THE UNIVERSITY OF ILLINOIS LIBRARY Cb"50.7 I-PGb cop. ACIHGII1TUK WON CIRCUI CHECK FOI C1RCULATI! FERTILIZER REQUIREMENTS OF SWEET CORN By W. A. HUELSEN and M. C. GILLIS UNIVERSITY OF ILLINOIS AGRICULTURAL EXPERIMENT STATION Bulletin 417 CONTENTS PAGE PURPOSE OF EXPERIMENTS.. . 354 PLAN AND SCOPE OF EXPERIMENTS 354 The Experimental Fields 354 How Experiments Were Conducted 355 Methods of Presenting Experimental Data 364 INFLUENCE OF FERTILIZERS ON YIELD 370 EFFECTS OF NITROGEN 370 Nitrogen Alone 370 Nitrogen Increasing, Phosphorus Constant 372 Nitrogen Increasing, Potash Constant 373 Nitrogen Increasing, Phosphorus and Potash Constant 373 Analysis of Relative Nitrogen Efficiency in Different Combinations. 382 EFFECTS OF PHOSPHORUS 389 Phosphorus Alone 389 Phosphorus Increasing, Nitrogen Constant 391 Phosphorus Increasing, Potash Constant 391 Phosphorus Increasing, Nitrogen and Potash Constant 392 Analysis of Relative Phosphorus Efficiency in Different Combi- nations 397 Selection of Possible Optimum Ratios on Basis of Nitrogen and Phosphorus Efficiencies 403 EFFECTS OF POTASH 404 Potash Alone 404 Potash Increasing, Nitrogen Constant 404 Potash Increasing, Phosphorus Constant 405 Potash Increasing, Nitrogen and Phosphorus Constant 405 Analysis of Relative Potash Efficiency in Different Combinations... 407 Selection of Possible Optimum Ratios on Basis of Potash Efficiency 413 INFLUENCE OF FERTILIZERS ON MATURITY 414 NITROGEN IN RELATION TO MATURITY 416 PHOSPHORUS IN RELATION TO MATURITY 417 POTASH IN RELATION TO MATURITY 417 DISCUSSION OF INFLUENCE OF FERTILIZERS ON MATURITY 418 SELECTION OF OPTIMUM TREATMENT 419 SUMMARY 423 RECOMMENDATIONS 425 LITERATURE CITED 427 LIST OF TABLES 430 APPENDIX.. . 431 Urbana, Illinois July, 1935 Publications in the Bulletin series report the results of investigations made by or sponsored by the Experiment Station. Fertilizer Requirements of Sweet Corn By W. A. HUELSEN, Associate Chief in Olericulture, and M. C. GILLIS, formerly Associate in Olericulture* WEET CORN is the most important truck and canning crop grown in Illinois, and Illinois is the leading state in acreage and total production of this crop. Notwithstanding this prominence of sweet corn as a vegetable crop, comparatively little published in- formation is available concerning the many problems encountered every season in growing it. There is a particular dearth of reliable information in regard to the effectiveness of commercial fertilizers when used with sweet corn. Sweet corn is grown on a commercial scale in Illinois chiefly in certain parts of the central and northern sections of the state, where soil conditions are exceptionally favorable. Canners make a practice of contracting with only the most capable farmers who have good land and who rotate their crops with legumes. In spite of such care- ful choice of growers, sweet-corn yields are not as high as they should be, as is evident upon calculating the theoretical total yield that could be obtained from an acre on the basis of a single ear to the plant. The normal ear in late-maturing varieties weighs about 12 ounces unhusked. Multiplication of this weight by the normal number of plants per acre, which varies from 9,000 to 12,000, indicates that pro- duction should be from 6,750 to 9,000 pounds an acre. Even the smaller yield, however, is rather exceptional, tho yields as high as seven tons to the acre are occasionally recorded from limited acreages. Sweet-corn growers are familiar with calculations such as these and have made numerous attempts to increase their yields. The most obvious step has been to apply commercial fertilizers, but except in isolated instances their use has been abandoned because of very slight or even negative responses. Bushnell, 13 * who studied the effects of fertilizers on tomatoes, cabbage, cucumbers, and sweet corn, found that altho sweet corn responded better to potash than did cabbage, it gave the least response to nitrogen and phosphorus of any of the four crops. Lloyd 35 * found that manure increased yields of sweet corn, but that phosphorus gave favorable results only in certain com- * Acknowledgment is made to the following former members of the staff and graduate assistants for their help at various times in carrying on the work of this project: E. P. Lewis, H. F. Jenkins, R. W. Axt, L. A. Koritz, and C. P. Wilsie. *These numbers refer to literature citations, pages 427 to 429. 353 354 BULLETIN No. 417 [July, binations, that nitrogen reduced the yields, and that potash failed to give any appreciable result. It would be quite misleading to assume that this lack of favorable response by sweet corn to certain commercial fertilizers is due to a low requirement of plant food. As a matter of fact, according to Whiting, 55 * sweet corn requires comparatively large amounts of plant food. Evidently the sweet-corn plant is rather critical in its require- ments, and the selection of appropriate fertilizer ratios is not a simple matter, but one requiring intricate experiments carefully planned and accurately controlled. PURPOSE OF EXPERIMENTS The specific purpose of this work was to study the effects on yield and maturity of sweet corn of a large number of fertilizer combina- tions applied to a dark silt loam prairie soil typical of the soils on which sweet corn is grown in Illinois, the sweet corn being included in a four-year rotation commonly used thruout the state. Other prob- lems, such as methods of application, were postponed for later con- sideration.* In all, the experiments covered ten growing seasons (1923-1932), but only the fertilizer-ratio studies covering the period from 1923 to 1928 are reported here. Subsequent studies covering certain supplementary problems are being prepared for later publication. PLAN AND SCOPE OF EXPERIMENTS In order to carry out the purpose of these studies namely, to de- termine the most effective fertilizer combinations for the commercial production of sweet corn under Illinois conditions the type of soil on which the tests were made and the rotation and field methods used were as representative as possible of the commercial growing of sweet corn. Four fields near Urbana were selected that were large enough to supply one plot and a check plot for each fertilizer combination used in the experiments. The identity of plots and treatments was main- tained thruout the six years covered by the fertilizer-ratio studies. The Experimental Fields Soil Type. The experiment was laid out at Urbana on an upland prairie soil that includes several soil series common to the region. *A few statements and recommendations in regard to methods of applica- tion are made in the present bulletin. They are based on subsequent experi- mental work not reported here. 79J5] FERTILIZER REQUIREMENTS OF SWEET CORN 355 Three of the fields (Nos. 800, 900, and 1000) appeared to be practi- cally similar, but the fourth (Field 1300) was located partly on the Champaign moraine system and consisted mostly of a gravelly loam in a low state of fertility. Topography and Drainage. Fields 800, 900, and 1000 were slightly rolling and subject to sheet erosion. Field 1300 was quite rolling. In each field the plots were laid out in such a manner that the surface water flowed across them rather than lengthwise of them. Wide alleys gave an opportunity for diverting surface drainage in such a way as to reduce the damage to a minimum. Subsoil drainage in Fields 800 and 1000 was satisfactory, but in the others (Fields 900 and 1300) water collected in two small areas for twenty-four hours or more after heavy rains. The plots thus affected were abandoned for experimental purposes. Soil Acidity. Suitable tests in each field indicated a lime require- ment of two to three tons an acre. This deficiency was remedied by broadcasting the required amounts of limestone on each field. Previous History of Plots. Field 800 had been used for grain farming for an indefinite period. It was planted to wheat in 1918, 1919, and 1920, and in 1921 it was planted to field corn and manured in the fall. Field 900, located 80 rods north of Field 800, had also been used for grain farming. In 1918 it was planted to field corn, in 1919 to oats, in 1920 and 1921 to field corn. A small part of the north end had been planted to oats in 1921. At least two coats of manure had been applied between 1918 and 1921. Field 1000, located on a near-by farm, had been planted to a timothy-bluegrass pasture in 1919, 1920, 1921, and 1922. Field 1300 was located 40 rods east of Field 1000. It had been planted for an indefinite period to corn and oats. None of the fields had ever received an application of limestone or commercial fertilizer. How Experiments Were Conducted Rotation. A four-year rotation consisting of wheat or oats, red clover, and two sweet-corn crops was used in connection with these experiments. In years when small grain was grown in a given field, the grain was planted over the entire field, including alleys, as uni- formly as possible. Medium red clover was seeded at the proper time at the rate of 12 pounds an acre. The grain crop was cut in the usual manner and all straw, except the stubble, removed. In the following 356 BULLETIN No. 417 spring the first crop of clover was cut as hay and removed ; the second crop was plowed under in September or October. In subsequent tables, data are given separately for Field 800 in 1923 and Field 1300 in 1924 and 1925 under the heading "No clover in rotation." These fields were plotted, fertilized, and planted to sweet corn at the beginning of the experiment before any clover had been used. They therefore come under the separate heading mentioned above. Strictly speaking, Field 1000, which is placed under "First year after clover" in 1923 and "Second year after clover" in 1924, also should have been under "No clover in rotation," but as this field had been in livestock pasture for four years, it was thought best to consider the sod as equivalent to clover. Field Methods. The ground was fall-plowed by tractors in ac- cordance with the usual practice in Illinois. Spring preparation for the corn crop consisted of double-disking twice, after which the plots were laid out and the fertilizer broadcast by hand on the plots but not in the alleys between them. The fertilizer was always harrowed in at once with a spike-tooth harrow. The plots were then marked out very carefully and invariably planted within twenty-four hours. The corn was planted in check rows 42 by 42 inches apart, by means of a hand planter known to farmers as a "jabber," from which the mechanism had been removed. Four to six kernels were dropped by hand into the planter. The stand was thinned two to three weeks later to three plants per hill. Excess seed insured a practically perfect stand, barring such accidental losses as those from gophers or cutworms. The variety used thruout was Country Gentleman bred by the Illinois Agricultural Experiment Station. The crop was cultivated according to the usual Illinois methods. In experimenting with sweet corn, it is difficult to determine when to harvest each plot, especially since some treatments advance and others retard maturity. Appleman and Eaton, 4 * Culpepper and Ma- goon, 16 * and Meyers 39 * have shown, however, that maturity can be determined with reasonable accuracy by means of silk counts, a work- able method which has been used thruout these experiments. The method consists of examining each plot every day or two beginning soon after tasseling, and of counting daily the silks on all plants in the two center rows of each plot from the time silking is under way until the date when 75 percent of the theoretical possible number of silks appear.* The validity of this method will not be discussed here, as it is discussed in a publication now in preparation by the senior author. 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 357 That silk counts do not indicate absolutely the date when the crop is ready for harvest should be understood. They give only a close ap- proximation to the exact date, for under normal weather conditions at Urbana about 21 days are required for the crop to pass from the silking to the canning stage in the period between August 8 and Sep- tember 8. The final dates of harvest were checked further by means of Appleman's 2 - 3 * nail test. This test, familiar to all sweet-corn growers, consists of piercing one or more kernels with the thumb nail. The character of the exudate, according to Appleman, is a fairly reliable indication of its composition and therefore of the stage of maturity. Methods used in harvesting were as accurate as circumstances per- mitted. The ears from the border rows around the four sides of each plot were removed first. The plot proper was then snapped, the standing order to the workmen being to "snap everything showing a silk." A large number of useless culls were thus included, but on the other hand, no ears fit for canning were overlooked. The ears were then sorted, counted, and weighed by an experienced crew. The cull ears were returned to their respective plots and scattered. As soon as the corn was harvested, the stalks in the two center rows of each plot were cut and weighed for the "green fodder weights" mentioned later. These stalks were always returned to their respective plots and scattered. It should be noted that nothing more than good canning ears were removed from each plot. Plot Arrangement. The plots in the four fields were identical in size 31.5 by 80.5 feet, or .058213 acre (Figs. 1, 2, 3, and 4). This was the area over which the fertilizer was distributed. The outer boundaries of the plots coincided with the outside, or border, rows. During harvest, the corn from the border rows was removed first and not included in the calculated yields, as stated above, leaving a net plot 28 by 77 feet, or .04949+ acre, upon which basis the yields were calculated. As a planting distance of 42 by 42 inches was used thruout, the plots contained 10 rows each, 24 hills long; after the border rows were removed, 8 rows, 22 hills long, remained. The ratio between the total width and total length was 1:2.56 and the ratio between the net width and net length was 1:2.75. The distance between the outer boundaries of adjacent plots in each field was 8 feet. The distance between the outer boundaries of abutting plots was 8 feet in Field 1300 and 7 feet in the other fields. The plots were laid out each year by means of a transit, a bench mark having been established at the beginning of the project. The possible error by these methods was less than 1 inch. 358 BULLETIN No. 417 Uuly, In order that every plot receiving fertilizer treatment would be adjacent to a check plot, every third plot in each field was designed as a check. Conditions on adjacent plots were made as nearly identical as possible, with the single exception that no check plot was given fertilizer treatment. 4-44 C 442 441 C 440 424 C 422 421 C 420 414 C 412 C 411 410 C 404 402 C 401 400 C 244 242 C 241 C 240 224 C C 222 221 C 220 214 C 212 211 C 3 > 210 3 C 204 202 201 200 C 144 142 C 141 140 C 124 C 122 121 C 120 114 C 112 , C 110 104 C 102 C 101 100 C 044 042 C 041 040 C 024 022 C 021 C 020 014 C 012 Oil C 010 OO4 C 002 001 C FIG. 1. PLOT ARRANGEMENT IN FIELD 800 The fertilizer treatments applied to the plots are indicated by code num- bers (see pages 364-5). Check plots are designated by "C." The arrangement of treated plots and check plots charted here, and the treatment indicated for each plot, were retained without change thru the six years covered by these fertilizer experiments. (This explanation of the fertilizer layout for Fig. 1 applies also to Figs. 2, 3, and 4.) Fertilizers Used. The fertilizers used in varying dosages and varying combinations were the following: (1) Nitrate of soda, used for nitrogen thruout the experiment, was applied separately as a side dressing around the hills three to six weeks after planting, and then covered with a corn cultivator. (2) Superphosphate containing 16 percent available phosphoric acid was mixed, when so required, with 79J5] FERTILIZER REQUIREMENTS OF SWEET CORN 359 o O o O U O u u 5 (M (M * 2 -..Q-.CC7 fe S5 360 BULLETIN No. 417 IJuty, muriate of potash but never with nitrate. (3) Muriate of potash con- taining about 50 percent potassium oxid was used singly or in mixture with acid phosphate, as called for by the experiment. Each year the fertilizers were analyzed and the treatments made up to the required amounts on the basis of the special analyses. The fertilizer was broadcast by hand as uniformly and carefully as possible very early in the morning in order to eliminate the effect c 001 002 C 004 010 C 011 012 C 014 020 C 021 C c 022 024 C 040 041 C 042 044 C 100 101 C 102 C c 104 110 C 111 112 C 114 120 C 121 122 C 124 C c 140 141 c 142 144 C 200 201 C 202 204 C 210 C c 211 212 c 214 220 C 221 222 C 224 240 C 241 C c 242 244 c 400 401 C 402 404 C 410 411 C 412 C c 414 420 c 421 422 C 424 440 c 441 442 c 444 C FIG. 3. PLOT ARRANGEMENT IN FIELD 1000 of the wind. Applications were made to each sweet-corn crop, but no fertilizer was applied to either the small grain or clover. The amounts applied per four-year rotation may be readily determined, therefore, by doubling the designated treatments. In an extensive experiment of this kind there was opportunity for almost endless variations in layout and treatments. The plan finally adopted closely resembled that suggested by Spillman, 44 * with the exception that the initial treatments were doubled a second time. Each of the three critical plant- food elements was applied in single, in 1935} FERTILIZER REQUIREMENTS OF SWEET CORN 361 362 BULLETIN No. 417 double, and in quadruple dosages. A second element was then added to the first in single, double, and quadruple quantities. Finally the third element was added in the same proportions. A single fertilizer series consisted, therefore, of three dosages of the three elements applied in all the possible mathematical combinations. These totaled 63 sepa- rate treatments plus one with no fertilizer. Dosages were applied at the following rates per acre: Nitrogen (15 percent nitrate of soda) Single 50 pounds (7.5 pounds nitrogen) Double 100 pounds (15 pounds nitrogen) Quadruple 200 pounds (30 pounds nitrogen) Phosphorus (16 percent superphosphate) Single 200 pounds (32 pounds phosphorus pentaoxid) Double 400 pounds (64 pounds phosphorus pentaoxid) Quadruple 800 pounds (128 pounds phosphorus pentaoxid) Potassium (50 percent muriate of potash) Single 50 pounds (25 pounds potassium oxid) Double 100 pounds (50 pounds potassium oxid) Quadruple 200 pounds (100 pounds potassium oxid) The quadruple dosage of each ingredient was assumed to be in excess of actual requirements. The single dosage was believed to represent a minimum and the double dosage an optimum. The re- sults discussed later show that these assumptions were not correct in many cases, and that the real maximum was somewhere beyond the actual treatment. One advantage of the series of treatments recommended by Spillman 44 * is the large number of direct comparisons possible. In determining the effect of any one of the three single elements, 48 possible comparisons are involved. Sixteen comparisons may be made where any two elements vary, and four comparisons where all three vary. A summary showing, in terms of actual plant- food elements per acre, the individual fertilizer ingredients applied to each plot is given in Table 1. For the benefit of readers to whom this designation is unfamiliar, the applications are also expressed in terms of the nearest commercial fertilizer combinations. The slight discrepancy caused thereby is indicated. Many of the commercial combinations are not readily obtainable on the market, but it is usually possible to purchase similar ones. For example, if one wishes to apply an 0-16-6 fertilizer at the rate of 400 pounds an acre and cannot purchase this analysis, an 0-10-4, which is on the recommended list of standard fertilizer combinations according to Merz and Ross, 88 * may be substituted at the rate of 650 pounds an acre. Many other possible substitutions 19351 FERTILIZER REQUIREMENTS OF SWEET CORN 363 TABLE 1. FERTILIZER TREATMENTS PER ACRE: PLANT FOOD ACTUALLY APPLIED AND THE NEAREST EQUIVALENT APPLICATION IN TERMS OF STANDARD FORMULAE Code designation for treatment Treatment in terms of actual plant food Treatment in terms of nearest commercial fertilizer formula Deviation* of fertilizer formula from amount actually applied Nitrogen PiO. KjO Amount Formula Nitrogen KiO 001 Ibs. Ibs. Ibs. 25 50 100 'is 50 100 '25 50 100 'is 50 100 '25 50 100 'is so 100 'is so 100 'is 50 100 'is so 100 'is 50 100 'is so 100 'is so 100 'is so 100 'is so 100 '25 50 100 'is 50 100 Ibs. SO 100 200 200 200 200 400 400 400 400 400 800 800 800 800 50 200 200 400 200 200 200 400 400 400 400 400 800 800 800 800 100 200 200 400 200 200 200 400 400 400 400 400 800 800 800 800 200 375 375 375 200 200 200 400 400 400 400 400 800 800 800 800 N-P-K 0-0-50 0-0-50 0-0-50 0-16-0 0-16-12 0-16-24 0-8-24 0-16-0 0-16-6 0-16-12 0-16-24 0-16-0 0-16-3 0-16-6 0-16-12 15-0-0 4-0-12 4-0-24 2-0-24 4-16-0 4-16-12 4-16-24 2-8-24 2-16-0 2-16-6 2-16-12 2-16-24 1-16-0 1-16-3 1-16-6 1-16-12 15-0-0 8-0-12 8-0-24 4-0-24 8-16-0 8-16-12 8-16-24 4-8-24 4-16-0 4-16-6 4-16-12 4-16-24 2-16-0 2-16-3 2-16-6 2-16-12 15-0-0 8-0-7 8-0-14 8-0-28 15-16-0 15-16-12 15-16-24 8-8-24 8-16-0 8-16-6 8-16-12 8-16-24 4-16-0 4-16-3 4-16-6 4-16-12 Ibs. ".5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i " 2 2 2 2 2 2 2 2 Ibs. -i -2 -4 -i -2 -4 -i -2 -4 -i -2 -4 -i -2 -4 -i 2 -4 -i -2 -4 -i -2 -4 -i -2 -4 -i -2 -4 -i -2 -4 ' 1.25 2.50 5.00 -i -2 -4 -i -2 -4 -i -2 -4 002 004 010 32 32 32 32 64 64 64 64 128 128 128 128 '32 32 32 32 64 64 64 64 128 128 128 128 '32 32 32 32 64 64 64 64 128 128 128 128 '32 32 32 32 64 64 64 64 128 128 128 128 Oil 012 014 020 021 022 024 040 041 042 044 100. . 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 30 101 102 104 no Ill 112 114 120 121 122 124 140 141 142 144 200 201 202 204 210 211 212 214 220 221 222 224 240 241 242 244 400. . 401 402 404 410 411 412. . 414 420 421 422 424 440 441 442 444. . No deviation from the formulae occurred in the amounts of PiOi actually applied. 364 BULLETIN No. 417 [July, could be cited. As it is not possible to determine, by means of em- pirical experiments such as these, the exact quantity of each element required by the plant, reliable statements cannot be made as to whether or not a slight variation in the quantities applied would affect yields in any way. It is reasonably safe to assume, however, that a minor change in proportion or quantity would have but slight effect on the results, especially since plant requirements vary from season to season and from field to field. Methods of Presenting Experimental Data Methods of Calculation. The only corrections made for soil varia- tions were obtained by comparing the yield of each treated plot with that of the adjacent check. Treatments have been paired in each case with adjacent checks, and odds showing the significance of mean differences in yield have been obtained by the use of Student's method. 48 ' 49 * The odds are probably more important than the actual mean differences in determin- ing the significance of mean increases in yield. When the odds are above 30:1 it may be assumed that certainty is being approached and that there is a real difference in the yields due to fertilizer. When the odds are less than 30:1, the differences in yield probably indicate directional tendencies only. The preliminary experimental results obtained in 1922 have been omitted from all calculations. Definitions. The term "marketable ears" frequently referred to in the tables means ears which, under conditions in Illinois, are ac- cepted as suitable for canning. All smutted and rotten ears and those of abnormal shape were excluded regardless of size. Otherwise the grading was based entirely on size and on how well the ears were filled. Badly filled ears were classed as culls, and their weights are not included here. Reading Tables. In the subsequent discussion and in the tabulated data constant reference must be made to specific treatments. To de- scribe these in detail each time it is necessary to mention one of them would be extremely cumbersome and tiresome to read. Accordingly the authors have employed for this purpose the very simple code which they used in taking notes. Of the three dosages of each of the three principal plant nutrients applied, the first is single and is designated by the figure "1 ;" the second dosage is double the first and is designated by "2 ;" while the third dosage is quadruple the first and is designated by "4." 