCOCNOSO'OiO'-ICO C0U0TtOO>COr-«|> CNOS OS** 00-#COt^O'-iC0t>.00t>- CNCOCOCOCCCOCOC0COCN >> fl O o C 49 w % cfl O i-H OS os'-' ©OOCO^-'TfOTH'-tiOOO OOiOOTCOO^r-iOOiO-* 00 CN CN (N t>^ t>^ 00 OS* ^H 00 CNC5COCOCNCNCNCNCOCN CO CJ c t CO M 1 1 'I M c O >< H| o 3 ■^CO©CO©»O0000CO00 COCNC0-«f©>Ot>'©©CO iHCNCNCN>-i>-''-li-4lN'-i "8 0. CO o ©COOOt^OOCOCOOSCN-* ©CO'OO'-'COiOO'-i© COCOCOTjt^t-CO»OCOCOb-iO "- 1 CO ?2 ©©t^©kOt*©>0©t^ a* eoiooo©^co^©co© »0©©t>-»0«OCOCOt^'«*< '-' c % c cc s p. (- M : Ah ■ •J • 484 Bulletin No. 362 [December, stone, and rock phosphate. At Kewanee the use of rock phosphate in the manure system has given larger crop increases during each suc- ceeding rotation, but even in the last rotation the increases were hardly large enough to make this system any more profitable than the same system without the phosphate. In the crop-residues system where phos- phate was used increases were sufficiently large to make this system the most profitable. Potassium has been of no importance on either field. Suggestions for management — 1. The soils of this group are capable of intensive cultivation. It is important, however, that the crops be grown in a well-balanced crop rotation. Alfalfa, sweet clover, and the common clovers should be given careful attention from the soil-improvement point of view. 2. Altho these soils may grow good stands of the common clovers in favorable seasons without the application of limestone, yet the soils in this group are likely to be too sour for the successful growth of sweet clover and alfalfa without limestone. They should be carefully tested for acidity. The wise use of limestone upon them may be counted upon to bring good returns. 3. Phosphate may be used on these soils with profit. Its chief value may be expected in wheat increases and in better stands of legumes, especially of alfalfa and red clover. Rock phosphate may be applied at wheat-seeding time either by broadcasting or drilling at the rate of 500 to 1,000 pounds an acre. Other carriers of phosphorus, such as bone meal and superphosphate, may also be used, the choice resting on the relative economy of the carriers. If superphosphate is used, it should be applied at about one-half the rate of the rock phosphate. The need of the soil for phosphorus may be confirmed by a simple soil test (Bulletin 337) for readily available phosphorus. 4. Where livestock are fed, the resulting manure should be care- fully conserved and utilized. 5. Crop residues and leguminous green manures should be plowed into the soil regularly. 6. A combination of organic manures, limestone, and phosphate are recommended as a profitable combination on the soils in this group. Dark Soils With Open, Noncalcareous Subsoils (Group 4) This group of soils is not extensive in Illinois, occurring almost en- tirely in the northwestern part of the state. These soils are found only on rolling topography, are medium acid, light brown in color, and have a very pervious subsoil, tho not leachy. They are potentially not as productive as the soil in Groups 1, 2, or 3, but are well drained, easily worked, and with good farming are productive. 1930] Response of Illinois Soils to Soil Treatment 485 The three fields in the group — Dixon, Mt. Morris, and McNabb — have not been entirely alike in their response to the systems of soil treatment employed upon them (Table 20). The two fields in the semimature division — Dixon and Mt. Morris — have been somewhat similar in their responses, but the McNabb field, classified as a young soil, has not shown a similar sort of behavior. This is probably due to the fact that this soil has been formed under the influence of sedi- mentation. Fig. 14. — Wheat Yields on Dark-Colored Soils Increased by Soil Treatment Many dark-colored soils have become so impoverished that they give rather striking responses to some systems of soil treatment. Residues, limestone, rock phosphate, and potassium (K) tripled the wheat yields on this field, as may be noted from the acre-yields of grain (bushels) indicated above. (Mt. Morris field) The Dixon and Mt. Morris fields have both been responsive to farm manure, Dixon somewhat more than Mt. Morris. Both fields have been responsive to crop residues but not to the same degree as to the farm manure. At both places the influence from crop residues during the last rotation was not so great as in former rotations. Both fields were indifferent to limestone during the early periods, but during the last two rotations and especially during the last, limestone has been an important factor on both fields but a considerably greater one at Mt. Morris. Rock phosphate has tended to increase crop yields at both places, but the increases have not yet been sufficiently large to make the use of this material profitable. Potash has not been im- portant at either place. The McNabb field has not been profitably responsive to any sys- Bulletin No. 362 {December, U 1! *o $ Si la P 'COOOrH .lOlCOO •i-HCOt- • NO00 •OJCO-* -NOOi-tN '00O5O5IN' CM O rftO'-Hl^Oit^lNiOOJOl o ■^co ©£» o s s 41 O |2 £ ° 19801 Response of Illinois Soils to Soil Treatment 487 tem of soil improvement employed upon it during any of the five rotation periods it has been in operation. Unfortunately not all the systems of soil treatment employed on the other fields have been used at McNabb. The failure of farm manure, however, to influence crop yields, would indicate that other systems of soil treatment would probably be without influence. The high order of the crop yields in- dicates marked natural productiveness in this soil. Suggestions for management — The semimature soils of this group are of moderate natural pro- ductiveness. They are responsive to various systems of soil treatment and will satisfactorily grow the various corn-belt field crops, but for best results they will need careful management. Because of their some- what rolling nature, some attention may need to be given to erosion- control practices. 1. A systematic crop rotation should be employed on these soils. Legumes should be given a prominent place in the rotation. Red clover, which does very well on these soils, can also be used to ad- vantage in the rotation. Sweet clover and alfalfa may be used. Soy- beans make a good annual legume. 2. These soils should be carefully tested for acidity, and limestone applied in accordance with the results of the tests. 3. Altho rock phosphate has not yet given any marked effects on these soils, the results hint that phosphates may be of some value. It is suggested that tests be made for readily available phosphates in the soil. If abundant, the phosphates need not be applied in the immediate future. If absent or not very abundant, either rock phos- phate or superphosphate should be given careful trial before an ex- tensive use of either of them is made. It is suggested that either of these phosphates be mixed with the plowed soil at wheat-seeding time either by broadcasting or drilling, and that the wheat be followed by a good biennial or perennial legume. 