BULLETIN 332 JUNE 1961 Management of Irrigated Cotton Agric ultural Experiment Station UNIVERSITY AUBURN E. V. Smith, Director Auburn, Alabama CONTENTS Page EXPERIMENTAL PROCEDURE-----------------4 Nitrogen and Irrigation Experiment-4 Nitrogen and Variety Experiment-4 ----6 -6 Nitrogen Experiment----------------Cotton Spacing Experiments ------ Cotton Management and Variety Experiments-6 Furrow vs. Sprinkler Irrigation Experiment-7 RESULTS AND DISCUSSION----- ------ - 7 Yie ld - - - - - - - - - - - -- - - - - - - - - - - - - - - - - - - - Lodging and Boll Rot----------------- - 7 -13 B oll S iz e --- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -16 Plan t Heigh t-- - - - - - -- -- - - - - - - - - --- - - - - - - - - - - - -- - - - 17 Lint P ercentage ---- -------------------------------- 19 M ic ro n aire - - - - - - - - -- - - - - - - - - - - -- - - - - -- - - - - - - - - - - - - - 1 9 -- -- -- ------- 20 Stap le Len gth --- --- --- ---- ---- ------ O ther Fiber Properties ------------------------------ 21 Seed G ermination-----------------------------------21 SUMMARY AND CONCLUSIONS ---------------------------CITED ------------------------------------ 21 23 LITERATURE FIRST PRINTING 5M, JUNE 1961 Management of Irrigated Cotton Results of Cotton Irrzgation Management Studies in Alabama C. E. SCARSBROOK', O. L. BENNETT , L. J. CHAPMAN', 2 2 R. W. PEARSON , and D. G. STURKIE1 M production of cotton nearly Although crop failures resulting from every year in Alabama. drought: are rare, maximum cotton yields cannot be produced if the plants suffer for water even for short periods during the fruiting season (1,2,3). The plants produce and mature fruit when moisture is ample, but cease fruiting when moisture is deficient. When cotton yields are increased by irrigation, requirements for fertilizer, especially nitrogen, become greater (1,3,5,6). Although necessary, this high fertilization leads to problems in irrigated cotton. The large amounts of nitrogen needed for maximum production frequently produce large plants, cause lodging, make harvesting difficult, and create a condition favorable for boll rot organisms (1,3). Fiber properties of cotton are changed by irrigation (2,4,5). Irrigated cotton is more uniform in quality from year to year than cotton grown with rainfall only. A more uniform product should improve the competitive position of cotton with other fibers. Because of growing interest in irrigation as a means of improving cotton production, irrigation experiments were begun by Auburn University Agricultural Experiment Station and USDA Agricultural Research Service at several locations in the State. OISTURE DEFICIENCY limits ' Soil chemist, assistant in agronomy, and agronomist, respectively, Auburn University Agricultural Experiment Station. 2 Soil scientist, Agricultural Research Service, U.S. Department of Agriculture. 4 ALABAMA AGRICULTURAL EXPERIMENT STATION This publication presents results of irrigation experiments during the past 5 years to determine effect of nitrogen, moisture, varieties, topping, spacing, date of planting, and bottom defoliation on yield, fiber properties, and other characteristics of cotton. EXPERIMENTAL PROCEDURE Nitrogen and Irrigation Experiment Purpose of this experiment was to determine some of the factors that limit yields of cotton. Nitrogen and moisture were variables in the experiment. Management practices were designed for maximum yield without regard to economic return. The experiment was conducted on Greenville sandy loam at the Foundation Seed Stocks Farm, Thorsby. The area was subsoiled, limed to a pH of 6.0 to 6.5, fumigated, and a minor element mixture added. Annual