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 365 The generally accepted order of stating commercial fertilizer combinations is nitrogen-phosphorus-potassium (N-P-K). This order has been retained in the code (Table 1). Accordingly, Treatment 400 means that 30 pounds of nitrogen per acre was applied, Treatment 040 means 128 pounds of phosphoric acid per acre; and Treatment 004 means 100 pounds of potash (K 2 O) per acre. Treatment 444 means that all three elements were combined and the combination applied in quadruple quantities. Chemical symbols also have been used in the tables for the sake of brevity. "N" stands for the element nitrogen contained in sodium nitrate. The formula P 2 O 5 (phosphorus pentaoxid) is the usual method of expressing the percentage of available phosphorus in phosphatic fertilizers. Potash is designated as K 2 O (potassium oxid), representing the available potassium in potassium chlorid, or muriate of potash as it is called. Tables 2 to 9 inclusive, 11 to 13, 20 to 23, and 36 are so arranged that they may be read vertically or horizontally. Thus Table 2 read horizontally shows the results that were obtained by increasing nitro- gen and keeping phosphorus constant, as noted in the left-hand column. Read vertically, Table 2 gives the results due to increasing phosphorus and keeping nitrogen constant in the quantity noted at the head of each column. The tables involving combinations of the three critical nutrient elements will be confusing unless their construction is carefully noted and remembered. Table 5 is a good example. The treatment indi- cated at the top of each column of increases and odds is not complete ; it describes the dosages of only two of the three elements. The dosage of the third or varying element in each column is indicated by x, and the value of x is obtained by referring to the treatments indicated in the extreme left-hand column. Similarly, the treatment indicated in each row of the left-hand column is incomplete, and the value of x is obtained by referring to the treatments indicated at the top of the columns of increases and odds. Thus, the first line of Table 5 read horizontally gives the increases from Treatments 002, 102, 202, and 402. Such groups of four treatments in which the dosages of two elements are constant and the third ranges from "0" to "4" are designated as "sets." This particular set of treatments is ordinarily described in the subsequent text as Set xQ2. The second line read horizontally gives the results from Treatments 012, 112, 212, 412 (Set x\2}. The first vertical column of results gives the results from Treatments 002, 012, 022, 042 (Set 0*2), and the second vertical 366 BULLETIN No. 417 {.July, column of results gives the results from Treatments 102, 112, 122, 142 (Set 1x2). In the subsequent text consideration is limited to the differences between the treated plots and the adjacent checks. For total yields reference must be made to Table 39, Appendix. Each difference be- tween treated plot and check is itself a mean or average difference involving results obtained from several plots over several years. The odds are calculated, as stated previously, according to Student's method. Methods of Analysing the Results. The large number of treat- ments included in this experiment should make it possible to determine rather definitely the fertilizer requirements of sweet corn on the Illi- nois soils under test; but the very comprehensiveness of the experi- ment serves to bring out the complexity of a problem which super- ficially seems relatively simple. To illustrate: If only a half dozen or so treatments were involved in the experi- ment, there would be no trouble ordinarily in determining quite con- clusively the optimum one, provided the experiments were repeated often enough. However, with 63 fertilizer treatments, the number here involved, choosing the optimum ratios is quite another matter. A glance at the detail data on yields given in Table 39, Appendix, shows why this is so. Treatment 144, for example, which is credited with an increase of 55.58 percent over the check plot in the weight of marketable ears, outyielded all the other treatments by a consider- able margin. Is this treatment, then, the best of the sixty-three? If not, which treatment is the best? As a partial answer to the above questions, the probable errors of the differences between the percentage increases of the treatments giv- ing the largest and the second-largest increases over their respective check plots have been calculated, with the following results: Percentage increase Treatment 144 55.58 7.7 Treatment 122.. 44.47+ 8.1 Difference 11.11 11.2 A difference of 11.11 that has a probable error of 11.2 is not significant, and we must therefore conclude that Treatment 144 was not signifi- cantly better than Treatment 122. In all, 19 of the treatments listed in Table 39, Appendix, showed increases, in ton yields of marketable ears, of more than 30 percent over the respective check plots. The treatments may be ranked as follows on the basis of percentage in- creases: 1935} FERTILIZER REQUIREMENTS OF SWEET CORN 367 Rank 1 Treat- ment .. 144 Percentage increase over check 55.58 7.7 2 .. 122 44.47 + 8.1 3 . . 044 43.50 6.5 4 . . 142 40.11+5.8 5 . . 420 38.98 + 4.4 6 . . 114 38.54 + 5.1 7 . . 041 37.41 4.8 8 . . 042 37.28 + 4.5 9 . . 424 35.53 + 2.5 10.. 112 34.73 + 5.3 Rank 11 Treat- ment . . 121 Percentage increase over check 34.47 4.7 12 . . 141 32.76 6.3 13 .. 422 32.04 + 3.2 14 . . 212 31.95 6.3 15 .. 221 31.92 5.2 16 .. 220 31.50 + 4.8 17 . . 124 31.11 + 5.3 18 1140 30.12 6.1 ' ' \414 30 . 1 2 7.0 All the above increases are significant, that is, all are more than 3.2 times their probable errors, but the differences between the in- creases are not significant. Comparison of the increases produced by the treatments giving the highest and lowest percentage increases in this group of 19 shows the following: Percentage increase Treatment 144 55.58 7.7 Treatment 414.. 30.12 7.0 Difference 25.46 10.4 The difference between these increases, 25.46 10.4, is only 2.4 times its probable error and therefore is not significant. Any one of the 19 treatments may therefore be the optimum. It is clear that a highly critical analysis of the data is necessary in order to determine the optimum fertilizer ratio or ratios. It would be very difficult, if not impossible, to make such a determination by the usual methods employed by investigators. The device which may be used is the mathematical relationship existing between the treatments. If only four treatments were under consideration, the following interpretation could be made from the increases in yields of marketable ears expressed as percentages (Table 39, Appendix). Percentage increase Treatment 001 -8.98 2.7 Treatment Oil 13.91 4.0 Treatment 021 18.75 4.3 Treatment 041 37.41 4.8 Percentage increase due to phos- phorus (subtract increase with Tr. 001 from that of each succeeding treatment) 22.89 4.8 27.73 5.1 46.39 5.5 Among these four treatments, the increases due to phosphorus became successively larger with the larger dosages. In order that the per- centage increases due to phosphorus may be distinguished from the total percentage increases, the phosphorus percentages will be called phosphorus "efficiency factors." Thus the efficiency of phosphorus in 368 BULLETIN No. 417 [July, Treatment 041 is 46.39 5.5 percent. The potash efficiency in this group of treatments may be determined as follows: Treatment (P-K) Oil Percentage increase 13.91 40 Treatment (P) 010 Percentage increase 22 63 4- 4 8 Difference (potash effi- ciency) -8 72 + 6 2 021 18 75 + 4.3 020 10 02 + 2 7 8 73 + 5 1 041.. 37.41 + 4.8 040.. 19.45 + 4.0 17.96 + 6.2 Thus the potash efficiency in Treatments Oil, 021, and 041 (right- hand column above) was not statistically significant tho there was a very sharp upward trend in the efficiency of this element as successively larger amounts of phosphorus were added. The "efficiency factor" method of analyzing the data will be used to supplement the conven- tional analysis in the subsequent discussion. It will be used only with data involving weights of marketable ears, altho the data on numbers of ears and weights of green fodder could be interpreted in the same way. The efficiency factor for each element in each treatment is shown in Table 40, Appendix. The probable error for each efficiency factor has been calculated according to the formula P.E. = a 2 + b* + 2r ab ab where a and b represent the probable errors of the percentage increases in yield resulting from the two treatments being subtracted, and r represents the correlation between a and b. Since it is assumed that r = 0, the formula becomes P.E. = a 2 + b 2 The probable errors of the increased yields expressed as percent- ages were obtained according to the formula .6745S.D. P.E. = \/n in which S.D. means the standard deviation and n the number of observations. It is apparent, of course, that a very large number of comparisons are possible. Each yield increase is itself the mean difference between 12 annual crop yields and 12 adjacent check yields. This result is in turn subtracted from another similarly obtained ; the difference is the efficiency factor. Thus each efficiency factor is the result of calcula- tions involving 48 separate plot yields. These factors are present in 12 different groups, each group consisting of 16 treatments. In order to simplify the tables, only the mean factors, obtained by averaging 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 369 the results from each set of four treatments in which two elements were quiescent, are used. In specifying the set, the changing element is represented as x. An explanation of the way in which the top line of Table 14 is derived will serve as an example: Treat- ment 100 N efficiency factor . 5.51 + 5.0 Treat- ment 200 N efficiency factor . -2.91 4- 2.2 Treat- ment 400 N efficiency factor . -4.85 + 8.1 101 . -3.43 + 7.0 201 . 1.81 + 3.2 401 . 26.36 + 4.3 102 .26 + 4.9 202 . -4.54 + 5.0 402 . -4.64 + 4.6 104 . -8.28 + 5.0 204 . 1.74 + 6.7 404 . -5.82 + 4.9 (Set) I0x.. (Mean) .-1.48 + 2.8 (Set) 20*.. (Mean) . -.98 + 2.3 (Set) 40.v.. (Mean) 2.76 4- 2.8 In each set the nitrogen dosage is quiescent, the phosphorus dosage absent (tho in a different set of treatments it also might be quiescent), whereas the potash dosages are changing. As between three such sets of treatments, however, we have a reverse arrangement: nitrogen becomes the changing element while potash and phosphorus are the common, or quiescent, elements. Thus x indicates the changing ele- ment within a set of treatments, tho it becomes the symbol for one of the two quiescent elements among a group of sets. The factors for the individual treatments are taken from Table 40, Appendix, and the probable errors for the mean treatments are calculated according to the following formula: P.E. = -V n in which a, b, c, and d represent the probable errors of individual factors and n the number involved, which is 4 in each case. Since comparison of the means alone may lead to errors, the modes are likewise compared. For instance, if the increases from Set \Qx listed above are assumed to be a curve, Treatment 100 would be the mode, because it has the largest efficiency factor. The respective modes* may be compared in the same manner as the means, as shown in Table 15, among others. The maximum mean increases in yields in Table 16, however, are also modes which have been obtained from Table 40, Appendix, in a similar manner, the difference being that they are actual maximum increases in the mean yields instead of maximum efficiency factors. Thus there are three separate methods of interpreting the data, and these will be used thruout the discussions of experimental results. The validity of the efficiency- factor method had been discussed at length in a separate paper by the senior author, Huelsen. 31 * The "As used here and in subsequent portions of the text, "mode" means the point at which the maximum increase occurred. 370 BULLETIN No. 417 {.July, method of evaluating efficiency factors by comparing the modes of individual curves is, however, presented here for the first time. An attempt was also made to interpret the reciprocal relations be- tween the nutrient elements in physico-chemical terms. Because of inability to secure appropriate supporting evidence from analytical work, however, the physico-chemical interpretation was made entirely by inference, and the results, altho they support the interpretation by efficiency factors, are not included in this report of the experiments. INFLUENCE OF FERTILIZERS ON YIELD In the following pages the effects which the three major nutrient elements had on sweet-corn yields, when used alone and in the vari- ous combinations, are traced. All figures representing increases in yields indicate increases over the check plots. EFFECTS OF NITROGEN The effects of nitrate of soda, when applied alone and in combina- tion with one or both of the other elements, have been summarized in the accompanying tables. All comparisons are obtained by reading horizontally across the tables. Nitrogen, used either alone or in combination with phosphorus or potash, or both, as a fertilizer for sweet corn, appears to have certain limitations, and the optimum combinations of potash and phosphorus to be used with side-dressed nitrogen are not readily discernible. Nitrogen Alone Sodium nitrate applied in the rotation as a side dressing without an accompanying basal treatment of minerals produced variable effects on yield ranging from decided decreases to definite increases (Table 2). With no clover in the rotation, an initial treatment of 50 pounds of nitrate per acre resulted in a small increase in yield, but heavier appli- cations gave lower yields than the adjacent checks. In both the first and second years after clover, nitrate had no material effect on yields. The means of the plots receiving nitrate only, including all such plots in all three positions in the rotation, show increases in the weights of ears amounting to 5.51 percent for Treatment 100, 2.91 percent for Treatment 200, and 4.85 percent for Treatment 400 (Section A, Tables 11 and 12). The odds thruout are too small to in- dicate anything more than a tendency. According to the results herein obtained, growers would not be justified in side-dressing nitrate of soda when it is the only treatment. 79J5] FERTILIZER REQUIREMENTS OF SWEET CORN 371 TABLE 2. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SODIUM NITRATE AND SUPERPHOSPHATE (Figures indicate mean increases per acre over adjacent check plots) Phosphorus series* Nitrogen series* 0x0 1x0 2x0 4x0 0x0 1x0 2x0 4x0 Number of ears Tons marketable ears No clover in rotation xOO 613 23:1 849 21:1 1805 46:1 1327 4:1 - 192 1:1 -1152 12:1 1380 29:1 546 4:1 -666 4:1 1616 39:1 2842 35:1 148 1:1 .296 56:1 .370 10:1 .345 5:1 .136 15:1 .195 11:1 .391 16:1 .361 3:1 -.092 2:1 -.359 13:1 .467 27:1 .235 29:1 -.278 4:1 .578 58:1 .914 66:1 .027 1:1 Odds xlO . . 1017 70:1 1765 12:1 1239 5:1 Odds x20. . . Odds x40 .. Odds First year after clover xOO... -186 2:1 731 61:1 1334 22:1 1879 10:1 28 <1:1 457 2:1 1540 19:1 1541 29:1 49 1:1 1236 8:1 1459 11:1 849 5:1 .448 12:1 .118 3:1 .377 9:1 -.060 2:1 .246 30:1 .490 17:1 .636 11:1 -.032 1:1 .283 4:1 .564 17:1 .695 25:1 .028 4:1 .314 5:1 .595 22:1 .310 5:1 Odds xlO 1491 3:1 444 2:1 1099 13:1 Odds x20 . . Odds x40. . . Odds Second year after clover xOO . 566 3:1 748 5:1 1808 72:1 1930 27:1 -414 3:1 662 4:1 1596 13:1 2399 38:1 -822 5:1 -187 2:1 1914 26:1 1960 3332:1 .422 9:1 .248 19:1 .360 26:1 .234 3:1 .270 5:1 .673 253:1 .716 77:1 -.056 2:1 .189 3:1 .552 24:1 .912 55:1 -.162 3:1 .036 8:1 .778 72:1 .672 2499:1 Odds xlO... 1561 7:1 369 4:1 1086 13:1 Odds . . . x20 Odds x40... Odds This table and similar subsequent tables may be read either vertically or horizontally. Read either way, treatment code numbers are obtained by replacing the symbol for the changing dosage (x) by the corresponding figure in the code designation at the top of the columns or in the column at the left. Similar results from the use of nitrogen alone on various crops have been obtained by other investigators. Gardner, Noll, and Baker, 22 * for instance, in a 35-year rotation of corn, oats, wheat, and mixed hay found that nitrogen alone gave insignificant increases in the total yields of the four crops. On the other hand, Comin and Bushnell, 15 * in their experiments with sweet corn, found that nitrogen 372 BULLETIN No. 417 [July, gave larger increases when used alone than when used in combination with superphosphate. The results of the present experiments are probably more in accord with normal expectation on Illinois soils than are those of Comin and Bushnell. Nitrogen Increasing, Phosphorus Constant In fertilizers containing combinations of nitrogen and phosphorus, increases in yield due to nitrogen were much more consistent and were significantly greater than when nitrogen was used alone (Table 2). With no clover in the rotation the largest and most consistent increases in yields from these combinations occurred in Set *20. Treatment 410 also gave a large increase in yield with significant odds, but in Set xAQ the yield increases due to nitrate were smaller for the heavier dosages. During the first and also the second year after clover the yields increased in relation to the amount of nitrate applied in Set :r20 and in Set ^40 as far as Treatment 240. In Set .rlO phos- phorus alone (Treatment 010) gave larger increases in yield than any of the treatments containing nitrogen, but the odds are too small to be significant. The means of the plots receiving treatments of nitrogen and phos- phorus in combination, including all such plots in all positions in the rotation, show that the most consistent increases with significant odds occurred in Set ;r20 with the maximum increase at Treatment 420 (Section E, Tables 11 and 12). Thus, altho sweet corn does not draw as heavily as field corn upon the available supply of phosphorus in the soil (Whiting 55 *), it is evident an application of at least 64 pounds of P 2 O 5 per acre is necessary before nitrate becomes effective. W. H. Michaels, formerly of the Department of Horticulture, University of Illinois, in unpub- lished greenhouse pot-culture experiments with a P. inbred line of sweet corn found that successive dosages at the calculated acre- rate of 50, 150, and 250 pounds of 2-0-0 fertilizer made from sodium nitrate, gave, as compared with the check, increases in the green weights of 21-day-old seedlings of 22.2 percent, 15.6 percent, and 15.7 percent respectively. Gardner, Noll, and Baker 22 * found in experiments con- ducted in Pennsylvania, later confirmed by Gardner, Noll, and Lewis, 23 * that a plot receiving nitrogen and phosphorus yielded 34.1 percent more than the untreated checks, but one receiving nitrogen and potash yielded only 5.7 percent over the check. In these Pennsylvania experi- ments phosphorus was the limiting factor. 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 373 f Results obtained from the use of combinations of nitrogen and potassium (reported on later pages) indicate that phosphorus was the limiting factor in the soils involved in these experiments. Since many of the soils in central Illinois contain large amounts of potassium (even tho mostly in unavailable form), 29 * a treatment of nitrogen and phosphorus might be expected to give considerable increase in yield. The sweet-corn plant utilizes potash in relatively large quantities, as Whiting 55 * has shown, and this element is probably very necessary during the period of maturation. The increases obtained by using nitrogen and phosphorus without potash might be explained on the assumption that the addition of nitrogen increases the absorption of potash by the plant. Breazeale's 11 * experiments show that this is what occurs when phosphorus is not the limiting factor. [; Nitrogen Increasing, Potash Constant With no clover in the rotation and during both the first and second year after clover, the effects of nitrogen-potash fertilizer combinations on yields were extremely variable, and showed no definite tendencies (Table 3). Only in Set ;r04 during the second year after clover did nitrate in these combinations result in definite increases; but the odds are not significant. The mean increases in yield of the plots receiving nitrogen-potash combinations, including all such plots in all positions in the rotation, show that only Treatment 401 gave significant increases over the adjacent check (Section A of Tables 11 and 12). According to the Illinois soil survey, 29 * total phosphorus is low in many soils of Champaign county. While this does not necessarily indicate that available phosphorus also is low, and altho sweet corn requires less phosphorus than field corn, according to Whiting, 55 * it is probable that available phosphorus was deficient in the soils of most of the plots to a sufficient extent to make phosphorus the limiting factor when nitrogen was used only with potash. It is therefore not surpris- ing that nitrogen-potash combinations in these experiments gave variable results. ? Nitrogen Increasing, Phosphorus and Potash Constant The fertilizer analyses discussed under this heading are "complete," that is, they contain the three major plant- food elements. Compari- sons made in each table involve horizontal readings, and the discus- sions are confined to effects of nitrogen where phosphorus and potash were held constant. At each position in the rotations six comparisons 374 BULLETIN No. 417 {.July, TABLE 3. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SODIUM NITRATE AND POTASSIUM CHLORID ( Figures indicate mean increases per acre over adjacent check plots) Potash series Nitrogen series OOx 10* 20* 40* 00* 10* 20* 40* Number of ears Tons marketable ears No clover in rotation *00 .. 613 23:1 -889 4:1 -667 11:1 236 2:1 -192 1:1 596 3:1 188 1:1 -1044 2:1 -666 4:1 243 9:1 1124 5:1 -902 9:1 -.097 4:1 .014 2:1 .021 1:1 .136 15:1 -.300 4:1 -.458 5:1 .022 2:1 -.092 2:1 .071 2:1 .039 4:1 -.399 215:1 -.278 4:1 .114 6:1 .209 14:1 -.331 25:1 Odds xOl... -290 3:1 34 2:1 168 3:1 Odds *02... Odds *04 . Odds First year after clover *00... -186 2:1 -634 2:1 356 3:1 -768 12:1 28 <1:1 -857 31:1 -877 6:1 731 3:1 49 1:1 1249 155:1 315 3:1 -485 4:1 -.336 24:1 .030 2:1 .251 160:1 -.060 2:1 -.197 2:1 .181 4:1 -.354 28:1 -.032 1:1 -.264 66:1 -.302 6:1 .287 6:1 .028 4:1 .475 28:1 .054 2:1 -.131 3:1 Odds xOl... -941 37:1 101 2:1 646 38:1 Odds *02... Odds *04... Odds Second year after clover *00... 566 3:1 -1379 5:1 424 4:1 399 2:1 -414 3:1 -591 30:1 197 1:1 550 2:1 -822 5:1 768 5:1 -1450 16:1 1000 5:1 -.086 2:1 .043 2:1 -.130 2:1 .234 3:1 -.224 3:1 .229 5:1 .144 2:1 -.056 2:1 -.108 12:1 .187 5:1 .216 2:1 -.162 3:1 .295 10:1 -.405 6:1 .261 3:1 Odds xOl.., -314 3:1 -172 2:1 -495 3:1 Odds *02... Odds *04... Odds are possible where nitrogen varied in combination with constants of the four different dosages of phosphorus and potash. Each "com- parison" involves 16 treatment combinations. No Clover in Rotation. (1) K 2 O 25 pounds per acre constant (Table 4). In only a few treatments (Nos. Ill, 211, 121, and 221) did increasing the amount of nitrate of soda in combination with a constant amount of phosphorus (P 2 O 5 ) give increases in yield larger than those in which nitrate was omitted (Nos. Oil, 021, and 041). J935] FERTILIZER REQUIREMENTS OF SWEET CORN 375 TABLE 4. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SODIUM NITRATE AND SUPERPHOSPHATE WITH A SINGLE DOSAGE OF POTASSIUM CHLORID CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Phosphorus series Nitrogen series Oxl 1x1 2x1 4x1 Oxl 1x1 2x1 4x1 Number of ears Tons marketable ears No clover in rotation xOl . -290 3:1 323 2:1 2835 10:1 2397 603:1 -889 4:1 566 23:1 1165 7:1 -101 1:1 596 3:1 903 6:1 1253 603:1 -229 2:1 243 9:1 34 <1:1 -236 2:1 1650 26:1 -.097 4:1 .074 2:1 .869 16:1 .678 807:1 -.300 4:1 .176 24:1 .337 12:1 -.046 2:1 .071 2:1 .290 18:1 .382 57:1 .005 <1:1 .114 6:1 -.074 2:1 -.103 2:1 .566 74:1 Odds xll... Odds x21 . Odds x41... Odds First year after clover 01 -941 37:1 1321 45:1 760 4:1 1915 40:1 -634 2:1 824 16:1 1636 28:1 1835 79:1 -857 31:1 792 4:1 1657 46:1 1592 22:1 1249 155:1 824 4:1 1596 10:1 1200 21:1 -.336 24:1 .425 61:1 .292 6:1 .741 23:1 -.197 2:1 .175 3:1 .527 48:1 .742 124:1 -.264 66:1 .201 2:1 .601 30:1 .547 21:1 .475 28:1 .342 6:1 .550 7:1 .544 26:1 Odds xll... Odds x21 Odds *41 . . . Odds Second year after clover xOl... -314 3:1 708 5:1 359 4:1 1424 96:1 -1379 5:1 520 304:1 2667 43:1 2546 16:1 -591 30:1 838 61:1 2030 11:1 2784 45:1 768 5:1 1410 19:1 1717 14:1 1636 78:1 -.086 2:1 .145 3:1 .242 11:1 .584 100:1 -.224 3:1 .182 19:1 .968 58:1 1.060 24:1 -.108 12:1 .325 34:1 .742 13:1 1.027 108:1 .295 10:1 .583 20:1 .658 38:1 .608 158:1 Odds xll... Odds x21 Odds x41... Odds (2) K 2 O 50 pounds per acre constant (Table 5). Nitrate gave scat- tered increases in yield, but there was no consistent tendency toward increases. (3) K 2 O 100 pounds per acre constant (Table 6). Nitrate gave scat- tered increases in yield, but exhibited no definite tendency. (4) P 2 O 8 32 pounds per acre constant (Table 7). Nitrate gave scattered increases in yield, but exhibited no definite tendency. (5) P 2 O 6 64 pounds per acre constant (Table 8). A slight tendency to respond to increasing dosages of nitrate was noticeable, but the tendency 376 BULLETIN No. 417 TABLE 5. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SODIUM NITRATE AND SUPERPHOSPHATE WITH A DOUBLE DOSAGE OF POTASSIUM CHLORID CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Phosphorus series Nitrogen series 0x2 1x2 2x2 4x2 0x2 1x2 2x2 4x2 Number of ears Tons marketable ears No clover in rotation x02 . . 34 2:1 2108 23:1 1057 65:1 1596 73:1 -667 11:1 727 11:1 1421 27:1 1906 41:1 188 1:1 1529 806:1 491 3:1 -67 1:1 1124 5:1 364 2:1 1637 32:1 -6 <1:1 .014 2:1 .573 24:1 .022 1:1 .430 42:1 -.458 5:1 .255 15:1 .397 3:1 .603 32:1 .039 4:1 .395 59:1 .178 4:1 .062 2:1 .209 14:1 .051 1:1 .458 28:1 .071 1:1 Odds *12... Odds x22... Odds x42 Odds First year after clover x02... 101 2:1 145 1:1 1685 14:1 2198 79:1 356 3:1 1754 51:1 2768 45:1 1172 10:1 -877 6:1 1418 14:1 1152 19:1 1980 6:1 315 3:1 590 6:1 1555 239:1 448 5:1 .030 2:1 .061 1:1 .530 10:1 .809 47:1 .181 4:1 .622 25:1 .927 37:1 .687 22:1 -.302 6:1 .565 15:1 .527 30:1 .735 6:1 .054 2:1 .333 12:1 .429 79:1 .231 9:1 Odds x!2 . . Odds *22 .. Odds x42 . . . Odds Second year after clover x02... -172 2:1 1450 22:1 1531 48:1 1818 18:1 424 4:1 2465 46:1 2430 14:1 2298 18:1 197 1:1 1868 9:1 2864 49:1 1949 40:1 -1450 16:1 1076 22:1 2263 157:1 1677 42:1 .043 2:1 .510 11:1 .548 63:1 .716 85:1 .229 5:1 .827 48:1 .872 9:1 1.081 29:1 .187 5:1 .632 9:1 1.000 46:1 .725 90:1 -.405 6:1 .294 25:1 .881 510:1 .659 237:1 Odds x!2 . Odds x22... Odds x42... Odds was not pronounced enough to afford a basis for definite conclusions. Where potash was entirely omitted (Set .r20), nitrate was very effective in increasing the yields. (6) P 2 O 5 128 pounds per acre constant (Table 9). Scattered increases, sometimes quite large, were again obtained. First Year After Clover, (1) K 2 O 25 pounds per acre constant (Table 4). Nitrate showed a definite tendency to increase the yields in Set x2\ but not elsewhere. (2) K 2 O 50 pounds per acre constant (Table 5). In combinations such 1935} FERTILIZER REQUIREMENTS OF SWEET CORN 377 TABLE 6. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SODIUM NITRATE AND SUPERPHOSPHATE WITH A QUADRUPLE DOSAGE OF POTASSIUM CHLORID CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Phosphorus series Nitrogen series 0x4 1*4 2x4 4x4 0x4 1x4 2x4 4x4 Number of ears Tons marketable ears No clover in rotation x04 . . 168 236 -1044 -902 .021 .022 -.399 -.331 Odds 3:1 2:1 2:1 9:1 1:1 2:1 215:1 25:1 x!4.. . 1172 2222 876 875 .236 .636 .157 .358 Odds 10:1 7:1 13:1 3:1 5:1 18:1 11:1 6:1 x24 .. 646 1185 -1010 2957 .209 .381 -.357 .804 Odds 7:1 8:1 18:1 > 9999:1 5:1 17:1 17:1 10:1 *44.. . 1825 2074 1414 -909 .450 .731 .661 -.251 Odds 7:1 12:1 74:1 8:1 5:1 21:1 2064:1 5:1 First year after clover x04... 646 -768 731 -485 .251 -.354 .287 -.131 Odds 38:1 12:1 3:1 4:1 160:1 28:1 6:1 3:1 *14 .. 1204 1394 1289 1132 .439 .496 .479 .371 Odds 45:1 44:1 8:1 5:1 41:1 28:1 9:1 4:1 *24.. . 1103 2388 667 1676 .445 .680 .379 .557 Odds 31:1 24:1 4:1 505:1 27:1 20:1 5:1 495:1 x44 . 1774 2408 1346 586 .752 .955 .523 .212 Odds 20:1 14:1 14:1 9:1 22:1 24:1 27:1 6:1 Second year after clover x04 . . -495 399 550 1000 .130 .144 .216 .261 Odds 3:1 2:1 2:1 5:1 2:1 2:1 2:1 3:1 x!4... 2450 1884 1864 2541 .832 .740 .624 .984 Odds 15:1 24:1 41:1 41:1 15:1 30:1 40:1 65:1 *24.. . 1697 1848 2672 1556 .658 .460 .908 .654 Odds 25:1 13:1 56:1 27:1 39:1 34:1 78:1 60:1 *44. . . 3000 3051 1566 835 1.052 1.171 .718 .427 Odds 68:1 36:1 48:1 55:1 134:1 39:1 46:1 39:1 as Treatments 112 and 122, the addition of nitrate increased the yields over Treatments 012 and 022 respectively. In other combinations nitrate gave no increases. (3) K 2 O 100 pounds per acre constant (Table 6). The addition of 50 pounds of sodium nitrate per acre (Treatments 114, 124, and 144) gave increases over corresponding treatments where nitrate was omitted. Larger additions of nitrate failed, however, to give further increases. (4) P 2 O B 32 pounds per acre constant (Table 7). In two instances, 378 BULLETIN No. 417 [July, TABLE 7. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SODIUM NITRATE AND POTASSIUM CHLORID WITH A SINGLE DOSAGE OF SUPERPHOSPHATE CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Potash series Nitrogen series 01* Hi 21* 41* Olx llx 21x 41* Number of ears Tons marketable ears No clover in rotation xlO... 1017 70:1 323 2:1 2108 23:1 1172 10:1 849 21:1 566 23:1 727 11:1 2222 7:1 -1152 12:1 903 6:1 1529 806:1 876 13:1 1616 39:1 34 <1:1 364 2:1 875 3:1 .296 56:1 .074 2:1 .573 24:1 .236 5:1 .195 11:1 .176 24:1 .255 15:1 .636 18:1 -.359 13:1 .290 18:1 .395 59:1 .157 11:1 .578 58:1 -.074 2:1 .051 1:1 .358 6:1 Odds xll . Odds x!2 .. Odds *14 . . Odds First year after clover xlO... 1491 3:1 1321 45:1 145 1:1 1204 45:1 731 61:1 824 16:1 1754 51:1 1394 44:1 457 2:1 792 4:1 1418 14:1 1289 8:1 1236 8:1 824 4:1 590 6:1 1132 5:1 .448 12:1 .425 61:1 .061 1:1 .439 41:1 .246 30:1 .175 3:1 .622 25:1 .496 28:1 .283 4:1 .201 2:1 .565 15:1 .479 9:1 .314 5:1 .342 6:1 .333 12:1 .371 4:1 Odds all . Odds *12... Odds x!4.. . Odds Second year after clover xlO... 1561 7:1 708 5:1 1450 22:1 2450 15:1 748 5:1 520 304:1 2465 46:1 1884 24:1 662 4:1 838 61:1 1868 9:1 1864 41:1 -187 2:1 1410 19:1 1076 22:1 2541 41:1 .422 9:1 .145 3:1 .510 11:1 .832 15:1 .270 5:1 .182 19:1 .827 48:1 .740 30:1 .189 3:1 .325 34:1 .632 9:1 .624 40:1 .036 8:1 .583 20:1 .294 25:1 .984 65:1 Odds xll... Odds x!2... Odds x!4.. . Odds Treatments 112 and 114, nitrate increased yields over the respective treat- ments without nitrate. However, no definite trend developed. (5) P 2 O S 64 pounds per acre constant (Table 8). In Set x2\ nitrate gave successively larger increases in yield where 50 to 100 pounds were applied per acre, but 50 pounds per acre gave the largest increases in the sets having constants of 50 and 100 pounds K 2 O per acre. (6) P 2 O B 128 pounds per acre constant (Table 9). Nitrate increased the yields materially in only two instances (Treatment 140 and 144), and even here the odds indicate little more than a tendency. 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 379 TABLE 8. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SODIUM NITRATE AND POTASSIUM CHLORID WITH A DOUBLE DOSAGE OF SUPERPHOSPHATE CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Potash series Nitrogen series 02* 12x 22* 42* 02* 12* 22* 42* Number of ears Tons marketable ears No clover in rotation *20 . 1765 12:1 2835 10:1 1057 65:1 646 7:1 1805 46:1 1165 7:1 1421 27:1 1185 8:1 1380 29:1 1253 603:1 491 3:1 -1010 18:1 2842 35:1 -236 2:1 1637 32:1 2957 > 9999:1 .370 10:1 .869 16:1 .022 1:1 .209 5:1 .391 16:1 .337 12:1 .397 3:1 .381 17:1 .467 27:1 .382 57:1 .178 4:1 -.357 17:1 .914 66:1 -.103 2:1 .458 28:1 .804 10:1 Odds *21... Odds *22.. . Odds *24 Odds First year after clover *20. . . 444 1334 1540 1459 .118 .490 .564 .595 Odds 2:1 22:1 19:1 11:1 3:1 17:1 17:1 22:1 *21.. . 760 1636 1657 1596 .292 .527 .601 .550 Odds 4:1 28:1 46:1 10:1 6:1 48:1 30:1 7:1 x22... 1685 2768 1152 1555 .530 .927 .527 .429 Odds 14:1 45:1 19:1 239:1 10:1 37:1 30:1 79:1 *24 . 1103 2388 667 1676 .445 .680 .379 .557 Odds 31:1 24:1 4:1 505:1 27:1 20:1 5:1 495:1 Second year after clover *20 369 1808 1596 1914 .248 .673 .552 .778 Odds 4:1 72:1 13:1 26:1 19:1 253:1 24:1 72:1 x21... 359 2667 2030 1717 .242 .968 .742 .658 Odds 4:1 43:1 11:1 14:1 11:1 58:1 13:1 38:1 x22 . 1531 2430 2864 2263 .548 .872 1.000 .881 Odds 48:1 14:1 49:1 157:1 63:1 9:1 46:1 510:1 *24.. . 1697 1848 2672 1556 .658 .460 .908 .654 Odds 25:1 13:1 56:1 27:1 39:1 34:1 78:1 60:1 Second Year After Clover. (1) K 2 O 25 pounds per acre constant (Table 4). In Set x\\ the increases in yield, on the weight basis, became successively larger as nitrate was increased. An application of 50 pounds of nitrate per acre gave the largest increases, on the basis of weights of marketable ears, where the phosphorus constants were respectively 64 and 128 pounds P 2 O 5 per acre. (2) K 2 O 50 pounds per acre constant (Table 5). Nitrate in combina- tions containing 32 and 128 pounds P 2 O 5 per acre gave the largest in- 380 BULLETIN No. 417 Uuly, TABLE 9. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SODIUM NITRATE AND POTASSIUM CHLORID WITH A QUADRUPLE DOSAGE OF SUPERPHOSPHATE CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Potash series Nitrogen series Me 14* 24* 44* 04* 14* 24* 44* Number of ears Tons marketable ears No clover in rotation x40 1239 5:1 2397 603:1 1596 73:1 1825 7:1 1327 4:1 -101 1:1 1906 41:1 2074 12:1 546 4:1 -229 2:1 -67 1:1 1414 74:1 148 1:1 1650 26:1 -6 <1:1 -909 8:1 .345 5:1 .678 807:1 .430 42:1 .450 5:1 .361 3:1 -.046 2:1 .603 32:1 .731 21:1 .235 29:1 .005 <1:1 .062 2:1 .661 2064:1 .027 1:1 .566 74:1 .071 1:1 -.251 5:1 Odds *41 . . . Odds *42 Odds *44.. . Odds First year after clover *40. . . 1099 13:1 1915 40:1 2198 79:1 1774 20:1 1879 10:1 1835 79:1 1172 10:1 2408 14:1 1541 29:1 1592 22:1 1980 6:1 1346 14:1 849 5:1 1200 21:1 448 5:1 586 9:1 .377 9:1 .741 23:1 .809 47:1 .752 22:1 .636 11:1 .742 124:1 .687 22:1 .955 24:1 .695 25:1 .547 21:1 .735 6:1 .523 27:1 .310 5:1 .544 26:1 .231 9:1 .212 6:1 Odds *41 Odds *42 . . . Odds *44.. . Odds Second year after clover *40 . . 1086 13:1 1424 96:1 1818 18:1 3000 68:1 1930 27:1 2546 16:1 2298 18:1 3051 36:1 2399 38:1 2784 45:1 1949 40:1 1566 48:1 1960 3332 : 1 1636 78:1 1677 42:1 835 55:1 .360 26:1 .584 100:1 .716 85:1 1.052 134:1 .716 77:1 1.060 24:1 1.081 29:1 1.171 39:1 .912 55:1 1.027 108:1 .725 90:1 .718 46:1 .672 2499:1 .608 158:1 .659 237:1 .427 39:1 Odds *41 . . . Odds x42 .. Odds x44. . . Odds creases where the amount did not exceed 50 pounds sodium nitrate per acre. However, in Set x22, 100 pounds nitrate per acre gave the largest increases. (3) K 2 O 100 pounds per acre constant (Table 6). In the three sets of treatments considered here, the largest increases occurred with Treatments 414, 224, and 144, and the odds were large enough to be significant. It cannot be said, however, that nitrate exhibited a general tendency to in- crease yields further as successively larger applications were made. /9J5] FERTILIZER REQUIREMENTS OF SWEET CORN 381 (4) P 2 O a 32 pounds per acre constant (Table 7). In Set xll nitrate gave successively greater increases in relation to the amount applied. In Set x\2, however, the largest and most significant increase was secured with Treatment 112. In Set .rl4 the maximum increase due to nitrogen was in Treatment 414. (5) P 2 O 5 64 pounds per acre constant (Table 8). In Set 4:21 the largest and most significant increase resulted from Treatment 121. In Set .r22 nitrate gave successively larger increases as far as Treatment 222. In Set x24, however, the weights showed no definite trend, Treatment 224 producing the only increase that was larger than that produced by Treat- ment 024. On the basis of increase in number of cars there was a definite trend upward as far as Treatment 224. (6) P 2 O 5 128 pounds per acre constant (Table 9). The increases in number of ears in Set ^41 became successively larger as far as Treatment 241, but with respect to weights, Treatment 141 was the maximum. In the two other sets Treatments 142 and 144 produced respectively the largest increases. In the foregoing "complete" fertilizer combinations, nitrate gave large but inconsistent increases in yields. Its addition, in increasing amounts, to various constants of phosphorus and potash, with no clover in the rotation, gave highly variable responses. On the other hand, applied the first year after clover in identical combinations, it gave very definite responses on many plots. The quantity of phosphorus used in the combination appeared to have considerable influence upon the size of the increases resulting from the nitrate. These increases were smallest and the odds least significant where 32 pounds P 2 O 8 per acre was applied. In the second year after clover nitrate gave much larger increases where the applications of potash did not exceed 25 to 50 pounds K 2 O per acre. Here again nitrate responded least where the basal treatment of phosphorus was lowest. In general, side dressings of 7.5 to 15 pounds of nitrogen per acre gave increases larger than those resulting from the heaviest applications of 30 pounds. Ordinarily one would expect nitrate to be more effective on soils in which this element is depleted than on fertile soils, and to be less effective during the first and second years after clover than when no clover at all has been used. For example, in these experiments best results with nitrate would be expected with no clover in the rotation on Field 1300, which the average yields of the check plots (means of average yields given in Table 10) show to have been greatly depleted in fertility before clover was used ; and least results would be expected on the fairly fertile soil of Fields 800, 900, and 1000 (Table 10) during the first year after clover. The actual results, however, were contrary to expectations: nitrates proved most effective following clover in the rotation. 382 BULLETIN No. 417 TABLE 10. AVERAGE YIELDS OF CHECK PLOTS IN DIFFERENT FIELDS, BY YEARS, SHOWING EFFECT OF CLOVER IN ROTATION Field Year Position in rotation Marketable ears Tons fodder per acre Number per acre Tons per acre 800 1000 1000 1300 900 1300 800 900 800 1000 1000 1300 1923 1923 1924 1924 1925 1925 1926 1926 1927 1927 1928 1928 No clover in rotation 8 809 8 728 8 061 3 960 8 203 2 505 7 536 5 819 7 092 6 708 4 061 4 202 2.54 2.94 2.73 1.09 2.56 .68 2.44 1.78 2.28 2.21 1.15 1.14 3.94 3.88 3.19 1.62 5.41 1.82 3.68 4.66 2.58 2.85 2.96 2.05 First year after sod Second year after sod No clover in rotation First year after clover No clover in rotation First year after clover Second year after clover . . . Second year after clover . . . First year after clover Second year after clover . . . First year after clover From the data representing results obtained by side-dressing sodium nitrate as part of a complete fertilizer, (summarized as means in Sections B, C, and D of Tables 11, 12, and 13), it is evident that the smallest nitrate treatment (50 pounds per acre; i.e., 7.5 pounds of nitrogen per acre) gave larger and more consistent increases in yields than the heavier dosages. It is apparent, also, that the percentages of increase depended to a considerable extent upon the amounts and pro- portions of minerals which were used as a basal treatment. Analysis of Relative Nitrogen Efficiency in Different Combinations The preceding discussion concerning the effects of side-dressing sodium nitrate is useful in denning some of the limitations in the use of this salt. Considerable doubt still remains, however, concerning the specific quantities of sodium nitrate, and the proper basal treat- ment of accompanying minerals, which should be used to give the best results. Determination and analysis of the relative efficiencies of the various fertilizer elements in the different combinations used here will aid in answering these questions. Efficiency of Nitrogen When Used With Phosphorus. The rela- tions existing between nitrogen and phosphorus are shown in Tables 14, 15, and 16. The data in Table 14 reveal that the efficiency of nitrogen used with phosphorus was not only very low in general but significantly negative in several instances. The greatest efficiency of nitrogen occurred in Sets \2x, 22x, and 42x, of which Sets \2x and 1935} FERTILIZER REQUIREMENTS OF SWEET CORN 383 TABLE 11. MEAN PERCENTAGE INCREASES IN NUMBER OF MARKETABLE EARS DUE TO VARIOUS FERTILIZER TREATMENTS NITROGEN SERIES Potash increasing (A) Nitrogen increasing Phosphorus increasing (B) Nitrogen increasing 00* 10* 20* 40* Oxl 1x1 2x1 4x1 xOO 5.10 -15.32 1.90 -2.06 -2.99 -7.57 -4.28 4.03 -5.27 13.37* -1.07 -1.31 xOl.. -8.32* 15.14* 16.39* 32.76* -15.32 10.49* 32.66* 24.15* -7.57 14.32* 27.23* 22.28* 13.37* 12.96 19.48* 20.37* xOl -8.32* - .12 2.44 xll x02 x21 *04 x41 Phosphorus increasing (C) Nitrogen increasing Phosphorus increasing (D) Nitrogen increasing 0x2 1x2 2x2 4x2 0x4 1x4 2x4 4x4 *02... - .12 17.94* 21.34* 32.83* 1.90 30.61* 41.66* 26.32* -4.28 28.98* 24.18* 21.03* -1.07 10.62* 31.07* 9.45* x04. . . 2.44 26.98* 17.22* 38.07* -2.06 34.32* 34.70* 44.22* 4.03 23.79* 13.25 19.34* -1.31 25.42* 33.54* 3.21* x!2 *14. x22 x24 *42 x44 Phosphorus increasing (E) Nitrogen increasing Potash increasing (F) Nitrogen increasing 0x0 1x0 2x0 4*0 Olx llx 21x 41x xOO 24^37* 10.72 18.99* 5.10 12.31* 28.22* 28.40* -2.99 2.06 26.76* 22.64* -5.27 13.80 32.34* 14.59* *10... xll 24.37* 15.14* 17.94* 26.98* 12.31* 10.49* 30.61* 34.32* 2.06 14.32* 28.98* 23.79* 13.80 12.96 10.62* 25.42* xlO x20 x!2 x40 *14 Potash increasing (G) Nitrogen increasing Potash increasing (H) Nitrogen increasing 02x 12x 22x 42x 04x 14x 24x 44x x20... 10.72 16.39* 21.34* 17.22* 28.22* 32.66* 41.66* 34.70* 26.76* 27.23* 24.18* 13.25 32.34* 19.48* 31.07* 33.54* x40 18.99* 32.76* 32.83* 38.07* 28.40* 24.15* 26.32* 44.22* 22.64* 22.28* 21.03* 19.34* 14.59* 20.37* 9.45* 3.21 x2l x41 x22 x42 *24... x44... PHOSPHORUS SERIES Potash increasing (I) Phosphorus increasing Potash increasing (J) Phosphorus increasing 00* 01* 02* 04* 10* llx 12x 14* 0x0 24.37* 15.14* 17.94* 26.98* 10.72 16.39* 21.34* 17.22* 18.99* 32.76* 32.83* 38.07* 1*0 5.10 -15.32 1.90 -2.06 12.31* 10.49* 30.61* 34.32* 28.22* 32.66* 41.66* 34.70* 28.40* 24.15* 26.32* 44.22* 0*1 -8.32* - .12 2.44 1*1 0*2... 1*2 0*4 1x4. Potash increasing (K) Phosphorus increasing Potash increasing (L) Phosphorus increasing 20* 21* 22* 24* 40x 41x 42x 44x 2*0... -2.99 -7.57 -4.28 4.03 2.06 14.32* 28.98* 23.79* 26.76* 27.23* 24.18* 13.25 22.64* 22.28* 21.03* 19.34* 4x0 -5.27 13.37* -1.07 -1.31 13.80 12.96 10.62* 25.42* 32.34* 19.48 31.07* 33.54* 14.59* 20.37* 9.45* 3.21 2*1 4x1 . 2*2 4*2 2*4 4*4 *Statistically significant, odds of over 30:1, according to Table 39, Appendix. 384 BULLETIN No. 417 [July, TABLE 12. MEAN PERCENTAGE INCREASES IN WEIGHTS OF MARKETABLE EARS DUE TO VARIOUS FERTILIZER TREATMENTS NITROGEN SERIES Potash increasing (A) Nitrogen increasing Phosphorus increasing (B) Nitrogen increasing 00* lOx 20x 40x Oxl 1x1 2x1 4x1 xOO 5.51 -12.41 1.89 -4.70 -2.91 -7.17* -2.91 5.32 -4.85 17.38* -3.01 -2.24 xOl -8.98* 13.91* 18.75* 37.41* -12.41 9.07 34.47* 32.76* -7.17* 14.45 31.92* 26.20* 17.38* 16.06 22.35* 24.94* xOl -8.98* 1.63 3.58 xll x02 x21 x04 . . x41 Phosphorus increasing (C) Nitrogen increasing Phosphorus increasing (D) Nitrogen increasing 0x2 1x2 2x2 4x2 0x4 1x4 2x4 4x4 x02... 1.63 17.99* 18.52* 37.28* 1.89 34.73* 44.47* 40.11* -2.91 31.95* 29.93* 25 . 66* -3.01 12.14* 32.04* 13.13* x04 3.58 27.62* 21.36* 43.50* -4.70 38.54* 31.11* 55.58* 5.32 25.10* 16.50 27.27* -2.24 30.12* 35.53* 5.89 x!2 x!4 x22 x24 x42 44 Phosphorus increasing (E) Nitrogen increasing Potash increasing (F) Nitrogen increasing 0x0 1x0 2x0 4x0 Olx llx 21x 41x xOO 5.51 12.62* 28.93* -2.91 4.96 31.50* -4.85 14.81 38.98* xlO 22.63* 13.91* 17.99* 27.62* 12.62* 9.07 34.73* 38.54* 4.96 14.45 31.95* 25.10* 14.81 16.06 12.14* 30.12* xlO 22.63* 10.02* xll x20 x!2 .v4() 19.45* 30.12* 29.16* 15.73* x!4 Potash increasing (G) Nitrogen increasing Potash increasing (H) Nitrogen increasing 02x 12x 22x 42x 04x 14x 24x 44x x20... 10.02* 18.75* 18.52* 21.36* 28.93* 34.47* 44.47* 31.11* 31.50* 31.92* 29.93* 16.50 38.98* 22.35* 32.04* 35.53* x40 19.45* 37.41* 37.28* 43.50* 30.12* 32.76* 40.11* 55.58* 29.16* 26.20* 25.66* 27.27* 15.73* 24.94* 13.13* 5.89 x21 x41 x22 x42 . . x24 x44 PHOSPHORUS SERIES Potash increasing (I) Phosphorus increasing Potash increasing (J) Phosphorus increasing OOx Olx 02x 04x lOx llx 12x 14x 0x0... 22.63* 13.91* 17.99* 27.62* 10.02* 18.75* 18.52* 21.36* 19.45* 37.41* 37.28* 43.50* 1x0 5.51 -12.41 1.89 -4.70 12.62* 9.07 34.73* 38.54* 28.93* 34.47* 44.47* 31.11* 30.12* 32.76* 40.11* 55.58* Oxl -8.98* 1.63 3.58 1x1 0x2 1x2 0x4 1x4 Potash increasing (K) Phosphorus increasing Potash increasing (L) Phosphorus increasing 20x 21* 22x 24x 40x 41x 42x 44x 2x0... -2.91 -7.17* -2.91 5.32 4.96 14.45 31.95* 25.10* 31.50* 31.92* 29.93* 16.50 29.16* 26.20* 25.66* 27.27* 4x0 -4.85 17.38* -3.01 -2.24 14.81 16.06 12.14* 30.12* 38.98* 22.35* 32.04* 35.53* 15.73* 24.94* 13.13* 5.89 2x1 4x1 2x2 4x2 2x4... 4x4. . *Statistically significant, odds over 30: 1 according to Table 39, Appendix. 19351 FERTILIZER REQUIREMENTS OF SWEET CORN 385 TABLE 13. MEAN PERCENTAGE INCREASES IN WEIGHTS OF GREEN FODDER DUE TO VARIOUS FERTILIZER TREATMENTS NITROGEN SERIES Potash increasing (A) Nitrogen increasing Phosphorus increasing (B) Nitrogen increasing 00* lOx 20x 40* Oxl 1x1 2*1 4x1 xOO 9.74 2.09 28.22* 7.70 -4.86 -5.25 -0.20 24.66* -1.58 16.63* 6.26 -2.37 xOl -12.24 10.97 23.18* 32.29* 2.09 -1.77 26.66* 35.46* -5.25 10.04* 27.78* 33 . 20* 16.63* 18.05* 13.65 34.85* xOl -12.24 5.07 -2.44 xll *02 x21 x04 . . x41 Phosphorus increasing (C) Nitrogen increasing Phosphorus increasing (D) Nitrogen increasing 0x2 1x2 2x2 4x2 0x4 1x4 2x4 4x4 x02 5.07 13.58 25.62* 33.02* 28.22* 42.34* 34.30* 48.45* - .20 19.79 38.69* 40.71* 6.26 19.45* 35.15* 21.74* x04 -2.44 39.36* 33.74* 47.62* 7.70 35.91* 36.24* 68 . 36* 24.66* 29.81* 42.88* 52.05* -2.37 29.89* 40.80* 19.01* x!2 *14 x22 x24 x42 x44 Phosphorus increasing (E) Nitrogen increasing Potash increasing (F) Nitrogen increasing 0x0 1x0 2x0 4x0 Olx 11* 21* 41x xOO 9.74 14.71* 13.91* 23.09* -4.86 1.01 7.74 38.06* -1.58 -1.55 31.56* 26.32* xlO 15.64* 10.97 13.58 39.36* 14.71* -1.77 42 . 34* 35.91* 1.01 10.04* 19.79 29.81* -1.55 18.05* 19.45* 29.89* xlO 15.64* 11.46 1.26 xll x20 x!2 x40 x!4 Potash increasing (G) Nitrogen increasing Potash increasing (H) Nitrogen increasing 02* 12x 22x 42x 04x 14x 24* 44* *20. . . 11.46 23.18* 25.62* 33.74* 13.91* 26.66* 34.30* 36.24* 7.74 27.78* 38.69* 42.88* 31.56* 13.65 35.15* 40.80* x40 1.26 32.29* 33.02* 47.62* 23.09* 35.46* 48.45* 68.36* 38.06* 33.20* 40.71* 52.05* 26.32* 34.85* 21.74* 19.01* x21 x41 x22 *24 x42 x44 PHOSPHORUS SERIES Potash increasing (I) Phosphorus increasing Potash increasing (J) Phosphorus increasing OOx Olx 02* 04x 10* llx 12x 14* 0*0 15.64* 10.97 13.58 39.36* 11.46 23.18* 25.62* 33.74* 1.26 32.29* 33.02* 47.62* 1*0 9.74 2.09 28.22* 7.70 14.71 -1.77 42.34* 35.91* 13.91* 26.66* 34.30* 36.24* 23.09* 35.46* 48.45* 68 . 36* Oxl -12.24 5.07 -2.44 1*1 0*2 1*2. 0x4 1x4 Potash increasing (K) Phosphorus increasing Potash increasing (L) Phosphorus increasing 20x 21x 22* 24* 40* 41* 42x 44* 2*0... -4.86 -5.25 - .20 24.66* 1.01 10.04* 19.79 29.81* 7.74 27.78* 38.69* 42.88* 38.06* 33.20* 40.71* 52.05* 4x0 -1.58 16.63* 6.26 -2.37 -1.55 18.05* 19.45* 29.89* 31.56* 13.65 35.15* 40.80* 26.32* 34.85* 21.74* 19.01* 2x1 4x1 2x2 4x2 2x4 4x4 *Statistically significant, odds over 30:1 according to Table 39, Appendix. 386 BULLETIN No. 417 Uuly, TABLE 14. EFFECT OF PHOSPHORUS ON NITROGEN EFFICIENCY AS INDICATED BY SET AVERAGES BASED ON WEIGHTS OF MARKETABLE EARS" Mean Mean Mean Set nitrogen Set nitrogen Set nitrogen efficiency efficiency efficiency perct. perct. Perct. lOx. . - 1 . 48 2.8 20x. . . -.98 2.3 40*. . . 2.76 2.8 11* 3.20 3.2 21* -1.42 3.7 41* -2.26 3.6 12* 17.58 3.4 22* 10.30 3.2 42* 15.06 3.0 14* 5 23 4 1 24* -7.34 3.6 44*. 