4. As these soils are especially responsive to farm manure, every effort should be made to conserve and use on the soil all the manure it is possible to obtain in feeding operations. 5. Crop residues and leguminous green manures should be plowed into the soil regularly. 6. The use of potash on these soils apparently needs no considera- tion. 7. Since the soils in this group are likely to be more or less rolling and hence subject to erosion, erosion-control practices should be given attention. 8. Young soils such as those represented by the McNabb field ap- parently require no special attention with regard to soil treatment. Good cropping procedure appears to be the chief need. 488 Bulletin No. 362 [December, Dark Soils With Impervious, Noncalcareous Subsoils (Group 5) This group of soils is found, for the most part, in the southwestern part of the state. They occur on flat-lying areas, and both the surface and subsurface drainage are poor. They are characterized by a grayish brown surface soil, a gray subsurface, and a drab or gray- colored, impervious subsoil, and are medium to strongly acid. The character of the subsoil is such that these soils will not underdrain satisfactorily. Slick, or scald, spots are numerous. The four fields in this group — Carthage, Clayton, Lebanon, and Carlinville — have been somewhat similar in their responses to the systems of soil improvement employed upon them (Table 21). All have been responsive to farm manure, especially during the last rota- tion, when the crop increases were rather marked. In general the re- sponse to crop residues has not been so marked as to manure, tho fair responses have been obtained. The Carlinville field, representing the more-mature soils in this group, has been the least responsive to crop residues used alone. In all cases limestone has been more effective in the crop-residues system than in the manure system. The Carthage and Clayton fields were somewhat slow in responding to limestone in the beginning, but during recent rotations the results have been rather striking. Rock phosphate thus far has not been an important factor in the results obtained from any of these fields, tho during recent years there has been a tendency for it to exert a little more influence than during the earlier years. Potash in the form of kainit was of little influence on these fields until the fourth, or last, rotation period, when all four fields gave rather pronounced responses to it. In fact, the most profitable soil treatment in the residues system on all four fields was the system call- ing for crop residues, limestone, rock phosphate, and kainit. On soils of this character, especially where the use of limestone and sweet clover as a green manure has been prominent, the results indicate that a need for potash is likely to develop in time. Suggestions for management — Dark soils tending toward imperviousness in the subsoil represent more-mature soils than those in the groups thus far discussed. They are among the naturally least-productive dark-colored soils but are responsive to good systems of soil treatment and are capable of growing good corn-belt crops when properly cared for. Because of the impervious nature of the subsoils, drainage is a more important prob- lem than with the other dark-colored groups. 1. Good crop rotations are of prime importance on the soils of this group. Liberal use should be made of such legumes as sweet clover 1980] Response of Illinois Soils to Soil Treatment 489 o » PQ fc> DQ CO P O S n W '£> 02 —i <8 1 H 3 - fafi A g O c3 H a> * t« *< .9 iJ fac QQ fi- fe O H O fe H a> « o3t3 3 O CI S 03 ft 3P.J fed a as OCiCOCO'-l •S IN ©Tt o <8« o 5 O© ^co •t~CO<3> -INOOIO •00' OOOOOOOCOOOiOO ►J J SSSo'«tf«tf 490 Bulletin No. 362 [December, 1 5 O 1 OQ J c 00 05 P C/J OQ 'P O u 5 «< o 5 0Q u o 5 fe ^S d on 3 P l« t3 > 01 Pi >. w SI 2 o ed W IS H H a r/J 3 J g; hi; srl I7J M K rf < Q "S o ^5 H | fe W QJ 3 § E H j o o5 Em O H U w & 1 a H 3 pq 5 H a gfl o o oJ c3 3-^ 9« 0)3 fc£— . 5; « S3 0/ *«- 2 a o > >> JQ •8 •R §■8 0"G 03 S v ft S« >> 2.2 a > 03 . o "S* a S3 3 u ss > T3 «a a S3 ^5 I 0) J •A O ft ft H) B 05 3 03 S S 03 ■3 a « •8 o >H +» a OiO •CO-<3-© O OO'«*<«-iC0 OOCOO-tfr-iiNOCOiOCi P5NOH(OCi5- b- O cooi^co-^-tfOcooic i O t^ ■* "5 O 00 >0 i CN CN -< »-iT}<©iOiO-- b- o ^ CN CO ■* •* CO CO dSSSo'tftftfffJd 1980] Response of Illinois Soils to Soil Treatment 491 and red clover. The subsoils are not so impervious as to exclude the growing of alfalfa, tho this crop is not likely to do so well as on some other soils. Soybeans as an annual legume will do well on these soils. 2. Since these soils are usually sour, they need limestone for the best results with legumes. It will be well to test for intensity of acidity in order that the proper amounts of limestone may be applied. 3. Livestock feeding operations fit in well with the management of these soils, for the resulting manure when properly used has a marked influence on productivity. 4. Crop residues and leguminous green manures should be plowed into the soil regularly. 5. Altho phosphorus has not been of great importance thus far on these soils, its use in some form in connection with the application of potash should be given some attention. It is suggested that tests for readily available phosphorus be made as a guide to planning further trials with phosphates. In view of the fact that potash is be- ginning to have rather marked effects on these soils, and that on these fields the use of phosphates has always accompanied the ap- plication of the potash, it would seem desirable to conduct some trials of various phosphate-potash combinations, especially on farms where legumes are grown extensively, before planning for the wide use of either of these fertilizing materials. Such application may be made before planting either corn or wheat or both. 6. Careful attention should be given to drainage. The regular growing of sweet clover in rotation may be of some assistance in hastening the drying of these soils. Gray Soils With Impervious, Noncalcareous Subsoils (Group 7) This group of soils occurs in southern Illinois and includes soils popularly known as "gray prairie soils." They are characterized by a gray surface, light gray subsurface, and gray, impervious subsoil. They occur only on nearly flat areas, are strongly acid, and are naturally poorly drained. The character of the subsoil is such that tile will not draw satisfactorily, thereby making it necessary to drain by means of furrows and open ditches. The field results for this group of fields are shown in Table 22. The seven fields in this group — Ewing, Oblong, Odin, Newton, Raleigh, Toledo, and Sparta — are somewhat similar in their responses to systems of soil treatment even tho they vary somewhat as to degree of response. They all show a marked response to limestone. In fact, probably no system of soil treatment would be profitable on these soils that did not include limestone. Farm manure has given good results on all these fields, but without limestone the total level of production 492 Bulletin No. 362 [December, a | tin 5 o 3-3 c o * «*■£ sJ M— cS i« h o £g n •ss fa v £ /. CO T3.S > b M n | s o •c ft J a 5 o fe OQ o3 n O O fc J3 >> i»T o3 > e3 m 3 O fa C3 in c r/) CI o3 J >< < » « *h n & o $ H «a 1 3 h _d T3 >.