11 !ie BULLETIN 280 JUNE, 1951 STUDIES oj ORGANIC MATERIALS jo VEGETABLE CROPS AGRCUTUL ENT R . V. oDi ou , a of ALABMA di E. Drector V. Sith, POYTECH IC INTITUT uburnAlabam CONTENTS REVIEW OF LITERATURE --------------------- 3 SCOPE OF INVESTIGATION METHODS AND PROCEDURES --------------------------------------- 4 --------- 4------ PRESENTATION OF DATA----------------------------6 Effects of Winter and Summer Green-Manure Crops on Yields of Succeeding Vegetable Crops on Chesterfield Soil of Low Fertility -------------------- 6 Effects of Different Organic Materials on Vegetable Yields at Different Production Intensity Levels on Chesterfield Soil of Low Fertility-------------------- 11 Effects of Winter and Summer Legumes on Yields of Succeeding Crops of Vegetables on Norfolk Soil of Medium Fertility--------------------------------14 Comparative Effects of Different Kinds of Organic Materials on Yields of Vegetables-16 Special Studies Dealing with Manures, Commercial Fertilizers, and Minor Elements __________----------18 Effects of Mulching Materials on Crop Yields---------19 22 Effects of Organic Materials on Grade of Vegetablesof Repeated Applications of Organic Residual Effects -23 Materials on Vegetable Yields ___--------------Effect of Added Organic Materials on Soil Organic Matter Content----------------------------------29 Effects of Added Organic Materials on the Total Nitro------------------------- 4 gen Content of the Soil--Effects of Added Organic Materials on Soil Nitrates During the Growing Season---------------------______________35 Effects of Added Organic Materials on Soil Moisture During the Growing Season-----------------------------------38 Residual Effects of Added Organic Materials on the Soil Organic Matter Content-----------------------------------------41 Interrelation of Soil Treatments and the Organic Matter, Total Nitrogen, Nitrates, and Moisture in tie Soil -------- 43 Relationship Between Soil Nitrates During the Growing Season and Crop Yields-----------------------------------------45 DISCUSSIoN---------____------------------------------------------------------49 SUMMARY---------------------------------------------------------------------52 LITERATURE CITED --------------------------------------------------------- 55 7 APPENDIX FIRST PRINTING --------------------------------------------------------------------- 3M, JUNE, 1951 STUDIES "4h ORGANIC MATERIALS VEGETABLE CROPS L. M. WARE, Horticulturist W. A. JOHNSON, Assistant Horticulturist RESULTS of studies with use of organic materials on vegetable crops extending over a period of years are presented in this bulletin. As used herein, the term "organic materials" is applied to materials added to the soil either as green manures, as animal manures, or as mulching materials. The term "organic matter" is used to apply to these materials or other organic substances in the soil in the various stages of decomposition. "Humus" is used in the sense of the more or less stable end-product resulting from the process of decomposition of organic materials. Furthermore, the effects attributed to organic materials are considered to be the combined effects of the nitrogen, minerals, and carbonaceous matter that these materials contain and all effects that these have on plant growth and soil properties. REVIEW OF LITERATURE A close relationship exists between the organic matter of the soil, nitrogen of the soil, and soil fertility. The more stable forms of nitrogen are directly related to the organic matter and exist primarily as constituents of the soil humus (25). Jenny (11) has shown that organic matter in southern soils is low and that in regions having a similar precipitation-evaporation ratio for each drop of 10°C in mean annual temperature, the average organic matter cont tent of the soil increases two or three times. Marbut (14) has shown that nitrogen is low in the red and yellow soils, which are characteristic soils of the South. Funchess (7) has emphasized the seriousness of the low organic and nitrogen content of southern soil and the need of adding nitrogen for satisfactory yields. 4 ALABAMA AGRICULTURAL EXPERIMENT STATION Since the South has a high mean annual temperature, a high rainfall, and in general light soils, decomposition of organic matter and subsequent loss of nitrogen by leaching are high. It is, therefore, difficult to maintain and even more difficult to increase the organic matter in southern soils (10, 15, 21). Repeated applications, however, of large quantities of organic materials may slowly increase the soil organic matter content (8, 20, 29). Nitrogen available to crops may be released from applications of organic materials very soon after they are added (8, 13, 29). The amount of nitrogen released for plant use, however, is largely determined by the ratio of carbon to nitrogen (4, 6, 12, 18, 19, 23). In general, nitrates accumulate upon decomposition of materials having a carbon-nitrogen ratio less than 20 or 30 to 1. SCOPE OF INVESTIGATION The investigation has included studies of the immediate and residual effects of organic materials grown on the land and turned under, and of those introduced and incorporated in the soil or left on the surface as a mulch. The materials have included those high in nitrogen and those low in nitrogen. The value of organic materials has been measured by their effects on crop yields, on soil nitrates and soil moisture levels during the growth of crops, and by changes in the total nitrogen and organic matter content of the soil. The effectiveness of organic materials in supplying the nitrogen requirements of growing crops has been determined by comparison of yields of crops receiving organic materials and different rates of commercial nitrogen. Special attention has been given to studies dealing with the value of organic materials as one of a number of practices in intensive agriculture. Phases of this work have been reported in earlier publications (26, 28, 29, 30). METHODS AND PROCEDURES Only general methods and procedures are given at this point. Details are explained under each separate phase of the study as reported. The investigation was conducted at the Main Station, Auburn, in specially constructed concrete field bins (27). The bins were 1/320- and 1/640-acre in size. Before the experiments were ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 5 started, the soil in each series was composited among all bins and within each bin. Yields of crops were obtained by separate harvest periods and by different grades. Soil samples for analysis were taken by compositing the soil from eight borings at specified points in the bins. The samples represented the top 8 inches of soil. Current nitrate and moisture levels were obtained by determining the amount of nitrates and moisture in the soil at stated intervals during growth of the crops. Samples for total nitrogen and organic matter determinations were taken once yearly in the fall. The phenoldisulphonic acid method was used for nitrate determinations (22), the oven-dry method for moisture determinations (2), the Kjeldahl method modified to include nitrates for total nitrogen determinations (2), and the chromic acid method for organic matter determinations (1). The studies consisted of a number of series conducted in different sets of bins. The series designations correspond to bin number or numbers. In many instances, yields are expressed as the average of a number of crops over a number of years. The averages represent the total yields of all crops for the number of years involved, divided by the total number of crop years. Residual effects of organic materials were determined by continuing the experiment for a number of years after the last application of the materials. Records were kept on yields, soil organic matter content, and total nitrogen content during the residual period. Two phases of the investigation were conducted on a Norfolk soil of medium fertility (Series A4 and A7), two phases on a Chesterfield soil of medium fertility (Series B14 and B23), and four phases on a Chesterfield soil of low fertility (Series B1-B3, Series B2, Series B15-16, and Series B19-B21). In most series, one ton per acre of limestone was applied to all treatments at the beginning of the experiment. Minor or trace elements were applied at 3-year intervals to all Chesterfield soils. The minor elements consisted of 12.5 pounds of CuSO4.5H 20, 25.0 pounds of MgSO4.7H20, 5.0 pounds of MnSO 4.4H 20, 12.5 pounds of ZnSO 4.7H20, 12.5 pounds of FeSO4.7H 2 0, and 5.0 pounds of H3 B0 3 per acre. Detailed treatments for each series are given in the tables. 6 ALABAMA AGRICULTURAL EXPERIMENT STATION PRESENTATION OF DATA In presenting each phase of study, there is given a brief statement of its purpose, specific procedures used, and results obtained. Data relating to crop yields are presented first, and are followed by data on other effects. Certain relationships are then shown between the measured effects on the soil and crop yields. EFFECTS OF WINTER AND SUMMER GREEN-MANURE CROPS ON YIELDS OF SUCCEEDING VEGETABLE CROPS ON CHESTERFIELD SOIL OF Low FERTILITY This phase of the study consisted of growing and turning under of legume and nonlegume green-manure crops. A summer crop and a fall crop of vegetables followed turned winter cover crops, while a fall crop and a spring crop followed summer cover crops on the same plots. The soil was a Chesterfield of low fertility. All plots received a standard amount of phosphorus and potash. Nitrogen treatments consisted of 0, 30, and 60 pounds per acre of nitrogen, each with and without a legume. The nonlegume was grown only on plots receiving the highest rate of nitrogen. Treatments were in quadruplicates. Series B15-16 was assigned to this study. The primary objectives of this phase were to determine: (1) Increases in yields of vegetables resulting from turning of summer and winter legumes where no commercial nitrogen had been added, (2) amount of commercial nitrogen required to give increases in yield equivalent to those from legumes, (3) increases in yield from the legume when different amounts of commercial nitrogen were used, (4) increases in yield from different amounts of commercial nitrogen when a legume was turned, and (5) increases in yield from nonlegumes with commercial nitrogen. The upper rate of commercial nitrogen was set at 60 pounds per acre, an amount which was considered adequate to establish the foregoing objectives. The data show that this rate was adequate to establish all but the second objective. The average yields of all crops in each group for all years are given in Table 1. Comparative effects of selected treatments are shown graphically in Figure 1. The yields of the individual crops are given in Appendix Tables 1, 2, and 3, and manure crop weights given in Appendix Table 4. ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 7 Effects of Winter Green-Manure Crops on Yields of Summer Vegetables The average yield of five summer vegetables without commercial nitrogen and without winter legume was 3,286 pounds per acre (Table 1). The turning of a crop of vetch increased the yield to 12,400 pounds, whereas the addition of 30 pounds of commercial nitrogen per acre increased the yield to only 6,937 pounds; the addition of 60 pounds of commercial nitrogen increased yield TABLE 1. AVERAGE YIELDS AND INCREASES IN YIELD OF SUMMER AND FALL VEGETABLES FOLLOWING TURNED WINTER COVER CROPS AND OF FALL AND SPRING VEGETABLES FOLLOWING TURNED SUMMER COVER CROPS RECEIVING DIFFERENT RATES OF NITROGEN, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B15-16, 1940-1949 Fertilizer grades, . 1OOO llb. 1,000 x per acre Kinds of cover crops cover crops turned Yields per acre With Without cover cover Increases in yields from use of turned cover crops Amount Pounds 2 crops crops Per cent Pounds 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Vetch Vetch Vetch Rye Rye(R)' Vetch Vetch Vetch Bye Rye(R)' Cowpea Cowpea Cowpea Corn Corn(R)' Cowpea Cowpea Cowpea Corn Corn(R)' 3,236 6,937 8,929 8,929 8,929 FALL VEGETABLES Pounds 12,400 14,342 15,386 14,335 12,769 FOLLOWING SUMMER VEGETABLES FOLLOWING WINTER COVER CROPS 9,164 7,405 6,457 5,406 3,840 WINTER 283 107 72 61 43 COVER CROPS 4 2,558 8,174 11,563 11,563 11,563 FALL VEGETABLES 6,733 11,670 13,991 13,547 12,707 FOLLOWING 4,175 8,496 2,428 1,984 1,144 SUMMER COVER 168 43 21 17 10 CROPS 4 3,075 10,063 15,127 15,127 15,127 SPRING VEGETABLES 18,931 18,450 20,808 15,943 14,122 2,945 6,355 8,658 8,809 8,225 10,856 8,387 5,681 816 -1,005 1,291 1,064 767 918 334 853 88 38 5 -7 COVER CROPS 5 FOLLOWING SUMMER 1,654 5,291 7,891 7,891 7,891 78 20 10 12 4 SOne ton limestone and 10 pounds of borax per acre were applied to all treatments at the beginning of the experiment. Minor elements were applied to all treatments once each 3 years, beginning with an application in 1945. 2 Summer crops consisted of beans, lima beans, eggplant, pepper and tomatoes. ' The cover crop was cut and removed from area. 4Fall crops consisted of Chinese cabbage, collards, kohlrabi, mustard, onions, tendergreen and turnip. 5 Spring crops consisted of beans, beets, cabbage, carrots, chard, lettuce, onions, potatoes, radish, and spinach. 8 ALABAMA AGRICULTURAL EXPERIMENT STATION to only 8,929 pounds. The winter legume, therefore, increased the average yield of summer vegetables about 2.5 times as much as 30 pounds of commercial nitrogen or about 1.6 times as much as 60 pounds of commercial nitrogen. The higher rate of commercial nitrogen for this group was not adequate to establish the maximum value of legumes expressed in pounds of commercial nitrogen. This is established in another phase on the same soil. Turning under vetch on plots receiving no commercial nitrogen increased the average yield of summer vegetables 9,164 pounds per acre. On plots receiving 30 pounds of commercial nitrogen, the turning of vetch increased yields 7,405 pounds and on plots receiving 60 pounds of commercial nitrogen 6,457 pounds. The average yield of all summer crops following vetch was 12,400 pounds per acre without the addition of any commercial RELATIVE YIELDS 6.00 5.00 1 4-00 3.00 2.00 - 1. 00.00 . |: 1 f\ 1 I SUMMER CROPS FOLLOWING WINTER LEGUMES (5 CROPS) NO NITROGEN, SNO LEGUMES FALL CROPS FALL CROPS SPRING CROPS FOLLOWING FOLLOWING FOLLOWING WINTER SUMMER SUMMER LEGUMES LEGUMES LEGUMES (7 CROPS) (10 CROPS) (7 CROPS) SNO NITROGEN, SLEGUMES ~ 60 LB. NITROGEN, NO LEGUMES FIGURE I. Comparative yields of vegetable crops from use of legumes and commercial nitrogen, Chesterfield soil of low fertility, Series B15-16. ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 9 nitrogen. The average yield of plots receiving vetch was increased from 12,400 pounds to 14,342 pounds per acre by the addition of 30 pounds per acre of commercial nitrogen and increased to 15,386 pounds by the addition of 60 pounds of commercial nitrogen. The average yields of summer vegetables on plots receiving 60 pounds of commercial nitrogen and a turned crop of nonlegume was only 1,051 pounds less than the yield on plots receiving 60 pounds of nitrogen and a legume. Individual crops showed considerable differences in response to green-manure crops (Appendix Table 1). Increases resulting from vetch were 269 per cent for beans, 197 per cent for lima beans, 316 per cent for eggplants, 574 per cent for peppers, and 226 per cent for tomatoes. The yield increase of each of the individual crops following legumes was highly significant when used with no nitrogen, with 30 pounds, and with 60 pounds per acre of nitrogen. The increases in yield resulting from turning of the nonlegumes were also highly significant or significant in the case of all crops except lima beans. Effects of Winter Green-Manure Crops on Yields of Fall Vegetables Average yields for all years of seven fall vegetables following winter green-manure crops and receiving the several comparative treatments are given in Table 1. Yields of the individual crops are given in Appendix Table 2. The fall crops followed on the same plots as the summer crops just discussed. Increases in yields of fall crops following vetch were considerably less than increases in yields of summer crops immediately following the turning of vetch; the effects on fall crops, however, were pronounced, and the general pattern of response somewhat similar. Thirty pounds of commercial nitrogen increased the average yield of fall vegetables approximately 35 per cent more than vetch, while 60 pounds of commercial nitrogen increased the yield 116 per cent more. Increases in yield from the legume for most of the individual crops were generally significant or highly significant when used with each rate of nitrogen. The yield increases of Chinese cabbage, mustard, tendergreen, and turnip from use of the nonlegume were significant or highly significant, whereas increased yields of collards, kohlrabi, and onion were not significant (Appendix Table 2). 