19 49 3.0 See Table 40, Appendix, for detail data. A2x showed significant increases and Set 22x very nearly so. In other words, the efficiency of nitrogen with phosphorus was uniformly low except where 64 pounds P 2 O 5 per acre was applied basally. This dominance of the 64-pound P 2 O 5 dosage in increasing the efficiency of nitrogen in nitrogen-phosphorus combinations is further indicated by comparison of the modes in Table 15; Treatments 122, 220, and 420 are the highest in their respective groups. These results should not be stressed too greatly, however, because Treatments 220, 420, and 401 are the only ones statistically significant. Comparison of the treatments giving the maximum increases in yields (Table 16) shows that when all three elements were used, the single nitrogen treatment gave better yields than heavier applications. Treatments 144, 212, and 420 gave the largest increases in their re- spective groups. These results, which are only partially in agreement with the data in Tables 14 and 15, serve to show that mere yield increases over checks without further comparisons of interrelation- ships cannot be relied upon for adequate interpretation of experimental results such as these. Thus two important points regarding the relation between nitrogen and phosphorus are indicated by the data in Tables 14, 15, and 16, TABLE 15. EFFECT OF PHOSPHORUS ON NITROGEN EFFICIENCY AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN NITROGEN EFFICIENCY IN THEIR RESPECTIVE SETS" Treat- ment Nitrogen efficiency Treat- ment Nitrogen efficiency Treat- ment Nitrogen efficiency 100 perct. 5.51 5.0 201. perct. 1.81 3.2 401 perci. 26.36 4.3 112 16.74 7.3 212 13.96 8.0 414 2.50 8.8 122 25.95 9.3 220 21.48 5.5 420 28.96 5.2 144 12.08 10.1 240 9.71 5.7 440 -3.72 5.6 See Table 40. Appendix, for detail data. 79J5] FERTILIZER REQUIREMENTS OF SWEET CORN 387 TABLE 16. EFFECT OF PHOSPHORUS ON NITROGEN AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN WEIGHTS OF MARKETABLE EARS IN THEIR RESPECTIVE SETS Table from which data are taken Treat- ment Increase in yield Treat- ment Increase in yield Treat- ment Increase in yield 12. A 100. . . perct. 5. 51 5.0 204 perct. 5.32 5.9 401. . perct. 17.38 3.3 12. F 114 ... 38.54 5.1 212. 31.95 6.3 414 30.12 7.0 12. G 122 44.47 8.1 221 31.92 5.2 420 38.98 4.4 12. H 144 55 58 7 7 240 29 16 4 1 441 . 24.94 2.7 Treatment 220 had an efficiency of 31 .50 4.8 percent. namely: (1) that the maximum efficiency of nitrogen is associated with the smallest dosage; and (2) that an optimum application of phosphorus increases nitrogen efficiency to an appreciable extent. No definite reason can be advanced, as a result of these experi- ments, for the relations between nitrogen and phosphorus which have been recorded. MacTaggart, 36 * in a study of Canada field peas, soy- beans, and alfalfa, found that altho total dry matter and total nitrogen were greatly increased by added phosphorus, the percentage of ni- trogen was influenced to a less extent. Phosphorus applied in com- bination with nitrogen, potash, and sulfur acted in practically the same manner. Blair and Prince, 7 * who worked with field corn, reached somewhat similar conclusions, showing that the percentage of nitrogen in the dry matter was not influenced by the amount of phosphoric acid used. However, in later work with rape and buckwheat these investigators 8 * noted a slight increase in nitrogen recovery associated with increases in the amount of phosphoric acid. Breazeale 11 * ob- served that the absorption of nitrogen by wheat seedlings in culture solutions, as determined by dry weight and total nitrogen, was not in- fluenced materially by varying amounts of potash, phosphoric acid, and gypsum. There is no consistent evidence, from the literature reviewed, that phosphorus has any appreciable effect in increasing the availability of nitrogen. A tendency in that direction appears to be indicated in Table 14, but there are no supporting chemical analyses from these experi- ments available as proof. Efficiency of Nitrogen IV hen Used With Potash. In the brief discussion of the relations existing between nitrogen and potassium (page 373) the statement was made that the results were highly vari- able and the relationships difficult to define. These relations are given in summary form in Tables 17, 18, and 19. 388 BULLETIN No. 417 [July, TABLE 17.- -EFFECT OF POTASH ON NITROGEN EFFICIENCY AS INDICATED BY SET AVERAGES BASED ON WEIGHTS OF MARKETABLE EARS" Set Mean nitrogen efficiency Set Mean nitrogen efficiency Set Mean nitrogen efficiency 1x0. . perct. 6.27 2.8 2*0. perct. 2.65 2.7 4x0. perct. 3.14 2.6 1*1 .70 3.4 2x1 1.08 3.0 4x1 4.91 3.2 1x2 1x4 11.44 3.7 6.12 3.7 2x2 2x4 2.30 3.6 -5.47 3.5 4x2 4x4 5.28 2.7 -6.69 3.3 See Table 40, Appendix, for detail data. The probable errors in connection with the efficiency factors given in Table 17 are so large, with the exception of that for Set \x2, that the factors have little or no real meaning. As shown by a comparison of the modes (Table 18), potash had a relatively slight tendency to increase nitrogen efficiency where the single dosage of nitrogen was used. Treatment 122, with the single dosage of nitrogen, had the highest nitrogen efficiency but the efficiency factor was not statistically significant. Among the treatments having the double dosage of ni- trogen, Treatment 220 was the most efficient. Successive additions of potash caused a decrease in nitrogen efficiency. This was also true where the quadruple dosage of nitrogen was constant. Altho the re- sults were very inconclusive, Table 18 indicates that where 15 or 30 pounds of nitrogen per acre was used, the omission of potash was essential to secure the greatest efficiency of nitrogen. On the other hand, when 7.5 pounds of nitrogen was used, dosages of potash up to 50 pounds of K 2 O per acre sometimes gave slight increases in nitrogen efficiency. These relations between nitrogen and potash are further indicated in Table 19, where it is shown that it was only when nitrogen was not applied in excess of 7.5 pounds per acre that the yields in- creased in relation to increases in potash dosages. When 15 or 30 pounds of nitrogen per acre was applied, yields tended to remain static. TABLE 18. EFFECT OF POTASH ON NITROGEN EFFICIENCY AS INDICATED BY TREAT- MENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN NITROGEN EFFICIENCY IN THEIR RESPECTIVE SETS" Treat- ment Nitrogen efficiency Treat- ment Nitrogen efficiency Treat- ment Nitrogen efficiency 120 Perct. 18 91 47 220 perct. 21 48 5 5 420 perct. 28.96 5.2 121 15 72 64 221.. 13.17 6.7 401 26.36 4.3 122 25 95 93 212 13.96 8.0 422 13.52 5.6 144 . . . 12 08 10 1 204 1.74 6.7 424 14.17 4.2 See Table 40, Appendix, for detail data. 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 389 The important points brought out in Tables 17, 18, and 19 are therefore: (1) The most efficient fertilizer combination for sweet corn in these tests was Set \x2 (Table 17), and in this set the most efficient treatment was No. 122 (Table 18). (2) Potash applied in combination with double and quadruple nitrogen dosages tended to reduce nitrogen efficiency. TABLE 19. EFFECT OF POTASH ON NITROGEN AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN WEIGHTS OF MARKETABLE EARS IN THEIR RESPECTIVE SETS Table from which data are taken Treat- ment Increase in yield Treat- ment Increase in yield Treat- ment Increase in yield 12. E 12, B 12, C 12. D 140 percl. 30.12 6.1 34.47 4.7 44.47 8.1 55.58 7.7 220 perct. 31.50 4.8 31.92 5.2 31.95 6.3 27.27 3.1 420. perct. 38.98 4.4 24.94 2.7 b 32.04 3.2 35.53 2.5 121 221 441 122 212 422 144 244 424 Treatment 214 had an efficiency of 25.10 5.2 percent. Treatment 421 had an efficiency of 22.35 7.0 percent. Accordingly, if one expects side-dressed nitrate to give good re- sults, 50 pounds of sodium nitrate per acre is the maximum application, provided not more than 50 pounds of K 2 O per acre is used as part of the basal treatment. If phosphorus is used alone as the basal mineral, side-dressing quantities of sodium nitrate in excess of 50 pounds per acre would be permissible. EFFECTS OF PHOSPHORUS As stated before, phosphorus was probably the limiting factor in the soils used in these experiments. Unfortunately, during the early years of these experiments qualitative field tests for available phos- phorus, such as Bray's"* and Spurway's, 47 * were not available, and there was consequently no reasonably inexpensive way of finding out how the available phosphorus in these plots checked against that of the soils upon which sweet corn is usually grown elsewhere. Phosphorus Alone In view of the probable deficiency of available phosphorus in the soils of these plots, the heavier dosages of phosphorus were expected to give the larger and more consistent increases in yield. The results, however, were contrary to expectation, as shown below. With no clover in the rotation, the largest increase was obtained 390 BULLETIN No. 417 [July, by adding 64 pounds P 2 O 5 per acre, but the odds show that this was nothing more than a tendency (Table 20). The odds for the smaller increases obtained with 32 pounds P 2 O 5 per acre approach certainty as a limit. During the first and also during the second years after clover, the largest increases occurred with 32 pounds per acre, but the odds were not significant. The means of all plots receiving phosphorus alone, and including all positions in the rotation, show that Treatment TABLE 20. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SUPERPHOSPHATE AND POTASSIUM CHLORID (Figures indicate mean increases per acre over adjacent check plots) Potash series Phosphorus series OOx Olx 02x 04* OOx Olx 02x 04x Number of ears Tons marketable ears No clover in rotation 0x0 1017 70:1 323 2:1 2108 23:1 1172 10:1 1765 12:1 2835 10:1 1057 65:1 646 7:1 1239 5:1 2397 603:1 1596 73:1 1825 7:1 -.097 4:1 .014 2:1 .021 1:1 .296 56:1 .074 2:1 .573 24:1 .236 5:1 .370 10:1 .869 16:1 .022 1:1 .209 5:1 .345 5:1 .678 807:1 .430 42:1 .450 5:1 Odds Oxl . . . -290 3:1 34 2:1 168 3:1 Odds 0*2... Odds 0x4 Odds First year after clover 0x0 1491 3:1 1321 45:1 145 1:1 1204 45:1 444 2:1 760 4:1 1685 14:1 1103 31:1 1099 13:1 1915 40:1 2198 79:1 1774 20:1 -.336 24:1 .030 2:1 .251 160:1 .448 12:1 .425 61:1 .061 1:1 .439 41:1 .118 3:1 .292 6:1 .530 10:1 .445 27:1 .377 9:1 .741 23:1 .809 47:1 .752 22:1 Odds Oxl . . . -941 37:1 101 2:1 646 38:1 Odds 0x2 Odds 0x4 . Odds Second year after clover 0x0... 1561 7:1 708 5:1 1450 22:1 2450 15:1 369 4:1 359 4:1 1531 48:1 1697 25:1 1086 13:1 1424 96:1 1818 18:1 3000 68:1 -.086 2:1 .043 2:1 -.130 2:1 .422 9:1 .145 3:1 .510 11:1 .832 15:1 .248 19:1 .242 11:1 .548 63:1 .658 39:1 .360 26:1 .584 100:1 .716 85:1 1.052 134:1 Odds Oxl . . . -314 3:1 -172 2:1 -49S 3:1 Odds 0x2... Odds 0x4 . . . Odds 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 391 010 gave the largest increases and had significant odds (Section I, Tables 11 and 12). Similar effects of phosphorus have been noted by Schuster, 43 * Comin and Bushnell, 13 * Blackwell and Buie, 6 * and others. Phosphorus Increasing, Nitrogen Constant Much larger and more uniform increases in yields were obtained from the use of combinations of nitrogen and phosphorus than from applications of phosphorus alone (Table 2). With no clover in the rotation, yields increased (except those from Treatment 210) as applications of phosphorus were increased up to but not including the quadruple dosage. During both the first and second years after clover, sweet-corn yields again increased when larger amounts of phosphorus were applied. The increases were larger than when no clover was in the rotation, and the maximum was apparently beyond 128 pounds P 2 O 5 per acre. The only exception was Treatment 440, the results from which indicated that with a quadruple dosage of nitrogen constant, the maximum increase for phosphorus had been passed so far as weight of marketable ears was concerned. The means of the plots receiving nitrogen-phosphorus combina- tions, including all such plots in all positions in the rotation (Section E, Tables 11 and 12) show that altho the response of sweet corn to these fertilizer treatments as indicated by number of ears and weight of ears was not quite the same, the maximum increases were obtained for both numbers of ears and weights of ears when 64 pounds of P 2 O 5 per acre was applied (except Treatment 140, which gave the largest increases in Set IjrO). Phosphorus Increasing, Potash Constant Combinations of phosphorus and potash gave much better results than phosphorus applied alone. In general the yield increased in rela- tion to successive increments of phosphorus (Table 20). With no clover in the rotation, all these combinations gave increased yields over the checks, and the largest increases were obtained in Set Qx\. Dur- ing the first year after clover the highest and most consistent in- creases were obtained with Set 0^2, in which the largest increases occurred with the largest dosages of phosphorus. Set Qx\ gave large increases but they were not quite consistent, Treatment 021 being somewhat out of line with Treatments Oil and 041. The increases in Set 0x4 were slightly smaller, but were also (except in regard to number of ears) related to the amount of phosphorus added. During the second year after clover the yields on the basis of weight increased 392 BULLETIN No. 417 {.July, in relation to the amount of phosphorus in the combination, except with Treatment 024 in Set 0x4, where a slight discrepancy occurred. The means of the plots receiving applications of phosphorus-potash fertilizers, including all such plots in all positions in the rotation, show that in regard to both number and weight of marketable ears increases became successively larger in relation to the phosphorus dosage, except in one treatment, No. 024 (Section I, Tables 11 and 12). Phosphorus Increasing, Nitrogen and Potash Constant The fertilizer analyses discussed herein are "complete" analyses having different constants of nitrogen and potash with phosphorus varying. Each of the six comparisons at each position in the rotation involves 16 treatment combinations. No Clover in Rotation. (1) Nitrogen 7.5 pounds per acre constant (Table 21). In general, both in number and in weight of ears, increases were successively larger in relation to increased amounts of phosphorus in Sets \x\, 1*2, and 1*4. Exceptions to this trend occurred in Treat- ments 141 and 124. (2) Nitrogen 15 pounds per acre constant (Table 22). Yield increases due to phosphorus were very much less uniform than with 7.5 pounds nitrogen constant. The maximum increase in Set 2x1 occurred at Treat- ment 221, Treatment 241 giving no increase over the check. In Set 2*2 only Treatment 212, and in Set 2*4 only Treatment 244 gave significantly large increases. (3) Nitrogen 30 pounds per acre constant (Table 23). Phosphorus gave very erratic increases. There was considerable uniformity, however, in the trend of results in Set 4*4, the increases becoming greater in rela- tion to the dosage of phosphorus except in Treatment 444. (4) K 2 O 25 pounds per acre constant (Table 4). When the smaller dosages of nitrogen were constant (Sets 1*1 and 2*1), increasing applica- tions of phosphorus gave successively larger increases in yield, except in Treatments 141 and 241. On the other hand, phosphorus was ineffective with a high nitrogen constant (Set 4*1) except in Treatment 441. (5) K 2 O 50 pounds per acre constant (Table 5). Increases in yield became successively greater in relation to phosphorus dosages only in Set 1*2. Elsewhere the effects of phosphorus were somewhat erratic. (6) K 2 O 100 pounds per acre constant (Table 6). Successively larger increases in yield occurred with increased dosages of phosphorus in Set 1*4 except with Treatment 124, and in Set 4*4 except with Treatment 444. Treatment 244 was the only one in Set 2*4 giving a substantial increase in yield. First Year After Clover. (1) Nitrogen 7.5 pounds per acre constant (Table 21). The tendency for yields to increase in relation to the size of the phosphorus dosage was very marked. In but one instance (Treat- ment 142) was there any evidence that the maximum increase in yield had been passed. 1935} FERTILIZER REQUIREMENTS OF SWEET CORN 393 TABLE 21. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SUPERPHOSPHATE AND POTASSIUM CHLORID WITH A SINGLE DOSAGE OF SODIUM NITRATE CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Potash series Phosphorus series 10* 11* 12* 14* 10* 11* 12* 14* Number of ears Tons marketable ears No clover in rotation 1*0... 613 23:1 -889 4:1 -667 11:1 236 2:1 849 21:1 566 23:1 727 11:1 2222 7:1 1805 46:1 1165 7:1 1421 27:1 1185 8:1 1327 4:1 -101 1:1 1906 41:1 2074 12:1 .136 15:1 -.300 4:1 -.458 5:1 .022 2:1 .195 11:1 .176 24:1 .255 15:1 .636 18:1 .391 16:1 .337 12:1 .397 3:1 .381 17:1 .361 3:1 -.046 2:1 .603 32:1 .731 21:1 Odds 1*1... Odds 1*2... Odds 1*4... Odds First year after clover 1*0 . . -186 2:1 -634 2:1 356 3:1 -768 12:1 731 61:1 824 16:1 1754 51:1 1394 44:1 1334 22:1 1636 28:1 2768 45:1 2388 24:1 1879 10:1 1835 79:1 1172 10:1 2408 14:1 -.060 2:1 -.197 2:1 .181 4:1 -.354 28:1 .246 30:1 .175 3:1 .622 25:1 .496 28:1 .490 17:1 .527 48:1 .927 37:1 .680 20:1 .636 11:1 .742 124:1 .687 22:1 .955 24:1 Odds 1*1 ... Odds 1*2 .. Odds 1*4... Odds Second year after clover 1*0.. . 566 748 1808 1930 .234 .270 .673 .716 Odds 3:1 5:1 72:1 27:1 3:1 5:1 253:1 77:1 1*1... -1379 520 2667 2546 -.224 .182 .968 1.060 Odds 5:1 304:1 43:1 16:1 3:1 19:1 58:1 24:1 1*2... 424 2465 2430 2298 .229 .827 .872 1.081 Odds 4:1 46:1 14:1 18:1 5:1 48:1 9:1 29:1 1*4... 399 1884 1848 3051 .144 .740 .460 1.171 Odds 2:1 24:1 13:1 36:1 2:1 30:1 34:1 39:1 (2) Nitrogen 15 pounds per acre constant (Table 22). The trend was similar to that where 7.5 pounds of nitrogen was constant. Treatment 241 showed evidence of having passed the maximum increase in yield, and in Set 2x4, Treatment 214 gave increases only slightly less than Treatment 244. (3) Nitrogen 30 pounds per acre constant (Table 23). Phosphorus showed very little tendency to increase yields materially in combinations containing the low potash dosage (Set 4.rl), but was more effective in 304 BULLETIN No. 417 TABLE 22. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SUPERPHOSPHATE AND POTASSIUM CHLORID WITH A DOUBLE DOSAGE OF SODIUM NITRATE CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Potash series Phosphorus series 20* 21* 22* 24* 20* 21* 22* 24* Number of ears Tons marketable ears No clover in rotation 2*0.. . -192 1:1 596 3:1 188 1:1 -1044 2:1 -1152 12:1 903 6:1 1529 806:1 876 13:1 1380 29:1 1253 603:1 491 3:1 -1010 18:1 546 4:1 -229 2:1 -67 1:1 1414 74:1 -.092 2:1 .071 2:1 .039 4:1 -.399 215:1 -.359 13:1 .290 18:1 .395 59:1 .157 11:1 .467 27:1 .382 57:1 .178 4:1 -.357 17:1 .235 29:1 .005 <1:1 .062 2:1 .661 2064:1 Odds 2*1 ... Odds 2*2 . . Odds 2x4.. . Odds First year after clover 2*0... 28 <1:1 -857 31:1 -877 6:1 731 3:1 457 2:1 792 4:1 1418 14:1 1289 8:1 1540 19:1 1657 46:1 1152 19:1 667 4:1 1541 29:1 1592 22:1 1980 6:1 1346 14:1 -.032 1:1 -.264 66:1 -.302 6:1 .287 6:1 .283 4:1 .201 2:1 .565 15:1 .479 9:1 .564 17:1 .601 30:1 .527 30:1 .379 5:1 .695 25:1 .547 21:1 .735 6:1 .523 27:1 Odds 2*1... Odds 2*2 . . . Odds 2*4. . . Odds Second year after clover 2*0... -414 3:1 -591 30:1 197 1:1 550 2:1 662 4:1 838 61:1 1868 9:1 1864 41:1 1596 13:1 2030 11:1 2864 49:1 2672 56:1 2399 38:1 2784 45:1 1949 40:1 1566 48:1 -.056 2:1 -.108 12:1 .187 5:1 .216 2:1 .189 3:1 .325 34:1 .632 9:1 .624 40:1 .552 24:1 .742 13:1 1.000 46:1 .908 78:1 .912 55:1 1.027 108:1 .725 90:1 .718 46:1 Odds 2*1 ... Odds 2*2 . . . Odds 2*4. . . Odds the other two sets. It was evident that maximum increases from phos- phorus in these combinations had been passed in Treatments 442 and 444. (4) K 2 O 25 pounds per acre constant (Table 4). Phosphorus was most effective with the low nitrogen dosage (Set l;rl). In Set 2.rl the maxi- mum increase occurred with Treatment 221. Phosphorus dosages in Set 4x\ failed to give any substantial gains. (5) K 2 O 50 pounds per acre constant (Table 5). The maximum in- crease from phosphorus occurred with Treatment 122 in Set \x2. When the nitrogen dosage was doubled (Set 2x2), the maximum increase ap- 1935} FERTILIZER REQUIREMENTS OF SWEET CORN 395 TABLE 23. INCREASES IN YIELDS OF SWEET CORN DUE TO VARYING TREATMENTS OF SUPERPHOSPHATE AND POTASSIUM CHLORID WITH A QUADRUPLE DOSAGE OF SODIUM NITRATE CONSTANT (Figures indicate mean increases per acre over adjacent check plots) Potash series Phosphorus series 40x 41* 42x 44x 40* 41x 42x 44x Number of ears Tons marketable ears No clover in rotation 4*0... -666 4:1 243 9:1 1124 5:1 -902 9:1 1616 39:1 34 <1:1 364 2:1 875 3:1 2842 35:1 -236 2:1 1637 32:1 2957 >9999:1 148 1:1 1650 26:1 -6 <1:1 -909 8:1 -.278 4:1 .114 6:1 .209 14:1 -.331 25:1 .578 58:1 -.074 2:1 .051 1:1 .358 6:1 .914 66:1 -.103 2:1 .458 28:1 .804 10:1 .027 1:1 .566 74:1 .071 1:1 -.251 5:1 Odds 4x1... Odds 4x2 . . . Odds 4x4.. . Odds First year after clover 4x0... 49 1:1 1249 155:1 315 3:1 -485 4:1 1236 8:1 824 4:1 590 6:1 1132 5:1 1459 11:1 1596 10:1 1555 239:1 1676 505:1 849 5:1 1200 21:1 448 5:1 586 9:1 .028 4:1 .475 28:1 .054 2:1 -.131 3:1 .314 5:1 .342 6:1 .333 12:1 .371 4:1 .595 22:1 .550 7:1 .429 79:1 .557 495:1 .310 5:1 .544 26:1 .231 9:1 .212 6:1 Odds 4x1... Odds 4x2 . . . Odds 4x4... Odds Second year after clover 4x0... -822 5:1 768 5:1 -1450 16:1 1000 5:1 -187 2:1 1410 19:1 1076 22:1 2541 41:1 1914 26:1 1717 14:1 2263 157:1 1556 27:1 1960 3332 : 1 1636 78:1 1677 42:1 835 55:1 -.162 3:1 .295 10:1 -.405 6:1 .261 3:1 .036 8:1 .583 20:1 .294 25:1 .984 65:1 .778 72:1 .658 38:1 .881 510:1 .654 60:1 .672 2499:1 .608 158:1 .659 237:1 .427 39:1 Odds 4x1 ... Odds 4x2... Odds 4x4... Odds peared with Treatment 242. Quadrupled nitrogen dosages (Set 4x2} ma- terially reduced increases in yield, except that from Treatment 422. (6) K 2 O 100 pounds per acre constant (Table 6). Phosphorus gave successively larger increases in yield in combination with the single nitro- gen dosage (Set 1*4) until the maximum for the three sets was reached at Treatment 144. With the doubled nitrogen dosage (Set 2*4) the single dosage of phosphorus gave increases in yield practically as large as those from either of the heavier dosages. In combination with 30 pounds of 396 BULLETIN No. 417 {.July, nitrogen per acre, phosphorus in Set 4x4 gave successively larger in- creases except with Treatment 444. Second Year After Clover. (1) Nitrogen 7.5 pounds per acre constant (Table 21). Increases in yield were very large. In combination with all three potash dosages, yields measured by weights of marketable ears in- creased in relation to the dosage of phosphorus except with Treatment 124. As measured by numbers of marketable ears, the treatments giving largest increases in the respective sets were Nos. 121, 112, and 144. (2) Nitrogen 15 pounds per acre constant (Table 22). Increases were again very large, and in several cases they became successively larger an relation to the amount of phosphorus applied. Exceptions occurred in Treatments 242 and 244, in which the phosphorus dosages were evidently heavier than needed for maximum yields. (3) Nitrogen 30 pounds per acre constant (Table 23). Increases in yield became successively larger in relation to the dosage of phosphorus in Sets 4x1 and 4*2, except in the heaviest dosages (Treatments 441 and 442). In Set 4x4 the single phosphorus dosage (Treatment 414) gave the largest increase. (4) K 2 O 25 pounds per acre constant (Table 4). Phosphorus gave successively larger increases in yield with the larger dosages, except in Treatment 441. (5) K 2 O 50 pounds per acre constant (Table 5). Phosphorus gave large increases in yield, but treatments involving quadruple phosphorus dosages, when combined with double and quadruple nitrogen dosages, were evidently heavier than was necessary to give maximum increases in weights of marketable ears. On the basis of number of marketable ears, the double dosage of phosphorus gave largest increases in combinations containing nitrogen in double and quadruple amounts, but the single dosage of phosphorus gave largest increases when combined with the single dosage of nitrogen. (6) K 2 O 100 pounds per acre constant (Table 6). In Set 1*4 the heaviest phosphorus dosage gave the largest increase, but the trend was broken at Treatment 124. In Set 2*4 the maximum increase occurred with Treatment 224, and in Set 4*4 with Treatment 414. Phosphorus, in the foregoing "complete" fertilizer combinations, gave consistent increases in sweet-corn yields when used with certain dosages of nitrogen and potash, but gave erratic responses when other dosages of nitrogen and potash were used. Both with no clover in rotation and during the first and second years after clover, phosphorus gave substantial increases in yield when used with the smallest nitrogen dosage (7.5 pounds per acre). Effects of phosphorus in relation to potash in the complete fertilizers were somewhat obscured by relations between nitrogen and potash ; but, in general, in combinations contain- ing the smallest nitrogen dosage, heavy phosphorus dosages and light potash dosages, or light phosphorus dosages and heavy potash dosages resulted in increases in sweet-corn yields. 