° OOO 3* S 2 3% o3 <-> •COOO •COCOC5 •i-HOiOOiO • •i-tCO«-HCN • . r}< OS CO • HOtD • •ONU) •*OOJf- ■KJK500 • •t^lNOiO • OHOiCiOCNJC0 Tt* "5 T^ TJH . Sh 00 00 O i-h CO ■>*< CO 3COCOCOOO' — • ^ coo cot>eN 4 ioco r»-*»o s oo • -oo • • -o 2 HNtJNOHNHHO S 00 iO CO O b- 3 (NiCOCOC-l t* t- CO O «5 J5 i-i CO O -H NO)(0Q0ON itJ.CDCO^H(N00 !-Ht^ 05"- 1 (M 0> ^2 CO O f, 5 » £ 5 I! • -ICO CO •cococm • •O • HiON • K5N«3 00.T-lT}00COTt iO lO CO "* i O COt^O CO»OCO— lt^ — I— I— l»0 • 9» •OO00 •10000 • •t^OCO -NMOiO • 8 o • COCO • (NCOOO • o •. c 3 (5 o O -^co fl "#CN i-KN T-HCNJtN HI O id ,H M O ■"o ©COOt^CO— ..-l©t^00 £ >,« t>.©"5t^iOiO(NTt1 O o a **GOCOCO©©f».0— iiOG000©Tt*tN.COOlTt<>0 m ©■*COTf<— ICOCOIOCO— 1 -irHtNCN-i- KNCNCN-I co loa^iotoosoMS u^ -KN-tfrJt-iCNCO'*"'*-! : o< : :M : .-ihj : J.JJ • C > SSd* M tftfd 494 Bulletin No. 362 [December, e i i r A i ffl 7J T P o Uh s i u , — s -' m 5j 93 n fl Iz; 3 o t> fc T3 „ d DO. Bl 0Q 73 > C: S >. Oh 83 r K i a; y. o t: H d X H 0} ~ g H d | o •5 ft >> c c 3 o C4 -0 O 3 03 >> .O. .O 3 3 V u >> T3 3 § «C C O (3 T3 aj M o 03 H >• & 03 3 O O 09 3 i 3 £ 3 5 o a m o 33 09 ■n 3 T3 03 hi . 03 ?! O c & £ T3 a o t> 33 3 0) w c 6 T3 !* , 03 C hS -3 Ci^ 3 09 03 ft oj O %° ~-c a (h 09 ZZ 4s o o5 •*COCO ■COOOiO • -h >c co cm • ■CM*C5 • • | OOOcN • •f^OCO ■K5K500 • 00©COCCCO00»OCOO9t>i t^COC3©»OCOOOOOOCO HHfJ^OlOH S w— C-C- E/H -H rf iO CM CO CO * h. 00 © "— -HCM**CMlO00t^*.-H 3 ' CM CM ' 't-!-HCN Eh * r~ •* in co to cs 35 * co S_ OHOHOHIN1- © O CM CO -O © -H CO * 00 © -H iO © h- thCNJCN (NCMtN 00 O 00 CO o ■* CO o 5 i-( t~ Oi CO t^ 00 CO o> o »o ^ CNClC0CO^-irHCNCNn0 (N • O O 'O iO • •COCO-* •'OOMN • 0! O O CM.eC i • CMiOCO • O •iCCO CM -OS-^OOCO ■ •COCM-<*< -i-KM-^fC . '• CM i-H CM • l-H -H -H IQ " «© r^ tN OS iOO-Ht»i-iO»OCJ5t^Tj( >> *" ' cot^cor^os-H-HcocM-* o c Tj A ft s -3 C 5 K CO , CM 2 09 COO>-'C0cO-h00O9C35tJ< COt^CMCMCOCOCNOOOCO "3 1—1 C3 o 43 t^OSOSOSCOb-'OCDt^iO 5 o (N «© 3 OS a 1 1 1 o a CS C3S COCMt^t^t^CNO^OOOO 3 O^OOiOCDO-HkOTt* C O O 05OCDt^cOt^-*Tj. o o a fe ft 2f o CO* O-CS h fe ^ CO* lOOOCO h O O OO • -OO • • -0| ^ U^ -2 o 00 09 ^ -3 23 o CSiOcNCOf^cOCO—iasOO o £s iOt^-***iOCMCOCO* c?o ,H|H -Hrtl-H cc*- 1 OJ p 0*cMOS-H-HCO-HCOCN I 6 P*oo lOt^cOcCiOiOiOcOt--* eI i-ir^^ioosioio^osco 6° »OOSOSi-HCMCO»0*C350 -H^HCMCO-H-HCMCMCMi-H ^ :M : a, PhPl, • :.Jh3 • 1 c s^ ^c a PE PhPho' 19301 Response of Illinois Soils to Soil Treatment 495 is still so low that it is doubtful whether the farm-manure system alone would represent a profitable system of soil treatment on any of these fields. Fig. 15. — Livestock Systems of Soil Treatment Increase Yields of Wheat Many of the mature and old soils of the state show very striking response to systems of soil treatment either in livestock farming (above) or in grain farming (Fig. 16). On most of these light-colored soils limestone is of first im- portance. In fact, without limestone, manure applications on this field were in- effective, resulting in a yield of only 1 bushel an acre. (Newton field) Crop residues alone have not had a very noticeable effect on crop yields. This is due, no doubt, to the failure of legumes to grow where no limestone has been applied. Wherever limestone has been used, marked results have been obtained, the yields for each succeeding rotation usually having been considerably better than during the pre- vious rotation period. Increases during the last rotation have been especially striking. 496 Bulletin No. 362 [December, Rock phosphate has had little influence on this group of fields. On some of the fields there has been a tendency for the phosphate to exert a little more influence during recent years, but not to the extent of Fig. 16. — Grain Systems of Soil Treatment Increase Wheat Yields On many of the mature and old soils of the state striking increases in crop yields are obtained under a grain system of farming as well as under a livestock system. In the above pictures the figures indicate yields of grain per acre. As noted in connection with Fig. 15, limestone is usually of first importance on these soils. (Newton field) being very profitable. At Odin bone meal used in place of rock phos- phate has produced a response similar to that for rock phosphate on the other fields. Potash has given rather indifferent results until recent years. During the last two rotations, especially the last, the results from the use of potash have been striking on all fields, indicating that on soils of this character, where limestone and sweet clover had been used for 1930] Response of Illinois Soils to Soil Treatment 497 some years, a need for potash is likely to develop with continued cul- tivation. Suggestions for management — Soils that are so old that they have lost their dark color, and have developed a rather impervious subsoil, become difficult to drain and are likely to be rather low in natural productiveness. Where these conditions have developed to the extreme, the natural productiveness and the ability to respond to systems of soil treatment may become so low that any attempt to grow crops profitably is likely to fail. Fig. 17. — Soil Treatment Made the Difference Between a Good Crop and No Crop at All Manure, limestone, and phosphorus were responsible for the 50-bushel corn yield on the left. Corn failed completely on the untreated land at the right. (Ewing field) Such soils may be said to be marginal or even submarginal. Where the aging process has not advanced so far, the natural productive- ness may be low but the soil may still be capable of reaching a fairly good level of production under careful management. The results from this group of fields emphasize these facts. 1. While handicapped by poor natural drainage and the fact that tile drainage is rarely successful on these soils, considerable improve- ment can be effected by providing a thorogoing system of surface drains. The regular growing of sweet clover may also be of some help in causing more rapid drying. 