10 ALABAMA AGRICULTURAL EXPERIMENT STATION Effects of Summer Green-Manure Crops on Fall Vegetables Fall vegetables and later spring vegetables in this phase of the study were grown on the same plots after summer cover crops were turned. The average results for all crops are given in Table 1, while those for individual crops are presented in Appendix Table 2. On fall vegetables the effects of turning a summer legume were quite similar to those on summer vegetables following a turned winter legume crop. The average yield of the seven fall vegetables was increased from 3,075 pounds per acre to 13,931 pounds by turning a crop of cowpeas, while 30 pounds of commercial nitrogen increased the yield to 10,063 pounds and 60 pounds of commercial nitrogen to 15,127 pounds. The average yield was increased almost as much from the legume as from 60 pounds of commercial nitrogen per acre. Even though 30 and 60 pounds of nitrogen per acre were added, legumes still gave pronounced increases. The data in Appendix Table 2 indicate some differences between the individual fall vegetables in their response to commercial nitrogen and turned cover crops; the pattern of response, however, of the several crops is very similar. Yield increases of crops following the legume in most instances were highly significant; in only one instance was yield increase from the nonlegume significant. Effects of Summer Green-Manure Crops on Yields of Spring Vegetables The average yield of the 10 spring vegetables following summer green-manure crops is given in Table 1, and the yield of each crop is given in Appendix Table 3. Turning under a crop of cowpeas increased the average yield of spring vegetables from 1,654 pounds to 2,945 pounds, while the addition of 30 pounds of commercial nitrogen increased the yield to 5,291 pounds and the addition of 60 pounds of commercial nitrogen to 7,891 pounds. It is obvious, therefore, that the yield of spring crops was not increased very much by turning under cowpeas the previous summer followed by a fall vegetable crop. Evidently, the soil had been subjected to leaching winter rain. Thirty pounds of commercial nitrogen gave increases in yield almost three times as large as the legume. Turning the ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 11 legume gave an increase of only 20 per cent after 80 pounds of commercial nitrogen per acre had been added, while an increase of only 10 per cent resulted from the turned legume after 60 pounds of commercial nitrogen had been added. The turning of a nonlegume gave an increase of 12 per cent after addition of 60 pounds per acre of commercial nitrogen. Differences in yield of individual spring crops resulting from a turned summer legume were generally not significant. In no instance was the yield of a spring crop as high from applications of organic material as from 30 pounds of commercial nitrogen. EFFECTS OF DIFFERENT ORGANIC MATERIALS ON VEGETABLE YIELDS AT DIFFERENT PRODUCTION-INTENSITY LEVELS ON CHESTERFIELD SOIL OF Low FERTILITY The purposes of this phase of the study were to determine: (1) yields possible by progressively increasing fertilizer rates and organic materials singularly and in combinations, (2) relative value of different kinds of organic materials at three productionintensity levels, and (3) relative value of commercial fertilizers and different organic materials. The soil was a Chesterfield of low fertility. The series consisted of B19-B21. Treatments at the low production-intensity level consisted of applying 1,000 pounds of fertilizer per acre (6-10-6 grade), 6 tons of stable manure, and cowpeas grown at this level and turned. Treatments at the medium-intensity level consisted of 1,500 pounds of fertilizer per acre, 12 tons of stable manure per acre, and cowpeas produced at this level. Corresponding treatments at the high-intensity level were 2,000 pounds of fertilizer per acre, 18 tons of stable manure per acre, and cowpeas grown at this level and turned. Corn as a nonlegume was also grown at each intensity level; on the check plot the corn was removed and on another plot it was turned. Average yields of the seven spring crops and the six fall crops are given in Table 2; relative effects of selected treatments are shown graphically in Figure 2. Yields of the individual spring crops are given in Appendix Table 5 and those of the individual fall crops are presented in Appendix Table 6. Tonnages of cover crops turned by years are given in Appendix Table 7, and the approximate nitrogen content of each of the materials is given in Appendix Table 9. The average yields of spring crops were increased from 4,161 12 ALABAMA AGRICULTURAL EXPERIMENT STATION pounds per acre to 12,706 pounds as the fertilizer rate was increased from 1,000 pounds per acre to 2,000 pounds per acre plus 18 tons of animal manure per acre. The average yields of fall crops were increased from 8,132 pounds to 26,816 pounds per acre as the fertilizer was increased from 1,000 to 2,000 pounds per acre, 18 tons of animal manure were added, and a crop of cowpeas was turned. The average yields of the seven spring vegetables were increased from 4,161 to 5,458 to 5,584 pounds per acre as the fertilizer rate was increased from 1,000 to 1,500 to 2,000 pounds per acre, with no manures added or turned. The increases in yield of spring crops at the three intensity levels from turning cowpeas were 735 pounds per acre at the 1,000-pound fertilizer rate, 1,025 pounds at the 1,500-pound rate, and 950 pounds at TABLE 2. AVERAGE YIELDS AND INCREASES IN YIELD OF SPRING AND FALL VEGETABLES FROM USE OF DIFFERENT KINDS OF MANURES AT DIFFERENT PRODUCTIONINTENSITY LEVELS, CHESTERFIELD SOIL OF LOW FERTILITY, SERIES B19-B21, 1940-47 Treatmentsx ManuresAverage Average yields per acre Spring crops 3 Ferti2 Green lizer, Ani6-10-6 malncreases per acre per Cow- Corn acre pea Lb. Tons 1,000 1,000 1,000 1,000 0 0 6 6 __ T T - Fall crops' Total Lb. 8,132 15,373 16,748 24,528 from use of manures Lb. Pct. 7,241 8,616 16,391 89 106 202 Total Lb. 4,161 4,896 7,844 8,390 Increases from use of manures Lb. Pct. 735 3,683 4,229 18 89 102 yields of cover crops turned Lb. 12,218 22,705 R R 1,000 1,500 1,500 1,500 1,500 1,500 2,000 2,000 2,000 2,000 2,000 6 0 0 12 12 12 0 0 18 18 18 T R 8,161 5,458 6,483 10,003 11,280 11,270 5,584 6,534 12,706 12,144 12,033 4,000 1,025 4,545 5,822 5,812 950 7,122 6,560 6,449 96 19 83 107 106 17 128 117 115 19,428 10,186 16,776 23,329 26,089 24,926 10,836 16,346 25,924 26,816 24,827 11,296 6,590 13,143 15,908 14,740 6,010 15,588 16,480 14,491 139 65 129 156 145 58 151 159 140 15,316 12,678 24,735 23,226 13,220 27,458 29,495 T R T - T R R _ T T T 1 Minor elements were applied to all treatments once each 3 years beginning with an application in 1945. 2 In treatment marked T, the green manures were turned; those marked R were removed. 3 Spring crops consisted of beans, beets, cabbage, carrots, English peas, lettuce, and potatoes. 'Fall crops consisted of broccoli, Chinese cabbage, kohlrabi, mustard, onions, and turnips. ORGANIC RGANPIC MATERIAL STUDIES with VEGETABLE CROPS 13 aATERIAL STUDIES with VEGETABLE CROS1 .V SPRING f 1,500 LB. L.J6-10-6 FALL SPRING FALL (7 CROPS) (6 CROPS) (7 CROPS) (6 CROPS) (7 CROPS) (6 CROPS) 2,000 FALL SPRING 6-10- 6 LB. . 1~,500 LB. 6-10-6, 1,500 LB.6-10-6, VLi 12 TONS ANIMAL 0WPEAS. MANURE FIGURE 2. Comparative yields of vegetable crops from additional fertilizer and added manures, Chesterfield soil of low fertility, Series Bi 9-B21. 2,000-pound rate. The corresponding average increases from the application of stable manure at the three intensity levels were 3,683, 4,545, and 7,122 pounds per acre. It should be kept in mind that different rates of stable manure were added at the three intensity levels and that the stable manure was added in late winter just prior to the spring crops, whereas the cowpeas represent the growth made at the three respective levels and turned during the preceding summer. Yield increases from animal manure averaged considerably higher on plots receiving the higher fertilizer rates. The increases, however, were not in proportion to the increases in amount of manure applied. Increasing the rate of animal manure three times with the corresponding increase in fertilizer rates increased crop yield 92 per cent. The average yield of the six fall vegetables increased from 8,132 to 10,186 to 10,336 pounds per acre as the fertilizer rates were increased from 1,000 to 1,500 to 2,000 pounds per acre, with no manures added or turned. Cowpeas grown and turned just prior to planting the fall crops increased the average yield 7,241 pounds per acre at the 1,000-pound fertilizer rate, 6,590 pounds per acre 14 ALABAMA AGRICULTURAL EXPERIMENT STATION at the 1,500-pound rate, and 6,010 pounds per acre at the 2,000pound rate. On the other hand, the animal manures applied in late winter followed by an intervening spring crop of vegetables increased the average yields of fall vegetables 8,616 pounds, 13,143, and 15,588 pounds per acre, respectively, after the three fertilizer rates had been applied. The yield increases from the animal manure applied in late winter were 19 per cent higher at the 1,000-pound fertilizer rate, 99 per cent higher at the 1,500pound rate, and 159 per cent higher at the 2,000-pound rate than the cowpeas grown and turned immediately before the fall crops were planted. It is pointed out that commercial nitrogen above 90 pounds per acre failed to give increases in yield of fall or spring crops, whereas the addition of cowpeas or animal manure on plots receiving 90 pounds of commercial nitrogen resulted in marked increases in yield. EFFECTS OF WINTER AND SUMMER LEGUMES ON YIELDS OF SUCCEEDING CROPS OF VEGETABLES ON NORFOLK SOIL OF MEDIUM FERTILITY The purpose of this phase of the study was to determine the value of a turned legume crop in providing nitrogen requirements of vegetable crops on a soil somewhat heavier than the Chesterfield of low fertility. The topsoil was an introduced Norfolk sandy loam of moderate fertility, which was placed on a subsoil of Cecil clay. Four index crops were used to measure the relative value of legumes and commercial nitrogen. The treatments consisted of five rates of nitrogen with and without a legume crop grown and turned. The nitrogen rates were 0, 20, 40, 60, and 80 pounds per acre of commercial nitrogen. The study comprised Series A4. In Table 3 are given the average total and marketable yields of each crop for the 5-year period. Sweet corn and sweetpotato were used to measure the value of a winter legume on summer vegetables. Turnip was used to measure the value of a summer legume on a fall vegetable, while Irish potato was used to measure the value of a summer legume on a spring vegetable. The total yield of sweet corn receiving a turned crop of vetch but no commercial nitrogen was 8,642 pounds per acre. This yield was nearly equal to that obtained from 60 pounds per acre of commercial nitrogen. The turned vetch increased the yield of ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 15 corn 6,963 pounds per acre where no commercial nitrogen was added, 6,051 pounds where 20 pounds of nitrogen was applied, 3,245 pounds where 40 pounds of nitrogen was added, 2,011 pounds where 60 pounds of nitrogen was applied, and 1,422 where 80 pounds was added. The increase from vetch on limed plots receiving 80 pounds of nitrogen was 8,386 pounds per acre. Increases in yield of marketable corn resulting from a turned legume were 4,901, 5,438, 4,009, 1,809, and -258 pounds per acre when 0, 20, 40, 60, and 80 pounds per acre of nitrogen were added, respectively. On plots receiving lime and 80 pounds per acre of nitrogen, turned legumes resulted in an increase of 3,462 pounds per acre of marketable corn. Total yield of sweetpotatoes receiving vetch but no commercial nitrogen was just below the yield on plots receiving 60 pounds per acre of commercial nitrogen; marketable yields on the vetch plots were about the same as those on plots receiving 40 pounds per acre of commercial nitrogen without the legume. The total yield and the yield of marketable roots of fall turnips following a crop of turned cowpeas were somewhat below those of crops receiving 40 pounds of commercial nitrogen. The TABLE 3. YIELDS OF SPRING, SUMMER, AND FALL VEGETABLES RECEIVING DIFFERENT RATES OF NITROGEN WITH AND WITHOUT TURNED LEGUMES, NORFOLK SOIL OF MEDIUM FERTILITY, SERIES A4, 1943-47 Yields per acre of different vegetables Fertilizer grades, 1,000 lb. per acre Corn, sweet (5-yr. av.) With W'out winter winter legume legume Lb. Lb. 1,679 4,610 7,540 9,013 10,261 12,025 747 2,095 3,589 5,893 7,216 9,028 8,642 10,661 10,785 11,024 11,683 15,411 5,648 7,533 7,598 7,702 6,958 12,490 Fall turnips Sweet potatoes (5-yr. av.) (5-yr. av.) With W'out With W'out winter winter summer summer legume legume legume legume Lb. Lb. Bu. Bu. TOTAL YIELDS Spring potatoes (5-yr. av.) With W'out summer summer legume legume Bu. Bu. 46 86 129 174 223 194 12 37 62 95 123 118 50 87 139 178 207 206 19 40 72 100 123 121 0-10-7 2-10-7 4-10-7 6-10-7 8-10-7 8-10-71 0-10-7 2-10-7 4-10-7 6-10-7 8-10-7 8-10-71 185 325 374 423 468 486 118 224 246 278 308 303 407 400 438 426 487 490 253 253 292 259 322 281 10,626 14,281 29,986 86,290 37,373 89,362 YIELDS 2 27,053 32,021 36,401 38,676 38,993 41,904 14,609 16,211 18,122 18,519 18,426 19,496 MARKETABLE 6,266 8,201 16,436 19,400 19,760 20,729 1 Limestone was applied in 1943 at the rate of 1.5 tons per acre. 2Marketable yields for turnips represent the yield of roots. 16 ALABAMA AGRICULTURAL EXPERIMENT STATION total yield following cowpeas was 27,053 pounds per acre, whereas the yield following the addition of 40 pounds of commercial nitrogen was 29,986 pounds. Summer legumes resulted in only slight increases in yields of roots beyond the 40-pound rate of commercial nitrogen. On the other hand, the total yields of turnips continued upward through the 60- to 80-pound rates of commercial nitrogen. The yields of spring potatoes were not appreciably affected by the turned crop of cowpeas the preceding summer. This was true for total yields and also for yields of marketable potatoes. COMPARATIVE EFFECTS OF DIFFERENT KINDS OF ORGANIC MATERIALS ON YIELD OF VEGETABLES In Series B14 and A7, data are available on the comparative value of different forms of organic materials with other factors constant. RESULTS FROM SERIES B14. This study consisted of a compari- son of crop yields from the use of animal manure, vetch, and rye. All treatments received 1,000 pounds per acre of a 6-10-4 fertilizer. The manure consisted of an annual application of 12 tons per acre; the rye and vetch turned were the amounts grown on the land. Minor elements were added to all treatments. The soil was a Chesterfield of medium fertility. Results are given in Table 4. Animal manure increased yields of the individual crops considerably more than either vetch or rye. Rye gave yields as high as vetch. The yields of crops receiving animal manure and vetch were substantially the same as those receiving animal manure alone. RESULTS FROM SERIES A7. This study consisted of a comparison of crop yields from use of fixed quantities of introduced materials and from use of cowpeas and vetch grown as manure crops. The introduced materials consisted of 2 tons of dry sericea lespedeza per acre added in late winter and of 6 tons of green crotalaria per acre turned in summer. Early-planted spring crops were started where necessary before the vetch was turned by laying-off the rows, adding the fertilizer, and turning the vetch between rows at a later period. When sweetpotatoes were grown as a summer crop, 12,000 pounds of cowpeas per acre was introduced. All treatments received an application of 1,000 pounds 0 A 0 z *I m TABLE 4. AVERAGE YIELDS OF SPRING AND FALL VEGETABLES 1 RECEIVING DIFFERENT KINDS OF MANURES, CHESTERFIELD SOIL OF InI -0 r MEDIUM FERTILITY, SERIES B14, 1940-48 i- Treatments Fertilizer, 6-10-4 per acre Pounds 1,000 1,000 1,000 1,000 1,000 21Minor Average yields per acre Fall crops Summer crops Potatoes Beans, pole Tomatoes Corn, sweet al Increases Total Increases Total Increases (4-yr. av.) in yinrinain yield (4-yr. av.) yield (4-yr. av.) yield (4-yr. av. ) yield Bushels Bushels Bushels Bushels Bushels Bushels Pounds Pounds Pounds C m Manures Green2 Ani-AverageIncrses mal Kind amount m)per acre Tons 0 12 0 0 12 0 0 Vetch Rye Vetch 177 m (4-av.) 4,686 9,059 6,454 7,553 9,212 I 0 w I- 0 0 9,734 11,298 14,334 4,378 1,768 2,867 4,526 376 709 467 461 697 333 91 85 321 108 195 123 145 147 87 15 37 39 36 50 41 40 49 14 5 4 13 m A 0 elements were applied to all treatments once each year through 1945; thereafter applications were made each 3 years. Vetch and rye were grown on plots and turned; animal manure was applied in late winter. V4 18 18 TABLE ALABAMA ALABAMA AGRICULTURAL EXPERIMENT STATION DIFFERENT KINDS OF MANURES, AGRICULTURAL EXPERIMENT STATION 5. AVERAGE YIELDS AND INCREASES IN YIELDS OF SPRING AND EARLY SUMVEGETABLES RECEIVING MER AND FALL NORFOLK SOIL OF MEDIUM FERTILITY, SERIES A7, 1989-48 Treatments 1 2 Yields and increases in yields per acre summer crops3 Increases in total Total from manures Lb. Lb. 9,306 14,193 4,887 13,071 3,765 11,529 2,223 Fall crops4 Increases Total in total from manures Lb. Lb. 9,501 15,251 12,041 12,085 5,750 2,540 2,584 Spring and early Ferti Manures FertiIncreases lizer Amount Market- in market6-10-4izer, 6-10-4 acKind able able from per per acre per acre manures Lb. Lb. Lb. Lb. 1,000 0 0 6,976 1,000 Standard 16,000 12,049 5,073 1,000 Vetch 9,934 10,462 3,486 1,000 Cowpeas 14,217 9,260 2,284 was used as a standard practice with all crops. Standard manure treatment consisted of the addition of 2 tons per acre of dry sericea lespedeza in late winter and 6 tons of green crotalaria in summer. Vetch and cowpeas were grown and turned. 