19351 FERTILIZER REQUIREMENTS OF SWEET CORN 397 Analysis of Relative Phosphorus Efficiency in Different Combinations Efficiency of Phosphorus W hen Used With Nitrogen. Analysis of the relations between nitrogen and phosphorus by means of effici- ency factors gives more specific information than does an analysis on the basis of yields alone. Both Table 24, showing the effects of nitrogen on the mean efficiency of phosphorus, and Table 25, listing the maximum percentages of increase in phosphorus efficiency, reveal TABLE 24. EFFECT OF NITROGEN ON PHOSPHORUS EFFICIENCY AS INDICATED BY SET AVERAGES BASED ON WEIGHTS OF MARKETABLE EARS 6 Set Mean phosphorus efficiency Set Mean phosphorus efficiency Set Mean phosphorus efficiency 01*. . perct. 21.48 2.7 02*. . . Perct. 18.10 2.2 04*. . . perct. 35.35 2.8 llx 26.17 3.3 12* 37.17 3.7 14* 42.07 4.1 21* 21.03 3.4 22* 29.38 3.3 24* 28.99 3.2 4lx 16.46 3.1 42* 30 40 2 9 44* 13.10 2.4 See Table 40, Appendix, for detail data. that the efficiency of phosphorus reached a maximum in combinations containing 7.5 pounds of nitrogen per acre. With respect to increased dosages of phosphorus, 128 pounds P 2 O 5 per acre proved the most efficient dosage when nitrogen was omitted ; when nitrogen was in- cluded 64 pounds P 2 O 5 per acre proved more efficient than 128 pounds in two out of three combinations. Comparison of the maximum percentage increases in yield listed in Table 26 likewise shows the dominance of 7.5 pounds nitrogen per acre, but not of 64 pounds P 2 O 5 . The combinations giving the maxi- mum increases were: Without nitrogen Treatment 044 With 7.5 pounds nitrogen Treatment 144 With 15 pounds nitrogen Treatments 212, 220, or 221 With 30 pounds nitrogen Treatment 420 The effects of phosphorus are somewhat obscured in Table 26 by the relationship existing between nitrogen and potash. The reader will note that as the nitrogen dosage increases there is a tendency for the potash requirement to decrease (see discussion of nitrogen- potash relations, pages 387 to 389). It appears also that by using the proper amount of nitrogen the maximum efficiency of phosphorus can be attained with a very much smaller dosage than otherwise. 398 BULLETIN No. 417 \_July, TABLE 25. EFFECT OF NITROGEN ON PHOSPHORUS EFFICIENCY AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN PHOS- PHORUS EFFICIENCY IN THEIR RESPECTIVE SETS" Treat- ment Phosphorus efficiency Treat- ment Phosphorus efficiency Treat- ment Phosphorus efficiency 014. . perct. 24.04 + 6.3 b 021 perct. 27.73 + 5.1 041 perct. 46 39 5.5 114 43.24 + 6.4 121 46.88 6.8 144 60.28 + 8.6 212 34.86 7 9 221 39 09 5 5 241 33 37 5 1 414 32.36 + 7.9 420 43.83 + 5.1 440 20.58 4.8 -See Table 40, Appendix, for detail data. b Treatment 010 had an efficiency of 22.63 4.8 percent. This relationship between phosphorus and nitrogen is also evident from the data presented in Table 24, according to which the greatest efficiency in each series is shown to have coincided with certain well- defined combinations, as follows: Mode of the curve Next highest Sets Efficiency compared Set factor Olx-02x-04x 04* = 35.35 2.8 Ux-I2x-I4x 14* = 42.07 4.1 21x-22*-24:r 22* = 29.38 + 3.3 41x-42x-44x 42* = 30.40 2.9 Efficiency Set factor 01* = 21.48 2.7 12* = 37.17 3.7 24x = 28.99 + 3.2 41* = 16.46 3.1 Difference 13.87 3.9 4.90 5.5 .39 4.6 13.94 + 4.2 Set 04;r is thus shown to have been significantly higher in efficiency than the next ranking set. The difference in efficiency between Sets I4x and \2x, and also between Sets 22x and 24x, was too slight to be significant. Set 42x was, however, significantly more efficient than Set 41:r. Thus Sets O4.r, \2x, 22x, and 42x were either the highest, or virtually equal to the highest, in efficiency, indicating that in no instance is it necessary to use as much phosphorus when nitrogen forms a part of the combination as when nitrogen is omitted. Data in Table 25 bear out this conclusion when subjected to the same analysis (table should be read horizontally). Treatments 041, TABLE 26. EFFECT OF NITROGEN ON PHOSPHORUS AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN WEIGHTS OF MARKETABLE EARS IN THEIR RESPECTIVE SETS Table from which data are taken Treat- ment Increase in yield Treat- ment Increase in yield Treat- ment Increase in yield 12. I 014 perct. 27 62 5.4 024 perct. 21 36 3 4 044 perct. 43 50 6 5 12, J 114 38.54 5.1 122 44 47 8 1 144 55 58 7.7 12. K 212 31.95 6.3 221 31.92 5.2* 240 29.16 4.1 12. L 414 30.12 7.0 420 38 98 4 4 441 24 94 2.7 Treatment 220 gave an increase of 31 .50 4.8 percent. 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 399 114, 212, and 414 are either the modes in each series, or not significant- ly less than the modes. Unfortunately no chemical analyses were made of the soils and plants in these investigations and, therefore, an adequate explanation of these phenomena is out of the question. There is a possibility, however, that the added sodium nitrate increased the availability of the phosphates. Wagner, 54 * Greaves, 24 * Patten, 41 * and Spurway 45 * all have shown that sodium nitrate increases the availability of certain insoluble phosphates. Breazeale, 11 * in culture solution studies with wheat seed- lings, reached the conclusion that the absorption of phosphoric acid appears to be increased slightly by sodium nitrate. Fudge 20 ' 21 * found that nitrogenous salts which leave a sodium residue increase phosphate availability considerably. Greaves and Carter 25 * and MacTaggart, 36 * on the other hand, reached conclusions which indicate that sodium nitrate has no effect on the availability of phosphates, and Marais 37 * states that Prianishnikov and other Russian workers conclude that sodium nitrate may not only be ineffective, but actually depressing to the availability of phosphorus. The contradictory nature of the above citations is perhaps due to the types of soils or culture solutions used in the various experiments. However, the important point to consider is that, whatever the reason, nitrate of soda reacted in the soils used in these experiments in a manner that would seem to indicate that it does increase the availability of phosphorus. Efficiency of Phosphorus When Used With Potassium. The ef- ficiency of phosphorus was affected also by the potash used in combi- nation with it, as shown in Tables 27, 28, and 29. Set #14 had the highest phosphorus efficiency among the sets in which the single dosage of phosphorus was constant (Sets #10, #11, #12, #14) (Table 27). Where the double dosage was constant (Sets #20, #21, #22, #24), Set #22 had the highest phosphorus efficiency, TABLE 27. EFFECT OF POTASH ON PHOSPHORUS EFFICIENCY AS INDICATED BY SET AVERAGES BASED ON WEIGHTS OF MARKETABLE EARS* Set Mean phosphorus efficiency Set Mean phosphorus efficiency Set Mean phosphorus efficiency xlO perct. 14.32 2.7 x20 perct. 27.92 25 x40 Perct. 24.18 2.8 xll 16.17 3.0 x2l 29.67 3.2 x41 33.12 3.1 xl2 24.80 3.2 x22 31 .84 3 4 x42 29.64 3.4 x!4 29.86 3.6 x24 25.64 3.1 x44 32.57 3.5 See Table 40. Appendix, for detail data. 400 BULLETIN No. 417 [/M/.V, TABLE 28. EFFECT OF POTASH ON PHOSPHORUS EFFICIENCY AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN PHOS- PHORUS EFFICIENCY IN THEIR RESPECTIVE SETS* Treat- ment Phosphorus efficiency Treat- ment Phosphorus efficiency Treat- ment Phosphorus efficiency 010. . perct. 22.63 4.8 420 . . . perct. 43 83 + 5 1 240 perct. 32 07 4 6 Oil 22.89 + 4.8 121 46.88 + 6.8 041 46 39 + 5 5 212 34.86 + 7.9 122 42 58 9 4 142 38 22 + 7 5 114 43.24 6.4 424 37 77 + 4 5 144 60 28 + 8 6 See Table 40, Appendix, for detail data. but only by a small margin. Where the quadruple dosage was constant (Sets x40, x4\, x42, *44), Set *41 had the highest efficiency. Thus the character of the three modal sets, x\4, x22, x4\ which were very nearly alike in efficiency, having factors of 29.86 3.6, 31.84 3.4, and 33.12 3.1 respectively indicates that an inverse relationship existed between phosphorus and potash. A similar relationship is shown when the maximum increases in phosphorus efficiency in relation to potash are compared (Table 28). The modes in each set were as follows: Efficiency factor Treatment 114 ........................................ 43.24 6.4 Treatment 121 ........................................ 46.88 6.8 Treatment 144 ........................................ 60.28 + 8.6 These modes do not quite agree with the modes in Table 27. The fact that Treatment 121 is higher than Treatment 122 does not in- terfere with the idea of the inverse relationship between phosphorus and potash, but Treatment 144 is clearly out of line with that theory. The only possible explanation of this apparent inconsistency seems to be that in Table 27 the group with the quadruple dosage of phosphorus constant (Sets xAQ, x4\, x42, x44) tends to be bimodal, with sets TABLE 29. EFFECT OF POTASH ON PHOSPHORUS AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN WEIGHTS OF MARKETABLE EARS IN THEIR RESPECTIVE SETS Table from which data are taken Treat- ment Increase in yield Treat- ment Increase in yield Treat- ment Increase in yield 12, E 010. . . perct. 22.63 4.8 420 perct. 38 98 4 4 140 perct. 30 12 6.1 12, B 411 16.06 5.1 121 34.47 4.7 041 37.41 4.8 12, C 112 34.73 5.3 122. 44 47 8 1 142 40 11 5.8 12, D 114 38.54 5.1 424 35.53 2.5 144 55.58 7.7 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 401 and x44 as the two modes. This might be expected inasmuch as Set x22, the mode when a double dosage of phosphorus was constant (Sets x2Q, x2\, x22, and x24}, has the same ratio of P to K as has Set #44. In Table 28, also, the sets having 128 pounds P 2 O 5 per acre constant are bimodal and Treatments 041 and 144 are the modes. If this assumption is correct, Table 28 confirms the inverse relationship between phosphorus and potash which is shown in Table 27. The data given in Table 29 on the relations between phosphorus and potash based on the maximum increases in yields are, for the most part, in agreement with the foregoing interpretation. The modes in each set were as follows: Percentage increase Treatment 114 38.54 + 5.1 Treatment 122 44.47 8.1 Treatment 144 55.58 7.7 Treatments 114 and 122 agree perfectly with what one would expect from the data in Table 27, but the uniformly upward trend (showing no tendency toward bimodality) in the last column of Table 29, with Treatment 144 as the mode, does not. This may not be of great im- portance, however, as the differences between the yields of Treatments 041 and 142 were very slight. Thus it is apparent, especially from the data presented in Table 27, that in this experiment there existed an inverse relationship between phosphorus and potash in which phosphorus maintained a fairly stable equilibrium when the dosage increased at the same time the dosage of potash decreased. Altho there is no direct evidence of this relation- ship, because of lack of chemical analyses, this action apparently indi- mates that increases in the amount of potash applied to such soils as those under test tend to make phosphorus more available, so that small quantities of phosphorus applied in combination with large quantities of potash are just as effective as large quantities of phosphorus com- bined with small quantities of potash. A tendency also existed for large quantities of both elements in combination to be slightly more efficient, as shown by Set x44 and Treatment 144. A great deal of experimental work has been done on the question of the relations between phosphorus and potash, and some of the present results sug- gest a reason for the inverse relationship which has been noted, but unfortunately they do not provide the connecting link between crop yields and chemical phenomena.. Thomson 50 * showed that the solubility of phosphoric acid from superphosphate is not affected by 1- or 2-percent solutions of potas- sium nitrate. That the effect of potassium chlorid and other salts on 402 BULLETIN No. 417 [July, the solubility of phosphorus seems to be slight was the conclusion of Greaves, 24 * but this effect varied somewhat, according to the form of phosphorus, and increased when soil was added. Patten 41 * passed weak solutions of the salts KC1, K 2 SO 4 , KNO 3 , NaNO 3 , and Na 2 CO 3 thru quartz flour, sandy soil and fine clay to all of which phosphorus had been added, and obtained an increased concentration of phosphates compared with distilled water checks. He concluded that the solubility of the phosphorus is not increased directly, but that the increase is actually due to a disturbance and rearrangement of the equilibrium between the soluble material retained by the soil and soil solution. Likewise Greaves and Carter 25 * studied the effects of KNO 3 and KC1 on the solubility of soil phosphorus, and concluded that these salts increase the water-soluble phosphorus in the soil because of their action on soil microorganisms but not because of any direct solvent action. They showed that aqueous solutions of KNO 3 and KC1 dis- solve no more phosphorus from raw rock phosphate than does dis- tilled water. In a leaching experiment with acid and alkaline sandy loams, Spurway 45 * found that NaNO 3 , NaCl, KC1, CaCO 3 , and CaSO 4 , in the order given, increased the percentage of P 2 O 5 in soil extracts. Later Spurway 46 * found that added KC1 increased the solubility of phosphorus in CaH 4 (PO 4 ) 2 , and concluded that the salts of sodium and potash seem to hold applied phosphorus in a more soluble condition. According to Hock 28 * P 2 O 5 and K 2 O salts gave higher re- coveries for both when used in combinations than when used singly. The effects are by no means the same, however, for the absorption of P 2 O 5 is influenced much more than that of K 2 O. In studies with the Neubauer test Thornton 51 * found the absorption of phosphorus to be slightly increased by applications of potash. Later, however, Thorn- ton 52 * showed that the recovery of phosphorus in Neubauer tests is con- siderably increased when potash in the form of potassium chlorid is added to different forms of phosphorus. Altho the results of some of the early percolation and leaching experiments fail to show that potash increases the availability of phos- phorus, it is evident from later work, as shown by the above review, that such must be the case. In view of the large increases in phos- phorus efficiency which have been obtained by the use of potash in the experiments herein reported, the authors conclude that this indirect action of potash may be just as important as its direct action. It may be assumed that potash exerts a very marked influence in increasing the utilization of phosphorus by the plant. 1935] FERTILIZER REQUIREMENTS OK SWEET CORN 403 Selection of Possible Optimum Ratios on Basis of Nitrogen and Phosphorus Efficiencies The foregoing analysis of the relations between phosphorus and potash will serve to elucidate the somewhat conflicting results which have been obtained with the treatments containing the three elements nitrogen, phosphorus, potassium. The fertilizer combinations most closely approaching the optimum may also be selected with consider- ably greater certainty. From the analysis of the results of side-dressing nitrogen, the re- quirements of an optimum treatment when nitrogen was used in that way were found to be: (1) not more than 7.5 pounds nitrogen per acre when nitrogen was used with phosphorus and potash; (2) 64 pounds P 2 O 5 as a supplement to 7.5 pounds nitrogen when phosphorus was used in the combination; and (3) not more than 50 pounds K 2 O as a supplement to 7.5 pounds nitrogen per acre when potash was part of the treatment. Treatments 121 and 122 fulfill these requirements from the standpoint of nitrogen efficiency. In regard to the phosphorus dosage it was shown in the foregoing discussion that phosphorus attains it greatest efficiency in combinations containing 7.5 pounds nitrogen per acre, and further that the dosage of 64 pounds of P 2 O 5 per acre is the optimum quantity to use as a basal treatment. Where nitrogen is excluded entirely, 128 pounds P 2 O 5 is more efficient than 64 pounds. Thus far, Treatments 121 and 122 fulfill all requirements perfectly for both nitrogen and phosphorus. However, the question of the relations existing between phosphorus and potash must also be considered. As stated previously, phosphorus maintains an equivalent efficiency in three combinations, namely x\4, x22, and #41 ; and x2\ is only slightly below these. The combination #14, or 114 as shown by Table 28, might be discarded perhaps, as 7.5 pounds nitrogen plus 32 pounds P 2 O 5 per acre has been shown to be much less efficient than 7.5 pounds nitrogen plus 64 pounds P 2 O 5 per acre. The #41 combination may be retained, but only as Treatment 041, since the addition of nitrogen to 128 pounds P L ,O 5 per acre results (1) in a reduction of nitrogen efficiency compared with the addition to 64 pounds P 2 O 5 (Table 14), and (2) in no more than a slight in- crease in phosphorus efficiency (Table 24). Accordingly Treatment 041 may be retained as a possible optimum treatment. Likewise Treat- ment 121 may be retained, as the phosphorus efficiency of the com- bination x2\ is almost the same as that of #22 (Table 27) and is slightly higher than Treatment 122 (Table 28). 404 BULLETIN No. 417 [/w/y, Thus Treatments 121 and 122 fulfill, so far, the requirements of an optimum fertilizer ratio. Treatment 041, altho an incomplete ferti- lizer, may be added as the most promising combination of phosphorus and potassium. EFFECTS OF POTASH The effects of potash in relation to nitrogen and phosphorus have already been discussed in some detail in the sections dealing primarily with nitrogen and phosphorus. Accordingly this section contains some duplication of former statements repeated for clarity. Tables 3 to 9 and 20 to 23, to which many references will be made, should be read vertically for potash comparisons. Potash Alone The use of potash alone as a fertilizer cannot be recommended, for there is some evidence that even small dosages act unfavorably on yields (Table 3). With no clover in the rotation, potash had virtually no effect on yields. During the first year after clover a dosage of 25 pounds K,O per acre proved ineffective, and larger applications gave small but significant increases. During the second year after clover the results were variable, with small odds, and the tendency was for potash to depress yields. The mean percentages of increase for the plots receiving potash alone, including all such plots in all positions in the rotation, show that 25 pounds K 2 O per acre gave a significant decrease in yield and 50 and 100 pounds were not effective (Section A, Tables 11 and 12). Potash Increasing, Nitrogen Constant The relations between nitrogen-potash combinations have already been discussed at considerable length from the standpoint of nitrogen (pages 387 to 389), where it was pointed out that high variation in yields from nitrogen-potash fertilizers, with potash constant and nitrogen increasing, and the obvious absence of a specific trend indicate that phosphorus was the limiting factor in the soils of these experi- ments. With no clover in the rotation the results obtained from increasing potash in relation to nitrogen were likewise highly variable and the odds of slight significance in nearly all cases (Table 3). During the first year after clover the results apparently followed no specific trend, and during the second year after clover they were extremely variable. A comparison of the mean increases from the plots receiving nitrogen-potash combinations, including all such plots in all positions 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 405 in the rotation, also shows the absence of definite tendencies (Section A, Tables 11 and 12). A single treatment, No. 401, shows a definite and significant increase, which can hardly be accidental because the yields from four plots in as many fields over a period of six years are involved. Potash Increasing, Phosphorus Constant Phosphorus-potash fertilizer combinations with potash constant and phosphorus increasing were discussed above (pages 391-392) from the viewpoint of phosphorus, and substantial increases in yield and a certain inverse relationship between phosphorus and potash were pointed out. Likewise, in the phosphorus-potash combinations with potash in- creasing and phosphorus constant, definite increases were obtained, and the effectiveness of potash was apparently determined by the quantity of phosphorus used (Table 20). Where no clover was in- cluded in the rotation, the maximum increases in yield in each set were gained with Treatments 012, 021, and 041 respectively. This resembles the order 014, 022, and 041 in which one would expect to find maxi- mum increases, according to the inverse relationship apparently exist- ing between phosphorus and potash. During the first year after clover potash gave no definite response in combination with low phosphorus applications. The modal treatments in each combination were Treat- ments 010, 022, and 042. During the second year after clover the modes were Treatments 014, 024 and 044. It is quite evident that in the second year after clover there was a tendency for yields to increase directly in relation to the quantity of potash applied. The mean increases from the plots receiving the phosphorus-potash combinations, including all such plots in all positions in the rotation, show that the modal treatments were Treatments 014, 022, and 044 when yields were measured in terms of numbers of marketable ears (Section I of Table 11), and Treatments 014, 024, and 044 when yields were measured in terms of weights of marketable ears (Section I, Table 12). There is thus, according to these data, a fairly consistent tendency for the yields to increase directly in relation to increases in the applications of potash when used with phosphorus and without nitrogen. Potash Increasing, Nitrogen and Phosphorus Constant The fertilizer combinations discussed under this heading are com- plete analyses having different constants of nitrogen and phosphorus with potash varying. Sixteen treatment combinations are involved at each position in the rotation. 406 BULLETIN No. 417 No Clover in Rotation. (1) Nitrogen 7.5 pounds per acre constant (Table 21). In combinations containing single dosages of nitrogen and phosphorus (Set \\x), Treatment 114, in accordance with expectation, gave the largest increase in yield. In Set \2x Treatment 120 gave the largest increase in number of ears and ranked only slightly below Treat- ment 122 with respect to weight of increase. Treatment 144 gave the largest increase in Set 14*. (2) Nitrogen 15 pounds per acre constant (Table 22). Treatment 212 gave the maximum increase in Set 2\x. Potash gave decreasing responses in Set 22*. In Set 24* only Treatment 244, containing the heaviest potash dosage, gave an increase over Treatment 240, containing no potash. (3) Nitrogen 30 pounds per acre constant (Table 23). In Set 41* the treatment containing no potash (No. 410) gave the best results. This was also true in Set 42*, except that Treatment 424 gave a very small increase in number of ears over Treatment 420. In Set 44* Treatment 441 gave much the largest increase in yield. (4) P 2 O 5 32 pounds per acre constant (Table 7). Maximum increases in the three sets of treatments occurred with Treatments 114, 212, 410. (5) P 2 O 3 64 pounds per acre constant (Table 8). Excepting one very insignificant increase (weight of ears, Treatment 122), potash did not have any appreciable effect. (6) P 2 O 5 128 pounds per acre constant (Table 9). Maximum increases occurred with Treatments 144, 244, and 441. First Year After Clover. (1) Nitrogen 7.5 pounds per acre constant (Table 21). Maximum increases in the three sets occurred with Treat- ments 112, 122, 144. Set 14* showed evidence of bimodality, with Treat- ments 141 and 144 as the modes. Bimodality would be expected from the results already discussed. (2) Nitrogen 15 pounds per acre constant (Table 22). The modal treatments were Nos. 212, 221, 242. Only in ear weight in Set 24* was there any evidence of bimodality (Treatments 240 and 242). (3) Nitrogen 30 pounds per acre constant (Table 23). The modal treat- ments, measured by increases in ear weights, were Nos. 414, 420, 441. Measured by increases in number of ears, Treatments 410, 424, 441 ranked as the modes. The increases due to potash were in general rather small. (4) P 2 O 5 32 pounds per acre constant (Table 7). The modes of the three sets were Treatments 112, 212, and 414 with respect to ear weight, and Treatments 112, 212, and 410 in number of ears. (5) P 2 O 5 64 pounds per acre constant (Table 8). The modes with re- spect to ear weight were Treatments 122, 221, and 420. For number of ears they were Treatments 122, 221, and 424. (6) P 2 O, 128 pounds per acre constant (Table 9). The modes were Treatments 144, 242, and 441 for both number and weight of marketable ears. Second Year After Clover. (1) Nitrogen 7.5 pounds per acre constant (Table 21). The modes were Treatments 112, 121, and 144. With respect to number of ears there was evidence of bimodality in Set 14*, Treatments 141 and 144 being the modes; but in weight of ears, Treatment 142 was very slightly higher than Treatment 141. 