2. As these soils are usually very sour, the application of limestone constitutes the first essential soil-management practice. If funds can be obtained for investment in limestone, more rapid progress can be made in the improvement of these soils than if it is necessary to depend upon farming returns to pay for investments in limestone and other 498 Bulletin No. 362 [December, soil treatment materials. With some of the poorer soils the latter pro- cedure would be almost a hopeless task. On some of the better soils in this group, the careful cultivation of acid-tolerant crops, such as soy- beans, corn, wheat, timothy, redtop, etc., may provide returns suffi- cient for a small investment in limestone, which if properly used will within a few years be a stepping stone to larger investments. Altho much of this land is sour and in need of three to five tons of limestone as an initial application, there are areas of peculiar formation, known as slick spots, that need little or no limestone. In fact, limestone ap- plied to some of these areas may do more harm than good. To identify these areas, soil-acidity tests will be helpful. 3. Careful attention should be given to the rotation of crops on these soils. A poorly planned rotation will do much to delay progress in improving them. Sweet clover, an especially valuable legume to hasten the improvement of these soils, should be planted in the rotation in every possible place. The common clovers do not ordinarily grow satisfactorily, tho in some years alsike clover may make a good growth. Soybeans may well be included in the rotation but should probably be followed by some crop other than wheat. Some of the lespedezas, such as the Korean, may be good legumes, but as yet they have not been thoroly investigated. Pasture and forage crops may well be given a more prominent place in the rotation. Experiences thus far with alfalfa have not been very encouraging. 4. Altho phosphorus has not yet been of great benefit on these soils, it is possible that some form of phosphate used in connection with potash may be of considerable importance. Even tho these soils are low in available phosphates, yet it may be that with a good crop rotation, including the use of sweet clover, the supplying of available potassium may be a more important factor than the application of phosphates. The effectiveness of these two fertilizer materials may be more or less intimately related to their association with each other, and if so, their application together would be more effective than ap- plication made separately. These are matters, however, needing more detailed investigation. Farmers desiring to use either of these materials should give them a limited trial before using them extensively. 5. These soils are very responsive to farm manure. A more ex- tensive use of livestock in regions where these soils are found would be desirable from the standpoint of soil improvement. 6. Crop residues and leguminous green manures should be plowed into the soil regularly. 7. In the light of present knowledge, systems of soil treatment con- sisting either of manure and limestone, or sweet clover, limestone, phosphate, and potash will provide more or less opportunity for profit- able crop production. In the latter treatment the economic value of the phosphate has not yet been clearly established. 1930] Response of Illinois Soils to Soil Treatment 499 8. Soils similar to those at Oblong and Ewing are capable of reach- ing a fairly high level of production with the right sort of soil treat- ment. 9. Soils similar to those at Newton are capable of considerable improvement, but if the level of production is to be raised high enough to provide the opportunity for profitable crop production, careful attention must be given to the details of management. 10. Soils like those at Sparta approach marginal conditions. They will give fair response but it will be difficult to raise the level of pro- duction high enough to give the opportunity for profitable crop produc- tion. Perhaps some rotation and soil-treatment plan may yet be found that will give better results on soils of this kind. Yellow Soils With Noncalcareous Subsoils (Group 8) This group of soils is found on the undulating to rolling areas in the southern part of the state. The surface drainage is good to ex- Fig. 18. — Manure Is Not Sufficient for Old, Mature Soils On the above field the land to the left was treated with farm manure and the land to the right with farm manure and limestone. A mixture of timothy and clovers was sown alike on both areas. An excellent hay crop was harvested from the manure-limestone area. Only weeds, chiefly tickle grass, appeared on the area receiving manure alone. cessive and the underdrainage is good. This group of soils is charac- terized by a grayish yellow surface soil, a grayish subsurface, and a reddish yellow slightly compact subsoil. These soils are all acid and low in organic matter and nitrogen. The more-open members of this group will grow good alfalfa following proper treatment. 500 Bulletin No. 362 [December, The fields coming within this group — Enfield, Unionville, and West Salem (Table 23) — may all be classified as mature. These three fields have not agreed so well in their response to soil treatment as the fields in most of the other soil groups. This variation may in part be due to the generally more-rolling nature of these soils and the attendant lack of uniformity that is likely to accompany such conditions. It may also be due in part to some radical differences in the crop rotations that have been practiced upon these fields. In a general way these fields have responded to the various systems of soil treatment in a manner somewhat similar to the gray soils dis- cussed in Group 7. These yellow soils appear to have been slightly more responsive to phosphate but not to such an extent as to make phosphate a highly valuable soil-improvement material under the con- dition of its use. Suggestions for management — These yellow soils, like the gray soils in Group 7, are naturally very low in productive power. The general suggestions for the manage- ment of the gray soils will apply also to the management of the yellow soils. The yellow soils are usually better drained than the gray soils and are not characterized by such extensive development of an im- pervious subsoil as are the gray soils. For this reason it is possible to make use of more legume crops on the yellow soils than on the gray soils. Frequently alfalfa can be grown very successfully on the yel- low soils when the proper precautions are taken. Brownish Yellow Soils With Open, Noncalcareous Subsoils (Group 9) The soils belonging to this group occur in the