3 Spring and early summer crops consisted of beans, cabbage, potatoes, sweet corn, squash, and sweetpotatoes. crops consisted of broccoli, lettuce, onion, tendergreen, and turnip. 2 'Irrigation 'Fall per acre of 6-10-4 fertilizer and one-inch-per-week irrigation when rainfall failed to supply this quantity. The soil was a Norfolk sandy loam of medium fertility. Results are presented in Table 5. The average yields of spring and early summer crops were increased 4,887 pounds per acre by the introduced lespedeza and crotalaria, 3,765 by the vetch in late winter, and 2,223 by the cowpeas turned late in the previous summer. Yield increases of fall crops from the crotalaria and sericea were 5,750 pounds per acre, from vetch, 2,540 pounds, and from cowpeas 2,584 pounds. SPECIAL STUDIES DEALING WITH MANURES, COMMERCIAL FERTILIZERS, AND MINOR ELEMENTS This study was conducted on a soil that had failed to make satisfactory yields when any amount of commercial fertilizers was used. The purpose was to determine the extent to which increasing the nitrogen and dividing the fertilizer application would overcome the difficulty as compared to additions of manures, lime, and minor elements. The standard fertilizer rate in this experiment was 1,500 pounds per acre. Nitrogen supplied in the two fertilizer grades amounted to 90 and 180 pounds per acre. Fertilizers were applied as one application and as four applications. The organic materials consisted of 12 tons per acre of animal manure and of cowpeas grown ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 19 on the land. The minor-element mixture included copper, magnesium, manganese, zinc, iron, and boron. Treatments and results are given in Table 6. Data show that yields of spring and fall crops on this soil receiving 90 and 180 pounds per acre of nitrogen whether applied in one or four applications were comparatively low without manures. The yields of spring and fall crops receiving four applications of a commercial fertilizer containing 180 pounds of nitrogen ranged from one-twentieth to one-half as great as yields of those receiving four applications of commercial fertilizer containing 90 pounds of nitrogen plus stable manure. Lime did not greatly affect yields, and only in the case of beets were yields appreciably affected by minor elements. Much greater differences occurred between treatments in the spring than in the fall. Satisfactory yields occurred in the spring only when animal manure was used with divided applications of the commercial fertilizer. In the fall, yields from crops receiving manure were practically the same irrespective of whether commercial fertilizer was applied in one or in four applications. EFFECTS OF MULCHING MATERIALS ON CROP YIELDS The term "mulching materials," as used in this phase of study, is applied to materials added either to the surface of the soil or incorporated in the soil. With exception of mulch paper, the mulching materials added large quantities or organic matter to the soil and considerable quantities of nitrogen in the case of certain types of materials (Appendix Table 9). To a considerable degree, mulching materials may affect the water-holding capacity and temperature of the soil as well as surface temperatures. The effects of the materials on crop yields only are discussed here. Five materials were used as surface mulches. In establishing the surface mulch, 1.5 inches of each material except the paper mulch was added to the first crop; thereafter a 1.5-inch mulch was maintained by adding fresh material before planting the spring and the fall crops. Five mulching materials or combinations were incorporated in the soil. The amounts of the incorporated materials are indicated in the tables. In Table 7, the yields of two summer crops and two fall crops are given. Composition of the mulch was an important factor in 0 TABLE 6. YIELDS OF SPRING AND FALL VEGETABLES RECEIVING FERTILIZERS CONTAINING DIFFERENT AMOUNTS OF NITROGEN APPLIED IN SINGLE AND DIVIDED APPLICATIONS, MANURES, LIMESTONE, AND MINOR ELEMENTS, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B2, 1945-49 Treatments Fertilizer grades, 1,500 lb. per acre Number applications of fertilizer' Manures2 AniGe mal Green p acre Yields of vegetables per acre Limestone acre" per Minor elements per acrea Spring Fall Beets, Total CrTenderTotal Total green, totaltl total rI- N-P-K 6-8-4 12-8-4 6-8-4 12-8-4 6-8-4 6-8-4 6-8-4 6-8-4 6-8-4 6-8-4 6-8-4 No. 1 1 4 4 1 4 4 4 4 4 4 Tons 0 0 0 0 12 12 12 12 0 0 0 0 0 0 0 0 0 0 0 Cowpeas 0 0 Tons 0 0 0 0 0 0 1 1 1 1 1 Lb. 0 0 0 0 0 0 0 0 0 0 72.5 Lb. (5-yr. av.) 34 30 841 507 3,944 10,790 11,201 (3-yr. av.) Lb. (5-yr. av.) 2,027 2,438 7,580 2,772 9,899 17,641 21,261 (3-yr. av.) Lb. (5-yr. av.) Lb. (6-yr. av.) Lb. (6-yr. 1,713 1,716 6,138 6,570 5,211 12,879 13,298 (3-yr. av.) 12,124 10,790 11,347 10,442 22,710 23,209 24,744 (3-yr. av.) 15,728 12,557 16,368 15,644 31,683 34,111 32,732 (3-yr. av.) C - A C av.) 12,288 6,297 4,564 10,733 23,450 17,216 12,832 12,755 10,867 7,636 7,284 7,142 29,747 14,912 17,197 15,584 29,312 18,649 16,985 19,386 )25 m 13z 'vi z -o -O ZI ' When one application of fertilizer was made, all fertilizer was applied one week before planting; when four applications were made, one-fourth of fertilizer was applied before planting and the balance applied in three applications at 2-week intervals after crop was planted. 'Animal manure was applied in August of each year. 3One ton of limestone was applied at beginning of experiment. 'Minor element mixture was applied once each year. TABLE 7. AVERAGE YIELDS AND INCREASES IN YIELD FROM USE OF DIFFERENT MULCHING DIUM FERTILITY, SERIES B23, 1940-49 MATERIALS, CHESTERFIELD SOIL OF ME- 0 Q Treatments' Corn, (3-yr. av.) 1946-7, 1949 Total Lb. 4,725 6,195 8,413 5,527 8,319 10,941 8,907 6,577 7,358 8,069 7,972 9,370 6,451 7,225 6,862 7,027 Average yields and increases in yield per acre Summer crops sweet Tomatoes Gains Gains (4-yr. from )a from mulch 1940-43 mulch mamaterials Total terials Lb. 1,470 3,688 802 3,594 6,216 4,182 1,852 2,633 3,344 3,247 4,645 1,726 2,500 2,137 2,302 Bu. 406 434 682 422 451 720 722 535 589 506 517 617 501 523 448 500 Bu. 28 276 16 45 314 316 129 183 100 111 211 95 117 42 94 Fall crops Beans, pole Potatoes (4-yr. Gains Gains (4-yr. av.) from v .) from fro m 1944, mulch 1940-43 mulch 1946-48 mamaTotal terials Total terials Bu. 107 139 235 205 292 266 226 161 192 172 193 207 164 167 148 175 Bu. 32 128 98 185 159 119 54 85 65 86 100 57 60 41 68 Bu. 22 22 68 55 52 69 45 40 36 31 82 36 39 34 29 30 Bu. 0 46 33 80 47 23 18 14 9 10 14 17 12 7 8 z Mulching materials Kind None Mulch paper Sericea lespedeza Pine straw Oat straw Peanut hulls Peanut hulls Peanut hulls Peanut hulls Sericea lespedeza Sericea lespedeza Sericea lespedeza Amounts per acre 2 m straw straw straw straw 1-inch layer surface 1.5-inch surface 1.5-inch surface 1.5-inch surface 1.5-inch surface 1.5-inch incorporated 2 3.2 tons incorporated 4.8 tons incorporated 1.6 tons incorporated 3.2 tons incorporated 4.8 tons incorporated 3.2 9.6 8.2 9.6 6.4 6.4 tons tons tons tons tons tons incorporated incorporated incorporated incorporated incorporated incorporated m In 0 H Corn stalks-winter Green corn stalks-summer Crotalaria-winter Green soybean stalks-summer Alabama peat Alabama peat and lime3 1 All crops received 1,280 pounds 6-10-4 fertilizer per acre. Minor elements were applied to all treatments once each 3 years beginning in 1945. 2 Mulching materials were applied to each of two crops per year. The surface mulches were applied to a depth of 1.5 inches the first year and thereafter enough material was applied to maintain the 1.5-inch-depth. The same amount of peanut hulls was applied to the treatment with the 1.5-inch incorporated as was applied to the surface mulch treatment. For 1.5-inch mulch, it required the first year 25, 21, 20, and 16 tons of lespedeza straw, pine straw, peanut hulls, and oat straw per acre, respectively; to maintain this amount as a mulch it required 8.0, 7.5, 6.5, and 7.5 tons per acre per crop, respectively. 3 One ton of dolomitic limestone per acre was applied at the beginning of the experiment. 22 ALABAMA AGRICULTURAL EXPERIMENT STATION determining the effect on yields of the mulching material. Pine straw, a material low in nitrogen, gave relatively small increases in yields of summer crops, while oat straw gave intermediate increases. Lespedeza sericea straw and peanut hulls, both somewhat higher in nitrogen, resulted in large increases in yield of the summer crops. Yield increases from the legume types of mulching materials were determined largely by the amounts of the materials applied. A surface mulch of lespedeza straw resulted in an average increase of 3,688 pounds per acre in yield of sweet corn and 276 bushels in the yield of tomatoes. Incorporation of 1.6, 3.2, and 4.6 tons per acre of lespedeza gave average yield increases of sweet corn of 3,344, 3,247, and 4,645 pounds per acre, and increases of 100, 111, and 211 bushels per acre of tomatoes, respectively. Yield increases of corn of 1,852, 2,633, 4,182, and 6,216 pounds per acre resulted from 3.2 tons of peanut hulls incorporated in the soil, 4.8 tons incorporated, equivalent of 1.5 inches incorporated, and 1.5 inches as a surface mulch. Increases in yield of tomatoes were similar to those of corn for corresponding treatments. Increases in yield of fall crops from increased amounts of peanut hulls and lespedeza straw were very similar to those of summer crops. Pine straw and oat straw mulches, however, gave relatively larger yield increases in the fall than in the summer. Paper mulch and Alabama peat gave only moderate increases in yields. EFFECTS OF ORGANIC MATERIALS ON GRADE OF VEGETABLES Data presented thus far have dealt primarily with total yields. The yield of marketable products and percentage relation to total yields are of great importance to the vegetable grower. Records by grades were obtained in all series on crops normally graded. Data on the yield of marketable products and on the percentage of marketable grades are given for several series. In Table 8 and Table 9 are the results from Series B14 and Series B19-B21, respectively. Additional data on marketable yields from Series A4 and from Series A7 are given in Table 3 and Table 5. In general, the data show large increases in yield of marketable grades from organic materials where large increases have been obtained in total yields. The increases in the percentage of marketable grades are not generally as pronounced as the actual in- ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 23 TABLE 8. YIELDS AND PERCENTAGE MARKETABLE GRADES OF VEGETABLES RECEIVING DIFFERENT MANURE TREATMENTS, CHESTERFIELD SOIL OF MEDIUM FERTILITY, SERIES B14, 1940-48 Treatments' Manures Yields and percentage yields of marketable grades per acre FertiAnilizer, 6-10-6 mal per acre per acre Green 2 Corn, sweet, (4-yr. av.) Tomatoes, summer (4-yr. av.) Potatoes, fall 4 ( -yr. av.) Per cent Total Per cent Total Total Per cent market- market- market- market- market- marketable able able able able able Pounds Tons 1,000 1,000 1,000 1,000 1,000 0 0 0 12 12 0 Vetch Rye 0 Vetch Pounds Per cent Bushels Per cent Bushels Per cent 2,420 8,874 5,022 6,291 6,946 54 60 66 69 75 246 322 307 507 485 67 69 67 72 70 27 80 28 40 39 73 78 70 80 80 elements were applied to all treatments once each year through 1945 and thereafter applications were made once each 3 years. 2 Green manure crops were grown and turned. 'Minor creases in yield; however, they are consistent. A few instances are cited. In Series B14 (Table 8), the yield of marketable corn was increasd from 2,420 pounds to 6,946 pounds per acre as a result of adding animal manure and vetch, while the percentage of marketable grades was increased from 54 to 75 per cent. The yield of marketable tomatoes was increased from 246 to 507 bushels per acre as a result of adding animal manure; the percentage of marketable grades, however, increased only from 67 to 72 per cent. Yield of marketable grades of fall potatoes were not affected as much as the other two crops. In Series B19-B21, the yield of marketable spring cabbage on plots receiving 1,000 pounds per acre of a 6-10-6 fertilizer, was increased from 4,294 pounds per acre to 7,418 pounds from cowpeas turned the previous summer, while the percentage of marketable cabbage was increased from 87 to 49 per cent (Table 9). Six tons of animal manure increased the yield of marketable heads from 4,294 to 10,807 pounds per acre and the percentage of marketable heads from 37 to 53 per cent. RESIDUAL EFFECTS OF REPEATED APPLICATIONS OF ORGANIC MATERIALS ON VEGETABLE YIELDS In addition to information on the effects immediately following the addition of organic materials, it is important to know what effects may be expected in later years. In a number of series, TABLE 9. YIELDS AND PERCENTAGE OF MARKETABLE GRADES OF VEGETABLES RECEIVING DIFFERENT MANURES, AT DIFFERENT PRODUCTION-INTENSITY LEVELS, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-47 Treatments' Fertilizer, Ani6-10-6 mal per per acre acre Lb. Tons 0 1,000 1,000 0 6 1,000 1,000 6 1,000 6 1,500 1,500 1,500 1,500 1,500 2,000 2,000 2,000 2,000 2,000 0 0 12 12 12 0 0 18 18 18 Manures 2 Green Cowpea Yields and percentage yields of marketable grades per acre Lettuce, spring Potatoes, spring Kohlrabi, fall Cabbage, spring Carrots, spring Beets, spring (5-yr. av.) (3-yr. av.) (3-yr. av.) (4-yr. av. ) (4-yr. av.) (3-yr. av.) Total Per cent Heads Per cent Total Per cent Total Per cent Total Per cent Total Per cent Corn market- market- market- market- market- market- market- market- market- market- market- marketable able able able able able able able able able able able R Lb. 282 679 2,317 3,200 2,833 491 1,591 4,677 4,885 4,783 781 1,242 6,119 6,071 5,674 Pct. 34 45 69 76 74 47 70 84 88 85 60 66 89 92 89 Lb. 4,294 7,413 10,307 9,262 9,577 6,321 10,125 11,663 15,914 14,045 6,374 11,232 16,352 15,247 16,010 Pct. 37 49 53 51 52 41 51 55 61 56 41 56 59 58 60 Lb. 2,538 2,403 5,652 6,711 6,749 2,432 4,266 8,660 9,639 9,962 3,328 3,676 11,124 10,714 9,969 Pct. 58 60 79 76 82 60 75 85 85 86 67 68 87 88 90 Lb. 1,344 2,572 3,609 4,510 4,681 2,205 2,205 4,364 4,211 4,633 1,855 2,087 4,889 4,129 5,051 Pct. 40 64 71 68 66 58 60 74 65 73 51 59 73 75 75 Lb. 1,920 2,172 5,581 5,291 5,499 2,569 2,415 6,136 9,361 8,632 2,266 2,871 10,044 10,398 10,756 Pct. 35 35 35 31 32 28 25 29 37 35 24 28 38 38 39 Bu. 38 42 56 77 69 57 52 94 85 100 56 57 133 114 109 Pct. 58 58 62 67 68 65 64 70 67 72 68m 68 73 73 72 U- T R T __ __ T T T R T R T T T R R a X C C m m 1 Minor elements were applied to all treatments once each 8 years beginning with an application in 1945. 