79J5] FERTILIZER REQUIREMENTS OF SWEET CORN 407 (2) Nitrogen 15 pounds per acre constant (Table 22). In these three sets the modal treatments were Nos. 212, 222, and 241. There was no evidence of bimodality with high phosphorus dosage constant (Set 24.r). (3) Nitrogen 30 pounds per acre constant (Table 23). The three modes were Treatments 414, 422, 440 both for number and weight of marketable ears. Potash had a slight negative effect upon yields in Set 44x. (4) P 2 O 5 32 pounds per acre constant (Table 7). The modal treat- ments were Nos. 112, 212, and 414. All of these showed very large in- creases due to potash. (5) P 2 O 5 64 pounds per acre constant (Table 8). The modes were Treatments 121, 222, and 422 for both number and weight of marketable ears. (6) P 2 O 5 128 pounds per acre constant (Table 9). The modes of the three sets were Treatments 144, 241, and 440. Treatment 141 was almost as high as Treatment 144. In fact, potash showed only very small increases in yield as the dosages reach 50 and 100 pounds K 2 O per acre. In the foregoing "complete" fertilizers the action of potash was apparently affected by both nitrogen and phosphorus, and did not give the same results as in phosphorus-potash combinations. In general, inverse relationships were apparent between potash and nitrogen and between potash and phosphorus. Analysis of Relative Potash Efficiency in Different Combinations Efficiency of Potash When Used With Nitrogen. The effect of nitrogen on the efficiency of potash is shown in Tables 30, 31, and 32. All of the efficiency factors in Table 30 are low and, with the exception of those for Sets 1x2, 0x4, and 1x4, they are very low indeed. The only significant factor is that for the set having no nitrogen dosage (0*4). In fact, the only definite trend developing from the data presented in Table 30 does not concern potash-nitrogen relations at all, but is the increase in efficiency in Sets 0*1, 0x2, and 0x4, indicating that in phosphorus-potash mixtures the efficiency of potash increases in TABLE 30. EFFECT OF NITROGEN ON POTASH EFFICIENCY AS INDICATED BY SET AVERAGES BASED ON WEIGHTS OF MARKETABLE EARS" Mean Mean Mean Set potash Set potash Set potash efficiency efficiency efficiency perct. Perct. perct. Oxl. . 2.25 2.6 0x2 5 83 2 7 0x4 10 99 2 9 1x1 -3.32 3.5 1x2 11.00 3.8 1x4 10.84 3.6 2x1 .67 3.1 2x2 5.48 3.5 2x4 2.87 3.4 4x1 4.04 3.2 4x2 -2.59 2.7 4x4 1.16 3.0 See Table 40. Appendix, for detail data. 408 BULLETIN No. 417 {.July, TABLE 31. EFFECT OF NITROGEN ON POTASH EFFICIENCY AS INDICATED BY TREAT- MENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN POTASH EFFICIENCY IN THEIR RESPECTIVE SETS" Treat- ment Potash efficiency Treat- ment Potash efficiency Treat- ment Potash efficiency 041. . perct. 17.96 6.2 042 perct. 17.83 6.0 044 perct. 24.05 7.6 121 5.54 6.1 112 22.11 5.9 114 25.92 5.8 211 9 49 7 4 212 26 99 8 4 214 20.14 7.6 401 22.23 4.2 402 1.84 5.0 414 15.31 8.5 See Table 40, Appendix, for detail data. relation to the dosage. When nitrogen was increased with potash held constant (Table 30), the maximum efficiencies occurred in Sets 4x1, \x2, and 0*4, respectively, in the three groups being considered. This apparently indicates an inverse relationship between nitrogen and pot- ash, which is confirmed by similar modes in Table 31. But the maxi- mum increases in yield shown in Table 35 do not confirm this interpre- tation, for here yield and efficiency analyses do not coincide. This discrepancy was not entirely unexpected, because in dealing with yields alone, the influence of single elements cannot be segregated, and the weaker relations between nitrogen and potash may be entirely masked by the stronger relations between nitrogen and phosphorus. This tendency toward an inverse relationship between nitrogen and potash is brought out in the following comparison of maximum nitrogen and potash efficiencies: Maximum nitrogen efficiency (percentage) (Set averages from Table 17) Set 1x2 11.44 3.7 Set 2x0 2. 65 2. 7 Set 4x2.. 5.28 + 2.7 (Modes from Table 18) Treatment 122 25.95 9.3 Treatment 220 21.48 + 5.5 Treatment 420. . . 28.96 5.2 Maximum potash efficiency (percentage) (Set averages from Table 30) Set 0x4 10.99 + 2.9 Set 1x2 11.00 3.8 Set 4x1 4. 04 3. 2 (Modes from Table 31) Treatment 114 25.92 + 5.8 Treatment 212 26.99 + 8.4 Treatment 401 22.23 4.2 The average nitrogen efficiencies in Sets 2*0 and 4*2 are too small to warrant any comments. In Treatments 122, 220, and 420, however, the nitrogen efficiency remains fairly constant, and it should be noted that as nitrogen dosages increase potash dosages are reduced or elimi- nated, with the efficiencies remaining nearly constant. Similarly, in Treatments 114, 212, and 401 the potash efficiency remains fairly con- stant only when the nitrogen and potash dosages are in inverse relation. These data have been checked by calculating the factors for green 79J5] FERTILIZER REQUIREMENTS OF SWEET CORN 409 TABLE 32. EFFECT OF NITROGEN ON POTASH AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN WEIGHTS OF MARKETABLE EARS IN THEIR RESPECTIVE SETS Table from which data are taken Treat- ment Increase in yield Treat- ment Increase in yield Treat- ment Increase in yield 12,1 041. . perct. 37.41 4.8 042 perct. 37.28 4.5 044 Perct. 43.50 6.5 12. J 121 34 47 4 7 122 44 47 8 1 144 55 58 -t 7 7 12. K 221 31.92 5.2 212 31.95 6.3 244 27.27 3.1 12, L 441 24.94 2.7 422 32.04 3.2 424 35.53 2.5 fodder. On the green fodder basis the agreement between nitrogen and potash efficiency is much better defined than it is when based on marketable ears. The inverse relationship between nitrogen and potash is of great importance in determining optimum fertilizer ratios. Owing to the lack of chemical analyses in these experiments, the exact meaning of such an inverse relationship can only be inferred. 'Chemical studies bearing upon this problem have, however, been made by a number of other investigators. Huston 32 * stated that the sodium in 100 pounds sodium nitrate is capable of releasing 55 pounds of potash from zeolites, and Andre 1 * concluded that sodium nitrate in addition to furnishing available nitro- gen is valuable because it sets potassium free. Spurway, 45 * however, found that sodium nitrate is one of a number of salts which have a tendency to depress the solubility of potash. Hoagland and Davis 27 * explained the relations between sodium and potassium by suggesting that cations may be interrelated in the process of plant absorption. A relatively high concentration of Na ions may depress the absorption of K or Ca ions. Anions they found may show similar relations, as in Nitella the rate of penetration of NO 3 ions into the cell sap is significantly depressed by the presence of Cl ions in the solution. Thus present opinion, as represented by these citations, apparently supports the idea that sodium nitrate in large amounts does not in- crease but actually depresses the availability of potash, probably because of the Na ions present from added NaNO 3> but that, on the other hand, when KC1 is added, the absorption of NO 3 is retarded by the Cl ions. Greaves, Carter, and Goldthorpe 26 * have investigated the problem of nitrogen-potassium relations from the viewpoint of the soil biologist and have shown that sodium nitrate fails to stimulate nitrification but 410 BULLETIN No. 417 {.July, that potash used in the form of KNO 3 and KG acts as a stimulant. Stimulation occurs only in certain concentrations which, if exceeded, increase very rapidly into toxicity. In work with culture solutions Breazeale 10 * found that wheat seed- lings demand more potash when nitrogen is omitted. On the other hand, he found 11 * in later work that nitrogen absorption from sodium nitrate by wheat seedlings is not affected by potassium sulfate, sodium phosphate, or calcium sulfate. He found, also, that the absorption of potash from the nutrient solution increases when salts containing plant foods are added, and that this is more marked with salts containing nitrates than with others. Breazeale 11 * apparently reached conclusions somewhat different from those of Hoagland and Davis, 27 * who state that Cl anions which are added in potassium chlorid depress in turn the absorption of NO 3 . This difference in conclusions may be due to the fact that Breazeale used potassium sulfate instead of the chlorid. Another aspect of the relations between potash and nitrogen is presented by Janssen and Bartholomew, 33 * who, in work with tomatoes, found that the percentage of water-soluble and total nitrogen was greater in plants receiving low potash than in those treated with high potash. A high percentage of potash seems to be correlated with a low percentage of nitrogen in fertilizer ratios when the former element is present in the soil in amounts insufficient for normal growth. In later work Janssen and Bartholomew 34 * showed that there is more succulence in plants receiving high than in those receiving low potash, but that the dry weight decreases in relation to increases of potash. Clements 14 * in working with Scotch Beauty field peas concluded that total carbohydrates are most abundant where plants are grown in solutions containing the highest percentage of nitrates. In contrast, the highest percentages of organic nitrogen are found where the highest application of potash is used. The best plants, according to Clements are found between the two extremes. Thus it is evident from these citations, as well as from the data collected in the experiments reported herein, that the relations existing between potash and nitrogen are complex in nature. In the selection of optimum ratios in complete fertilizers it is apparently more diffi- cult to choose among various potash-nitrogen combinations than among either potash-phosphorus or phosphorus-nitrogen combinations. Efficiency of Potash When Used With Phosphorus. Phosphorus also exerts a considerable influence on potash, as shown by the data in Tables 33, 34, and 35. Potash and phosphorus, as indicated in the preceding discussion 1935] FERTILIZER REQUIREMENTS OF SWEET COKN 411 TABLE 33. EFFECT OF PHOSPHORUS ON POTASH EFFICIENCY AS INDICATED BY SET AVERAGES BASED ON WEIGHTS OF MARKETABLE EARS" Set Mean potash efficiency Set Mean potash efficiency Set Mean potash efficiency xOl perct. 2.23 2.5 x02 perct. .04 3.1 x04 Perct. 1.05 2.6 xll - .38 3.2 xl2 10.45 3.4 xl4 16.59 3.7 X 2\ .48 3.4 X 22 3.88 3.4 *24 1.23 3.0 *41 6.71 3.3 *42 5.43 3.6 x44 9.44 3.6 See Table 40, Appendix, for detail data. of phosphorus efficiency (pages 397 to 402), are in inverse relationship with each other. This inverse relationship is, to a limited extent, evident from the data presented in Table 33, in which the maximum efficiencies for each potash constant are those for Sets #41, x\2, and #14. Of these, only that for Set #14 is statistically significant. There is a tendency, however, for high potash and low phosphorus or, in- versely, high phosphorus and low potash, to be associated in the modal treatments. According to the data presented in Table 34, the maximum in- creases in potash efficiency for the respective potash constants occurred with Treatments 041, 212, and 114 if Treatment 401 is excluded because it contains no phosphorus. These phosphorus-potash combi- nations are the same as those that exhibited maximum potash efficien- cies in Table 33. The maximum percentage increases in yields for the respective potash constants (Table 35) occurred with Treatments 041, 122, and 144; and assuming Treatment 144 to be one mode in a bimodal curve, as in the previous discussion, Treatment 114 would be the other mode. Again the data point to an inverse relationship between phosphorus and potash. Altho, as previously stated (page 401), these phosphorus-potash re- TABLE 34. EFFECT OF PHOSPHORUS ON POTASH EFFICIENCY AS INDICATED TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN POTASH EFFICIENCY IN THEIR RESPECTIVE SETS' BY Treat- ment Potash efficiency Treat- ment Potash efficiency Treat- ment Potash efficiency 401. perct. 22.23 4.2 402 perct. 1.84 5.0 204 perct. 8.23 6.3 211 9 49 7 4 212 26.99 8.4 114 25.92 5.8 021 8.73 5.1 122 15.54 9.0 024 11.34 4.3 041 17 96 6 2 042 17 83 6.0 144 25.46 9.8 See Table 40, Appendix, for detail data. 412 BULLETIN No. 417 TABLE 35. EFFECT OF PHOSPHORUS ON POTASH AS INDICATED BY TREATMENTS THAT GAVE MAXIMUM PERCENTAGE INCREASES IN WEIGHTS OF MARKETABLE EARS IN THEIR RESPECTIVE SETS Table from which data are taken Treat- ment Increase in yield Treat- ment Increase in yield Treat- ment Increase in yield 12. A 401 perct. 17.38 3.3 102 ... perct. 1 . 89 4.7 204 perct. 5.32 5.9 12, F 411 16.06 5.1 112 34.73 5.3 114 38.54 5.1 12, G 121 34 47 4 7 122 44.47 81 424. 35.53 + 2.5 12, H 041 37.41 4.8 142 ... 40.11 5.8 144 55.58 7.7 actions cannot be explained absolutely, because no chemical analyses are available, it is quite probable that the inverse relationship that ap- pears to exist is a result of changes in the availability of soil potash in the presence of phosphorus. Current opinions of soil chemists on the interactions of phosphorus and potash, however, are far from agreement. Among those who hold in general that phosphorus does not increase the availability of potassium are Tressler and Spurway. Tressler, 53 * who worked with Dunkirk silt loam, found that additions of di- and tri-calcium phosphate had no effect on the availability of soil potash, that monocalcium phosphate, on the other hand, had a negative effect, but that calcium sulfate liberated potash in appreciable quantities. Since superphosphate contains all three forms of calcium phosphate as well as calcium sulfate, it might be assumed that the latter salt was entirely responsible for the action observed. Spurway 45 * went further still against the belief that phosphorus liberates soil potash when he observed that not only monocalcium phosphate, but tricalcium phosphate and even superphosphate itself depressed the solubility of potassium in the soil. Thornton, 51 * however, obtained merely neutral results. By means of the Neubauer test he found that potash absorption was not affected by any concentration of phosphorus used in his experiments. Opposed to these conclusions are the findings of a number of other investigators. Huston 32 * stated that the calcium sulfate in 100 pounds of ordinary superphosphate is capable of releasing 18 pounds of potash. Curry and Smith 17 * observed that superphosphate in contact with five different soil types liberated considerable quantities of potassium, and they believed that similar reactions occur in the field. Emerson and Barton 19 * found that the solubility of soil potassium, as indicated by its recovery from plants, was increased by superphosphate, manure, and combinations of both. Hock 28 * found that combinations of phosphorus and potash salts increased their mutual recovery as compared with 1935~\ FERTILIZER REQUIREMENTS OF SWEET CORN 413 recovery of each when applied singly, but that, in the combination, the absorption of P 2 O 5 appeared to be affected much more than that of K 2 O. Neubauer, Bonewitz, and Schottmuller, 40 * using the Neu- bauer test on different soil types, found an apparent increase in potash absorption by plants following the use of stall manure, basic slag, and superphosphate. This increased absorption by the plants was actually due to the increased availability of soil potash. Superphosphate ap- parently decreased the absorption of potash by soil. Dreyspring and Heinrich, 18 * also using the Neubauer method, found that the solubility of soil potash was increased by applications of superphosphate and Thomas slag. They believed that this activation of potassium was due to free H S PO 4 and CaH 4 (PO 4 ) 2 . They acknowledged, however, that calcium sulfate may also have had some effect. Since phosphoric acid in applied fertilizers seems capable of increasing the root-solubility of soil potassium, they assumed that, conversely, the potash in fertilizers can also activate the phosphoric acid in the soil. In conclusion they stated that phosphoric acid will increase the absorption of potash from fertilizers as well as from the soil, and that added potash may increase the absorption of both added and soil phosphoric acid. It will be observed that Dreyspring and Heinrich agree with Neu- bauer et al, but reach conclusions which are quite different from those of Thornton. In general, opinion on this subject is very much divided. It is quite possible that the conflict in results obtained might be trace- able to the different soils which were used by the various investiga- tors. Apparently, as indicated by the greater efficiency of potash in certain potash-phosphorus combinations used in these experiments, the responses of the Illinois soils tested here are such that potash availability is increased to some extent by the addition of phosphorus. Selection of Possible Optimum Ratios on Basis of Potash Efficiency Upon a basis of nitrogen and phosphorus efficiencies Treatments 041, 121, and 122 survived (page 403), as apparently fulfilling the requirements of optimum treatments for sweet corn on the soils used in these experiments. Upon the basis of potash efficiency, however, these treatments were not particularly outstanding. Of course it must be remembered that the mean efficiency of potash in relation to nitro- gen (Table 30) was relatively low in all types of combinations. Treat- ments \x2, 0;r4, and 1*4 were the highest in potash efficiency, but only Treatment 0x4 has an efficiency factor more than 3.2 times its probable error. Treatments of the Qx\ and \x\ types fluctuate around 414 BULLETIN No. 417 [July, zero in potash efficiency. Treatment 041 has a potash efficiency in relation to nitrogen of 17.96 6.2 (Table 31), Treatment 121 an efficiency of 5.54 6.1, but Treatment 122 does not appear. A point of considerable interest is the high potash efficiency of Treatment 114, which is 25.92 5.8. When the effect of phosphorus on mean potash efficiency is ex- amined (Table 33) Set #14, with an average factor of 16.59 3.7, is the only one that proves statistically significant. Treatments 041, 121, and 122 can scarcely be eliminated because of their low potash efficiency, however, since this condition seems to be the rule in all types of treatments except x\4. Since Treatment 114 has a high indi- vidual potash efficiency, 25.92 5.8 (Table 31), it is added to the list of tentative optimum treatments, the discussion of which will be resumed later (page 419). INFLUENCE OF FERTILIZERS ON MATURITY From the standpoint of the crop, commercial fertilizers are used for two purposes to increase the total yield and to advance maturity. A great deal of experimental work has been conducted on fertilizers and their effects on maturity. The literature reporting this work need not be reviewed here, because the results of the experiments under discussion do not differ materially from expectation. According to Russell 42 * nitrogenous nutrients affect the Vegetative growth and, if present in excessive amounts, retard ripening. Phosphorus, on the other hand, promotes growth of the roots during the early life of the plant, but later on it hastens the ripening process. Potash exerts an influence on the vigor and general health of the plant ; it is intimately connected with photosynthesis and translocation of carbohydrates ; and it influences the formation and especially the weight of grain. Potas- sium-starved plants are not only stunted in growth in the same way that plants are that lack nitrogen and phosphorus, but they may even fail to reach maturity. Beyond this, potash seems to have little effect on maturity. The data on soil treatments in relation to maturity have been sum- marized briefly in Table 36. Quantities therein represent the mean number of days required for sweet corn on each treated plot to reach 75 percent of full silking compared with the respective adjacent checks. Negative quantities indicate that the sweet corn receiving the treat- ment matured earlier than the check, and positive quantities, later. The value of silk counts as an index of maturity has already been pointed out (page 356). J9J5] FERTILIZER REQUIREMENTS OF SWEET CORN 415 TABLE 36. EFFECT OF SOIL TREATMENTS ON MATURITY AS INDICATED BY NUMBER OF DAYS SILKING WAS RETARDED" OR ADVANCED IN COMPARISON WITH THE RESPECTIVE CHECKS (Negative numbers indicate days earlier than adjacent checks; positive numbers indicate days later than adjacent checks.) NITROGEN SERIES Potash increasing* (A) Nitrogen increasing Phosphorus increasing* (B) Nitrogen increasing 00* 10* 20* 40* 0*1 1*1 2*1 4*1 *00 .08 2.00 - .33 1.25 2.08 1.33 1.67 - .25 .08 - .83 .58 1.33 *01 2.25 - .67 -3.33 -5.33 2.00 - .83 -4.67 -4.42 1.33 - .83 -3.67 -4.25 - .83 -2.67 -1.92 -3.25 xOl 2.25 .33 .92 jell *02 x21 x04 *41 Phosphorus increasing (C) Nitrogen increasing Phosphorus increasing (D) Nitrogen increasing 0*2 1*2 2*2 4*2 0*4 1*4 2*4 4*4 x02... .33 -2.25 -2.41 -5.08 - .33 -2.92 -3.67 -4.92 1.67 -1.92 -4.08 -2.50 .58 -1.58 -2.83 .33 *04 .92 -3.58 -3.17 -5.00 1.25 -3.92 -3.50 -5.17 - .25 - .75 -2.73 -3.33 1.33 -3.17 -3.75 .67 xl2 x22 *14 *24 x42 *44 Phosphorus increasing (E) Nitrogen increasing Potash increasing (F) Nitrogen increasing 0*0 1*0 2*0 4*0 01* 11* 21* 41* 00 .08 -1.08 -3.50 -4.92 2.08 .42 -2.67 -4.45 .08 -1.17 -4.33 -3.17 xlO -2.92 - .67 -2.25 -3.58 -1.08 - .83 -2.92 -3.92 .42 - .83 -1.92 - .75 -1.17 -2.67 -1.58 -3.17 *10 -2.92 -1.67 -2.33 *11 *20 *12 *40 *14 Potash increasing (G) Nitrogen increasing Potash increasing (H) Nitrogen increasing 02* 12* 22* 42* 04* 14* 24* 44x x20... -1.67 -3.33 -2.41 -3.17 -3.50 -4.67 -3.67 -3.50 -2.67 -3.67 -4.08 -2.73 -4.33 -1.92 -2.83 -3.75 *40 -2.33 -5.33 -5.08 -5.00 -4.92 -4.42 -4.92 -5.17 -4.45 -4.25 -2.50 -3.33 -3.17 -3.25 .33 .67 x2l *41 x22 *42 x24 *44 PHOSPHORUS SERIES Potash increasing (I) Phosphorus increasing Potash increasing (J) Phosphorus increasing 00* 01* 02* 04* lOx 11* 12* 14* 0*0... -2.92 - .67 -2.25 -3.58 -1.67 -3.33 -2.41 -3.17 -2.33 -5.33 -5.08 -5.00 1*0 .08 2.00 - .33 1.25 -1.08 - .83 -2.92 -3.92 -3.50 -4.67 -3.67 -3.50 -4.92 -4.42 -4.92 -5.17 0*1 . 2.25 .33 .92 1x1 0x2 0x4 1x2 1x4 Potash increasing (K) Phosphorus increasing Potash increasing (L) Phosphorus increasing 20* 21* 22* 24* 40* 41* 42* 44* 2*0 . 2.08 1.33 1.67 - .25 .42 - .83 -1.92 - .75 -2.67 -3.67 -4.08 -2.73 -4.45 -4.25 -2.50 -3.33 4x0 .08 - .83 .58 1.33 -1.17 -2.67 -1.58 -3.17 -4.33 -1.92 -2.83 -3.75 -3.17 -3.25 .33 .67 2x1 4x1 . . . 2x2 . . . 4x2 2x4 4x4 The sections in this table may be read either vertically or horizontally. Read either way, treatment code numbers are obtained by replacing the symbol for the changing dosage (*) by the corresponding figure in the code designation at the top of the columns or in the column at the left. 416 BULLETIN No. 417 [July, NITROGEN IN RELATION TO MATURITY Nitrogen Alone. Increasing the nitrate dosages did not seem to affect maturity materially, altho there was a tendency for it to retard ripening (Section A, Table 36). Nitrogen Varying, Phosphorus Constant. Increasing the amounts of nitrate in combination with a single dosage of phosphorus (Set .#10) seemed to retard maturity slightly (Section E, Table 36). On the other hand, nitrate seemed to hasten maturity when used in combi- nation with 64 or 128 pounds P 2 O 5 per acre. Nitrogen Varying, Potash Constant. With the single potash dosage constant, increasing dosages of nitrate appeared to hasten maturity slightly (Set .#01), but with heavier dosages of potash constant, nitrate gave variable results (Section A, Table 36). Nitrogen Varying, Phosphorus and Potash Constant. (1) K 2 O 25 pounds per acre constant (Section B, Table 36). In Set .