application of 210 pounds per acre each of P20 5 and K20 was made. Coker 100A was grown for 2 years (1956-57) and Deltapine 15 for 2 years (1958-59). An attempt was made to maintain complete boll weevil control, but it was never entirely successful. Control was excellent except when weevils swarmed in from surrounding nonirrigated cotton that had matured. These three moisture treatments were used: (1) not irrigated, (2) irrigated when approximately 65 per cent of available soil maoisture was lost from the surface 2 feet of soil (intermediate irrigation), and (3) irrigated when about 30 per cent of available moisture was lost (high irrigation). Furrow irrigation was used. Rainfall and irrigation records are given in Table 1. Nitrogen and Variety Experiment The main purpose of this experiment was to determine the upper limits of nitrogen fertilization that can be used on some wilt-resistant cotton varieties without excessive lodging. Work was done on Independence loamy fine sand at the Plant Breeding Unit, Tallassee. This experiment was conducted in 1958 and 1959 on soil severely infested with the fusarium wilt-nematode complex. The area was fumigated each year and 300 pounds each of P 20 5 and K20 was applied. Irrigation was by the sprinkler method. z TABLE 1. IRRIGATION AND RAINFALL RECORDS, Two ALABAMA LOCATIONS, 1956-59 M z 0 1956 Month Rain- Rainfall and irrigation per month 1958 1957 rigation IrRain-nIrrigation RainRainRain 1959 Irrigation fall Intermediate In. Thorsby ___- High In. ____ fall In. 6.06 5.50 2.81 3.10 5.56 Intermediate In. ---- High In. ____ fall fal In. 1.67 6.97 9.73 3.15 5.16 Inrrigtion iatee High In. 0.75 fll In. 7.88 2.51 3.86 2.73 4.94 ite In. In. In. Foundation Seed Stocks Farm, May --------------------4.05 June--------------1.07 July 2.44 August 3.62 3.25 In. 0.75 1.50 3.33 __ ---------------------------------------3.20 September -------6.75 _-- 1.75 2.75 3.30 7.80 1.75 8.00 2.00 5.07 _- 3.00 6.50 3.79 -- 3.86 __ 1.75 3.50 1.88 _ 2.75 5.00 5.00 0 TOTAL -_______ 14.43 11.70 23.03 10.07 13.29 __-7.61 26.68 4.61 5.58 -__4.19 21.92 7.13 12.75 Tennessee Valley Substation, Belle Mina 7.22 ___1.88 April------------- May -----------June------------July ------------August __________ 2.69 3.37 2.82 2.00 2.00 4.00 3.54 3.50 2.65 2.00 4.00 3.14 2.60 9.06 ___ __ 6.44 5.83 2.62 6.00 September,______. TOTAL________ 3.38 2.61 4.00 __ 2.03 6.80 6.00 -__ 1.78 5.31 4.00 4.00 6.42 2.43 --U' 22.09 12.00 20.40 12.00 29.50 27.93 6.00 6 ALABAMA AGRICULTURAL EXPERIMENT STATION Nitrogen Experiment This experiment was conducted for 2 years, 1956 and 1959, on Dewey silty clay loam at the Tennessee Valley Substation, Belle Mina. The purpose was to determine response of irrigated cotton to nitrogen fertilization. The area was fertilized with 100 pounds per acre each of P 20 5 and K20. The variety planted was Empire. Irrigation was by the sprinkler method. Rainfall and irrigation records are given in Table 1. Cotton Spacing Experiments The cotton spacing experiments were done on two soil types at two locations - Chesterfield sandy loam on the Agronomy Farm, Auburn, and on Independence loamy fine sand, Plant Breeding Unit, Tallassee. Auburn 56 was grown in 1959 with plant populations of 5,000, 10,000, and 30,000 plants per acre. This corresponds to drill row spacings of 30, 15, and 5 inches in 40-inch rows. Fertilizers were applied at the per acre rate of 300 pounds each of N, P20 5 , and K20. Irrigation, applied as needed by visual inspection, was by the sprinkler method on the Independence soil and the furrow method on the Chesterfield soil. Cotton Management and Variety Experiments It was anticipated that cotton grown with high rates