2 In treatments marked T, the green manures were grown and turned; those marked R were removed. -z o z ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 25 studies were continued for 3 years after applications of organic materials were discontinued. Results obtained in Series B19-B21 are presented. In Table 10, are given the average and relative yields of four fall vegetable crops produced over a 9-year period when organic materials were added, and the yields of the same crops after the organic applications were discontinued. The same information is given for spring crops in Table 11. Treatments are indicated in the tables. Results are graphically presented in Figures 3 and 4. The animal manures were added in late winter before spring vegetables were planted; the cowpeas and corn were turned in late summer before fall vegetables were planted. The study was made at each of three production-intensity levels. The last application of the organic materials was made in 1947, when yields for that year were below average. During the period when manures were being added, turning under cowpeas increased average yields of fall vegetables 76 RELATIVE YIELD 2.0 0:. PERIOD MANURES ADDED (1939-47) 1,500 LB. 6-10- 6 RESIDUAL PERIOD, FIRST YEAR (1948) RESIDUAL RESIDUAL PERIOD, PERIOD, SECOND YEAR THIRD YEAR (1949) (1950) ;"1,500 LB.6-10-6, 12 TONS ANIMAL MANURE ill 1,500 LB. 6-10-6, COWPEAS FIGURE 3. Residual effects of manures on average yields of four fall vegetables, Chesterfield soil of low fertility, Seris B19-821. 26 ALABAMA AGRICULTURAL EXPERIMENT STATION 26 ALABAMA AGRICULTURLEPRMN TTO RELATIVE YIELD 2.00 1.00 . J . . . . .er;. . r... ..... d.~ r " ".00 iw C' .i PERIOD MANURES ADDED RESIDUAL RESIDUAL RESIDUAL PERIOD, PERIOD, PERIOD, FIRST YEAR SECOND YEAR THIRD YEAR (1948) 5 00 LIAtv1500 66-1010 (1939-47) LB.fl1 (1949) (1950) 1~l500 LB.6-10-6 LB. 6 -106 COWPEAS 2L 12 TONS ANIMAL MANURE FIGURE 4. Residual effects of manures on average yields of four sprung vegetables, Chesterfield soil of low fertility, Series Bi 9-B21. per cent at the low-intensity level, 48 per cent at the mediumintensity level, and 53 per cent at the high-intensity level. At the low-intensity level one year after the last application of organic materials, the yields of plots on which cowpeas were turned averaged 30 per cent higher than those of plots without cowpeas, and averaged 19 per. cent higher after 2 years. At the mediumintensity level, yields on plots one year after the last crop of cowpeas was turned were 18 per cent, and after 2 years 4 per cent above the check plots. At the high-intensity level, the yields were 20 per cent the first year and 27 per cent the second year above the check plots. By the third year, practically all differences had disappeared at each level.. Yields of fall vegetables on plots receiving animal manures during the treatment period averaged 92 per cent above the check. plots at the low-intensity level, 101 per cent at the mediumintensity level, and 119 at the high-intensity level. One and 2 years after the last manure application, yields were 31 and 26 0 TABLE 10. RESIDUAL EFFECTS OF MANURES ON THE YIELDS OF FALL VEGETABLES, CHESTERFIELD SOIL OF LOW. FERTILITY, SERIES B19-B21, 1939-50 Treatments' Friie, 6-10-6 FrilzrAia Z Average yields per acre' Relative yields MnrsFirst Greene period, manures added' per acre per acre Cowpea Tons Lb. 0 0 - Corn 1939-47 Lb. 458 8,742 15,354 22,798 18,884 11,124 16,508 1947 Lb. 0 5,469 9,430 10,007 manuresperiod,1950 added 1948 1949 Residual no period, manures added' 1939-47 1947 First Residual period, no manures added I-n 1948 Pct. 100 130 131 1949 Pct. 100 119 126 1950 Pct. 4 m 1,000 1,000 1,000 1,000 1,000 1,500, 1,500 1,500 1,500 1,500 2,000 2,000 2,000 2,000 2,000 0 0 6 6 6 0 R R R T T - 16,815 Lb. 349 10,089 13,155 13,181 Lb. 986 8,727 10,425 10,954 Lb. 90 10,076 10,515 10,994 Pct. 100 176 192 Pct. 100 172 183 100 104 109 TR R T R R T 13,197 12,288 8,090 9,549 17,574 14,890 14,659 17,306 13,226 11,030 11,673 12,096 12,486 11,347 12,793 12,937 261 216 100 148 241 225 100 118 0 12 12 12 0 0 18 18 18 T T T - 22,321 23,936 24,274 10,555 16,187 12,678 17,053 16,042 6,499 8,269 20,739 22,199 20,605 14,921 15,159 14,598 11,354 14,474 14,307 14,435 14,486 13,430 13,574 201 214 218 100 153 157 211 198 100 127 -118 100 141 151 141 100 104 174 148 152 126 124 113 100 101 128 130 125 100 127 112 113 113 100 101 I. T 'Minor elements were applied to all treatments once each 3 years beginning with an application in 1945. 2Itreatments marked T, the green manures were turned; those marked R were removed. last year green manures were turned was 1947. 4Fall crops consisted of collard, kohlrabi, mustard, and turnip. 23,156 23,472 23,139 14,983 16,659 15,744 18,870 23,751 15,709 24,083 21,645 100 120 16,576 17,571 15,319 14,534 16,246 13,804 219 222 219 231 256 242 151 153 138 146 155 135 108 121 103 The IN TABLE 11. RESIDUAL EFFECTS OF MANURES ON THE YIELDS OF SPRING VEGETABLES, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-50 Treatments Manures Fertilizer 6-10-6 Green Animal Corn acre per Cowper Tons 0 1 Average yields per acre4 2 2 Relative yields First period, 3 manures added 1947 1940-47 Pct. 100 110 172 183 178 100 117 173 200 199 Pct. 100 112 180 175 174 100 137 161 209 218 Residual period, no manures added 1950 1948 1949 Pct. 100 107 139 142 128 100 92 116 105 112 Pct. 100 98 110 133 139 100 117 159 137 163 100 109 154 159 188 Pct. 100 104 123 121 132 100 106 146 138 143 100 100 160 149 154 First period, manures added 1947 1940-47 Lb. 1,713 6,628 7,312 11,427 12,112 11,774 8,234 9,672 14,258 16,482 16,393 Lb. 4,090 8,180 9,193 14,763 14,305 14,244 9,996 13,699 16,128 20,897 21,774 Residual period, no manures added 1950 1948 1949 Lb. 1,743 9,886 10,578 13,730 14,064 12,640 14,189 12,995 16,438 14,850 15,945 Lb. 892 7,780 7,646 8,526 10,326 10,807 9,897 11,582 15,718 13,541 16,117 Lb. 742 10,591 11,001 13,060 12,797 13,948 12,874 13,628 18,745 17,732 18,364 Lb. 0 1,000 1,000 1,000 1,000 1,000 1,500 1,500 0 0 6 6 6 R R T R T -- T R c -I 0 0 T 1,500 1,500 12 12 T R __ T I- 1,500 2,000 2,000 12 0 0 T R F 100 100 100 9,293 13,510 12,081 15,643 8,446 90 9,855 12,025 14,021 10,140 13,482 117 100 184 109 21,599 219 17,089 14,290 18,495 22,232 R 18 2,000 107 209 163 20,117 16,735 14,785 17,622 19,681 T 18 2,000 207 167 100 T 17,463 20,128 15,566 17,427 20,822 18 2,000 1 Minor elements were applied to all treatments once each 3 years beginning with an application in 1945. 2 In treatments marked T, the green manures were turned; those marked R were removed. 3 The last year in which green manures were turned was 1947. SSpring crops consisted of cabbage, carrots, lettuce, and potatoes. m x m -4 m z I z 0 ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 29 per cent higher at the low-intensity level, 41 and 28 per cent higher at the medium-intensity level, and 51 and 46 per cent higher at the high-intensity level than the checks. By the third year the differences were about 10 per cent. Residual effects of animal manures in combination with cowpeas or corn were not very different from those of animal manure alone. Residual effects of cowpeas on spring crops were quite different from those on fall crops (Table 11). During the period when organic materials were being applied, yields of all spring vegetables following turned crops of cowpeas averaged only 10 per cent higher than the average check plot yields at the lowintensity level and 17 per cent higher at the medium- and highintensity levels. While fluctuating somewhat, yields of spring crops during the residual period indicated very little residual effect from turning under cowpeas. Three years after organic materials were discontinued, plots that had animal manure applications averaged 23, 46, and 60 per cent higher yields than the check plots at the three intensity levels. It is pointed out that the yield of fall crops at the high-intensity level was 27 per cent above that of the check plots 2 years after the last application of cowpeas, whereas the yield of spring crops during the period when the cowpeas were being turned was only 17 per cent above that of the check plots at the same intensity level. EFFECT OF ADDED ORGANIC MATERIALS ON SOIL ORGANIC MATTER CONTENT As previously stated, it is difficult under southern conditions to increase the organic matter content of a soil by addition of organic materials. In a number of series, annual determinations were made of organic matter in the soil. In other series, these determinations were made at less frequent intervals. Results of Studies in Series B19-B21 In Table 12 are given the data on organic matter content of the soil for the different organic treatments in Series B19-B21. The organic matter content of the soil in the series was quite low; however, some of the treatments applied repeatedly over a period of years gave highly significant increases in the amounts of organic matter content. 30 ALABAMA AGRICULTURAL EXPERIMENT STATION TABLE 12. ORGANIC MATTER CONTENT OF SOIL RECEIVING DIFFERENT KINDS OF MANURES OVER A PERIOD OF YEARS AT DIFFERENT PRODUCTION-INTENSITY LEVELS, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-46 Treatments Fertilizer, 6-10-6 Organic matter content of soil Green 2 Manures Animal Tons Cowpea Average all 1940 1945 years per acre Pounds Corn Per cent Per cent (1940-46) Per cent 0 1,000 0 0 R R 0.52 .57 0.62 .62 0.64 .66 1,500 2,000 1,000 1,500 2,000 1,000 1,000 1,000 1,500 1,500 1,500 2,000 2,000 2,000 Least significant difference at 0 0 0 0 0 6 6 6 12 12 12 18 18 18 T T T R R .60 .59 .62 .71 .62 .64 .64 .72 .71 .74 .98 1.00 1.07 1.16 1.29 1.41 1.53 1.45 1.74 .14 .19 .66 .66 .71 .74 .72 .90 .93 .98 1.02 1.07 1.14 1.17 1.26 1.28 .07 .09 R T T R T T R T __ .05 level .01 level .67 .67 .74 .69 .79 .72 .81 .79 .74 .12 .16 T xFertilizer was applied to each of two crops year year; manures were applied once each year. 2 In treatments marked T, green manures were turned; those marked R were removed. Increases in the organic matter content was closely related to the amount and kind of organic materials added. Animal manures affected the organic matter content considerably more than green manures. The average organic matter content at the end of 6 years was 0.62 per cent for treatments receiving 1,000 pounds of fertilizer but no organic materials. On plots on which no cover crop was turned under, the organic content of the soil in plots receiving annually different amounts of animal manure were as follows: 6 tons of manure per acre, 0.93 per cent; 12 tons, 1.16 per cent; and 18 tons, 1.53 per cent. These amounts represent increases in actual percentages of organic matter of 0.81, 0.54, and 0.91 for the three rates, respectively'. A difference of 0.14 per cent was sufficient for stacentage increases. 'Represent increases in the percentage of organic matter content and not per- ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 31 tistical significance at the .05 degree level and of 0.19 per cent at the .01 degree level. The average increases in actual percentage of soil organic matter content at the three production-intensity levels for the 6th year range from 0.07 to 0.10 on plots receiving a crop of cowpeas when used without animal manure. When cowpeas were used in combination with 6 tons of animal manure per acre, the increase in percentage attributable to the legume was 0.14. However, when cowpeas were used with 12 tons of animal manure, the increase in percentage of organic matter content attributable to the legume was 0.25; and when used with 18 tons of animal manure the credit to the legume was 0.21. The last two differences, while quite low, were highly significant statistically. Results of Studies in Series B14 Data on organic matter content of soil receiving different organic materials and treatments are given in Table 13 for series B14. Treatments are given in the table. The organic matter content of the soil in plots receiving no organic materials was 0.74 per cent at the end of 7 years. The amounts of soil organic matter of plots receiving the different organic materials were as follows: vetch, 1.03 per cent; rye, 1.10 per cent; 12 tons manure, 1.38; and 12 tons manure plus vetch, 1.52 per cent. A difference of 0.28 in percentage content TABLE 13. ORGANIC MATTER CONTENT OF SOIL RECEIVING DIFFERENT KINDS OF MANURES OVER A PERIOD OF YEARS, CHESTERFIELD SoIL OF MEDIUM FERTILITY, SERIES B14, 1940-46 lizer, 6-10-4 Ferti- Treatments Manures' Green Animal Kind Average amount per acre Organic matter content of soil Average of 1940 1940 1946 1946 5 years ( 1940-42, 1945-46) per acre Pounds Tons 0 12 0 0 12 0 0 Vetch Rye Vetch Pounds 0 0 9,784 11,298 14,334 .05 level .01 level Per cent 0.66 .79 .74 .76 .81 .12 .17 Per cent 0.74 1.88 1.03 1.10 1.52 .28 .40 Per cent 0.76 1.09 .98 .90 1.21 .09 .12 1,000 1,000 1,000 1,000 1,000 Least significant difference at Vetch and rye were grown and turned; animal manure was applied in late winter. 32 TABLE ALABAMA AGRICULTURAL EXPERIMENT STATION 14. ORGANIC MATTER AND TOTAL NITROGEN CONTENT OF SOIL RECEIVING DIFFERENT KINDS OF MANURES OVER A PERIOD OF YEARS, NOR- FOLK SOIL OF MEDIUM FERTILITY, SERIES A7, 1938-45 Treatments Fertilizer, 1 Manures Kind 2 Organic matter and total nitrogen content of soil Organic matter content Total 6-10-4 per acre Average amounts per acre 1940 1945 (1940-45) nitrogen 1945 Pounds 1,000 1,000 1,000 1,000 None s Standard Vetch Cowpeas Pounds 0 16,000 9,934 14,217 Per cent 1.07 1.82 1.43 1.12 Per cent 1.07 1.67 1.33 1.12 Per cent 1.07 1.69 1.36 1.12 p. p. m. 293 472 403 338 Least significant difference at 1 .05 level .01 level .34 .46 .10 .16 .09 .12 40 53 Irrigation was used as a standard practice with all crops. Standard manure treatment consisted of the addition of 2 tons per acre of dry sericea lespedeza in late winter and 6 tons of green crotalaria in summer. Vetch and cowpeas were grown and turned. 2 was significant. The average amount turned annually was 9,734 pounds of vetch and 11,298 pounds of rye per acre. The amount of vetch turned on plots also receiving animal manure was 14,334 pounds per acre. Results of Studies in Series A7 Data on the organic content of the soil in Series A7 and the treatments are given in Table 14. The addition of 2 tons of dried lespedeza sericea and 6 tons of green crotalaria per year by the end of 8 years had increased the organic matter content of the soil from 1.07 per cent to 1.67 per cent. Turning annually an average of 9,934 pounds of vetch per acre had resulted in an increase in the soil organic matter content from 1.07 to 1.33 per cent. An average of 14,217 pounds of cowpeas per acre turned under had increased the percentage from 1.07 to 1.12. Increases from vetch and the standard treatment were highly significant. Results of Studies in Series B23 Data on organic matter content of the soil receiving different mulching materials and the different treatments are given in Table 15. The mulching materials on the surface were not included in the sample. On treatments receiving a surface mulch, there TABLE 15. ORGANIC MATTER AND TOTAL NITROGEN CONTENT OF SOILS RECEIVING DIFFERENT MULCHING MATERIALS, CHESTER- O z FIELD SOIL OF MEDIUM FERTILITY, SERIES B28, 1940-49 Organic matter Total nitrogen 1949 p.p.m. 817 307 847 594 782 693 1040 540 619 579 629 787 451 481 1074 1094 144 200 Treatments x Organic matter and total nitrogen content of soil 2 Amount per acre Mulching materials Kind None Mulch paper Sericea lespedeza straw Pine Straw Oat Straw Peanut Hulls Peanut hulls Peanut hulls Peanut hulls Sericea lespedeza straw Sericea lespedeza straw Sericea lespedeza straw Corn stalks-winter Green corn stalks-summer Crotalaria-winter Green soybean stalks-summer Alabama peat 3 Alabama peat and lime Least significant difference at 1940 Pct. 0.66 .64 .71 .64 .69 .67 .86 .72 .71 .67 .69 .71 .66 .59 .59 .67 .16 .22 1942 Pct. 0.76 .72 1.45 .98 1.00 .97 1.88 1.19 1.45 1.09 1.03 1.22 1.07 .98 1.48 1.48 .33 .45 3. m -I m 1945 Pct. 0.76 .69 2.38 1.43 1.41 1.83 1.93 1.14 1.28 1.07 1.38 1.80 1.02 1.00 2.26 2.52 .28 .38 1948 Pct. 0.62 .62 1.52 1.72 1.86 2.00 1.98 1.17 1.45 1.10 1.59 2.05 1.24 1.31 8.40 3.40 .64 .88 1-inch layer surface 1.5-inch surface 1.5-inch surface 1.5-inch surface 1.5-inch surface 2 1.5-inch incorporated 3.2 tons incorporated 4.8 tons incorporated 1.6 tons incorporated 3.2 tons incorporated 4.8 tons incorporated 3.2 tons incorporated 9.6 tons incorporated 3.2 tons incorporated 9.6 tons incorporated 6.4 tons incorporated 6.4 tons incorporated .05 level .01 level (4-yr. av.) Pct. 0.71 .67 1.52 1.19 1.24 1.24 1.67 1.05 1.22 .98 1.17 1.45 1.00 .97 1.93 2.02 .21 .29 I- -I C ,m 'in m m -4 A r"o m w n 0 Ma 1 All crops received 1,280 pounds of 6-10-4 fertilizer per acre. 2 Mulching materials were applied