#11 there was a very slight tendency for nitrate to hasten maturity. With in- creased phosphorus (Sets .#21 and .#41), nitrate in the heavier dosages exercised a slightly retarding effect. (2) K 2 O 50 pounds per acre constant (Section C, Table 36). In the set containing the low phosphorus dosage (.#12) nitrate had a slightly retarding effect, which became more pronounced in Set #42. With 64 pounds of phosphorus per acre (Set .#22) nitrate had a tendency to hasten maturity. (3) K 2 O 100 pounds per acre constant (Section D, Table 36). Nitrate appeared relatively ineffective with dosages of 32 and 64 pounds phosphorus per acre constant, but had a retarding effect with the quadrupled dosage of phosphorus constant. (4) P 2 O 5 32 pounds per acre constant (Section F, Table 36). Apparently nitrate in these combinations was not particularly effective in influencing maturity. In Set #11 nitrate hastened maturity to some extent, but in Sets x\2 and #14 it appeared to retard ripening slightly. (5) P 2 O 5 64 pounds per acre constant (Section G, Table 36). In Set x2\ a single dosage of nitrate promoted maturity by more than a day, and in Set x22 the double dosage of nitrate was most effective. In Set #24, however, the high potash dosage appeared to prevent nitrate from being particularly effective. (6) P 2 O 5 128 pounds per acre constant (Section H, Table 36). With the high phosphorus dosage constant, nitrate in all dosages exercised a definite retarding effect upon maturity. 19351 FERTILIZER REQUIREMENTS OF SWEET CORN 417 PHOSPHORUS IN RELATION TO MATURITY Phosphorus Alone. The lowest dosage appeared to be just as efficacious as the highest in hastening maturity (Section I, Table 36). Phosphorus Varying, Potash Constant. Added increments of phosphorus exerted a very strong effect upon maturity irrespective of the potash in the combination (Section I, Table 36). The heaviest phosphorus treatments advanced maturity very considerably. Phosphorus Varying, Nitrogen Constant. Increasing phosphorus in relation to the three nitrogen constants hastened maturity greatly ( Section E, Table 36). Phosphorus Varying, Nitrogen and Potash Constant. (1) Nitro- gen 7.5 pounds per acre constant (Section J, Table 36). Phosphorus exerted a very strong effect toward earlier maturity regardless of the potash constant. (2) Nitrogen 15 pounds per acre constant (Section K, Table 36). The effects were similar to those obtained when 7.5 pounds nitrogen per acre were constant. (3) Nitrogen 30 pounds per acre constant (Section L, Table 36). With high nitrogen and low potash constant, phosphorus, in increas- ing dosages, hastened maturity, but with the double dosage of potash constant, the heaviest phosphorus dosage retarded maturity slightly. The same was true with quadruple potash constant. (4) K 2 O 25 pounds per acre constant (Section B, Table 36). With low potash, increasing the phosphorus dosage hastened maturity regardless of the amount of nitrogen used. (5) K 2 O 50 pounds per acre constant (Section C, Table 36). With double potash and low nitrogen constant, maturity was advanced as phosphorus increased (Set \x2), but in Set 2:r2 the earliest ma- turity occurred with Treatment 222. In Set 4x2 maturity was pro- gressively earlier only as far as Treatment 422. (6) K 2 O 100 pounds per acre constant (Section D, Table 36). In Set 1x4 maturity became progressively earlier in relation to the amount of phosphorus. This also occurred in Set 2x4 but maturity was not advanced so greatly. In Set 4*4 Treatment 424 gave the earliest maturity, but Treatment 444 definitely retarded it. POTASH IN RELATION TO MATURITY Potash Alone. The low potash treatment retarded maturity more than two days, but with increasing dosages this retarding effect was not so marked (Section A, Table 36). 418 BULLETIN No. 417 [July, Potash Varying, Nitrogen Constant. Maturity was definitely de- layed by most of these treatments (Section A, Table 36). There was, however, no definite trend. Potash Varying, Phosphorus Constant. In Set 01* Treatment 014, having the heaviest potash dosage, was the only one giving earlier maturity than Treatment 010 (Section I, Table 36). In Set 02* the treatment containing the single dosage of potash was more effective than the others. The same occurred in Set 04*. Potash Varying, Nitrogen and Phosphorus Constant. (1) Nitro- gen 7.5 pounds per acre constant (Section J, Table 36). Increasing dosages of potash were to some extent effective in promoting maturity. (2) Nitrogen 15 pounds per acre constant (Section K, Table 36). In Set 21* potash advanced maturity progressively up to Treatment 212, and in Set 22* as far as Treatment 222. In Set 24* potash re- tarded maturity slightly compared with Treatment 240. (3) Nitrogen 30 pounds per acre constant (Section L, Table 36). Potash advanced maturity in Set 41*, but was ineffective in Set 42*. In Set 44* all dosages of potash except the smallest (Treatment 441) retarded maturity. (4) P 2 O 5 32 pounds per acre constant (Section F, Table 36). With low phosphorus, potash advanced maturity progressively in Set 11*, but in Set 21* Treatment 212 hastened ripening most. In Set 41* potash affected maturity more strongly, the high treatment hastening maturity considerably. (5) P 2 O 5 64 pounds per acre constant (Section G, Table 36). In Set 12* Treatment 121 advanced maturity most, while in Set 22* Treatment 222 was best. Potash was not effective in Set 42*. (6) P 2 O 5 128 pounds per acre constant (Section H, Table 36). Potash exerted a very slight effect in Set 14*, and in Set 24* there was some retardation due to potash. However, in Set 44* potash re- tarded maturity very definitely, when applied in the higher dosages. DISCUSSION OF INFLUENCE OF FERTILIZERS ON MATURITY Nitrate of soda was not at all consistent in its influence on the maturity of sweet corn. Nitrate alone had virtually no effect, but in combination with sufficient phosphorus, it hastened maturity. Added in increasing amounts to various potash constants, it hastened maturity slightly when a single dosage of potash was held constant, but gave variable results with heavier dosages of potash. In complete fertilizers the influence of nitrate was determined to a large extent by the nature 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 419 of the combination. In general, nitrate was least effective in combi- nations with quadruple phosphorus and quadruple potash dosages. Of the three fertilizer components, phosphorus had the most distinct effect on maturity. The results were similar to those obtained by Buie, Currin, Kyzer, and Warner 12 * with cotton. Used alone, in combination with potash, or in combination with nitrogen, phosphorus hastened maturity considerably. In complete fertilizers, phosphorus advanced maturity rather consistently, except where quadruple dosages were used with the heavier dosages of nitrogen and potash. Maturity was retarded by potash used alone or in combination with nitrogen, but was advanced apparently by the single dosage of potash combined with double or quadruple dosages of phosphorus. In com- plete fertilizers, potash hastened maturity only in certain combinations ; as the constants of nitrogen increased, potash was effective only where low phosphorus entered into the combination. Fertilizers containing both quadruple nitrogen and quadruple phosphorus dosages retarded maturity progressively with increased dosages of potash. On the other hand, in combinations containing quadruple nitrogen and single phos- phorus, potash effectively advanced maturity. In general, potash used in complete fertilizers had an uneven effect on maturity. SELECTION OF OPTIMUM TREATMENT At the outset of this study the authors held the opinion that sweet corn is rather critical in its plant- food requirements, and that it re- sponds well to fertilizers only when the proper ratios of nitrogen, phosphorus and potash are applied. That this assumption was correct has been shown repeatedly by the large increases in yield secured in these experiments when certain combinations of the nutrient elements were used, and failure to secure significant increases or even any increases at all when other combinations were used. Upon the basis of relative efficiencies of the three nutrient elements, six combinations were found to be especially significant" those of Set \2x from the standpoint of reciprocal efficiencies of nitrogen and phosphorus, Set \x2 from the standpoint of nitrogen and potassium, and Sets xl4, x22, x4l with reference to phosphorus and potassium, the last two elements apparently bearing an inverse relationship in regard to reciprocal efficiencies and consequently offering a wider range of significant combinations. From these combinations Treatments 041, 121, 122, and 114 seem to meet the optimum requirements more closely "See discussions of possible optimum treatments on pages 403 and 413. 420 BULLETIN No. 417 [July, than any of the remaining 59 treatments. As these ratios are evidently quite diverse and as they differ materially in the relative efficiency of the various elements, there remains the possibility of further selection within this group. The four treatments are compared in Tables 37 and 38, in the latter of which certain additional treatments are in- cluded in order to facilitate the comparisons. Treatment 041, having a significant phosphorus efficiency and a potash efficiency which is comparatively high but not statistically sig- nificant, was probably the best of the ratios containing minerals only. Treatments 014, 021, 022 and 042 were all very much inferior. One fundamental objection which may be raised against Treatment 041, however, is that of high cost because of the large quantity involved 800 pounds of 0-16-3 per acre. One possibility of avoiding this high cost and at the same time of retaining the ratio would be to cut the application in half. The effect of such a treatment is not directly ascertainable from the results of these experiments, but may be de- termined indirectly thru the efficiencies of Treatments 021 and 020, which are equivalent respectively to half of Treatments 042 and 040. The mean efficiency of Treatment 021 was 12.15 2.4 and that of Treatment 020 was 10.02 2.7 (Table 38). The mean efficiency of Treatment 02i/ (half of Treatment 041) would probably lie either between 10.02 and 12.15 or very close to them. On a basis of yield increases, Treatment 02i/-> would probably lie between 10.02 2.7 and 18.75 4.3, the percentage increases of Treatments 020 and 021 respectively. In view of the foregoing relationships the authors conclude that, altho applications of 800 pounds of 0-16-3 per acre gave substantial increases in yield, it is probable that when smaller applications are made, 0-16-6 will give somewhat better returns. Mineral applications having more than 6 percent potash are not recommended unless nitrate also is added. Treatment 121, altho it gave good results, has several inherent weaknesses. It has a slightly negative potash efficiency and, in ad- dition, the low nitrogen efficiency common to all of the types of mix- tures represented by Set 1*1. Its actual mean efficiency, 22.71 3.7 (Table 37), is lower, but not significantly lower, than that of Treat- ment 122 or 144. This ratio is equivalent to 400 pounds of a 0-16-6 ferilizer plus 50 pounds of nitrate per acre. It is not recommended so highly as is Treatment 122. Treatment 114, with a mean actual efficiency of 26.69 3.8 (Table 37) was superior to either Treatment 121 or 041 despite the low mean nitrogen efficiencies of the 11* and 1*4 types of mixtures. In phos- 1935} FERTILIZER REQUIREMENTS OF SWEET CORN 421 ffi O tst- to 9f ^ ^ 00 00 M OH n c u 1 -H-H -H-H -H-H -H-H-H-H f elements in sets H-H -H-H i/i cs i/~. I/I f*j ?N *O i nutrient elemen -0 ui tsoo ;-H-H-H only phosphorus ENTS A iCHING H $ factors < nh or of eac 1 3- 5 ? B | 2 * c V E U Out i 1 1 & | !g ; "( 1 I V V i tel in Id H 1 : T i q : hi 1 1 1 1 1 IN! ,i *= - M^: S-a a-S g-S S3 53 58 2(2 z le 40, Appendix. : of zero is incliu TABLE 37. EFFICIENCV 1 I 1 { i 1 1 t f C o ! 1 1 z (2 dl : : S-=j= o^c l||s Data taken from Tab b Nitrogen with a valu 422 BULLETIN No. 417 [July, phorus efficiency the ll;tr and x\4 types rank very well, and in potash efficiency they are very much higher than any of the others of the group under consideration. The amount of potash and phosphorus in Treatment 114 is equivalent to 400 pounds of 0-8-24 plus 50 pounds of sodium nitrate per acre. This ratio differs so widely from any of the other types showing good performance, that the authors do not recom- mend it for commercial use unless local tests show that it is better than some of the others. Treatment 122 was, in general, the best of the four optimum treat- ments (Table 37). The nitrogen efficiency in the 12.r and I;r2 types of mixtures is considerably higher than in either of the other two combin- ations under consideration. The actual nitrogen efficiency of Treat- ment 122 (25.95 9.3) is much higher and more nearly significant than that of Treatment 121 or 114. In mean phosphorus efficiency the \2x and x22 types of treatments are about equal or superior to any of the others, and this relationship also holds for the actual efficiency. The mean potash efficiencies of the \x2 and x22 types are not as high as in the \x\ and ;rl4 types, and the actual efficiency (15.54 9.0) is not significant. Thus, altho not one of the four treatments is ideal in all respects, Treatment 122 is undoubtedly superior in general to the others. Be- cause it was high in efficiency, gave much better results than the com- TABLE 38. YIELD INCREASES AND EFFICIENCIES OF RECOMMENDED TREATMENTS, AND YIELD INCREASES AND EFFICIENCIES OF SIMILAR BASAL TREATMENTS WITHOUT THE SIDE-DRESSING OF NITROGEN* Phosphorus-potassium Code No. of treat- ment applications broadcast Sodium side-dressed Increase in weights of marketable ears Mean efficiency Commercial formula Amount per (N-P-K) acre Ibs. Ibs. perct. perct. 014 0-8-24 400 27.62 5.4 9.68 3.2 114 0-8-24 400 SO 38.54 5.1 26.69 3.8 021 0-16-6 400 18.75 4.3 12.15 2.4 121 0-16-6 400 'so 34.47 4.7 22.71 3.7 022 0-16-12 400 18.52 4.6 8.46 2.4 122 0-16-12 400 'so 44.47 8.1 28.02 5.3 041 0-16-3 800 37.41 + 4.8 21.45 2.8 141 0-16-3 800 'so 32.76 6.3 14.39 5.0 042 0-16-6 800 37.28 4.5 17.83 2.6 040 0-16-0 800 19.45 + 4.0 19.45 4.0 020 0-16-0 400 10.02 2.7 10.02 2.7 The odds for each treatment are greater than 30: 1. 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 423 bination of minerals alone in Treatment 041, and is one of the smaller applications, the authors consider it to be the best of the 63 treatments. Treatment 122 is equivalent to 400 pounds per acre of an 0-16-12 ferti- lizer plus 50 pounds per acre of sodium nitrate side-dressed. As men- tioned previously, nitrate of soda should be used only as a side dress- ing made from 30 to 60 days after planting. In these experiments the nitrate was applied by hand around each hill, but in commercial prac- tice, since it would be applied in strips to one or both sides of the row, more than 50 pounds per acre would undoubtedly be required in obtaining equivalent results. Without exception, all the fertilizer treatments recommended above hasten the maturing of sweet corn from three to five days. This is an important consideration, not so much because an additional margin is given against early fall frosts as because the planting season may be extended to almost a week later in the spring. SUMMARY Data from six years' experiments have been presented and evidence offered that the three major plant-food elements nitrogen, phos- phorus, and potassium interact in a manner which affects markedly the yield and maturity of sweet corn. The more important points brought out in this study are the following: Yield Increases Nitrogen Efficiency. The effectiveness of sodium nitrate as a side dressing was dependent upon the amount of nitrate used, the ratio of other minerals used, the type of rotation practiced, and the time at which the sodium nitrate was applied: 1. When sodium nitrate was used as a side dressing without an accompanying basal treatment of one or both of the mineral salts, the increases in yield were inconsistent, and nitrogen efficiency varied around the zero point. 2. When the basal mineral treatment consisted of phosphorus, in- creases in yield were more consistent than when either nitrogen or phosphorus was used alone. The maximum efficiency of nitrogen used with phosphorus was associated with 50 pounds of sodium nitrate and 64 pounds of P 2 O S per acre. 3. When the basal mineral treatment consisted of potash, increases in yield were very inconsistent, probably because of a deficiency of available phosphorus in the soil. 424 BULLETIN No. 417 [July, 4. Sodium nitrate as a supplement to combinations of phosphorus and potash gave better results than as a supplement to either mineral alone. Maximum nitrogen efficiency was associated with a treatment composed of 50 pounds of sodium nitrate side-dressed as a supplement to 64 pounds of P 3 O 6 and 50 pounds of K 2 O per acre. Nitrogen efficiency decreased when sodium nitrate was applied in quantities of more than 50 pounds per acre unless the basal potash dosage was reduced greatly or omitted. 5. Nitrogen gave better results on soils having sufficient organic matter supplied by plowing under legumes than on soils where sweet corn was grown without clover in the rotation. Phosphorus Efficiency. The usefulness of superphosphate as a fertilizer ingredient also was affected by the ratios of the other minerals used in the combinations, and by the type of rotation maintained: 1. Small dosages of superphosphate applied alone gave larger increases in yield than heavier dosages applied alone. 2. Combinations of phosphorus and nitrogen gave considerably larger yields than were obtained from phosphorus alone. The maxi- mum efficiency of phosphorus when used with nitrogen was associated with an application of 50 pounds of sodium nitrate per acre. 3. Combinations of phosphorus and potash also gave better results than did phosphorus alone. The efficiency of phosphorus in these com- binations increased as the amount of phosphorus used was increased. 4. In complete fertilizers adequate amounts of phosphorus were essential. The maximum efficiency of phosphorus was reached in combinations containing 50 pounds of sodium nitrate per acre supple- menting 64 pounds of P 2 O 6 per acre. Phosphorus and potash had a distinctly inverse relationship, on the basis of marketable ears, whereby phosphorus maintained an equivalent efficiency when the smallest phos- phorus dosage was combined with the heaviest potash dosage or the heaviest phosphorus dosage with the smallest potash dosage. 5. Phosphorus gave uniformly better results when clover was used in the rotation than when it was not included. The increases in phosphorus efficiency in combinations containing both nitrogen and potash indicated that the two other elements were important in increasing the availability of phosphorus to the plant. Potash Efficiency. The role of potash as a fertilizer ingredient was strongly dependent upon the ratio of the other minerals used with it: 1. Muriate of potash used alone failed to increase yields appre- ciably, and in many instances appeared to be injurious. 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 425 2. Combinations of potash and nitrogen gave highly variable re- sults, indicating that phosphorus was the limiting factor. In efficiency, potash and nitrogen gave evidence of being in inverse relationship to each other. 3. Combinations of potash and phosphorus gave substantial in- creases in yield; the efficiency of potash increased with increasingly larger applications. Potash and phosphorus also showed a tendency toward an inverse relationship. I Advance in Maturity of Crops Nitrogen Action. When used alone, nitrogen had no consistent influence on maturity. Used in combination with adequate phosphorus, it hastened maturity. Combinations of nitrogen and potash advanced maturity only to a slight extent and only in combinations containing the single dosage of potash. In complete fertilizers nitrogen gave variable results, being least effective in advancing maturity in those combinations that contain the maximum dosages of both phosphorus and potash. Phosphorus Action. Much more than either nitrogen or potash, phosphorus hastened maturity. Phosphorus proved least effective when applied in maximum dosages in combinations containing some of the larger amounts of nitrogen and potash. Potassium Action. Potash used alone or in combination with nitrogen retarded maturity. Small amounts of potash combined with adequate dosages of phosphorus advanced maturity very materially. Potash forming part of a complete fertilizer did not give consistent results either in hastening or in retarding maturity. RECOMMENDATIONS A few general rules have been evolved in the application of fertilizers to soils of the dark silt loam prairie type used in these ex- periments which should be taken into consideration before specific recommendations for fertilizing sweet corn are made. Treatments of single fertilizer salts should usually be avoided because their efficiency values are low and sometimes even negative. Mixtures of two salts containing nitrogen and phosphorus or phosphorus and potash give good results if the proper ratios are used. Upon the basis of the results obtained in this study, the following suggestions for fertilizing sweet corn are presented: 426 BULLETIN No. 417 [July, 1. Use a rotation including legumes in order to secure maximum responses from commercial fertilizers. 2. Where nitrogen is omitted, apply 800 pounds of an 0-16-3 fertilizer per acre broadcast. 3. If it is desired to apply less than 800 pounds of fertilizer (with- out nitrogen) per acre, an 0-16-6 combination will probably prove superior to 0-16-3. 4. Mineral fertilizers applied without nitrogen should contain not more than 6 percent potash. 5. For consistent responses with three-element fertilizer combina- tions, apply 400 pounds of 0-16-12 supplemented by 50 pounds of side- dressed sodium nitrate per acre (Treatment 122). This treatment, of all the 63 investigated, is apparently the best. 6. Under some conditions the 0-16-12 analysis mentioned above may possibly be reduced with advantage to 0-16-6, but the amount of nitrate used as a side-dressing should not be changed. (Treatment 121). 7. An application of 400 pounds of an 0-8-24 fertilizer, plus side- dressed sodium nitrate at the rate of 50 pounds per acre (Treatment 114), may prove profitable under some conditions. 8. Nitrate of soda should be applied 30 to 60 days after the corn is planted. The quantities of sodium nitrate recommended here are based on applications made by hand around the hill. a If machines are used to apply this salt in continuous strips, the amounts per acre will probably have to be increased. 'Fertilizer recommendations which have been made as a result of these ex- periments, but previous to their publication here, were limited to phosphorus- potash combinations. Such mixtures have given excellent results in many in- stances, especially when applied around the hill with the corn-planter fertilizer attachment. A considerable portion of the sweet-corn acreage in the northern part of Illinois is being fertilized with 0-16-6 applied around the hill at the rate of about 100 pounds an acre. This is equivalent to one-fourth of the quantity of salts contained in Treatment 021. A good many efforts have been made by the senior author to introduce complete fertilizer analyses, but without success, owing to the fact that nitrogen, even in the form of sodium nitrate, applied around the hill at the time of planting frequently seems to exercise a depressive effect on yields. This statement is supported by considerable experi- mental evidence which is not reported here. The important point to remember is that nitrogen used as a side-dressing applied later may react quite differently from nitrogen forming part of a complete analysis and applied at the time of planting. (For further discussion of this subject see 111. Agr. Exp. Sta., 45th Ann. Rpt., pp. 218-220.) 1935] FERTILIZER REQUIREMENTS OF SWEET CORN 427 LITERATURE CITED 1. ANDRE, M. G. Deplacement de la potasse contenue dans certaines roches feldspathiques par quelques substances employees comme engrais. Compt. Rend. Acad. Sci. [Paris] 157, 856-858. 1913. 2. APPLEMAN, C. O. Reliability of the nail test for predicting the chemical composition of green sweet corn. Jour. Agr. Res. 21, 817-820. 