of nitrogen and moisture would lodge. This would create a condition favorable for boll rot. To solve these expected problems, a cotton management study was begun in 1956 and a variety study in 1957, both on Greenville sandy loam at the Foundation Seed Stocks Farm, Thorsby. Rate of fertilization in both experiments was 300 pounds of N and 210 pounds each of P 2 0 5 and K20 per acre. In the management study, initial treatments were: (1) bottom defoliation with magnesium chlorate of, the lower 2 feet of the plant when three-fourths of the bolls were of mature size; (2) picking all squares to simulate complete loss of fruit to insects to determine effect on plant height; (3) topping to a height of 4 feet when the plants reached 41/2 feet; and (4) planting at both the recommended time and I1month later. Other topping heights were included in the tests in subsequent years. The variety was Coker 100A. MANAGEMENT of IRRIGATED COTTON 7 Varieties were added or dropped from the variety experiments based on their lodging performance without regard to wilt-resistance or other characteristics that might make them suitable for the area. Furrow vs. Sprinkler Irrigation Experiment Auburn 56 cotton was grown in 1959 on Chesterfield sandy loam at the Agronomy Farm, Auburn, with plant populations of 30,000 per acre. Fertilizers at the rate of 800 pounds per acre each of N, P2 0 5 , and K20 were applied. Irrigation was supplied as needed by furrow or by sprinkler. RESULTS and DISCUSSION Yield The Greenville sandy loam at Thorsby is an excellent soil for cotton. Yields for the 4-year period were exceptionally high even when no nitrogen or irrigation was applied, Table 2. TABLE 2. EFFECT OF NITROGEN AND MOISTURE ON YIELD OF SEED COTTON ON GREENVILLE SANDY LOAM, THORSBY, ALABAMA, 1956-591 Nitrogen applied, pounds per acre Not irrigated Lb. 1,728 1,940 1,868 1,905 2,101 2,688 2,615 2,602 2,606 Yield of seed cotton per acre 111\1 ~1~ Intermediate High irrigation irrigation Lb. Lb. 2,495 3,636 3,889 4,136 2,198 8,299 4,052 4,010 2,745 3,966 4,461 4,304 3,480 4,335 4,405 4,331 .... 2,463 3,448 3,687 4,927 2,213 3,322 3,967 5,073 2,987 4,395 4,805 5,336 3,222 4,181 4,813 4,400 4,221 4,302 1956 0 60 120 240. 1957 0 60 120 240_ 1958 0---------------------------- 120 240 360 1959 0 120 240 360 480 720 3,941 3,771 3,506 2,171 2,246 2,151 2,168 SCoker 100A was the variety in 1956-57 and Deltapine 15 in 1958-59. 8 ALABAMA AGRICULTURAL EXPERIMENT STATION With no N added, irrigating at the intermediate moisture level increased yield an average of 578 pounds seed cotton for the 4 years. A further increase in moisture had no effect on yield. These results show that the rate of N must be in proportion to the rate of moisture if profitable responses are to be obtained from high rates of either. For example, in 1956 and 1957 there was a yield response to only 60 pounds of N without irrigation, to 120 pounds of N with intermediate moisture, and to 240 pounds of N with the highest rate of moisture. Clearly, if maximum returns are to be realized from large amounts of fertilizer and moisture, they must be applied in conjunction with other good management practices. An important characteristic of cotton grown with high rates of nitrogen and moisture is that a major portion of the crop matures late in the season, Figure 1. Much of the irrigated cotton matures after harvesting nonirrigated cotton. Boll weevils often migrate into irrigated cotton from surrounding nonirrigated fields when cotton has matured. Thus, two serious problems that are Seed cotton pounds per acre 5000 High irrigationu 4000 S/ 3000 - . .. lntermediate irrigation / "' No irrigation 1000 Sept. I