to each of two crops per year. The surface mulches were applied to a depth of 1.5 inches the first year and thereafter enough material was applied to maintain the 1.5-inch-depth. The same amount of peanut hulls was applied to the treatment with the 1.5-inch incorporated as was applied to the surface mulch treatment. For 1.5-inch mulch it required the first year 25, 21, 20, and 16 tons of lespedeza straw, pine straw, peanut hulls, and oat straw per acre, respectively; to maintain this amount as a mulch it required each year 8.0, 7.5, 6.5, and 7.5 tons per acre per crop, respectively. SOne ton of dolomitic limestone per acre was applied at the beginning of the experiment. w w 34 ALABAMA AGRICULTURAL EXPERIMENT STATION was considerable incorporation of the materials into the soil, although the materials were raked to the centers between rows at the time land was prepared, fertilized, and planted. At the end of 9 years, the organic matter content of the soil in plots receiving no mulching materials was 0.62 per cent. For the same year, the organic content of the soil receiving the surface mulch of sericea was 1.52 per cent, of pine straw 1.72 per cent, of oat straw 1.86 per cent, and of peanut hulls 2.00 per cent. Soils receiving 3.2 tons per acre of incorporated peanut hulls by the 9th year had an organic matter content of 1.17 per cent; those receiving 4.8 tons of peanut hulls, a content of 1.45 per cent; and those receiving the same amount as the 1.5inch surface mulch but incorporated in the soil, a content of 1.98 per cent. Soils that had received 1.6 tons, 8.2 tons, and 4.8 tons per acre annually of sericea lespedeza incorporated into the soil showed an organic matter content of 1.10, 1.59, and 2.05 per cent, respectively. The organic matter content of soils receiving 6.4 tons per acre annually of Alabama peat was 8.40 per cent. These differences were highly significant. EFFECTS OF ADDED ORGANIC MATERIALS ON THE TOTAL NITROGEN CONTENT OF THE SOIL The close relationship between soil organic matter and the more stable forms of nitrogen has been pointed out. The amount of total soil nitrogen was determined at occasional intervals in but most but not all of the series. Samples for total nitrogen were taken in late fall. In all instances at least one vegetable crop was grown between the turning or application of organic materials and taking of samples. Since the samples, however, were taken before heavy winter rains, there were often considerable quantities of inorganic nitrogen included in the total nitrogen determinations. Results of Studies in Series A7 The amounts of total nitrogen in the soil for Series A7 are given in Table 14. Treatments are indicated in the table. The total nitrogen content of the soil in plots receiving no organic materials was 293 p.p.m. at the end of 8 years; it was 838 p.p.m. in soils on plots receiving cowpeas, 408 p.p.m. in soils on plots receiving vetch, and 472 p.p.m. in soils on plots in which sericea and crotalaria were introduced. These differ- ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 35 ences were highly significant for the vetch and the standard treatment, and significant for cowpeas. Results of Studies in Series B23 Data on soil nitrogen in Series B23 are given in Table 15. The data show a range of soil nitrogen content from 307 p.p.m. to 1,074 p.p.m. The amount of nitrogen in the soil reflected rather closely the amount and nitrogen content of the mulching materials added. It must be kept in mind that each treatment received the equivalent of 76.8 pounds per acre of commercial nitrogen twice annually and that the bacteria decomposing the materials will make use of the nitrate nitrogen added if the nitrogen in the materials is low. The soil receiving surface mulches of pine straw, peanut hulls, oat straw, and lespedeza sericea straw in the order named had nitrogen content of 594, 693, 782, and 847 p.p.m. On plots where peanut hulls equivalent to the 1.5-inch surface mulch were incorporated, the soil contained 1,040 p.p.m. of nitrogen. The nitrogen content of the soil receiving 1.6, 8.2, and 4.8 tons per acre per year of dry lespedeza sericea in the order named was 579, 629, and 787 p.p.m. The application of 6.4 tons per acre annually for 8 years of Alabama peat gave a soil with 1,074 p.p.m. of nitrogen. Increases were generally highly significant except for the green materials in combinations. EFFECTS OF ADDED ORGANIC MATERIALS ON SOIL NITRATES DURING THE GROWING SEASON Organic materials added to the soil may make nitrates available to crops in at least two important ways. Materials high in nitrogen upon decomposition may release nitrates within a short time after the materials have been applied; or the nitrogen in the more permanent forms of organic matter in the soil built up from repeated addition of organic materials may slowly decompose, releasing a part of the nitrogen existing as a component part of the organic complex. It must be realized that soil nitrates fluctuate greatly and often within a short period of time. This is because they are absorbed by crops, leached by heavy rains, and subject to conversion to organic forms through the cycles of microbial activity. The amount of nitrates in the soil, however, is a general index of the amount and composition of organic matter and activity of micro-organisms in the soil. 36 ALABAMA AGRICULTURAL EXPERIMENT STATION In a number of series, periodical nitrate determinations were made during the growing season of the crops under study. A few selected data are presented. Results of Studies in Series B14 In Table 16 are given the average nitrate contents of the soil in Series B14 for each of the four periods at which determinations were made during 1944 and 1946-48. Also, there are given the average nitrate contents of the soil for the four periods for each of the 4 years. The crop grown was sweet corn, which is a very heavy feeder of nitrogen. Commercial nitrogen at rates of 0, 60, 90, and 120 pounds per acre were added. Differences in nitrates in plots receiving and not receiving organic treatments at the same fertilizer rate provide a basis for measuring the effects of added organic materials. The total amounts of nitrogen were divided; in 1944 and 1946 two applications were made, while in 1947 and 1948 the nitrogen was applied in three applications. The data indicate wide variations in nitrate content between years, between periods during the growing seasons, and between treatments. Differences between treatments by years are generally significant or highly significant. Soil nitrates were relatively high during the first three periods of growth. As the crop began to use large amounts of nitrates, they were greatly reduced. During the last period of growth, they were very low in the case of certain treatments. When no commercial nitrogen or organic nitrogen was added, the average nitrate content for the four periods for the 4 years was 8 p.p.m.; the average content where 60 pounds of commercial nitrogen per acre was added was 23 p.p.m. in one set of duplicated plots and 22 p.p.m. in another. On plots receiving 60 pounds per acre of commercial nitrogen, 12 tons of animal manure increased the average nitrate content to 41 p.p.m., a crop of vetch increased the content to 38 p.p.m., and a crop of rye raised the average to 33 p.p.m. The average nitrate content of the soil in the four periods was 76 p.p.m. in plots receiving 12 tons of animal manure and vetch. At the second period the average nitrate content for the 4 years was 107 p.p.m. for the combination treatment, and 65 p.p.m. for the animal manure alone and 67 p.p.m. for the vetch alone. TABLE 16. NITRATE CONTENT OF SOIL RECEIVING DIFFERENT MANURE TREATMENTS DURING THE GROWTH OF SWEET CORN, CHES- 0 TERFIELD SOIL OF MEDIUM FERTILITY, SERIES B14, 1944, 1946-48 Treatments FertiManure lizer, 1 6-10-6 Animal Green per acre per acre Lb. 1,000 0 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,000 1,0006 1,500 2,000 1,000 Tons 0 0 12 0 0 0 12 0 0 12 6 6 12 12 12 12 0 Irrigation per week2 Average nitrate content of soil during the growth of sweet corn Average nitrates by two- and threeweek periods for all years' 1st 2nd 3rd 4th Av. Average nitrates by years for first three periods" 1944 1946 1947 1948 z rm p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. p.p.m. In. 19 88 86 23 20 33 5 15 38 0 0 13 3 8 7 8 6 9 10 0 4 0 45 63 47 50 11 41 65 52 0 37 0 67 45 41 89 88 7 67 46 32 0 Vetch 47 56 31 30 10 33 40 56 0 27 Rye 19 49 53 17 6 27 42 33 1 28 0 103 71 43 26 48 7 67 54 62 1 0 98 43 24 44 41 4 34 68 56 1 Vetch 33 38 15 22 23 30 5 35 0 18 0 145 71 39 74 65 55 11 104 1 89 Vetch 91 49 84 39 7 51 41 72 84 1 Vetch 87 67 39 43 23 46 10 63 1 53 Rye 184 91 76 76 59 32 98 107 0 66 Vetch 107 68 38 66 56 58 12 79 1 73 Vetch 157 85 42 63 69 73 14 100 1 88 Vetch 181 87 77 60 17 80 99 111 1 94 Vetch 73 50 37 26 6 37 56 36 1 48 Rye 10 45 67 50 51 Average 21 55 22 17 16 .05 level Least significant 76 81 80 22 24 .01 level difference at turned under. 1 Green manure crops were grown and 2 Irrigation consisted of the application of 1 inch of water per week if rainfall the preceding week failed to supply this amount and plants or soil indicated a need for water. nitrates are for each period for the 4 years. average nitrates by years are for the first three periods for each year. Minor elements were applied to all treatments except this one. im w U- 0u ''Ahe Tverage ' Iu 38 ALABAMA AGRICULTURAL EXPERIMENT STATION Results of Studies in Series B19-B21 The average nitrate contents of the soil in Series B19-B21 during the growing season for spring and fall crops are given in Table 17. Data are for 4 separate years and for a 7-year average. Soil nitrates and increases in nitrates resulting from use of manures were considerably higher in the fall than in the spring. The 7-year average nitrate content of the soil during the fall in plots receiving 2,000 pounds of fertilizer per acre was 16 p.p.m. higher in plots receiving a summer legume, 50 p.p.m. higher in those receiving 18 tons of animal manure and 76 p.p.m. higher in those receiving 18 tons of animal manure and a legume than in plots receiving no organic materials. The corresponding nitrate increases in the spring were 8, 9, and 10 p.p.m. Differences between treatments of 10 p.p.m. in the fall and of 4 p.p.m. in the spring were required for high significance. EFFECTS OF ADDED ORGANIC MATERIALS ON SOIL MOISTURE DURING THE GROWING SEASON Organic matter in the soil is known to affect to some extent the amount of water held by soils. This may in part account directly and indirectly for yield increases. It may also affect biological activity resulting in changes in organic content and the forms of soil nitrogen. Data from Series B19-B21 are presented to indicate effects of organic materials on moisture in the soil during the growing period of fall and spring crops. The moisture percentages for each year represent the average of three determinations and the percentages for each period the average of the 3 years. Results are presented in Tables 18 and 19. During the spring growing season, the differences in average soil moisture of plots receiving no organic materials and of those receiving 6, 12, or 18 tons of animal manure per acre were highly significant. Differences in the average moisture content between plots receiving 6 and 12 tons and also between those receiving 12 and 18 tons of manure per acre were likewise highly significant. At no intensity level were the average differences due to a turned legume significant. Differences were significant between treatments consisting of nonlegumes turned and nonlegumes removed at the medium- and high-intensity levels, but not at the lowintensity level. The average difference in soil moisture content 0 TABLE 17. NITRATE CONTENT OF SOIL RECEIVING DIFFERENT Kmm s OF MANURES AT DIFFERENT PRODUCTION-INTENSITY LEVELS WHEN GROWING SPRING AND FALL VEGETABLES, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-46 z Treatments Average nitrate content of soil during growth of vegetables' Spring Fall Fi Animal per acre Pounds Tons 0 0 1,000 0 0 1,500 2,000 0 1,000 0 1,500 0 0 2,000 6 1,000 1,000 6 6 1,000 12 1,500 1,500 12 12 1,500 2,000 18 2,000 18 2,000 18 Least significant difference at Fertilizer, 6-10-6' per acre Manures Green Cowpea R R R R - 1940 p.p.m. 0 7 10 15 7 9 18 6 8 8 9 14 11 19 16 12 6 8 1941 p.p.m. 4 18 23 26 20 26 30 20 18 19 25 27 26 33 28 33 6 8 1945 p.p.m. 5 9 13 17 11 16 16 17 23 22 25 31 30 35 40 42 5 7 1946 p~p.m. 6 16 25 29 17 25 32 18 21 24 30 36 28 46 50 45 8 11 Av. v (7-yr.) 1940-46 Av. 1940 p.p.m. 1941 1945 p.p.m. 1946 p.p.m. 3 13 17 20 12 18 23 14 17 17 21 26 22 29 31 30 3 4 p.p.m. 7 26 45 44 34 53 62 37 61 65 79 77 92 80 89 103 20 p.p.m. 8 20 27 36 19 27 37 28 32 43 52 54 76 81 97 97 3 4 (7-yr.) 1940-46 p.p.pm. -i f 0- --- T T T - T - R T R T - T T R T - .05 level .01 level 4 10 11 14 15 16 18 18 19 22 25 28 30 34 37 39 5 7 15 9 67 104 110 99 133 169 109 103 148 153 151 171 222 197 243 30 40 6 28 8 44 39 55 60 41 48 65 65 68 85 94 101 120 8 10 HI 'Fertilizer 2 "Nitrate was applied to each of 2 crops per year; animal manure was applied once each year. treatments marked T, green manures were turned; those marked R were removed. 1In content is the average of all nitrate determinations made during the growth period. Iw to 40 40 ALABAMA ALABAMA AGRICULTURAL EXPERIMENT STATION AGRICULTURAL EXPERIMENT STATION of plots receiving no manure and of those receiving 18 tons of animal manure and a turned nonlegume was 2.93 per cent. A difference in percentage of 0.56 was highly significant. During the growth of fall crops, the average differences were significant between treatments receiving no organic treatments and those receiving 12 and 18 tons per acre of animal manure and manure crops; differences were not significant between treatments receiving no organic materials and those receiving only manure crops. It should be pointed out that increases in soil moisture resulting from the addition of organic materials do not mean equivTABLE 18. AVERAGE SOIL MOISTURE CONTENT DURING THE GROWING PERIOD OF SPRING VEGETABLES OF SOIL RECEIVING DIFFERENT KINDS OF MANURES AT DIFFERENT PRODUCTION-INTENSITY LEVELS, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1945-47 Treatments Manures 1 Average moisture content of soil during the growing period By periods3for all years 1st Pct. 7.04 7.21 6.92 7.14 7.26 7.27 7.16 7.70 7.98 8.05 8.34 9.41 8.71 10.07 10.72 10.32 .05 .01 2nd Pct. 5.90 5.95 6.00 6.05 6.18 6.11 6.43 6.88 7.15 7.10 7.68 8.00 7.95 8.73 9.00 9.07 level level 3rd Pct. 6.80 6.92 6.74 6.77 7.12 7.14 6.78 7.52 7.53 7.48 7.87 8.31 8.03 8.76 9.03 9.04 1945 Pct. 6.61 6.78 6.74 6.80 6.91 7.05 6.90 7.40 7.59 7.53 7.81 8.48 8.33 9.11 8.83 9.03 .59 .79 By years for 4 all periods 1946 Pct. 6.31 6.56 6.34 6.40 6.57 6.44 6.56 6.86 7.15 6.96 7.25 7.48 7.29 7.63 8.13 8.30 1.42 1.90 1947 Average Pct. Pct. 6.82 6.74 6.56 6.76 7.07 7.03 6.90 7.83 7.93 8.15 8.83 9.76 9.07 10.82 11.79 11.11 .77 1.02 6.58 6.69 6.55 6.65 6.85 6.84 6.79 7.36 7.55 7.54 7.96 8.57 8.23 9.19 9.58 9.48 0.42 0.56 FertiGreen2 lizer, Ani6-10-6 mal per acre per Cow- Corn acre pea orn Tons Lb. __ R 0 0 R 0 __ 1,000 R 0 1,500 __ R 0 2,000 1,000 1,500 2,000 1,000 1,000 1,000 1,500 1,500 1,500 0 0 0 6 6 6 12 12 12 T T T _R T T R T T R T 2,000 18 2,000 18 18 T 2,000 Least significant difference at SFertilizer was applied to each of two crops per year; animal manure was applied once each year. 2 In treatments marked T, green manures were turned; those marked R were removed. SThe average moisture content by periods is the moisture content in the soil at approximately 3, 6, and 9 weeks after crop was planted. The average moisture content by years is for the first three periods for each year. ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 41 TABLE 19. AVERAGE SOIL MOISTURE CONTENT DURING THE GROWING PERIOD OF FALL VEGETABLES OF SOIL RECEIVING DIFFERENT KINDS OF MANURES AT DIFFERENT PRODUCTION-INTENSITY LEVELS, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1945-47 Treatments Manures 1 Average moisture content of soil during the growing period By periods 3for all years 2nd Pct. 5.42 5.47 5.50 5.42 5.43 5.50 5.50 5.60 5.83 5.77 3rd Pct. 6.61 6.61 6.94 6.42 6.62 6.21 6.66 6.59 7.05 7.25 7.63 7.64 7.21 8.68 8.55 8.08 By years for all periods' 1947 Average 1945 1946 Pct. Pct. Pct. Pct. 5.74 6.29 5.16 5.78 5.79 6.22 5.10 6.05 5.87 6.59 5.05 5.97 5.71 6.28 4.89 5.98 5.81 6.36 5.00 6.07 5.67 5.97 4.90 6.14 5.77 6.17 5.11 6.04 5.93 6.41 5.18 6.21 6.18 6.43 5.47 6.65 6.17 6.71 5.28 6.54 6.44 6.82 5.72 6.78 6.63 6.82 5.61 7.45 6.35 6.33 5.62 7.09 7.20 7.78 6.23 7.58 7.33 7.91 6.37 7.70 7.08 7.38 6.31 7.54 0.46 .77 .38 .30 0.62 1.03 .51 .41 Ferti2 Green lizer, Ani6-10-6 mal per acre per Cow- Corn acre pea Lb. 0 1,000 1,500 2,000 1,000 1,500 2,000 1,000 1,000 1,000 1,500 1,500 1,500 Tons 0 0 0 0 0 0 0 6 6 6 12 12 12 __ __ T T T 1st Pct. 5.21 R 5.29 R 5.17 R 5.30 R 5.37 __ 5.30 5.16 R T 5.61 5.67 5.50 5.84 6.06 5.95 T __ T __ - R T R T 18 2,000 18 2,000 18 2,000 Least significant difference at T 5.86 6.18 5.89 6.46 6.45 6.76 6.67 6.69 6.46 .05 level .01 level 1 Fertilizer was applied to each of two crops per year; animal manure was applied once each year. 2 In treatments marked T, green manures were turned; those marked R were removed. SThe average moisture content by periods is the moisture content in the soil at approximately 3, 6, and 9 weeks after crop was planted. ' The average moisture content by years is for the first three periods for each year. alent increases in available moisture. The wilting percentage of Chesterfield soil receiving 12 tons of animal manure per acre was approximately 0.50 higher than that of soil receiving no organic materials. RESIDUAL EFFECTS OF ADDED ORGANIC MATERIALS ON THE SOIL ORGANIC MATTER CONTENT The data presented have shown that repeated applications of organic materials to the soil result in appreciable increases in soil organic matter. The persistence of this organic matter in the soil after treatments end is important. 42 ALABAMA AGRICULTURAL EXPERIMENT STATION Presented in Table 20 are the data on organic matter content of the soil in Series B19-B21 for 1 and 3 years following the last use of organic materials. Certain of these data are presented graphically in Figure 5. The data indicate that increases in organic matter content of the soil resulting from use of organic materials are maintained for a number of years. The organic matter content of the soil receiving 6 tons of animal manure and a legume was 1.09 per cent the last year manures were used and 0.98 per cent 3 years later. The corresponding percentages for the treatments receiving 12 tons per acre of animal manure and a summer legume were 1.33 and 1.16 per cent; for treatments receiving 18 tons of animal manure and a summer leTABLE 20. RESIDUAL EFFECTS ON ORGANIC MATTER CONTENT OF SOIL FROM USE OF DIFFERENT KINDS OF MANURES AT DIFFERENT PRODUCTION-INTENSITY LEVELS, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1947-49 Treatments' Fertilizer, Manures Animal Tons 0 0 0 0 0 0 0 6 6 6 12 12 12 18 18 18 ---Corn Organic matter content in soil Residual period 1948 Pct. 0.48 . .50 .62 .57 .57 .75 .67 .67 .81 .95 1.14 1.19 1.22 1.36 1.54 1.69 1950 Pct. 0.54 .54 .60 .62 .59 .64 .69 .86 .84 .98 1.12 1.24 1.16 1.38 1.38 1.26 6-10-6 Lb. Green2 Last year of first period 19473 Pct. 0.57 .57 .69 .62 .60 .81 .66 .66 .88 1.09 1.20 1.48 1.33 1.64 1.64 1.66 per acre per acre Cowpea 0 1,000 1,500 2,000 1,000 1,500 2,000 1,000 1,000 1,000 1,500 1,500 1,500 2,000 2,000 2,000 - R R R R T T T -- - T R T _ R T T R T T .10 .16 .16 .05 level Least significant .16 .21 .21 .01 level difference at 1 Fertilizer was applied to each of two crops per year; animal manure was applied once each year. treatments marked T, green manures were turned; those marked R were removed. During residual period corn was grown in all plots and tops removed; the roots were left in the soil. $ The last year of the first period was the last year in which manures were applied. 'In ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 43 PER CENT ORGANIC CARBON IN SOIL I.00 .80 .6o M .4 6-10-6 YEAR 16106 LAST MANURES TONS RESIDUAL PERIOD, COWPEAS, RESIDUAL2 TONS_12 PERIOD, ,"}oo APPLIED (1947) 6-I-6 ?+ -6-10-6 ,oLB. LB. 6-106,o B6oo 5 B1,500 N, ,5, 12 TONS OWPEAS FIRST YEAR (1948) THIRD YEAR (1950) COWPEAS ANIMAL MANURE 12 TONS ANIMAL MANURE FIGURE 5. Residual effects of added manures on organic matter in the soil, Chesterfield soil of low fertility, Series B19-B21. gume, the percentages were 1.66 and 1.26. The organic matter added by successive applications of organic materials are not, therefore, quickly lost. INTERRELATION OF SOIL TREATMENTS AND THE ORGANIC MATTER, TOTAL NITROGEN, NITRATES, AND MOISTURE IN THE SOIL The data reported thus far have dealt primarily with effects of organic treatments on crop yields or on the soil constituents. Little attention has been given the interrelations of treatments and the several soil constituents. Data in Table 21, which show certain relationships, have been arranged in ascending order of intensity of treatments. Presented according to different treatments are the amounts of organic matter, total nitrogen, nitrates, and moisture of the soil during the spring and fall growing seasons. The data show that as the treatments became more and more intensive the amount of organic matter, total nitrogen, nitrates, TABLE 21. RELATION OF SOIL TREATMENTS TO SOIL ORGANIC MATTER CONTENT AND TOTAL SOIL NITROGEN AND TO NITRATES AND MOISTURE OF SOIL DURING GROWING SEASON, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-48 Treatments arranged in order of increasing intensiveness Feri-Manures FertiGreen1 Animal lizer Cowper per acre 6-10-6 acre pea Corn Pounds Soil organic matter Total soil nitrogen Average 1940-46 Amount 1945 Fall growing season nitrates2 Average of 7-years Spring growing season SolSi moisture3 Average of 3-years Per cent nitrates olSi2 moistures Average of 3-years Per cent 1948 p.p.m. 178 199 202 214 231 226 240 293 300 360 439 396 494 571 641 696 69 92 Average of 7-years 0 1,000 1,500 2,000 1,000 1,500 2,000 1,000 1,000 1,000 1,500 1,500 1,500 2,000 2,000 2,000 Tons 0 0 0 0 0 0 0 6 6 6 12 12 12 18 18 18 - -- R R R R - T T T T R T R T TT R T .05 level .01 level Least significant difference at 'In The Per cent 0.64 .66 .66 .66 .71 .74 .72 .90 .93 .93 1.02 1.07 1.14 1.17 1.26 1.28 .07 .09 Per cent 0.62 .62 .64 .64 .72 .71 .74 .93 1.00 1.07 1.16 1.29 1.42 1.53 1.45 1.74 .14 .19 p.p.m. 6 28 38 44 39 55 60 41 48 65 65 68 85 94 101 120 8 10 p.p.m. 3 13 17 20 12 18 23 14 17 17 21 26 22 29 31 30 3 4 5.74 5.79 5.87 5.71 5.81 5.67 5.77 5.93 6.18 6.17 6.44 6.63 6.35 7.20 7.33 7.08 0.46 0.62 6.58 6.69 6.55 6.65 6.85 6.84 6.79 7.36 7.55 7.54 7.96 8.57 8.23 9.19 9.58 9.48 0.42 0.56 r- ecc c 2x r m iU- 3m 1- z Sz m 0 treatments marked T, the green manures were turned; those marked R were removed. average represents determinations made at four periods each year for 7 years. 2 3The average represents determinations made at three periods each year for 3 years. z ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 45 and moisture in the soil progressively increased. With only very minor exceptions, the order of treatments and the order of amounts of organic matter, nitrogen, nitrates, and moisture were similar. Organic treatments determined the organic matter, total nitrogen content of the soil, and soil moisture during the growing season. Nitrogen in the fertilizer affected soil nitrates about as much as organic treatments. RELATIONSHIP BETWEEN SOIL NITRATES DURING THE GROWING SEASON AND CROP YIELDS It has been shown that organic treatments affect the amount of nitrates in the soil during the early and mid periods of growth, although crops remove large quantities of nitrogen. A very close relationship has been found between soil nitrates and crop yields. This relationship is shown in Figures 6, 7, and 8. Yield increases followed very closely increases in soil nitrates. The yields with all crops shown except sweet corn continued to increase up to the highest amount of nitrates found. With sweetcorn, yields did not increase for increases in nitrate above 64 p.p.m. 46 ALABAMA AGRICULTURAL EXPERIMENT STATION 46 ALABAMA AGRICULTU 5 10 P.P.M. NITRATES 15 IN 20 SOIL 25 FIGURE 6. Relation of soil nitrates to yields of different spring vegetable crops, Chesterfield soil of low fertility, Series B19-B21. ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 47 ORGANIC MATERIAL STUDIES with VEGETABLE CROS4 POUNDS 40,000 32,000 24,000 16,000 Tunip Y=-4 323+60988X+3811l0XI 8,000 10 POUNDS 10000 20 30 40 50 60 70 Onion .8,000 6,000 ,000 12103+ 8,000 10 PORPM 20 IRAT 30 IN 40 SO 498 50 60 70 FIUE72e0tofsi0ntae0oyilso0ifeetfl Chetefildsol erilty Sristard21 f lw egtbecos 48 ALABAMA AGRICULTURAL EXPERIMENT STATION POUNDS 15,000 12,000 9,000 6,000 6,000 3,000 10 20 30 40 50 P.P.M. NITRATES IN SOIL 60 70 Y=- 37504 4558X- 308Xt FIGURE 8. Relation of soil nitrates to yield of sweet corn, Chesterfield soil of medium fertility, Series B14. DISCUSSION There are a number of ways in which uses of organic materials on vegetable crops differ from their uses on field crops. Vegetables are grown on fewer acres of land, are more intensively handled, and in general offer possibility of higher gross returns per acre than field crops. These facts make possible and feasible use on vegetable crops of larger amounts of materials and the use of materials not available in large enough quantities for field crops. This is especially true for home and market garden areas. A few of the differences in the kinds and amounts of organic materials used with field and vegetable crops and differences in their effects on soils are briefly discussed. INCREASING ORGANIC MATTER AND TOTAL NITROGEN IN THE SOIL Many investigators and workers have pointed out the low amount of organic matter in the soils of the South and the difficulty of increasing the amount present (7, 10, 11, 14, 21). It is frequently stated that methods used in organic matter determinations are not accurate enough to measure the small increases obtained by turning under of organic materials. This may be ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 49 true for certain materials applied in certain quantities but not for other materials applied in different quantities. This investigation indicates that only very small increases in organic matter content of the soil were obtained from turning under legumes or nonlegumes over a period of 6 to 9 years. The increases usually have not been significant, or where significant the increases were too low to be of practical importance (Tables 12, 13, 14, 15). Turning under 6, 12, or 18 tons of animal manure per acre over a period of years not only has given increases in soil organic matter that are statistically significant but increases that should be of practical value (Table 12). Likewise, the use of mulching materials either on the surface or incorporated in the soil has increased the organic matter content of the soil very materially (Table 15). Increases in total nitrogen in the soil have followed increases in soil organic matter content as a result of the addition of organic materials (Tables 14, 15). Not only did certain of the organic treatments increase the organic and total nitrogen content of the soil during the period of application but the residual effects are apparent for 2 and 3 years after the last application with indications that the effects will persist for a number of years longer. These results are not necessarily contrary to the general results obtained in the South (10, 15, 21). They do point to the differences that result in use of different kinds of organic materials applied in quantities not generally feasible with field crops. These results, as do the results with field crops, show only small increases in soil organic matter from turning under cover crops (Tables 12, 13, 14, 15). INCREASES IN SOIL NITRATES FROM USE OF ORGANIC MATERIALS Increases in soil nitrates resulting from use of organic materials do not necessarily depend upon increases in the more stable forms of organic and total nitrogen content of the soil. Turning under legumes may liberate considerable amounts of nitrates within a short period. The nitrate content of the soil is extremely variable. Nitrates are subject to leaching and to use by growing crops and by soil bacteria; nitrate formation, furthermore, is subject to variations in temperature and moisture conditions of the soil. Despite these factors, average increases in soil nitrates, as determined 50 ALABAMA AGRICULTURAL EXPERIMENT STATION in the soil during the growing season over a period of years, were obtained by adding legumes, animal manures, and combinations of animal and green manures. The increases resulting from turning under legumes alone were not very high, but often were high enough for significance (Tables 16, 17). Increases from animal manure or from combinations of animal manure and green-manure crops generally exceeded considerably the amounts necessary for high significance. The nitrate content of soil and differences in nitrate content due to organic treatments were considerably higher during summer and fall periods than during the spring period (Tables 16, 17). Furthermore, yields were very closely related to nitrates found in the soil during the early- and mid-growing periods. USE OF NONLEGUMES AND Low-NITROGEN MATERIALS Caution is generally necessary in the use of nonlegumes as green-manure crops because of the depression of nitrates following their use with subsequent reduction in crop yields (6, 12, 19, 23). This would be expected where adequate nitrogen is not available in the soil or where liberal quantities of commercial nitrogen have not been added. In growing vegetables, usually adequate quantities of commercial nitrogen are added in addition to such amounts as may be supplied by the cover crop. In this study, rye resulted in yields of the several crops as high as vetch when 1,000 pounds per acre of a fertilizer, carrying 60 pounds of nitrogen, was used with both (Table 4). The soil nitrates likewise were about as high in the soil receiving nonlegumes as in those receiving legumes where 60 pounds per acre of commercial nitrogen had been added (Table 16). Furthermore, the average yields of vegetables were not reduced by heavy mulches of pine straw or of oat straw where 76.8 pounds of commercial nitrogen per acre had been added; yield of fall crops were actually increased 100 per cent or more by these materials (Table 7). RELATIVE VALUE OF ORGANIC MATERIALS AND OF COMMERCIAL NITROGEN IN PRODUCING VEGETABLES It is generally assumed that nitrogen is the principal factor responsible for crop yield increases resulting from use of organic materials. Evidence from long-time experiments shows that the same yield may be produced from adequate quantities of com- ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 51 mercial nitrogen as from legumes (3, 8). Data from this study do show a very close relationship between treatments, nitrates found during the growing season, and crop yields. They show, however, that on certain soils, large yield increases are obtained from the use of animal manures and legumes after adequate quantities of commercial nitrogen have been added (Figure 2). The distinction is made here between the addition of adequate quantities of nitrogen and the presence and accessibility of this nitrogen to the growing crop when it is needed. The ultimate measure of relative value is in crop response. On a Norfolk soil of average fertility, commercial nitrogen gave yields as high as legumes; furthermore, after maximum or near-maximum yields were reached from use of commercial nitrogen, only small or no yield increases were obtained by the further addition of legumes (Table 3). Results with commercial nitrogen and organic materials were quite different on a Chesterfield soil of low fertility (Table 2, Figure 2). The average yields of six fall vegetables increased from 8,132 to 10,186 to 10,336 pounds as fertilizers containing 60, 90, and 120 pounds of commercial nitrogen per acre were applied; yet after 120 pounds of commercial nitrogen per acre was applied, yields were increased to 16,346 pounds by addition of cowpeas or increased to 25,924 by addition of animal manure (Table 2). On the other hand, the additional 30 pounds of commercial nitrogen above the 90-pound rate resulted in no yield increase. The addition of cowpeas to the plots receiving 90 pounds of commercial nitrogen, however, resulted in a yield increase from 10,186 to 16,776 pounds per acre; the addition of animal manure increased the yield from 10,186 to 23,329 pounds per acre. Minor elements were applied to all treatments. On another Chesterfield soil of low fertility, a commercial fertilizer carrying 180 pounds per acre of nitrogen produced only 507 pounds of beets per acre, while the commercial fertilizer carrying 90 pounds per acre of nitrogen and animal manure resulted in a yield of 10,790 pounds; corresponding yields for the