1921. 3. - Forecasting the date and duration of the best canning stage for sweet corn. Md. Agr. Exp. Sta. Bui. 254. 1923. 4. and EATON, S. V. Evaluation of climatic temperature efficiency for ripening processes in sweet corn. Jour. Agr. Res. 20, 795-805. 1921. 5. BEAR, F. E., and SALTER, R. M. The residual effects of fertilizers. W. Va. Agr. Exp. Sta. Bui. 160. 1916. 6. BLACKWELL, C. P., and BUIE, T. S. Fertilizer experiments. S. C. Agr. Exp. Sta. Bui. 209. 1921. 7. BLAIR, A. W., and PRINCE, A. L. Influence of varying ratios of phosphoric acid and potash on crop yield and nitrogen recovery. Soil Sci. 17, 327- 332. 1924. 8. - The availability of nitrogen in nitrate of soda, am- monium sulfate, and dried blood when the amounts of phosphoric acid and potash are varied. Soil Sci. 19, 467-476. 1925. 9. BRAY, R. H. A field test for available phosphorus in soils. 111. Agr. Exp. Sta. Bui. 337. 1929. 10. BREAZEALE, J. F. The relation of sodium to potassium in soil and solution cultures. Jour. Amer. Chem. Soc. 28, 1013-1025. 1906. 11. - The effect of one element of plant food upon the absorption by plants of another element. Ariz. Agr. Exp. Sta. Tech. Bui. 19. 1928. 12. BUIE, T. S., CURRIN, R. E., KYZER, E. D., and WARNER, J. C. Fertilizer rotation experiments at the Pee Dee Station. S. C. Agr. Exp. Sta. Bui. 262. 1929. 13. BUSHNELL, JOHN. The relative response to fertilizers of cabbage, tomatoes, cucumbers, and sweet corn. Proc. Amer. Soc. Hort. Sci. 27, 516-519. 1930. 14. CLEMENTS, H. F. Plant nutrition studies in relation to the triangular system of water cultures. Plant Phys. 3, 441-458. 1928. 15. COMIN, DONALD, and BUSHNELL, JOHN. Fertilizers for early cabbage, to- matoes, cucumbers, and sweet corn. Ohio Agr. Exp. Sta. Bui. 420. 1928. 16. CULPEPPER, C. W., and MAGOON, C. A. Studies upon the relative merits of sweet corn varieties for canning purposes and the relation of maturity of corn to the quality of the canned product. Jour. Agr. Res. 28, 403-443. 1924. 17. CURRY, B. E., and SMITH, T. O. Granitic soil potassium and its relation to the production of hay. N. H. Agr. Exp. Sta. Bui. 170. 1914. 18. DREYSPRING, C., and HEINRICH, F. Experiments carried out at the Ham- burg Experimental Station, XVIII. Increased root-solubility of potash contained in the soil as a result of phosphoric acid fertilization. Super- phosphate 4, 1-10, 46-59. 1931. 19. EMERSON, PAUL, and BARTON, JOHN. The potassium-nitrogen ratio of red clover as influenced by potassic fertilizers. Jour. Amer. Soc. Agron. 14, 182-192. 1922. 20. FUDGE, J. F. Influence of various nitrogenous fertilizers on availability of phosphate. Jour. Amer. Soc. Agron. 20, 280-293. 1928. 21. - - The influence of various nitrogenous fertilizers on the availability of phosphate and potassium. Ala. Polytech. Inst. Agr. Exp. Sta. Bui. 227. 1928. 428 BULLETIN No. 417 [July, 22. GARDNER, F. D., NOLL, C. F., and BAKER, P. S. Thirty-five years' results with fertilizers. Penn. State Col. Agr. Exp. Sta. Bui. 146. 1917. 23. - and LEWIS, R. D. Forty years' results with ferti- lizers: general fertilizer experiments. Penn. State Col. Agr. Exp. Sta. Bui. 175. 1922. 24. GREAVES, J. E. Effects of soluble salts on insoluble phosphates. Jour. Biol. Chem. 7, 287-319. 1910. 25. - - and CARTER, E. G. The action of some common soil amend- ments. Soil Sci. 7, 121-160. 1919. 26. - and GOLDTHORPE, H. C. The influence of salts on the nitric-nitrogen accumulation in the soil. Jour. Agr. Res. 16, 107-135. 1919. 27. HOAGLAND, D. R., and DAVIS, A. R. Suggestions concerning the absorption of ions. New Phytol. 24, 99-111. 1925. 28. HOCK, A. Absorption of phosphoric acid and potash in Neubauer plant germination experiments. Das Superphosphat 6, 167-172. 1930. (Abs. in Chem. Abs. 25, 371. 1931.) 29. HOPKINS, C. G., MOSIER, J. G., VAN ALSTINE, E., and GARRETT, F. W. Champaign county soils. 111. Agr. Exp. Sta. Soil Rpt. 18, 1-61. 1918. 30. HUELSEN, W. A. Getting maximum results from sweet corn fertilizers. Canning Age 9, 309-312. 1928. 31. - Efficiency factors and their use in determining optimum fertilizer ratios. Jour. Agr. Res. 45, 675-704. 1932. 32. HUSTON, H. A. Field tests with fertilizers. 8th Internatl. Cong. Appl. Chem. 15, 139-144. 1912. 33. JANSSEN, GEORGE and BARTHOLOMEW, R. P. The translocation of potassium in tomato plants and its relation to their carbohydrate and nitrogen dis- tribution. Jour. Agr. Res. 38, 447-465. 1929. 34. - The influence of the potash concentration in the culture medium on the production of carbohydrates in plants. Jour. Agr. Res. 40, 243-261. 1930. 35. LLOYD, J. W. Fertilizing tomatoes, sweet corn, and muskmelons in a three- year rotation. 111. Agr. Exp. Sta. Bui. 364. 1931. 36. MACTAGGART, ALEXANDER. The influence of certain fertilizer salts on the growth and nitrogen-content of some legumes. Soil Sci. 11, 435-456. 1921. 37. MARAIS, J. S. The comparative agricultural value of insoluble mineral phosphates of aluminum, iron, and calcium. Soil Sci. 13, 355-410. 1922. 38. MERZ, A. R., and Ross, W. H. The computation of fertilizer mixtures from concentrated materials. U. S. Dept. Agr. Dept. Bui. 1280. 1924. 39. MEYERS, M. T. Determining the date of silking in experiments with corn. Jour. Amer. Soc. Agron. 22, 280-283. 1930. 40. NEUBAUER, H., BONEWITZ, W., and SCHOTTMULLER, A. Andert sich wahrend einer Vegetationszeit der Vorrat des ungediingten und gediingten Bodens an wurzelloslichen Pflanzennahrstoffen? Ztschr. Pflanzenernahr., Diingung u. Bodenkunde 12, Teil A, 108-114. 1928. 41. PATTEN, H. E. Effect of soluble salts on the absorption of phosphates by soils. Jour. Phys. Chem. 15, 639-658. 1911. 42. RUSSELL, E. J. Soil conditions and plant growth. 6th ed. Longmans, Green and Co. New York. [1932]. 43. SCHUSTER, G. L. Fifteen years of field experiments with manure, fertilizers and lime on Sassafras Silt Loam Soil. Del. Univ. Agr. Exp. Sta. Bui. 137 (Tech. Bui. 4). 1924. 44. SPILLMAN, W. J. A plan for the conduct of fertilizer experiments. Jour. Amer. Soc. Agron. 13, 304-310. 1921. J9J5] FERTILIZER REQUIREMENTS OF SWEET CORN 429 45. SPURWAY, C. H. The effect of fertilizer salts treatments on the composition of soil extracts. Mich. Agr. Exp. Sta. Tech. Bui. 45. 1919. 46. Some factors influencing the solubility of phosphorus in soil-acid phosphate mixtures. Soil Sci. 19, 399-405. 1925. 47. - A test for water-soluble phosphorus: Studies on water-soluble phosphorus in field soils. Mich. Agr. Exp. Sta. Tech. Bui. 101. 1929. 48. STUDENT. The probable error of a mean. Biometrika 6, 1-25. 1908. 49. - - Tables for estimating the probability that a mean of a unique sample of observations lies between oo and any given distance of the mean of the population from which the sample is drawn. Biometrika 11, 414-417. 1917. 50. THOMSON, ARVED. Experimentelle Studien zum Verhalten des Sandbodens gegen Superphosphate. Biedermann's Centbl. 19, 585-588. 1890. 51. THORNTON, S. F. Experiences with the Neubauer method for determining mineral nutrient deficiencies in soils. Tour. Amer. Soc. Agron. 23, 195-208. 1931. 52. - - The Neubauer method as applied to the determination of the availability of phosphate materials. Jour. Assoc. Off. Agr. Chem. 14, 292-295. 1931. 53. TRESSLER, D. K. The solubility of the soil potash in various salt solutions. Soil Sci. 6, 237-257. 1918. 54. WAGNER, PAUL. Ammoniaksalz oder Chilisalpeter. Biedermann's Centbl. 28, 367-370. 1899. 55. WHITING, A. L. Plant food removed from soil by sweet corn. The Canner 58, 27-28. 1924. 430 BULLETIN No. 417 {.July, LIST OF TABLES NO. PAGE 1. Fertilizer treatments per acre: plant food actually applied and the nearest equivalent application in terms of standard formulae 363 2. Increases in yields of sweet corn due to varying treatments of sodium nitrate and superphosphate 371 3. Same, for sodium nitrate and potassium chlorid 374 4. Same, for sodium nitrate and superphosphate with a single dosage of potassium chlorid constant 375 5. Same, with double dosage of potassium chlorid constant 376 6. Same, with quadruple dosage of potassium chlorid constant 377 7. Same, for sodium nitrate and potassium chlorid with a single dosage of superphosphate constant 378 8. Same, with double dosage of superphosphate constant 379 9. Same, with quadruple dosage of superphosphate constant 380 10. Average yields of check plots, showing effect of clover 382 11. Mean percentage increases in number of marketable ears due to various fertilizer treatments 383 12. Same, for weights of marketable ears 384 13. Same, for weights of green fodder 385 14. Effect of phosphorus on nitrogen efficiency as indicated by set averages based on weights of marketable ears 386 15. Same, as indicated by treatments that gave maximum percentage in- creases in nitrogen efficiency in their respective sets 386 16. Effect of phosphorus on nitrogen as indicated by treatments that gave maximum percentage increases in weights of marketable ears 387 17. Effect of potash on nitrogen efficiency as indicated by set averages based on weights of marketable ears 388 18. Same, as indicated by treatments that gave maximum percentage in- creases in nitrogen efficiency in their respective sets 388 19. Effect of potash on nitrogen as indicated by treatments that gave maximum percentage increases in weights of marketable ears 389 20. Increases in yields of sweet corn due to varying treatments of super- phosphate and potassium chlorid 390 21. Same, with a single dosage of sodium nitrate constant 393 22. Same, with a double dosage of sodium nitrate constant 394 23. Same, with a quadruple dosage of sodium nitrate constant 395 24. Effect of nitrogen on phosphorus efficiency as indicated by set averages based on weights of marketable ears 397 25. Same, as indicated by treatments that gave maximum percentage in- creases in phosphorus efficiency in their respective sets 398 26. Effect of nitrogen on phosphorus as indicated by treatments that gave maximum percentage increases in weights of marketable ears 398 27. Effect of potash on phosphorus efficiency as indicated by set averages based on weights of marketable ears 399 28. Same, as indicated by treatments that gave maximum percentage in- creases in phosphorus efficiency in their respective sets 400 29. Effect of potash on phosphorus as indicated by treatments that gave maximum percentage increases in weights of marketable ears 400 30. Effect of nitrogen on potash efficiency as indicated by set averages based on weights of marketable ears 407 31. Same, as indicated by treatments that gave maximum percentage in- creases in potash efficiency in their respective sets 408 19351 FERTILIZER REQUIREMENTS OF SWEET CORN 431 NO. PAGE 32. Effect of nitrogen on potash as indicated by treatments that gave maximum percentage increases in weights of marketable ears 409 33. Effect of phosphorus on potash efficiency as indicated by set averages based on weights of marketable ears 411 34. Same, as indicated by treatments that gave maximum percentage in- creases in potash efficiency in their respective sets 411 35. Effect of phosphorus on potash as indicated by treatments that gave maximum percentage increases in weights of marketable ears 412 36. Effect of soil treatments on maturity of sweet corn 415 37. Efficiency of the separate elements as combined in treatments 041, 121, 122, and 114 421 38. Yield increases and efficiencies of recommended treatments and of similar basal treatments without nitrogen 422 39. Mean yields and yield increases on treated plots over respective adja- cent check plots 432 40. Efficiency factors of the three nutrient elements in the various dosages and combinations. . 435 APPENDIX 432 BULLETIN No. 417 [July, TABLE 39. MEAN YIELDS AND YIELD INCREASES ON TREATED PLOTS OVER RE- SPECTIVE ADJACENT CHECK PLOTS" Treatment Yield from treated plot Yield from check Increase with treatment Odds Percentage increase Dev. P. E. Number of marketable ears per acre 001.. 6 273 6 842 569 144 73:1 8.32 +21 3 9 002 5 970 5 977 ' 7 92 <1'1 12 1 5 1 004 6 123 5 977 146 162 3:1 2 44 27 9 010 7 124 5 728 1396 + 283 224:1 24.37 5.0 4 9 Oil 6 595 5 728 867 230 57-1 15 14 40 3 8 012 7 041 5 970 1071 287 57:1 17.94 48 3 7 014 7 582 5 970 1611 328 224-1 26 98 55 4 9 020 7 736 6 987 749 + 258 21 -1 10 72 37 2 9 021 8 132 6 987 1145 354 31:1 16.39 5.1 3.2 022 8 391 6 915 1476 251 666-1 21 34 36 5 9 024 8 082 6 895 1187 + 190 948-1 17.22 28 6 2 040 7 080 5 950 1130 225 259:1 18.99 3.8 5 041 7 586 5 714 1872 197 > 9999-1 32 76 34 9 5 042 7 772 5 851 1921 229 > 9999-1 32 83 39 8 4 044 7 960 5 765 2195 + 319 1932:1 38.07 5.5 6.9 100.. . 5 440 5 176 264 202 4:1 5.10 3.9 1.3 101 5 229 6 176 946 417 10-1 15 32 6 7 2 3 102 6 603 6 480 123 + 170 2:1 1 90 + 27 7 104 6 095 6 223 128 230 2:1 2.06 3.4 6 110 6 987 6 221 766 + 152 259- 1 12 31 + 25 5 Ill 6 933 6 275 658 +111 666-1 10 49 18 5.9 112 7 398 5 664 1734 244 2799:1 30.61 4.3 7.1 114 6 903 5 139 1764 + 234 3332-1 34 32 46 7 5 120 7 316 5 706 1610 184 > 9999-1 28.22 3.2 8 8 121 7 565 5 702 1862 + 275 1 799 1 32 66 48 6 8 122 7 883 5 564 2318 + 353 1444-1 41 66 + 63 6 6 124 7 406 5 499 1908 + 342 494:1 34.70 + 6.2 5.6 140 7 947 6 189 1758 377 169:1 28.40 6.0 4.7 141 8 164 6 576 1588 + 334 188-1 24 15 + 50 4 8 142 8 307 6 576 1731 + 289 714:1 26.32 4.4 6 144 8 280 5 741 2539 + 393 1221-1 44 22 68 6 5 200.. . 5 578 5 751 172 194 2-1 2 99 33 9 201 6 052 6 548 496 + 150 27-1 7 57 2.3 3 3 202 5 665 5 918 253 295 2:1 4.28 4.8 .9 204 5 854 5 627 227 + 345 2-1 4 03 58 7 210 6 103 5 980 123 283 1:1 2.06 52 .4 211 6 666 5 830 835 250 35-1 14 32 43 3 3 212 7 103 5 507 1596 + 294 400-1 28 98 54 5 4 214 7 164 5 787 1377 274 259:1 23.79 4.8 5.0 220 7 196 5 677 1519 248 860-1 26 76 44 6 1 221 7 849 6 169 1680 268 989-1 27.23 43 6.3 222 7 996 6 438 1557 297 323:1 24.18 4.6 5.2 224 8 017 7 079 938 351 14-1 13.25 49 2 7 240 8 568 6 987 1582 244 770:1 22.64 3.5 6.5 241 8 418 6 884 1534 330 169-1 22 28 48 4 6 242 8 390 6 932 1458 455 30-1 21.03 66 3.2 244 8 861 7 425 1436 204 2532:1 19.34 2.8 7.0 400... 6 899 7 282 384 173 9:1 5.27 2.4 2.2 401 7 146 6 304 843 143 399-1 13.37 23 5 9 402.. . 6 489 6 559 70 289 <1:1 1.07 5.4 .2 404 7 085 7 179 94 273 1:1 1.31 4.4 .3 410 7 066 6 209 857 296 21:1 13.80 4.8 2.9 411 7 166 6 344 822 285 21:1 12.96 4.5 2.9 412 7 250 6 554 696 203 40:1 10 62 3.1 3.4 414 7 583 6 046 1537 382 78:1 25.42 6.4 4.0 420 ,X (101 6 048 1956 295 1555-1 32.34 49 6.6 421 7 226 6 048 1178 352 35:1 19.48 5.7 3.4 422 7 644 5 832 1812 143 >9999-l 31 07 24 12 7 424 7 788 5 832 1956 173 >9999:1 33.54 3.0 11.3 440 8 201 7 157 1044 259 78:1 14.59 3.6 4.0 441 8 615 7 157 1458 174 >9999:1 20.37 2.4 8.4 442 8 617 7 873 744 227 33:1 9.45 2.9 3.3 444 7 902 7 655 246 187 4:1 3.21 2.5 1.3 The increases in yield shown in the fourth column are averages of annual yield differences rather than differences between the averages shown in the second and third columns. 79J5] FERTILIZER REQUIREMENTS OF SWEET CORN 433 TABLE 39. MEAN YIELDS AND YIELD INCREASES ON TREATED PLOTS OVER RE- SPECTIVE ADJACENT CHECK PLOTS Continued Treatment Yield from treated plot Yield from check Increase with treatment Odds Percentage increase Dev. P. E. Tons of marketable ears per acre 001 1.958 2.150 .193 .058 33:1 8 98 2 7 3 3 002 1.875 .844 .030 .034 2; 1 63 16 9 004 1.911 .844 .066 .058 3: 3.58 3.2 1.1 010 2.156 .754 .397 .084 179- 22 63 48 4 7 01 1 1.998 .754 .244 .070 43: 13.91 4.0 3 5 012 2.218 .879 .338 095 46: 17 99 50 3 6 014 2.398 .879 .519 + .102 276: 27.62 54 5 1 020 2.459 2.235 .224 .060 57: 10.02 2.7 3.7 021 2.654 2.235 .419 .094 132- 18 75 43 4 4 022 2.617 2.208 .409 .101 83: 18.52 4.6 4 024 2.596 2.139 .457 .072 989: 21.36 3.4 6.3 040 2.229 .866 .363 .076 198: 19.45 40 4 8 041 2.472 .799 .673 .086 4999: 37.41 4.8 7.8 042 . 2.516 .832 .683 + .082 >9999- 37 28 45 8 3 044 2.561 .784 .776 .115 1799: 43.50 65 6 7 100. . . 1.667 .580 .087 .082 3: 5.51 5.0 1.1 101 1.637 .869 -.232 .124 7: 12.41 6.5 1.9 102 1.990 .953 .037 .095 1: 1 89 47 4 104 1.908 .002 -.094 .080 3: 4.70 3.9 1 2 110 2.150 .909 .241 .053 151: 12 62 27 4 6 111 2.140 .962 .178 .068 16: 9.07 35 2 6 112 2.320 .722 .598 .092 1221: 34.73 5.3 6.5 114 2.200 .588 .612 .080 3332- 38 54 51 7 6 120 2.345 .818 .526 .070 3332: 28.93 39 7.5 121 . . 2.442 .816 .626 .086 3332- 34 47 47 7 3 122 2.522 .745 .776 .142 400- 44.47 81 5 5 124 2.242 .710 .532 .090 666: 31.11 5.3 5.9 140 2.566 .972 .594 .121 224: 30.12 6.1 4.9 141 2.638 .987 .651 .125 323: 32.76 6.3 5.2 142 2.784 .987 .797 .115 1932: 40.11 5.8 6.9 144 2.718 .747 .971 .134 3332- 55.58 77 7 2 200.. . 1.698 .750 .051 + .038 2: -2.91 2.2 1.3 201 1.903 .050 .147 .038 66: 7.17 1.8 3.9 202 1.800 .853 -.054 .097 2: 2 91 48 6 204 1 .822 .730 .092 .105 2: 5.32 5.9 0.9 210 1.925 .834 .091 .100 2- 4 96 55 9 211 2.092 .827 .264 .092 21: 14.45 5.0 2.9 212 2.251 .706 .545 .106 293: 31.95 6.3 5.1 214 2.228 .781 .447 .093 198- 25.10 52 4 8 220 2.267 .724 .543 .083 1332: 31.50 4.8 6.5 221 2.451 .858 .593 .098 811 31 92 52 6.1 222 2.595 .998 .598 .102 666: 29.93 5.2 5.8 224 2.619 2.248 .371 .130 17- 16 50 59 2 8 240 2.871 2.222 .648 .091 1499: 29.16 4.1 7.1 241 2.750 2.179 .571 .107 354: 26.20 4.8 5.3 242 2.757 2.194 .563 .160 43: 25 66 7.3 3.5 244 2.904 2.281 .622 .070 9999: 27.27 3.1 8.9 400. . . 2.099 2.206 .107 .057 6: 4 85 2 6 1 9 401 2.209 1.882 .327 .063 195: 17.38 3.3 5.2 402 1.933 1.993 -.060 .086 2: 3.01 4.3 0.7 404 2.185 2.235 .050 .086 2: 2.24 3.7 0.6 410 2.225 .938 287 095 25- 14 81 49 3 411 2.299 .980 .318 .103 27: 16.06 5.1 3.1 412 2.309 .060 .250 .067 57: 12.14 3.3 3.7 414 2.471 .899 .572 .130 123: 30.12 7.0 4.4 420 2.623 888 736 083 .<)')')<) 38 98 44 8 9 421 2.310 .888 .422 .131 31: 22.35 7.0 3.2 422 2.419 .832 .587 .058 >9999: 32.04 3.2 10.1 424 2.483 .832 .651 .046 >9999: 35.53 2.5 14.2 440 2.648 2.289 .360 .092 68: 15.73 4.0 3.9 441 2.860 2.289 .571 .063 >9999: 24.94 2.7 9.1 442 2.878 2.544 .334 .080 99: 13.13 3.1 4.2 444 2.590 2.445 .144 .074 7: 5.89 3.1 1.9 434 BULLETIN No. 417 [.July, TABLE 39. MEAN YIELDS AND YIELD INCREASES ON TREATED PLOTS OVER RE- SPECTIVE ADJACENT CHECK PLOTS Concluded Treatment Yield from treated plot Yield from check Increase with treatment Odds Percentage increase Dev. P. E. Tons of green fodder per acre 001.. 3.243 3.694 -.452 .265 6:1 12.24 7.2 1 7 002 3.355 3.193 . 162 + . 108 5: 5.07 3.4 1.5 004 3.114 3.193 -.078 + .109 2: 2 44 35 7 010 3.194 2.762 .432 .110 73: 15.64 4.0 3.9 Oil 3.065 2 762 .303 .104 22: 10 97 38 2 9 012 3.428 3.018 .410 .131 28: 13.58 4.4 3 1 014 4.206 3.018 1.188 .152 4999: 39.36 5.0 7.8 020 3.822 3 430 .393 139 19: 11 46 41 2 8 021 4.224 3.430 .795 .137 610: 23.18 4.0 5 8 022 . 4 280 3 407 873 180 198: 25 62 53 4 8 024 4.558 3 408 1.150 .168 1866: 33.74 50 6 8 040 3.185 3.180 .004 .105 <1: 1.26 31.5 .04 041 . ... 3.852 2 911 940 152 908: 32 29 52 6 2 042 3.782 2 844 .939 + .162 610: 33 02 57 5 8 044 4.098 2.776 1.322 .144 >9999: 47.62 52 9.2 100.. . 2.839 2.587 .252 .212 3: 9.74 8.1 1.2 101 2.973 2 912 061 + 226 1: 2 09 + 70 3 102 3.857 3 008 849 123 1932: 28.22 4.1 6 9 104 3.386 3.143 .242 + .170 4: 7.70 5.5 1.4 110 3 354 2 924 430 106 83- 14 71 36 4 1 111 3.102 3 158 056 087 2: 1.77 30 6 112 3.849 2 704 1.145 + .144 4999: 42.34 5.3 8.0 114 3 482 2 562 920 + 098 >9999- 35 91 38 9 4 120 3.455 3 033 .422 + 100 99: 13.91 33 4.2 121 3.920 3 095 .825 .177 169: 26.66 5.7 4.7 122 4 134 3 079 1 056 + 200 339- 34 30 65 5 3 124 3.974 2 917 1 057 .185 553: 36.24 64 5.7 140 3.907 3.174 .733 + .155 179: 23.09 4.9 4.7 141 4 202 3 102 1 100 + 178 948- 35 46 57 6 2 142 4.604 3 102 1 503 138 >9999: 48.45 4.4 10 9 144 4.726 2.807 1.919 .243 4999: 68.36 8.6 7.9 200.. . 2.447 2.572 .125 .076 5: 4.86 3.0 1.6 201 3 031 3 200 168 088 7- 5 25 28 1.9 202 3 058 3 064 006 177 <1: 0.20 + 6.6 .03 204 3.315 2.660 656 + . 159 88: 24.66 6.0 4.1 210 . 2 895 2 866 029 + 144 1: 1 01 50 0.2 211 3.703 3 366 338 + 105 31: 10.04 31 3.2 212 3 494 2 916 577 + 185 28- 19 79 64 3 1 214 . . 3 910 3 012 898 + 132 1799- 29 81 44 6 8 220 3.160 2 934 227 133 6: 7.74 4.6 1.7 221 3.721 2.912 .809 .138 638: 27.78 4.8 5.8 222 4 047 2 918 129 136 >9999- 38 69 47 8.3 224 4.765 3.335 430 180 2499: 42.88 5.4 8.0 240 4.502 3.261 .241 .175 1499: 38.06 5.4 7.1 241 4.287 3 218 068 + 194 431- 33 20 6.0 5.5 242 4.832 3.434 398 .228 860: 40.71 6.7 6.1 244 4.814 3.166 .648 .165 >9999: 52.05 5.2 10.0 400.. . 3.294 3.348 -.053 .084 2: 1.58 2.6 0.6 401 3.548 3.042 506 132 48: 16.63 4.4 3.8 402 3.190 3.002 188 .139 4: 6.26 4.5 1.4 404. . . 3.663 3.752 -.089 .169 2: -2.37 4.7 0.5 410 3.359 3.412 053 302 <1: 1.55 7.8 0.2 411 3.890 3.296 .595 .137 109: 18.05 4.2 4.3 412 4.256 3 563 693 180 63: 19.45 5.1 3.8 414 4.376 3.369 1 007 .201 241: 29.89 6.0 5.0 420 3.942 2 997 946 183 308- 31 56 6.1 5.2 421 3.406 2.997 .409 .184 10: 13.65 6.2 2.2 422 . 3 827 2 831 995 127 4999- 35 15 4.5 7.8 424 3.986 2.831 1 155 .132 >9999: 40.80 4.6 8.8 440 4.603 3.644 .959 .176 400: 26.32 4.9 5.4 441 4.914 3.644 1 270 216 666: 34.85 5.9 5.9 442 5.264 4.324 .940 .115 4999: 21.74 2.6 8.2 444 5.146 4.324 822 152 369: 19.01 3.5 5.4 FERTILIZER REQUIREMENTS OF SWEET CORN 435 40. EFFICIENCY FACTORS OF THE THREE NUTRIENT ELEMENTS IN THE VARIOUS DOSAGES AND COMBINATIONS (Calculated on the basis of weights of marketable ears) Treat- ment Increase in yield over adjacent checks Treatments subtracted* Efficiency factors' 1 N P0, KiO N PO KjO 001 perct. -8.98 2.7 perct 5.51 5.0 -3.43 7.0 .26 4.9 -8.28 5.0 -10.01 5.5 -4.84 5.3 16.74 7.3 10.92 7.4 18.91 4.7 15.72 6.4 25.95 9.3 9.75 6.3 10.67 7.3 -4.65 7.9 2.83 7.3 12.08 10.1 -2.91 2.2 1.81 3.2 -4.54 5.0 1.74 6.7 -17.67 7.3 .54 6.4 13.96 8.0 -2.52 7.5 21.48 5.5 13.17 6.7 11.41 6.9 -4.86 6.8 9.71 5.7 -11.21 6.8 -11.62 8.6 -16.23 7.2 -4.85 2.6 26.36 4.3 -4.64 4.6 -5.82 4.9 -7.82 6.8 2.15 6.5 -5.85 6.0 2.50 8.8 28.96 5.2 3.60 8.2 13.52 5.6 14.17 4.2 -3.72 5.6 -12.47 5.5 -24.15 5.5 -37.61 7.2 perct. perct. -8.98 2.7 1.63 1.6 3.58 3.2 002 1 63 1.6 004 3.58 3.2 010 . . 22.63 4.8 22.63 4.8 22.89 4.8 16.36 5.2 24.04 6.3 10.02 2.7 27.73 5.1 16.89 4.9 17.78 4.7 19.45 4.0 46.39 5.5 35.65 4.8 39.92 7.2 Oil 012 014 020 021 022 024 040 13.91 4.0 17.99 5.0 27.62 5.4 10.02 2.7 18.75 4.3 18.52 4.6 21.36 3.4 19 45 4.0 001 002 004 66i 002 004 010 010 010 020 020 020 -8.72 6.2 -4.64 6.9 4.99 7.2 8.73 5.1 8.50 5.3 11.34 4.3 041 042 044 100 101 37.41 4.8 37.28 4.5 43.50 6.5 5.51 5.0 -12.41 6.5 1.89 4.7 -4.70 3.9 12.62 2.7 9.07 3.5 34.73 5.3 38.54 5.1 28.93 3.9 34.47 4.7 44.47 8.1 31.11 5.3 30.12 6.1 32.76 6.3 40.11 5.8 55.58 7.7 -2.91 2.2 -7.17 1.8 -2.91 4.8 5.32 5.9 4.96 5.5 14.45 5.0 31.95 6.3 25.10 5.2 31.50 4.8 31.92 5.2 29.93 5.2 16.50 5.9 29.16 4.1 26.20 4.8 25.66 7.3 27.27 3.1 4 85 2 6 oo i 002 004 010 on 012 014 020 021 022 024 040 041 042 044 66i 002 004 010 Oil 012 014 020 021 022 024 040 041 042 044 001 002 004 HI" 101 102 104 100 101 102 104 100 101 102 104 200 201 202 204 200 201 202 204 200 201 202 204 040 040 040 HID 100 100 11(1 110 110 120 120 120 140 140 140 200 200 200 210 210 210 220 220 220 240 240 240 17.96 6.2 17.83 6.0 24.05 7.6 -17.92 8.2 -3.62 6.9 -10.21 6.3 102 104 110 7.11 5.7 21.48 7.4 32.84 7.1 43.24 6.4 23.42 6.3 46.88 6.8 42.58 9.4 35.81 6.6 24.61 7.9 45.17 9.0 38.22 7.5 60.28 8.6 111 -3.55 4.4 22.11 5.9 25.92 5.8 112 114 120 121 5.54 6.1 15.54 9.0 2.18 6.6 122 124 . . 140 141 2.64 8.8 9.99 8.4 25.46 9.8 142 144 200. . 201 .... -4.26 2.8 8.23 6.3 202 204 210 211 7.87 5.9 21.62 5.3 34.86 7.9 19.78 7.9 34.41 5.3 39.09 5.5 32.84 7.1 11.18 8.3 32.07 4.6 33.37 5.1 28.57 8.7 21.95 6.7 9.49 7.4 26.99 8.4 20.14 7.6 212 214 220 221 .42 7.1 -1.57 7.1 -15.00 7.6 222 224 240 . ... 241 -2.96 6.3 -3.50 8.4 -1.89 5.1 242 244 400 401 17.38 3.3 -3.01 4.3 -2.24 3.7 14.81 4.9 16.06 5.1 12.14 3.3 30.12 7.0 38.98 4.4 22.35 7.0 32.04 3.2 35.53 2.5 15.73 4.0 24.94 2.7 13.13 3.1 5.89 3.1 001 002 004 010 Oil 012 014 020 021 022 024 040 041 042 044 400 401 402 404 400 401 402 404 400 401 402 404 400 400 400 410 410 410 420 420 420 440 440 440 22.23 4.2 1.84 5.0 2.61 4.5 l'.25 7.1 -2.67 5.9 15.31 8.5 -16^63 8.3 -6.94 5.4 -3.45 5.1 9.21 ' 4.8 -2.60 5.1 -9.84 5.1 402 404 19.66 5.5 -1.32 6.1 15.15 5.4 32.36 7.9 43.83 5.1 4.97 7.7 35.05 5.4 37.77 4.5 20.58 4.8 7.56 4.3 16.14 5.3 8.13 4.8 410 411 412 414 . 420 421 422 424 440 441 442 444 The percentage increase obtained with each treatment is subtracted from the percentage increase obtained with the treatment listed in the column at the left to derive the efficiency factor of each element indicated. b The "efficiency factor" of any one element in a given combination may be expressed as the difference between the effectiveness of the given combination and the effectiveness of a corresponding combination with the one element left out.