neighborhood of streams in the central and northwestern parts of the state. Their topography varies from flat to rolling, with accompanying variation in the character of the soil. The flat areas, which are not extensive, are underlain by an impervious subsoil, while the rolling areas are friable thruout the profile. These soils are light-colored, friable, low in organic matter and nitrogen, and are medium acid. They are productive when well managed but require attention to the organic matter and nitrogen supply. Only one field comes within this group, the field at Springvalley in Bureau county. The soil here may be classified as semimature. But since sedimentation and erosion have both been factors in its develop- ment, the Springvalley field is not a typical representative of the group. The field results for the Springvalley field are presented in Table 24. During the three rotations this field has been in operation farm manure and crop residues have proved the most effective systems of 1930] Response of Illinois Soils to Soil Treatment 501 a £c S o fl+s fl p c h «1 M-h «H O £ « 03 a> u _ 1 aj O 03 CO t- 2 > >> X! CO T3 >> §7! S'C c S 03 ft 8. c 3f.S >"£ 03 g a a o o 8 3 -5 -a t> P T3 tfl 53 y3 fl t o a T3 0) fl ft 03 & £ 03 £ a a> a 03 a 3 O a T3 P a «j a 03 2 H -^co 0 • iOCOt~© ooooocNcot-^©©'-*© 00Ci00C0c0cO'<* io oo r^- co rH^HfNlO Ot^OOCO'-' • • • •© . CO iO iO CO CO CO 00 iO ■* i , CN i-( IO CN CO t^ 00 ■«*< i-H i-i Ji t^«OoJrH06rHTjI|>CNCO r-KNCO-*r-(CNCOCOTt©.-'CT>aor~coa>ao >COCOt>.i-HO'Ot-00 I CN ■* ■* >-H .-H CN CN t* ' 00©CN00(N'*'<*'*CN© * "3 oo tj< t>- co b- io a> *■* «o ID — I CO CN id 00 ■ hi Ih ©SSSoOScictJpSol 502 Bulletin No. 362 [December, a ^ c « o 11 a e a »- sS-o sJ M~ S K I fc.2 'S O «3 J 01 U ► fl m ca P >> CO ,fl to OQ T3 p i a C «< o o a h £ a g 3 •a > -a d 4 4) c M O 03;j3 *2 O CO a 1 5 a o J J w 03 ^ ? z 03 o 0) Eh c3 73 g 1 H9 e 1 1 03 CO 03 w 3 t* s g 43 J a -*3 s r/j fa o 1 o O w fa fa T3 1 CO CM fa S3 H fl il S) a> £ o 00 CN > o Oh Nooiaomoo • CO iO 00 b- »0 CN © "5 ICNCO i-lCNCOOO t^CN<* COOOCOh- iC-.osaseo»o 4 OS OS © CO 00 "5 CO 00 00 J; iH CN CO --H -^ t>- CN CN l» E- (ONINffiOHHH sJ. CO CO b- O OS OS CN b- o . OS 00 ■* CO © CO b- b- i-H is "5 OS C> i-H CO t> 00* O CM* C0C0O5r}*'<*lTt<00t>.CO CO 00 OS ■* OS 00 CO t-t OS . CM O 00 ■* CO i-i >C 00 CO .2 eo o6 d co >o i-< co o i> ^ CM CO CO i-H CN CN CO CO Pnffa 1930] Response of Illinois Soils to Soil Treatment 503 02 « P go >> » "S p a s ^ a > H If 03 CO II 02 d O O a c3 W OQ O M PQ o h ■" s-< d P 03 > S 03 t3 5 a> c3 o > -' in , HHOOOlHOlO^^OO j? lOosoJdr^t^TjIiOTjioo -^ «* •«* »0 T* ^ lO "HO Tj< . "5 CO CO 03 © 00 00 c© 00 lO ^ co-*o6co'dt^05oiico CO-*Tj O I- 3 ■3-8 3 O a> a ?l o 00 CN 3° on « ¥ 2 ■tfCOcOeCtO^oOCNOCN 00C0O5C3icOt>.l>.CX)00t~ OSCO CCcMcN ^ OO • •©© • • •( ooiOb-iOTtit^aJost-'** . SOHCOCOiflHtOOO ,5 00 CN t-~ t^ O cN © © c£> © OOOOOOMONiflM ,0 O CN CO iO b- 00 ,5 s § > a ° a o fs 2 la £ S « o pi =5 c d£ a O © a; &. ^ ?3 S H h ° a ® li 1 Is ft ^ a cq a ft _: o •8 8 s ^co is 02 a 01 a 00 cS o> o £ xi £ >>« 3 i«« .S '55 (0 «8 .«oeooo>i5ic->*t-»t--t^ CD iO CO Tjf lO CO iO © -©C>3M©Tj< I "* © b- CO rj* . © CO i-l ■* OO O iO iti CO >o ,o t>- 1^ CC CO Tt< i/5 © lO CO t> . N CN| t- © iO >0 00 b- OO © ,§ i-joioo'eocoeo^leoci PL, CM 508 Bulletin No. 362 [December, Winter grains and grass crops should predominate. Alfalfa is an ex- cellent crop for these soils. Dry summers, however, are likely + o be somewhat severe on this crop. 2. Limestone should be applied as it is needed. 3. Phosphates are likely to pay well. They should be used in < m- nection with the legume crops. Corn appears to respond especially well to phosphate on this type of soil. 4. All the organic manures possible should be incorporated. 5. Potash apparently is not needed. Whether a need will develop at some future time remains to be seen. PART III. IMPORTANT GUIDING PRINCIPLES IN SOIL MANAGEMENT The crop-yield data from the Illinois soil experiment fields re- viewed and summarized on the preceding pages emphasize several broad principles. 1. The soils of Illinois vary greatly in their natural productiveness. 2. Illinois soils in general are susceptible of great improvement. 3. No single system of treatment will apply to all the soils of the state. Every farm presents its own particular problems, the solution of which will be facilitated by the knowledge derived from these long- time experiments. 4. Soils are dynamic rather than static. They are constantly changing, never being quite the same today as they were yesterday. It naturally follows that they will vary from time to time in their response to fertilizer treatments and to management, and this fact calls for more careful study of soils by the farmer. Thus the general character of the yields obtained from any particu- lar soil will be in a large measure the result of the combined influence of natural forces operating thru the soil and of man who can vary the details of soil management. Soils Constantly Changed by Natural Forces Soils are not inert substances, like the rocks from which they were formed. Transformations are continually taking place within them as a result of physical, chemical, and biological influences. Soils go thru various stages of development. The rock materials from which they are derived are subject to the soil-forming processes of nature, commonly designated as weathering. When these processes have had only partial opportunity for action on the rock material, the soil is said to be young and immature. When they have had op- portunity for full play, the soil is said to be mature. In other words, the materials from which soils are formed tend to come into equilib- 1930] £ ;, Response of Illinois Soils to Soil Treatment 509 rium \vith the prevailing weathering forces, after which they change but ljjile from the continued influence of these forces. he various stages thru which soils go from origin to maturity are evident from the changes that develop in structure. Before the soil^orming processes have acted upon the soil-forming materials, no definite structure is apparent. But with the passing of time, struc- ture becomes more and more evident thru the formation of a series of horizontal layers, each of which possesses more or less definite characteristics. The arrangement of these layers, or "horizons," from the surface down is called the "soil profile. " In a humid region the top layer, or horizon, of the soil profile tends to acquire organic matter and to lose a part of its materials thru leaching; this portion of the soil is commonly known as the leached layer. Below this layer is another which tends to accumulate the materials lost from the layer above; this second layer is known as the layer of