same treatments of carrots were 2,772 and 17,641 pounds, and of mustard 6,570 and 12,879 pounds (Table 6). The yields of fall tendergreen for corresponding treatments were 10,442 and 23,209 pounds, and for fall turnips 15,644 pounds and 34,111 pounds per acre. The addition of minor elements without animal manure resulted in an increase in the yield of beets but did not increase the yields of other crops. From previous studies at this 52 ALABAMA AGRICULTURAL -EXPERIMENT STATION Station, it has been shown that yield increases were not obtained from applications above 90 to 120 pounds per acre of commercial nitrogen (28). RESIDUAL EFFECTS OF ADDED ORGANIC MATERIALS Results of these studies show that the addition of organic materials increases the organic and total nitrogen content of the soil and that these increases are reflected in increased crop yields during the time of the application and for a few years after the last application (Tables 10, 11). The data, however, show that by the end of 3 years the effects on vegetable yields from green manures largely disappeared and the effects of animal manure were greatly reduced (Figures 3 and 4). The loss in soil organic matter after the last application has been less rapid (Table 20, Figure 5). These results are in contrast with results from some of the long-time experiments. Hall (8) states that barnyard manure on the Rothamstead Station applied at the rate of 14 tons per acre over a period of 20 years was affecting crop yields 47 years after the last application. In this study on a light, open, Chesterfield soil under conditions of high rainfall and high temperatures, residual effects have disappeared at a very rapid rate, with indications that after 4 or 5 years differences in yield will have little practical significance. It should be pointed out that in most of the longtime experiments with organic materials no commercial nitrogen was added to the contrasting treatments. In this study different rates of commercial nitrogen have been added during both the period of application and the residual period. The addition of commercial nitrogen would reduce the contrast between treatments. SUMMARY Results are presented in this bulletin of studies with the use of organic materials on vegetable crops. The term "organic materials," as used in this publication, is applied to materials added to the soil either as green manure, as animal manure, or as mulching material. The investigation included studies of the immediate and residual effects of organic materials grown on the land and turned under and of those introduced and incorporated in the soil or left on the surface as a mulch. The value of organic materials was measured by effects on ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 53 crop yields and on soil nitrates and soil moisture during the growth of crops, and by changes in the total nitrogen and organic matter content of the soil. Studies were conducted in specially constructed field bins on composited soils. Four phases of the investigation were conducted on a Chesterfield soil of low fertility, two phases on a Chesterfield soil of medium fertility, and two phases on a Norfolk soil of medium fertility. On a Chesterfield soil of low fertility (Table 1), turning under a winter legume increased the average yields of summer vegetables 283 per cent and of fall vegetables 163 per cent; the average yields of fall vegetables were increased 353 per cent and of spring vegetables 78 per cent by turning under summer legumes. The average yield of summer vegetables on the Chesterfield soil of low fertility was increased about 60 per cent more from a turned winter legume than from 60 pounds per acre of commercial nitrogen; the average yield of fall vegetables after an intervening crop of summer vegetables was increased from turned winter legumes somewhat less than from 30 pounds of commercial nitrogen. The average yield of fall vegetables was increased from turned summer legumes nearly as much as that from 60 pounds per acre of commercial nitrogen, while the yield of spring vegetables was increased about one-third as much as that from 30 pounds of commercial nitrogen. After 30 pounds per acre of commercial nitrogen was added to the Chesterfield soil of low fertility, a turned winter legume increased the yield of summer vegetables 107 per cent and the yield of fall vegetables 43 per cent. Turned summer legumes increased the yield of fall vegetables 83 per cent but of spring vegetables only 20 per cent after 30 pounds of commercial nitrogen had been added. On a second Chesterfield soil of low fertility (Table 2), summer legumes and animal manures gave large increases in yields of fall vegetables after applications of commercial nitrogen adequate for maximum production had been added. The average yield of six fall crops from the application of 90 pounds of commercial nitrogen, normally adequate for near-maximum yields, was only 10,186 pounds; additional fertilizer carrying 30 pounds of nitrogen gave practically no increase in yield. The addition of cowpeas, however, gave yields of 16,766 pounds, or the addition of 12 tons of animal manure yielded 28,329 pounds. Animal ma- 54 ALABAMA AGRICULTURAL EXPERIMENT STATION nures at the rates applied increased yields more than did turning under legumes or nonlegumes grown on the soil. On the Norfolk soil of medium fertility, commercial nitrogen, in general, produced yields as high as green manures. When rates of nitrogen sufficient for maximum yields without a manure had been added, turning under a legume gave little or no increase in yield (Table 3). Surface mulches of legume origin resulted in yield increases of summer vegetables ranging from 68 to 132 per cent, while those of a nonlegume origin gave increases ranging from 4 to 76 per cent. The increases in yield of fall vegetables from surface mulches of legume and nonlegume origin ranged from 92 to 214 per cent (Table 7). On a Chesterfield soil of low fertility receiving 2,000 pounds per acre of a 6-10-6 fertilizer throughout the experiment and organic material for the first 9 years, average yield increases of fall vegetables 2 years after the last addition or organic materials were as follows: 27 per cent where cowpeas had been turned, 46 per cent where 18 tons of animal manure per acre had been added, and 55 per cent where 18 tons of manure had been added and cowpeas had been turned (Table 10). On plots on which cowpeas had been turned annually for 9 years, the average yield of spring vegetables, 3 years after the last crop was turned, was practically the same as the check; the average yield of plots receiving 18 tons of animal manure was 60 per cent higher than the plot receiving no organic materials (Table 11). The repeated turning of crops of legumes or nonlegumes on a light Chesterfield soil failed to give differences in soil organic matter content high enough for significance when used without other sources of materials; small but significant differences in soil organic matter were obtained from summer cover crops when used in combination with animal manure (Table 12). On a Chesterfield soil of low fertility, the repeated application of 6, 12, and 18 tons of animal manure per acre by the 6th year had resulted in increases in soil organic matter content of 0.31, 0.54, and 0.89 per cent, respectively. An increase of 0.19 per cent was adequate for high significance (Table 12). Material increases in total soil nitrogen resulted from repeated applications of organic materials to the soil for a period of years. On a Norfolk soil after eight treatments, the amounts of total nitrogen in the plots were as follows: check plot, 293 p.p.m.; ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 55 plots in which lespedeza and crotalaria were introduced, 472 p.p.m.; plots in which crops of vetch and crops of cowpeas were turned, 403 p.p.m. and 338 p.p.m., resectively (Table 14). Organic mulches had increased the amount of total nitrogen in the soil after 10 applications from 317 p.p.m. to amounts ranging from 500 to 1,000 p.p.m. (Table 15). Nitrates in the soil during the growing period of crops were increased by turning under legumes, by application of animal manures, and by combination of the two treatments. In general, the increases were above those required for high significance in the fall but barely significant in the spring (Table 17). Nitrate levels were closely related to amount of commercial nitrogen and organic materials added (Table 16, 17). Yields were closely related to the amounts of soil nitrates during the growing season (Figure 8). LITERATURE CITED ALLISON, L. E. Organic soil carbon by reduction of chromic acid. Soil Sci. 40: 311-320. 1935. (2) ANONYMOUS. Official and tentative methods of analysis of the association of official agricultural chemists, 4th edition. George Banta Publishing Company, Menasha, Wis. 1935. (3) BAILEY, R. Y., WILLIAMSON, J. T., and DUGGAR, J. F. Experiments with legumes in Alabama. Ala. Agr. Expt. Sta. Bul. 232. 1930. (4) BLAIR, A. W., and PRINCE, A. L. The influence of heavy applications of dry organic matter on crop yields and on nitrate content of the soil. Soil Sci. 25: 281-287. 1928. (5) BRIGGs, L. J., and McLANE, J. W. The moisture equivalent of soils. U. S. Dept. Agr. Bur. Soils Bul. 45. 1907. (6) BROWN, P. E., and ALLISON, L. E. The influence of some common humus-forming materials of narrow and wide nitrogen-carbon ratios on bacterial activity. Soil Sci. 1: 49-75. 1916. (7) FUNCHESs, M. J. Nitrogen in southern agriculture. Proc. Eleventh Ann. Cony. Nat. Fert. Assoc. 1934-35. (8) HALL, A. D. The book of the Rothamsted experiments. E. P. Dutton & Company, N. Y. 1917. (9) HARPER, H. J. The accurate determination of nitrates in soils. Ind. Eng. Chem. 16: 180-183. 1924. (10) JENNY, HANS. Soil fertility losses under Missouri conditions. Mo. Agr. Expt. Sta. Bul. 324. 1933. . A study of the influence of climate upon the nitrogen (11) and organic matter content of the soil. Mo. Agr. Expt. Stat. Res. Bul. 152. 1930. (1) 56 ALABAMA AGRICULTURAL EXPERIMENT STATION (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) H. L. On the influence of the carbon : nitrogen ratios of organic material on the mineralisation of nitrogen. Jour. Agr. Sci. 19: 71-82. 1929. JONES, RANDALL J. Nitrogen losses from Alabama soils in lysemeters as influenced by various systems of green manure crop management. Jour. Amer. Soc. Agron. 34: 574-585. 1942. MARBUT, C. F. The relation of soil type to organic matter. Jour. Amer. Soc. Agron. 21: 943-950. 1929. MILLER, M. F. Studies in soil nitrogen and organic matter maintenance. Mo. Agr. Expt. Sta. Res. Bul. 409. 1947. LYON, T. L., and WILSON, B. D. Some relations of green manure to the nitrogen in the soil. N. Y. Agr. Expt. Sta. Memoir 115. 1928. RICHARDS, L. A., and WEAVER, L. R. Fifteen-atmosphere percentage as related to the permanent wilting percentage. Soil Sci. 56: 331339. 1943. JENSEN, SALTER, R. M., and SCHOLLENBERGER, C. J. Farm manure. Ohio (25) (26) Agr. Expt. Sta. Bul. 605. 1939. SALTER, F. J. The carbon-nitrogen ratio in relation to the accumulation of organic matter in soils. Soil Sci. 31: 413-430. 1931. STURKIE, D. G., and GRIMES, J. C. Kudzu, its value and use in Alabama. Ala. Agr. Expt. Sta. Cir. 83. 1939. THOMPSON, L. J. JR., and SMITH, F. B. Organic matter in Florida soils. Fla. Agr. Expt. Sta. Bul. 433. 1947. WRIGHT, C. H. Soil analysis, physical, and chemical methods. Thomas Murby & Co., London. 1934. WAKSMAN, S. A. Influence of microorganisms upon the carbonnitrogen ratio in the soil. Jour. Agr. Sci. 14: 555-562. 1924. . On the origin and nature of the soil organic matter or soil "humus": V. The role of microorganism in the formation of "humus" in the soil. Soil Sci. 22: 421-436. 1926. Baltimore. 196. Humus. The Williams and Wilkins Company. WARE, L. M. The effects of fertilizers, organic materials, and irrigation on the yield of certain truck crops. Proc. Amer. Soc. Hort. Sci. 39: 363-366. 1941. and JOHNSON, W. A. Use of field bins for experimental studies with vegetable crops. Proc. Auburn Conf. on Statistics Applied to Research. pp. 54-60. 1948. . Fertilizer studies with vegetable crops on representative soils in Alabama. Ala. Agr. Expt. Sta. Bul. 269. 1949. . Some effects of repeated applications of manures and fertilizers on the organic, nitrate, and moisture content of soil and on the yield of truck crops. Proc. Amer. Soc. Hort. Sci. 53: 375-386. 1949 . Value of irrigation with different fertility treatments for vegetable crops. Ala. Agr. Expt. Sta. Bul. 276. 1950. (27) (28) (29) (30) ORGANIC ORGANIC MATERIAL STUDIES with VEGETABLE CROPS MATERIAL STUDIES with VEGETABLE CROPS 57 57 APPENDIX APPENDIX TABLE 1. YIELDS AND INCREASES IN YIELDS OF SUMMER VEGETABLES FOLLOWING TURNED WINTER COVER CROPS AND RECEIVING DIFFERENT RATES OF NITROGEN, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B15-16, 1940-49 Fertilizer grades, 1,000 lb. per acre' 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Kind of cover crops 2 turned Vetch Vetch Vetch Rye Rye (R) Vetch Vetch Vetch Rye Rye (R) Vetch Vetch Vetch Rye Rye (R) Vetch Vetch Vetch Rye Rye (R) Vetch Vetch Vetch Rye Rye (R) Yields per acre 3 Without cover crops 36 71 123 123 123 67 132 171 171 171 7,434 16,152 20,198 20,198 20,198 764 2,803 3,181 8,181 3,181 74 150 190 190 190 With cover crops 133 150 178 142 135 199 210 221 188 176 30,908 36,292 38,019 86,253 33,415 5,148 5,497 6,780 5,979 3,554 241 289 310 303 257 Increases from use of cover crops Crops Amount 97 79 55 19 12 182 78 50 17 5 23,474 20,140 17,821 16,055 13,217 4,384 2,694 3,599 2,798 373 167 139 120 113 67 Per cent 269 111 45 15 10 197 59 29 10 3 316 125 88 79 65 574 96 118 88 12 226 93 63 59 85 Beans, bush Total, bu. (5-yr. av.) Beans, lima Total, bu. (5-yr. av.) Eggplant Total, lb. (5-yr. av.) Pepper, Pimento Total, lb. (3-yr. av.) Tomatoes Marketable, bu. (4-yr. av.) SOne ton limestone and 10 pounds of borax were applied per acre to all treatments at the beginning of the experiment. Minor elements were applied to all treatments once each 8 years, beginning with an application in 1945. 2Cover crops marked (R) were cut and tops removed. ' Least significant differences at the .05 and .01 levels for bush beans are 18 and 25, for lima beans 21 and 29, for eggplant 5,427 and 7,430, for pimento pepper 1,549 and 2,125, and for tomatoes 45 and 62, respectively. 58 58 ALABAMA AGRICULTURAL EXPERIMENT STATION APPENDIX TABLE 2. YIELDS AND INCREASES IN YIELDS OF FALL VEGETABLES FOLLOWING TURNED WINTER AND SUMMER COVER CROPS AND RECEIVING DIFFERENT RATES OF NITROGEN, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B15-16, 1940-49 l Crops Kind Ferti- of Yields, per acre 3 Increases from use grades, 1,000 lb. per acretre cover crops Without cover crops With cover crops of cover crops Amount Per cent Cabbage, Chinese 0-10-6 Total, lb. 3-10-6 (3-yr. av.) 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 Vetch Vetch Vetch Rye Rye (R) Cowpea Cowpea Cowpea Corn 1,140 6,007 13,512 13,512 13,512 3,043 14,929 27,298 27,298 6,698 13,645 18,T49 18,513 18,227 24,568 30,204 35,858 26,492 5,558 7,638 4,737 5,001 4,715 21,525 15,275 8,560 488 127 35 37 35 6-10-6 Collards Total, lb. (5-yr. Corn (R) Vetch Vetch Vetch Rye Rye(R) Cowpea Cowpea Cowpea Corn Corn (R) Vetch Vetch Vetch Rye Rye (R) Cowpea Cowpea Cowpea Corn Corn (R) Vetch Vetch Vetch Rye Rye (R) r 27,298 2,555 8,348 11,204 11,204 11,204 2,399 8,578 12,528 12,528 12,528 503 2,713 3,494 3,494 3,494 784 3,537 4,395 4,395 4,395 1,907 6,151 9,306 9,306 9,306 7 26,761 6,236 11,415 12,694 12,156 10,501 11,489 15,070 17,074 14,241 12,052 2,564 -806 707 102 31 -3 -537 3,681 3,067 1,490 952 -703 9,090 6,492 4,546 1,713 -476 2,061 888 644 -512 -487 4,259 2,081 1,169 247 -- ,429 1 4,211 2,537 3,107 4,186 3,193 -2 144 37 13 8 -6 379 76 36 14 -4 410 33 18 -15 -14 543 59 27 6 -33 av.) 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Koblrabi Marketable, lb. (3-yr. av.) 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 3,601 4,138 2,982 3,007 5,043 5,618 5,564 4,642 2,966 6,118 8,688 12,413 13,492 12,499 _ 7 v Mustard Total, lb. (2-yr. 221 41 33 45 34 (Continued) 'One ton limestone and 10 pounds of borax were applied per acre to all treatments at the beginning of the experiment. Minor elements were applied to all treatments once each 3 years, beginning with an application in 1945. 2 Cover crops marked (R) were cut and tops removed. av.) 