Oct. INov. Harvesting date I Dec.I FIG. 1. Irrigated cotton that receives high rates of nitrogen matures later than does nonirrigated cotton, as shown here. Cumulative yields are shown for cotton that received 240 pounds N in 1957 at Foundation Seed Stocks Farm, Thorsby. MANAGEMENT of IRRIGATED COTTON 9 TABLE 3. EFFECT OF IRRIGATION AND NITROGEN ON TUE YIELD OF EMPIRE COTTON ON DEWEY SILTY CLAY LOAM, TENNESSEE VALLEY SUBSTATION BELLE MINA, ALABAMA, 1956-59 Nitrogen applied, pounds per acre Nonirrigated 1956 Lb. 1.,408 1,430 1,360 Yield of seed cotton per acre 1957 1958 1959 Average Lb. Lb. Lb. Lb. 1,711 2,149 2,139 2,178 2,411 2,188 2,159 3,121 3,045 8,073 3,267 1,864 2,278 2,183 60-------------------------------------120-------------------------------------Irrigated 120------------------------------------- o--------------------------------------- 60 0 2,382 2,220 2,110 2,324 2,064 --------------------------------------------- 3,004 2,178 3,094 ------------------------------------3,274 3,559 2,837 2,139 3,060 intensffied by irrigation are: (1) controlling boil weevils, and (2) harvesting losses resulting from unfavorable weather in the fall. The maximum yields of about 5,000 pounds of seed cotton the largest ever recorded in Alabama. They compare favorably are with that Alabama has a yield potential similar to that of other cotton growing areas. The relationship between nitrogen and moisture is yields from any section of the United States. This illustrates illustrated by the results on Dewey silty clay soil, Table 3. There was a yield response to only the first 60 pounds of N without irrigation; however, the irrigated cotton responded to the second 60-pound increment of N. Yields of irrigated cotton at 0, 60, and 120 pounds of N per acre were 356, 559, and 877 pounds more TABLE 4. YIELD OF SEED COTTON FROM FIVE VARIETIES GROWN IRRIGATION AT FIVE RATES OF NITROGEN, TALLASSEE, ALABAMA, UNDER further 1958-59 Variety 1958 Auburn 56______________ Per acre yield of seed cotton, from five nitrogen rates 60lb. Lb. 3,657 120 lb. 180 lb. Lb. 3,659 240 lb. Lb. 3,949 300 lb. Average Lb. 3,875 Lb. 3,905 Lb. 3,809 Plains_________________ Coker 100A____________ Stoneville 7 3,677 3,357 3,588 3,518 3,837 3,986 3,719 3,797 3,432 3,131 3,713 3,781 3,391 3,133 3,725 3,487 3,567 3,702 Deltapine 15 1959 Auburn 56_____________ Plains_________________ Coker 100A_____________ Stoneville7 Deltapine 15 3,324 2,263 1,974 2,065 2,202 2,066 3,485 2,273 1,833 1,871 1,985 2,320 3,317 2,417 1,917 1,722 1,811 1,952 3,560 2,179 1,586 1,640 1,720 1,697 3,011 2,017 1,423 1,527 1,630 1,469 3,339 2,230 1,747 1,765 1,870 1,901 ----------- 10 10 ALABAMA AGRICULTURAL EXPERIMENT STATION than from the same levels of N without irrigation. Yields at this location were much lower than those obtained on the Greenville soil. There was no response to nitrogen on the Independence loamy fine sand, Table 4. This. river terrace soil supplied sufficient nitrogen to produce as much cotton as limiting production factors, such as boll weevil control, would permit. This relatively high native nitrogen level has been confirmed by other field experiments at Tallassee. The low yields in 1959 were caused by inadequate boll weevil control. Weevils were resistant to the chlorinated hydrocarbon insecticides being used 100 per cent before the resistance was discovered. Even with the application of insecticides to which the weevils were notre TABLE 5. EFFECT OF PLANTING DATE, TOPPING, AND BOTTOM DEFOLIATION YIELD AND BOLL SIZE OF COTTON, THORSBY, ALABAMA, 1956-59 ON and infestation reached Time of planting' Treatment Seed cotton yield per acre Boils per pound of seed cotton No. Lb. 1956 Early_____ Early