accumulation. Below these two layers lies still another, which is less weathered and which, on the whole, resembles the original material from which the soil is being formed. As a soil becomes older and more mature, the horizons become more clearly defined. In the more mature soils the upper layers may develop distinctive variations within themselves. In very old soils the leached layer may be characterized by impoverishment, and the layer of accumulation by the development of a compact, impervious nature. These conditions in very old soils may cause them to ap- proach marginal characteristics so far as crop-producing power is con- cerned. Soils are classified according to the similarity of their profiles. Any particular soil type must conform to fairly definite profile character- istics. Because of the complexity of the factors that enter into the origin of soil-forming materials, and because of the processes that influence the formation of soils from them, it can be readily seen that the soil types are likely to be numerous and in all degrees of produc- tiveness and of ability to respond to systems of soil treatment. How Farm Practices Influence Soil Productivity The opportunity that a farmer has to give direction to the crop- producing powers of soils is clearly illustrated by a study of old field experiments. The Morrow plots, established on the University campus in 1876, are interesting in this connection. Corn has been grown con- tinuously on one plot from 1876 to the present time, a period of fifty- two years. Yield records are available since 1888. When these yields are averaged by six-year periods to smooth out seasonal fluctuations, an enlightening series of results is obtained. The yields have declined steadily from 54 bushels in the beginning to 21 bushels in 1928. In considering these results the question naturally arises as to what 510 Bulletin No. 362 [December, the trend of crop yields would have been in case some modification in management had occurred. A modification was instituted in 1904. Since that time, the south one-half has received manure, limestone, and phosphate applications. An average of the yields obtained from this half by six-year periods reveals another series of interesting re- sults. Yields tended to rise more or less rapidly from 1904 to 1912, but from 1912 to 1923 they leveled out, and since 1923 they have been gradually declining. The general average of the yields, however, has been higher on the half receiving soil treatments (Fig. 19). -^-^— No Soil Tr««tmtnt Soil Tr«tm«nk MLP — — — 55 Bu 50 « AO 35 JO U 20 13 10 1 s fv A A ZA r\ v / w \t V \ 1 \^ / v h\ J ^ X N»^ V A S" 1866 1695 1898 1905 1908 1915 1918 1923 1«6 Fig. 19. — Effect on Soil Productivity of Growing Corn Year After Year With and Without Soil Treatment Over a period of forty years corn yields have steadily declined where no soil treatment has been applied. The broken line shows how applications of manure, limestone, and phosphorus have increased yields. (Six-year movable averages from the Morrow plots, University of Illinois.) Since the use of soil treatment in this experiment has shown marked influence on the productivity of the soil, the question arises as to the influence of other modifications in management. In addition to the growing of corn continuously, two other cropping schemes with and without soil treatment have also been practiced. Corn and oats have been grown in one rotation and corn, oats, and clover in another. Un- fortunately there was not sufficient land to grow all crops in each system each year; consequently corn has been produced simultaneously on all plots only once every six years. Since the beginning of the soil-treatment applications in 1904, this has happened only four times. The average yields for these four years are recorded in Table 27. The plan of cropping and the treatment of the soil, both factors under the control of the farmer, have had a marked influence on the crop-producing power of the soil. The largest increase in yield, nearly 1930] Response of Illinois Soils to Soil Treatment 511 Table 27. — Average Acre-Yields of Corn on Morrow Plots in Years When Corn Was Harvested From All Plots (1907, 1913, 1919, 1925) Soil treatment applied Yields where corn is grown every year Yields in rotation with oats Yields in rotation with oats and clover bu. 23 42 bu. 34 55 bu. 52 68 Phosphate 200 percent, was the result of the combined influence of crop rotation and soil treatment. From the above yields the relative influence of the natural pro- ductivity of the soil, the soil treatment, and the crop rotation for the two- and three-year rotations can readily be calculated (Table 28) . In the two-year rotation of corn and oats the soil itself proved the most important factor in the crop yields obtained, the soil treatment next, and the rotation last. The soil and soil-treatment factors were somewhat alike, and each was about twice as important as the rotation factor. In the three-year rotation including red clover a different re- Table 28. — Relative Influence of Soil, Soil Treatment, and Crop Rotation on Yields of Corn in Two- and Three-Year Rotations (Morrow plots, average of years 1907, 1913, 1919, 1925) Factor Corn, oats rotation Corn, oats, clover rotation Soil perct. 42 38 20 perct. 34 23 Crop rotation 43 lationship exists. Here the rotation factor was the most important, the soil factor second, and the treatment factor last. Where corn was grown continuously, the soil was a more important factor in the yields obtained than was the soil treatment. With poorly planned crop rotations the soil was clearly the most important factor in the crop yields obtained on these plots. Where a better balanced rotation, including the use of red clover was used, the rotation itself assumed first place as a factor influencing crop pro- duction. Thus careful attention to crops and crop rotation is a prob- lem of first importance in the management of farm lands. The importance of carefully planned crop rotations in the man- agement of farm lands is further emphasized by the Morrow plots in connection with the results obtained from soil treatment. In all three 512 Bulletin No. 362 [December, systems of cropping a somewhat uniform soil treatment, consisting of manure, limestone, and phosphate, was employed. An average of the crops grown during the twelve-year period ending in 1927 shows that the soil treatment was twice as effective when corn, oats, and red clover were grown in rotation as when corn was grown continuously. These results are presented in Table 29. Table 29. — Net Acre-Values of Crop Increases Resulting From Manure, Limestone, and Phosphate When Used With Different Cropping Systems (Morrow plots, average of years 1916-1927) System