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 , Least significant differences: Vetch 3878 Cowpea Chinese cabbage .05 Collards Kohlrabi Mustard 2419 1638 1626 .01 5312 3302 2240 2227 .05 7820 2381 1536 .01 10726 3264 2112 ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 5 59 APPENDIX TABLE 2. (Continued) YIELDS AND INCREASES IN YIELDS OF FALL VEGETABLES FOLLOWING TURNED WINTER AND SUMMER COVER CROPS AND RECEIVING DIFFERENT RATES OF NITROGEN, CHESTERFIELD SOIL OF LOW FERTILITY, SERIES B15-16, 1940-49 Crops liter grades, 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Ferti- Kind of cvro Yields per acre 3 Without With cover crops coer Increases from use o oe AmutPrcn AmutPrcn oe rp crover 2 rp acre lb.tured per ar crops Mustard Total, lb. (2-yr. av.) Cowpea Cowpea Cowpea Corn Corn (R) Vetch Vetch Vetch Rye Rye( R) Cowpea Cowpea Cowpea Corn Corn(R) Vetch Vetch Vetch Rye 1,959 6,196 10,435 10,435 10,435 2,462 4,510 5,436 5,436 5,436 2,487 4,732 6,519 6,519 6,519 416 4,486 8,397 8,897 8,397 12,807 17,232 19,597 12,871 10,416 4,488 5,244 5,585 5,248 4,787 4,885 7,978 9,297 6,144 5,982 1,773 7,910 11,245 12,883 12,646 10,848 11,036 9,162 2,436 -19 554 178 88 23 0 Onion Total, lb. (3-yr. av.) 2,026 734 149 -188 82 16 3 -12 -649 2,398 3,246 2,778 -375 -537 1,357 3,424 2,848 4,486 4,249 6,317 8,205 8,889 3,506 -3 96 69 43 -6 -8 Tendergreen Total, lb. (1-yr. av.) 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Rye(R) Cowpea Cowpea Cowpea Corn Corn(R) Vetch Vetch Vetch Rye 326 76 34 53 51 1,176 179 95 38 -9 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Turnip 537 4,576 9,338 9,338 9,338 6,097 18,358 23,115 23,115 23,115 6,854 12,781 18,227 12,844 8,512 13,739 23,809 27,589 25,902 24,657 -826 Total, lb. (4-yr. av.) 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Rye(R) Cowpea Cowpea Cowpea Corn Corn (R) 7,642 5,451 4,474 2,787 1,542 17,487 12,894 7,955 746 125 30 19 12 7 240 63 29 3 -9 1One ton ments at the beginning of the experiment. Minor elements were applied to all treatments once each 3 years, beginning with an application in 1945. crops marked (R) were cut and tops removed. significant differences: Vetch Cowpea limestone 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 7,298 20,469 27,548 27,548 27,548 24,785 33,363 35,503 28,294 24,958 -2,590 and 10 pounds of borax were applied per acre to all treat- 'CLeast over .05 Mustard Onion Tendergreen Turnip 858 2464 2406 .01 1178 3373 3296 .05 2816 1267 3110 3373 .01 3584 1728 4262 4621 60 ALABAMA AGRICULTURAL EXPERIMENT STATION APPENDIX TABLE 3. YIELDS AND INCREASES IN YIELDS OF SPRING VEGETABLES FOLLOWING TURNED SUMMER COVER CROPS AND RECEIVING DIFFERENT RATES OF NITROGEN, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B15-16, 1940-49 Fertilizer grades, 1,000 lb. per acre ' 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 8-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Kind of Yields per acre3 With cover crops 29 50 64 62 51 1,204 5,330 8,102 7,825 7,228 1,013 3,605 6,938 5,757 5,893 2,902 5,807 6,271 6,504 6,165 2,736 5,370 8,333 8,493 8,963 Increases from use of cover crops Crops Without cover cropned cover 2 crops turned Cowpea Cowpea Cowpea Corn Corn(R) Cowpea Cowpea Cowpea Corn Corn(R) Cowpea Cowpea Cowpea Corn Corn(R) Cowpea Cowpea Cowpea Corn Corn(R) Cowpea Cowpea Cowpea Corn Corn(R) 20 38 47 47 47 184 3,533 6,981 6,981 6,981 232 2,380 6,355 6,355 6,355 1,042 5,297 5,994 5,994 5,994 1,760 4,743 8,473 8,473 8,473 Amount 9 12 17 15 4 1,020 1,797 1,121 844 247 781 1,225 583 -598 -462 1,860 510 277 510 171 976 627 -140 20 490 Per cent 45 82 86 82 9 554 51 16 12 4 337 51 9 -9 -7 179 10 5 9 3 55 13 -2 0 6 Beans, bush Total, bu. (3-yr. av.) Beets Marketable, lb. (3-yr. av.) Cabbage Marketable, lb. (5-yr. av.) Carrots Marketable, lb. (6-yr. av.) Chard Total, lb. (5-yr. av.) (Continued) 'One ton limestone and 10 pounds of borax were applied per acre to all treatments at the beginning of the experiment. Minor elements were applied to all treatments once each 3 years, beginning with an application in 1945. 2 Cover crops marked (R) were cut and tops removed. Least significant differences at the .05 and .01 levels for bush beans are 10 and 13, for beets 1,754 and 2,406, for cabbage 2,048 and 2,816, for carrots 1,267 and 1,741, and for chard 1,690 and 2,304, respectively. ' ORGANIC MATERIAL STUDIES with VEGETABLE CROPS APPENDIX TABLE 3. (Continued) 61 YIELDS AND INCREASES IN YIELDS OF SPRING CHESTERFIELD SOIL OF Low VEGETABLES FOLLOWING TURNED SUMMER COVER CROPS AND RECEIVING DIFFERENT RATES OF NITROGEN, FERTILITY, SERIES B15-16, 1940-49 Crops Fertilizer grades, 1 000 lb. 1,000 Ib. per acre' 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 8-10-6 6-10-6 6-10-6 6-10-6 Kind of cover crops turned Cowpea Cowpea Cowpea Corn Corn(R) Cowpea Cowpea Cowpea Corn Corn(R) Cowpea Cowpea Cowpea Corn Corn(R) Cowpea Cowpea Cowpea Corn Corn(R) Cowpea Cowpea Cowpea Corn Corn(R) Yields per acre3 Without cover crops 1,805 9,638 11,523 11,523 11,523 2,109 5,293 7,677 7,677 7,677 24 46 62 62 62 1,618 6,074 10,291 10,291 10,291 7,206 14,067 19,064 19,064 19,064 With cover crops 4,624 10,970 12,550 14,573 12,950 2,579 5,908 7,350 7,933 7,399 40 64 87 86 67 2,607 7,082 10 572 10,611 9,751 10,183 16,977 23,288 23,526 21,956 Increases from use of cover crops of cover crops Amount 2,819 1,332 1,027 3,050 1,427 470 615 -327 256 -278 16 18 25 24 5 .89 1,008 281 820 -540 2,927 2,910 4,164 4,462 2,892 Per cent 156 14 9 26 12 22 12 -4 8 -4 67 89 40 89 8 61 17 8 3 -5 41 21 22 28 15 Lettuce Total, lb. (4-yr. av.) Onion Total, lb. (4-yr. av.) Potatoes Marketable, bu. (5-yr. av.) Radish Marketable, lb. (5-yr. av.) Spinach, N.Z. Total, lb. (3-yr. av.) SOne ton limestone and 10 pounds of borax were applied per acre to all treatments at the beginning of the experiment. Minor elements were applied to all treatments once each 3 years, beginning with an application in 1945. 2 Cover crops marked (R) were cut and tops removed. 3 Least significant differences at the .05 and .01 levels for lettuce are 1,809 and 2,470, for onion 678 and 934, for potatoes 7 and 10, for radish 1,101 and 1,510, and for N. Z. Spinach 4,672 and 6,400, respectively. APPENDIX TABLE 4. YIELDS OF DIFFERENT COVER CROPS GROWN, TURNED, OR REMOVED, CHESTERFIELD SoIL OF Low FERTILITY, SERIES B15-16 Treatments Fertilizer Kinds of grades, cover 1,000 per acre Yields of cover crops per acre by years 1939 Pounds 1940 Pounds 653 701 675 1,088 768 11,792 12,896 13,392 6,358 6,838 9,510 9,229 9,171 6,957 7,062 1941 Pounds 11,376 10,144 10,886 6,458 7,133 19422 Pounds 26,752 23,456 24,160 10,272 9,760 1943 Pounds 1944 Pounds 1945 Pounds 1946 1947 1948 1949' Average r Pounds Pounds Pounds Pounds Pounds 4,752 3,917 4,010 15,206 15,629 20,842 15,626 17,242 12,560 12,538 elements 19,101 13,219 11,082 17,680 14,846 13,440 13,440 13,440 9,296 8,586 13,319 11,896 11,948 12,603 11,503 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 0-10-6 3-10-6 6-10-6 6-10-6 6-10-6 Vetch Vetch Vetch Rye Rye(R)' Cowpea Cowpea Cowpea Corn Corn(R)' WINTER COVER CROPS 17,482 15,402 7,306 16,922 19,792 14,122 5,853 14,320 5,987 21,082 14,000 14,160 16,320 11,504 15,562 22,640 13,962 11,786 13,078 19,981 SUMMER COVER CROPS > 0 13,472 12,726 18,602 19,402 23,520 13,722 12,912 12,922 19,296 19,754 23,120 10,640 8,656 21,178 23,120 19,152 13,450 12,621 9,536 8,000 2,704 2,922 11,344 4,176 2,061 963 3,402 7,456 5,920 2,480 ' Fertilizer applied to each of two vegetable crops per year and not to cover crops. Minor ments once each 3 years, beginning wit an application in 1945. 2For cowpea and corn yield, 10,000 pounds of each was introduced and turned in addition SAdditional vetch was introduced to give yields as shown. SCover crops were grown and removed. 19,088 16,268 11,872 14,827 15,290 14,922 2,240 6,680 1,840 5,056 were applied to all treat- a r m M m to amounts produced. Z -4 -4 O Z 0 APPENDIX TABLE 5. YIELDS OF SPRING VEGETABLES RECEIVING DIFFERENT MANURES AT DIFFERENT PRODUCTION-INTENSITY CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-47 LEVELS, Treatments Fertilizer, Manures Animal Tons 0 0 0 6 6 6 0 0 12 12 12 0 0 18 18 18 R R T T R __ T R R T T R T R T T Green Corn 3 Yields per acre of different vegetables Beans (4-yr.av.) Bu. 3 43 50 87 97 100 68 67 129 120 126 70 70 136 140 185 Roots Beets (3-yr. av.) Marketable Total Cabbage (4 yr. av.) Marketable heads Carrots (4-yr. av.) Marketable Roots Total M Lb. 1,248 4,404 4,038 7,143 8,775 8,208 4,074 5,687 10,199 11,312 11,616 4,963 5,378 12,736 12,141 11,187 (Continued) M 6-10-6 Lb. 0 1,000 1,000 1,000 1,000 1,000 1,500 1,500 1,500 1,500 1,500 2,000 2,000 2,000 2,000 2,000 TotaP Lb. 2,881 11,706 15,101 19,619 18,209 18,393 15,492 19,777 21,144 26,303 25,171 15,562 20,185 27,586 26,281 26,634 per acre Cowpea T Lb. 0 119 277 1,148 1,668 1,404 192 781 2,428 2,710 2,564 346 619 3,293 4,002 8,260 Lb. 0 282 679 2,817 3,200 2,833 491 1,591 4,677 4,885 4,783 781 1,242 6,119 6,071 5,674 Lb. 81 837 1,511 3,371 4,186 3,810 1,045 2,287 5,589 5,538 5,598 1,297 1,886 6,857 6,630 6,400 Lb. 967 4,294 7,413 10,307 9,262 9,577 6,321 10,125 11,663 15,914 14,045 6,374 11,232 16,352 15,247 16,010 Lb. 208 1,514 1,501 3,459 4,080 4,025 1,408 2,580 5,098 5,805 5,984 2,067 2,250 6,544 6,859 5,792 Lb. 247 2,538 2,403 5,652 6,710 6,749 2,482 4,266 8,660 9,639 9,962 3,828 3,676 11,124 10,714 9,969 m " y 1 Minor elements were applied to all treatments once each 8 years beginning with an application in 1945. SIn treatments marked T, the green manures were turned; those marked R were removed. SLeast significant differences at the .05 and .01 levels for beans are 42 and 57, for beets 2,765 and 8,699, for cabbage 3,033 and 4,070, and for carrots 1,664 and 2,227, respectively. a APPENDIX TABLE 5. (Continued) YIELDS OF SPRING VEGETABLES RECEIVING DIFFERENT MANURES AT DIFFERENT PRODUCTION- INTENSITY LEVELS, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-47 Treatments Fertilizer, 6-10-6 per acre Pounds 0 1,000 1,000 1,000 1,000 1,000 1,500 1,500 1,500 1,500 1,500 2,000 2,000 2,000 2,000 2,000 1 Minor Yields per acre of different vegetables' English pea (4-yr. av.) Total3 Bushels 24 84 39 70 71 71 36 45 81 82 84 28 39 85 77 84 Lettuce (3-yr. av.) Potatoes (5-yr. Manures Animal per acre Tons 0 0 0 6 6 6 0 0 12 12 12 0 0 18 18 18 2 Green Cowpea Corn Marketable heads Pounds 153 1,920 2,172 5,581 5,291 5,499 2,569 2,415 6,136 9,361 8,632 2,266 2,871 10,044 10,398 10,756 To Pounds 397 5,453 6,276 16,162 17,122 17,131 9,028 9,532 20,851 25,054 24,585 9,480 10,078 26,679 27,123 27,576 Bushels 14 88 42 56 77 69 57 52 94 85 100 56 57 133 114 109 av.) Bushels 33 66 72 91 115 102 88 81 134 127 138 82 84 182 157 152 aI - T T T T - R R R T R R T R R T W a a C 7- T T m x no m elements were applied to all treatments once each 3 years beginning with an application in 1945. 'In treatments marked T, the green manures were turned; those marked R were removed. 'Least significant differences at the .05 and .01 levels for English peas are 47 and 63, for lettuce 3,238 and 4,326, and for potatoes 19 and 26, respectively. z aI O' -4 0 APPENDIX TABLE 6. YIELDS OF FALL VEGETABLES RECEIVING DIFFERENT MANURES AT DIFFERENT PRODUCTION-INTENSITY LEVELS, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-47 Treatments Manures Z Yields per acre of different vegetables Kohlrabi 2 4 Turnip Fertilizer, 6-10-6 .Animal per acrep per acre Green CowCorn pea R BroccoliCm (2-yav.) Cabbage (3-yr. av.) Total Total' (yr.. av.)Mustard Marketable(3y.al)(-rav StemsTotal Total Total Roots Total Pounds 0 Tons 0 1,000 1,000 1,000 1,000 1,000 1,500 0 0 6 6 6 0 T T T T T T R R T R - Pounds 831 6,149 7,193 7,974 12,095 11,104 6,649 Pounds 383 Pounds Pounds Pounds 0 0 145 Pounds 820 Pounds 5,491 7,289 10,317 8,231 4,704 10,138 27,306 28,561 47,847 34,163 12,826 409 1,127 1,624 2,082 2,462 1,019 798 2,099 1,344 2,572 3,609 4,510 4,681 2,205 3,888 4,015 5,102 6,647 7,040 3,796 5,261 9,796 13,265 17,165 14,797 11,183 6,592 18,316 1,664 3,463 Pounds 135 Pounds 797 7,312 15,107 15,437 18,903 15,379 15,639 9,392 17,450 15,664 28,157 28,352 39,274 30,902 30,374 20,205 37,744 M 1,500 1,500 0 7,333 10,054 29,427 51,064 45,026 16,085 29,244 54,647 53,397 50,006 44,885 2,205 3,652 6,528 6,383 3,639 3,554 6,685 5,529 6,776 5,908 8,128 'MIninor 2 1,500 1,500 2,000 2,000 2,000 2,000 2,000 12 12 0 0 18 18 18 12 R - T R R T 12,095 11,513 4,642 6,521 11,808 11,840 9,490 1,912 2,112 746 879 1,915 1,467 2,086 4,211 4,633 1,855 2,087 4,889 4,129 5,051 4,364 18,351 19,392 6,827 11,780 18,086 17,639 19,435 12,672 11,117 5,734 7,059 10,541 18,447 10,445 9,095 18,698 19,245 8,826 14,541 17,821 17,971 16,998 41,536 41,520 18,829 29,247 39,443 41,402 38,384 m 0 elements were applied to all treatments once each 3 years beginning with an application in 1945. for kohlrabi 1,562 and 2,086, for mustard 2,547 and 3,418, for onion 2,022 and 2,701, and for turnip 5,312 and 7,014, respectively. 'Las treatments marked T, the green manures were turned; those marked R were removed. 3Broccoli was harvested as greens; the crop was planted too late to produce heads in late winter. significant differences at the .05 and .01 levels for broccoli are 3,315 and 4,442, for Chinese cabbage 7,104 and 9510, stem often 'Enlarged referred to as bulbs. J1 0% APPENDIX TABLE 7. YIELDS OF DIFFERENT COVER CROPS GROWN, TURNED, OR REMOVED, CHESTERFIELD SOIL OF Low FERTILITY, SERIES B19-B21, 1940-47 Treatments' Manures Ferti- Ferti 6-10-6 Ani- Green2 lier, real per acre per acre Yields of cover crops per acre 1940 1941 1942 1948 1944 1945 1946 1947 Average Pounds Tons 0 1,000 1,000 1,000 1,000 1,000 1,500 1,500 1,500 1,500 1,500 2,000 2,000 2,000 2,000 2,000 0 0 0 6 6 6 0 0 12 12 12 0 0 18 18 18 Corn(R) Corn(R) Cowpea(T) Corn(R) Cowpea(T) Corn(T) Corn(R) Cowpea(T) Corn(R) Cowpea(T) Corn(T) Corn(R) Cowpea(T) Corn(R) Cowpea(T) Corn(T) Pounds Pounds 4,928 6,358 11,286 8,233 14,458 9,370 8,557 11,280 13,830 15,152 12,909 10,870 11,203 15,587 13,498 14,038 1,200 2,224 7,872 6,390 13,062 6,528 3,472 8,544 14,944 13,110 14,806 4,118 8,342 25,312 13,958 22,730 Pounds 2,336 5,210 11,520 17,440 23,520 20,521 7,200 12,000 27,481 26,640 29,376 8,064 12,320 33,600 29,338 34,922 Pounds 640 1,082 18,200 6,160 23,322 9,296 2,237 13,360 13,018 24,080 13,802 2,122 12,122 10,800 24,442 14,800 Pounds 3,738 6,864 15,786 25,280 26,880 25,728 9,712 17,424 35,078 27,882 37,744 11,744 17,210 36,848 32,240 42,752 Pounds 1,818 3,056 17,088 14,362 34,128 19,354 4,058 18,410 26,102 37,066 29,770 4,330 19,802 34,282 39,920 40,506 Pounds 762 2,896 4,458 5,722 21,120 7,712 2,010 3,578 14,154 26,896 15,690 2,730 5,162 23,418 34,160 24,768 Pounds 1,840 5,456 16,538 18,784 25,152 24,016 8,922 16,826 33,296 27,050 31,712 10,544 19,600 41,059 32,106 41,440 Pounds 2,158 4,143 12,218 12,796 22,705 15,316 5,771 12,678 22,239 24,735 23,226 6,815 13,220 27,613 27,458 29,495 A a c c m no m 1Fertilizer and animal manure were applied to vegetables and not to cover crops. Minor elements were applied once each 3 years, beginning with an applicatioinin 1945. 2 M z --i --I Green manure crops were grown in all plots; those marked R were removed and those marked T were turned. 0 z ORGANIC MATERIAL STUDIES with VEGETABLE CROPS 67 APPENDIX TABLE 8. YIELDS OF WINTER AND SUMMER COVER CROPS GROWN OR TURNED, NORFOLK SOIL OF MEDIUM FERTILITY, SERIES A4, 1943-47 Average yields per acre to vegetable crops, 1,000 lb. per acre etilzer Winter legumes' For For sweetpotatoes sweet corn (5-yr. av.) (5-yr. av.) Pounds Pounds 10,851 12,991 14,088 16,511 17,354 21,992 Summer legume Cowpeas grown for fall turnips and (5-yr. av.) Pounds 24,353 25,282 26,872 26,186 23,193 25,770 0-10-7 2-10-7 4-10-7 6-10-7 8-10-7 8-10-7 + lime 13,644 19,213 18,659 18,296 14,253 17,770 1Vetch was the winter legume for sweet corn in 1943-45 and for sweetpotatoes 1943-45 and 1947. In other years blue lupine was grown and turned. APPENDIX TABLE 9. TOTAL NITROGEN IN MATERIALS USED AS MANURES 1 Materials used Kind Total nitrogen Per cent 1.272 0.515 1.080 0.527 0.740 0.323 0.899 0.554 0.845 0.811 0.635 0.777 0.658 1.936 materials referred to as dry were air dried; mature dry represents plants that matured and dried before taken from field. 2 Immature green corn stalks represent stalks of approximately one-half mature size and were grown on area following vegetables that had received high rates of fertilizer. ' Sericea lespedeza straw used had only a portion of its leaves. 'All Alabama peat, dry Corn stalks, mature dry Corn stalks, immature green' Cowpea vines, mature green Crotalaria, mature dry Crotalaria, mature green Lespedeza straw', mature dry Oat straw, mature dry Peanut hulls Pine straw Soybean vines, mature dry Soybean vines, mature green Vetch, mature green Stable manure with straw, dry