Not topped Topped 48 inches Bottom defoliated Not topped Topped 48 inches Bottom defoliated Early -----------Late------------- 4,154 3,772 Late Late------------1957 Early_______________________ 3,523 3,644 3,277 3,039 71 77 81 64 66 72 59 61 Early ------------ Not topped Topped 42 inches 3,574 3,976 3,150 2,795 2,812 3,019 2,340 4,019 4,066 3,772 3,415 3,052 3,590 3,419 3,237 3,599 Early_______________________ Topped 48 inches Early______________________ Bottom defoliated Late ------------------------N ot topped Late ---------------42 inches Topped _------ 58 67 61 60 Late------------Topped 48 inches Late ------------------------Bottom defoliated 1958 Early ________ _---------- 62 63 Early Not Topped 42 inches topped Early____________ Early____________ Topped 48 inches Bottom defoliated Nut topped 62 62 62 68 65 68 68 Late-,------------- Late-_______Topped 42 inches Late ------- ______ Late-------------1959 Early------------ Topped 48 inches Bottom defoliated 73 3,914 60 4,562 60 Early____________ Topped 48 inches 3,817 57 'Cotton planted 4/15/56 and 5/10/56; 4/16/57 and 5/22/57; 4/14/58 and 5/21/58; 4/14/59. Early ---------- Topped 42 inches Not topped MANAGEMENT of IRRIGATED COTTON 11 sistant, it was late in the season before they were under control. A total of 28 dustings or sprayings was applied during the season. This experiment indicates the necessity of keeping insects under control if high yields are to be obtained. Cotton planted at the recommended date yielded more than plantings made about 1 month later, Table 5. In 3 years, the earlyplanted cotton averaged 752 pounds more seed cotton than the later planting. An explanation for the higher yield is that with adequate moisture, fertilization, and insect control the cotton produced fruit until frost. Thus, a 1-month delay reduced the amount of time available for fruit production. Bottom defoliation with magnesium chlorate caused a 3-year average loss of 491 pounds of seed cotton. Immature bolls failed to mature after the defoliant was applied. This was probably the cause of the yield reduction. Topping nearly eliminated lodging without causing a reduction in yield. In fact, in 1959 there was a large increase in yield from the 42-inch topping. This was the result of reduced boll rot. Topping appears to be a sound practice, especially where cotton is to be machine picked. The uniform height without lodging should result in improved picker efficiency. Another advantage is that the machine operator can more easily see the rows, a difficult task in lodged cotton. TABLE 6. YIELDS OF COTTON VARIETIES GROWN WITH IRRIGATION AND 800 POUNDS PER ACRE OF NITROGEN, THORSBY, ALABAMA, 1957-59 Yield of seed cotton per acre Variety 1957 Lb. 4,142 4,270 4,334 8,468 3,850 4,288 4,210 4,273 3,781 3,622 3,564... 3,404 2,880 1,814 1958 Lb. .. 3,941 8,903 3,778 4,033 3,618 1959 Lb. 3,338 3,614 8,919 3,614 4,446 3,779 . - Average Lb. 3,740 3,942 4,052 3,620 4,110 3,895 Auburn 56 ---Plains ------- Empire ....... Coker 100A Stoneville 7 Deltapine 15 ... Stoneville 8202 Empire x Acala Plains 491-2 Deltapine S.L... Dixie King All-in-One ---Pope ......... Hi-bred Rex -... . - ... Acala 4-42 Acala 44. ----------------------------------------------- 3,814 3,419 4,340 3,595 4,009 - 3,507 4.175 12 ALABAMA AGRICULTURAL EXPERIMENT STATION Several varieties of both wilt-resistant and wilt-susceptible types yield satisfactorily under irrigation and high fertility, Table 6. With a rate of 300 pounds per acre of N, yields in excess of 4,000 pounds of seed cotton were not unusual. However, differences of 1,000 pounds of seed cotton between varieties in a season were common. Such large differences between varieties are rarely observed under nonirrigated conditions. The main reason for the superiority of Auburn 56 at Tallassee in 1959 was its rapid fruiting characteristics, Table 4. A small crop was made before the weevils destroyed nearly all the young fruit. TABLE 7. EFFECT OF COTTON PLANT POPULATION ON YIELD, LINT PERCENTAGE, BOLL ROT, BOLL SIZE, MICRONAIRE, AND STAPLE LENGTH, AUBURN AND TALLASSEE, ALABAMA, 19591 Plants per acre, no. Nitrogen applied, lb. per acre Yield per acre Lint Lb. Auburn 30,000 10,000 5,000 Tallassee 30,000 10,000 5,000_... 