Value $ 5.05 9.31 Corn, oats, clover 10.15 J Sweet clover seeded in oats and used as a green manure for corn. Thus results from the Morrow plots, as well as from the other Illinois soil experiment fields, emphasize the fact that an Illinois farmer, to make the most of his opportunities, must adjust his crop rotations and his soil treatments to fit in with the natural produc- tivity of his soils. SUMMARY The farm lands of Illinois include many types of soil varying widely in productiveness and in response to soil treatment. In order to obtain information that will aid farmers in planning systems of treatment for their own lands, the Illinois Agricultural Experiment Station has under operation experiment fields on representative types of soil in all sections of the state. These fields have been treated and studied for periods varying from fifteen to more than fifty years, periods long enough to demonstrate some rather fundamental princi- ples with respect to soil treatment practices. The results reported in this bulletin are based on experiments conducted on twenty-eight of these fields, the important lessons of which may be listed as follows: 1. The immature, dark-colored soils of Illinois are much more productive than the mature, light-colored soils. The value of the crop yields obtained from the most productive field is about ten times as large as that obtained from the least productive field. Dark- colored soils on the average are three to four times as productive as the light-colored soils. Some Illinois soils are naturally so productive that they provide excellent opportunities for profitable cropping; 1930] Response of Illinois Soils to Soil Treatment 513 others are so low in natural productiveness that they constitute a challenge to the most skilful farming. 2. Used alone, farm manure is an effective fertilizer on all kinds of soil, but the degree of response to it varies greatly. On some soils it has added more than $9 an acre annually to the value of the crops grown; on other soils it has increased crop values only $2 an acre annually. 3. The more highly productive soils can usually be made still more productive by the plowing down of crop residues without ad- ditional treatment. On one such field this system has added nearly $9 an acre annually to the value of the crops grown. The moderately productive and less productive soils do not give very marked responses to this system of soil treatment. 4. Limestone applied in addition to farm manure or crop residues has increased the value of the crops grown as much as $17.75 an acre annually on some soils. This is a return of more than $35 a ton for the limestone used. The more productive, dark-colored soils do not give so great a response as the light-colored soils, tho on many of them the returns have been very profitable. The proper use of limestone is fundamental to the management of most Illinois farm lands. The need for limestone can be readily determined by soil tests. 5. Soils deficient in available phosphorus give good response to phosphates whether applied in livestock or in crop residues systems of farming. On some soils phosphates have added more than $10 an acre annually to crop values. The low response on other fields sug- gests that farmers need to know the phosphate requirements of their fields before applying this material. Tests are now available by which this need may be readily determined. 6. The light-colored, more mature soils give strikingly greater responses to potassium fertilizers than do the dark-colored, less ma- ture soils. On most fields of light-colored soils the use of potassium has become profitable. The less productive dark-colored soils have also tended to give profitable responses to potash fertilizers. 7. The less productive light-colored soils are four to five times as responsive to effective systems of soil treatment as are the dark- colored soils, tho the degree of response varies greatly within each of these groups. 8. From the farmer's point of view the degree of response which a soil shows to soil treatment is of less importance than the total level of crop production. Some fields have given excellent crop increases as a result of soil treatment, considered on a percentage basis or in relation to fertilizer cost, but they are naturally so unproductive that it is doubtful whether even with the best of treatment they can be farmed with profit. 514 Bulletin No. 362 [December, 9. No single system of soil treatment can be applied with equal success to all the soils of the state. Every farm presents its own particular problems, the solution of which will be facilitated by the knowledge derived from these long-time experiments. 10. Because of the ever-changing nature of soils, the response to a given soil treatment or management practice changes over a period of years, thus necessitating adjustments from time to time if the best results are to be obtained. 11. Study of these experiments and others closely related to them indicates that in planning effective systems of soil treatment and man- agement for any particular soil due attention must be given to the proper balancing of the following factors: a. Adequate drainage b. Proper tillage c. Adjustment of soil reaction with limestone when necessary d. Establishment of balanced crop rotations e. Regular replenishment of active organic matter f. Purchase and application of mineral plant-food elements to supply deficiencies 12. Suggestions as to ways in which the above factors may be taken into consideration in the management of each of the ten groups of soils discussed in this bulletin are given in Part II, where results from different systems of treatment and management on twenty- eight Illinois experiment fields are analyzed and summarized. 