5,000 SCotton Pct. 39.1 39.3 38.4 Seed cotton Bolls Staple loss Lodged per lb. Micro- length from plants seed naire in boll rot plants sto naire in. per acre Lb. Pct. No. No. 164 99 187 2 6 34 6 15 2 11 6 36 66 63 60 70 73 68 65 70 67 4.4 4.5 4.5 4.1 4.6 4.6 4.3 4.5 4.6 34 34 34 35 35 35 35 35 35 300 300 8........ 300 120 300 120 300 120 300 3,424 3,493 3,159 2,860 2,523 3,035 2,472 2,803 2,396 35.2 495 35.4 500 36.3 694 36.8 1,163 36.5 646 37.0 535 variety-Auburn 56. TABLE 8. EFFECT OF FURROW VS. SPRINKLER IRRIGATION ON YIELD OF SEED COTTON, LINT PERCENTAGE, BOLL ROT, LODGED PLANTS, BOLL SIZE, MICRONAIRE, AND STAPLE LENGTH, CHESTERFIELD SANDY LOAM SOIL, AUBURN, ALABAMA, 1959 Method of irrigation Yield cotton per acreper seed Lint loss from boll rot acre Seed Lodged plants Bolls per pound seed cotton Micronaire Staple length in 312 in. No. 34 84 84 Furrow Sprinkler None Lb. 3,474 3,571 1,615 Pct. 37.6 37.7 37.1 Lb. 181 207 8 Pct. 2.1 2.2 0 No. 66 66 76 4.4 4.4 4.1 MANAGEMENT of IRRIGATED COTTON 13 A single year's results of spacing experiments on Chesterfield sandy loam and Independence loamy fine sand indicate that the 10,000 and 30,000 plant populations may give slightly higher yields than 5,000 plants per acre, Table 7. One year's results on Chesterfield sandy loam soil at Auburn showed no difference in yield when furrow was compared with sprinkler irrigation, Table 8. Lodging and Boll Rot Boll rot usually increases in direct proportion to the amounts of nitrogen and moisture added, Tables 7 and 9. These, however, are not a direct cause of the boll rot. Large amounts of nitrogen and moisture used together cause rank growth, which provides conditions generally favorable for growth of boll rot organisms. However, boll rot does not invariably result from rank growth. For example, rank growth always resulted from high rates of nitrogen and moisture, but in 1958 boll rot was much less severe than in other years, Table 9. TABLE 9. EFFECT OF NITROGEN AND MOISTURE ON BOLL ROT, THORSBY, ALABAMA, 1956-59 Nitrogen applied, pounds per acre Seed cotton loss from boll rot, per acre Not irrigated Lb. 2 2 4 26 0 29 28 90 8 40 78 91 0 0 Intermediate irrigation Lb. 33 127 262 361 10 29 87 187 7 57 100 93 34 385 654 679 High irrigation Lb. 48 152 247 545 2 55 118 306 7 83 98 124 14 771 954 1,180 1,209 1,800 1956 0 60 120 240 1957 0 60 120 240 1958 0 120 240 360 1959 0 120 240 360 480 720 -.. -0 0 14 ALABAMA AGRICULTURAL EXPERIMENT STATION '14 ALABAMA AGRICULTURLEPIMN STIO TABLE 10. BOLL ROT, LODGING, AND PLANT HEIGHTS OF COTTON GROWN UNDER IRRIGATION AND 300 POUNDS OF NITROGEN, THORSBY, ALABAMA, 1957-59 Loss of seed cotton from boll rot, per acre Variety 1957 1958 Lb. Lb. Aul burn 56________ 1,024 Plai ins_____________ 751 694 Em pire-------------575 261 Col ker 100A_______ 1,094 443 601 187 Sto] neville 7 De] tapine 15.