1930] Response of Illinois Soils to Soil Treatment 514a APPENDIX Table 30. — Nitrogen and Phosphorus Contents and Acidity Reaction of Samples of Soil Taken From Untreated Plots of Illinois Experiment Fields (Based on laboratory analysis) Fields are arranged according to general soil groups. The soil types are designat- ed by the Illinois type name and also by the type name (in parentheses) of the Bureau of Soils, U. S. Department of Agriculture, in cases where correlations have been made. , T ., Phosphorus Reaction Nitro- Field Predominating soil type Depth of gen Readily Comber sample total Total available pH acidity Group 1 — Dark soils with heavy, noncalcareous subsoils Semimature soils inches perct. perct. SidelH Black Clay Loam, Poorly 0-10 .287 .042 High 5.80 Medium Drained Phase (Loes- 10-20 .194 .045 High 6.30 Slight sial clyde clay loam) 20-26 .093 .035 High 6.95 Very slight Young soils Aledo Brown Silt Loam On Clay 0-9 .255 .057 Medium 5.25 Medium (Grundy silt loam) 9-19 .170 .051 Medium 5.67 Medium 19-30 .081 .047 High 5.80 Slight LaMoillei Black Clay Loam, Poorly 0-10 .369 .065 High 5.90 Slight Drained Phase (Loes- 10-20 .210 .062 High 6.45 Medium sial clyde clay loam) 20-27 .056 .046 High 6.40 Slight Minonk Black Clay Loam, Poorly 0-9 .377 .065 High 5.75 Slight Drained Phase (Loes- 9-18 .185 .056 High 6.40 Very slight sial clyde clay loam) 18-25 .090 .046 High 6.70 None Average of young soils 334 .062 High 5.65 Slight 188 .056 High 6.20 Slight 076 .046 High 6.30 Very slight Group 2 — Dark soils with heavy, calcareous subsoils Young soils (Influenced by sedimentation) Hartsburg Black Clay Loam (Grundy 0-9 .252 .055 High 6.20 Very slight silt loam) 9-19 .147 .052 High 6.75 None 19-25 .074 .048 High 7.35 None Young soils (Influenced by erosion) Joliet 2 Brown Silt Loam On Cal- 0-9 .259 .045 Low 5.30 Strong careous Drift (Clarion 9-19 .132 .042 Medium 5.95 Medium silt loam) 19-25 .082 .037 High 7.25 None Group 3 — Dark soils with noncalcareous subsoils Semimature soils Urbana 3 Brown Silt Loam (Musca- 0-6 % -216 Low 5.00 Medium tine silt loam) 6^-20 .185 Low 5.55 Slight 20-40 .083 Low 6.20 Very slight Young soils Kewanee Brown Silt Loam (Musca- 0-9 .248 .042 Low 5.30 Strong tine silt loam) 9-18 .159 .036 Low 5.45 Medium 18-25 .077 .032 Medium 5.55 Medium Group 4 — Dark soils with open, noncalcareous subsoils Semimature soils Dixon Light Brown Silt Loam 0-9 .184 .044 Low 5.30 Strong (Tama silt loam) * 9-18 .102 .046 Low 5.30 Strong 18-24 .063 .041 Medium 5.40 Medium Mt. Morris Light Brown Silt Loam 0-8 .181 .037 Low 5.50 Strong (Tama silt loam) 8-20 .104 .043 Low 5.25 Strong 20-26 .061 .043 Medium 5.38 Strong The analyses reported in the above table were made under the direction of E. E. DeTurk, Chief in Soil Technology, in charge of the soil analysis of the Soil Survey. The soils were surveyed and classified under the direction of R. S. Smith, Chief in Soil Physics, in charge of Soil Survey mapping. J Areas of three other types are to be found on this field. 2 Areas of one other type are to be found on this field. 3 Samples were taken from arbitrary depths rather than from horizons. 4 Soil correlation is somewhat uncertain. 514b Bulletin No. 362 [December, Table 30. — Continued Predominating soil type Depth of sample Nitro- gen total Phosphorus Readily Total available Reaction Field pH Comber acidity Average of semimature soils .182 .103 .062 .040 .049 .042 Low Low Medium 5.40 5.25 5.40 Strong Strong Strong Young soils (Influenced by sedimentation) McNabb Brown Silt Loam 0-9 9-19 19-25 .185 .130 .082 .048 .034 .039 High Low High 5.80 5.90 5.70 Medium Medium Medium Group 5 — Dark soils with impervious, noncalcareous subsoils Semimature soils Carthage 2 Grayish Brown Silt Loam on Tight Clay (Grundy silt loam, grayish phase) 0-9 9-20 20-26 .163 .116 .075 .045 .044 .036 Low Low Medium 5.60 5.50 5.98 Strong Medium Medium Clayton Brown Silt Loam On Clay (Grundy silt loam) 0-9 9-18 18-24 .163 .120 .086 .045 .041 .034 Low Low Low 5.50 5.75 6.15 Medium Medium Slight Lebanon Grayish Brown Silt Loam On Tight Clay (Grundy silt loam, grayish phase) 0-8 8-21 21-26 .096 .077 .064 .028 .025 .032 Medium Medium High 5.90 6.45 6.40 Strong Medium Slight Average of semimature soils .138 .104 .073 .039 .037 .034 Low Low Medium 5.70 5.90 6.40 Medium Medium Slight Mature soils Carlinville 1 GrayishBrownSiltLoamOn Tight Clay (Grundy silt loam, grayish phase) 0-9 9-20 20-26 .140 .098 .075 .045 .029 .027 Low Low High 5.40 6.30 6.75 Strong Medium Slight Group 7 — Gray soils with impervious, noncalcareous subsoils Old soils (mode Ewing irately well drained) Gray Silt Loam On Tight Clay 0-8 8-20 20-26 .114 .074 .069 .024 .019 .021 Low Low Low 5.05 5.00 5.20 Very strong Very strong Very strong Oblong Grav Silt Loam On Tight "Clay 0-8 8-21 21-26 .134 .072 .063 .038 .026 .029 Low Low Low 5.00 4.95 5.60 Very strong Strong Strong Average of old soils (mod- erately well drained) .124 .073 .066 .031 .022 .025 Low Low Low 5.00 5.00 5.40 Very strong Very strong Strong Old soils (poorly drained, slick spots numerous) Newton Gray Silt Loam On Tight 0-8 Clay 8-22 22-27 .126 .064 .060 .031 .025 .027 Low Low Low 4.55 5.25 5.25 Strong Strong Medium Odin Gray Silt Loam On Tight Clay 0-8 8-19 19-24 .118 .079 .073 .027 .025 .030 Low Low Medium 5.20 5.30 5.80 Very strong Strong Very strong Raleigh 5 Gray Silt Loam On Tight Clay 0-8 8-23 23-27 .100 .062 .051 .036 .034 .037 Low Low Low 5.00 5.10 5.20 Strong Medium Medium Toledo Gray Silt Loam On Tight 0-9 Clay Variable .136 J. 066 \.060 .027 .023 .020 Low Low Low 4.95 5.20 6.05 Very strong Strong Strong Average old soils (poorly drained, slick spots numerous) .120 .068 .061 .030 .027 .028 Low Low Low 4.90 5.20 5.60 Very strong Strong Strong Old soils (very poorly drained, slick spots nui Sparta Light Gray Silt Loam On Tight Clay merous) 0-7 7-16 16-21 .062 .045 .043 .031 .028 .036 Medium Medium High 5.80 5.05 4.85 Very strong Very strong Very strong x Areas of three other types are to be found on this field. 2 Areas of one other type aie to be found on this field. 6 Areas of two other types are to be found on this field. 1930] Response of Illinois Soils to Soil Treatment 514c Table 30. — Concluded _ Phosphorus Reaction Field Predominating soil type Depth of gen Readily Comber sample total Total available pH acidity Group 8 — Yellow soils with noncalcareous subsoils Mature soils Enfield^ Yellow-Gray Silt Loam On 0-8 .077 .034 Low 6.10 Medium Medium-Plastic Clay 8-24 .050 .033 Low 5.20 Medium 24-26 .038 .028 Medium 5.10 Strong Unionville Yellow-Gray Silt Loam 0-7 .069 .030 Low Strong 7-19 .042 .027 Low 5.10 Strong 19-24 .040 .026 Medium 5.05 Strong West Salem* Yellow-Gray Silt Loam On 0-8 .097 .029 Low 5.30 Strong Tight Clay 8-26 .053 .032 Low 4.90 Strong 26-31 .042 .029 Low 5.05 Strong Average of mature soils 081 .031 Low 5.70 Strong 048 .031 Low 5.05 Strong 040 . 028 Medium 5 . 05 Strong open, .150 .093 .061 ms and .028 .025 .018 ly land .074 .063 .056 ^reas^of three other types are to be found on this field. 5 Areas of two other types are to be found on this field. Group 9 — Brownish yellow soils with open, noncalcareous subsoils Semi-mature soils (much sedimentation and erosion) Springvalleys Brownish Yellow Gray Silt 0-9 .150 .034 Loam (Clinton silt 9-18 .093 .026 loam) 18-25 .061 .030 Medium Medium High 5.80 5.70 6.03 Medium Medium Medium Group 14 — Sandy loams and sands Semimature soils Oquawka Dune Sand, Terrace (Plain- 0-9 .028 .037 field sand) 9-18 .025 .039 18-25 .018 .030 High High High 6.70 6.70 6.80 Slight Slight Slight Group 16— Hilly land Mature soils Elizabeth- town Yellow Silt Loam 0-7 .074 .039 7-15 .063 .041 15-20 .056 .039 Low Medium High 5.30 5.15 5.10 Medium Medium Strong