___ 274 436 Sto] neville 3202_ 368 Em pire x Acala_ 568 __ Plai 491-2 1,117 __ De] ltapine S.L. __429 __ Dix :ie King----- 1,255 All--in-One 1,161 Pop )e __ --------- 1,191 Hi-1 1,044 Rex 379 Acaila 4-42 Acaila 44 -----77 ins --- ----,bred -------- -____ __ -- __ 513 Plant height D egree of lodging at frost 1959 Av. 1957 1958 1959 1957 1958 1959 Akv. Lb. Lb. In. In. In. In. 65 1,778 1,401 Med. High 57 ---- 73 67 2,180 1,208 High High High 72 60 68 1,431 756 Med. Med. Med. 58 70 69 66 1,629 1,055 High High High 57 72 70 66 1,108 632 Low 70 72 72 Low Low 65 1,248 653 Low Low Low 68 62 70 73 Low --- -- - 55 __ _-Med. --- -- - 59 __ __ High --- -- - 62 __ -- Low --- - 60 -- High -57 --- - Hi -- - 56 -- H igh --- ---- 52 -54 --64 High ____ 76 74 75 1,139 826 Low Low 78 78 78 Low Low 1,247 662 __ -_-High -_- ---__High -- Varieties differed drastically in lodging and in losses from boll rot, Tables 10, 11, 12. Lodging varied from almost complete lodging to none. The least lodging was exhibited by Stoneville 7, Deltapine 15, Smooth Leaf Deltapine, Acala 4-42, and Acala 44. These varieties are not wilt-resistant and should not be planted on wilt-infested soil. Auburn 56 and Empire lodged less than any of the other wilt-resistant varieties. Although tendency to lodge is a varietal characteristic, lodging of a given variety may TABLE 11. LODGING OF FIVE COTTON VARIETIES GROWN UNDER IRRIGATION AT FIVE RATES OF NITROGEN, TALLASSEE, ALABAMA, 1958-59 Variety Lodging percentage from five nitrogen rates per acre 60 lb. 120 lb. 180 lb. 240 lb. 300 lb. Av. Pct. Pct. Pct. Pct. Pot. Pet. 0 3 19 0 0 0 0 1 0 4 16 25 21 1 11 7 11 6 1 4 21 30 54 5 35 2 14 21 5 17 30 66 53 0 14 6 22 51 6 22 46 56 83 8 19 12 17 37 2 11 23 36 46 3 16 5 13 23 3 12 1958 Auburn 56 Plains____ ___. Coker 100A__ Stoneville 7-- Deltapine 151959 Auburn 56__. Plains ------- Coker 100A_. Stoneville 7__ Deltapine 15_ MANAGEMENT of IRRIGATED COTTON 15 MANAGEMENT of IRRIGATED COTTON 1 TABLE 12. SEED COTTON Loss FROM BOLL ROT, TALLASSEE, ALABAMA, 1958-59 Per acre seed cotton loss from boll rot, five nitrogen rates 60 lb. 120 lb. 180 lb. 240 lb. 300 lb. Av. Lb. Lb. Lb. Lb. 641 Lb. 718 Lb. 518 1958 Auburn 56_________________________ 458 220 552 Plains --------------------------------214 587 648 Coker 100A ---------------------- 545 270 315 Stoneville 7..______________________. 370 164 518 Deltapine 15 80 255 273 902 665 524 399 778 486 603 381 --------------------290 522 700 728 452 260 232 1959 Auburn 56_________________________ 456 197 495 Plains -------------------------------241 554 396 Coker 100A_______________________ 561 347 763 Stoneville 7..______________________. 416 176 630 Deltapine 15 --------------------- 384 238 497 536 525 616 832 723 734 457 512 619 537 338 396 vary considerably depending on weather, soil type, and geographical location. example, Auburn 56 lodged 46 per cent with 300 pounds: of N at Tallassee in 1958, whereas with the same treatment at Auburn in the same year there was only 1 per cent lodging. Difference in lodging between varieties is illustrated in Figure 2. There was no clear general relationship between lodging and boll rot. In some years the greatest amount of boll rot occurred on the most severely lodged cotton. However, in other years lodging and boll rot were not related. Apparently, weather and For other conditions have more effect on the growth of organisms. than does lodging. Even without lodging growth may be so rank as to present conditions favorable for boll rot similar to that in lodged cotton. boll rot 7. At Auburn on plant spacings of 30, 15, and 5 inches, lodging was 34, 6, and 2 per cent. Cotton branches on the thicker spacings intermingled, thus tending to support each other. High rates of nitrogen should not be used unless lodging is controlled by variety selection or topping. Experience indicates that a: given rate of N usually causes less lodging on sandy upland soils than on finer textured bottom land. There was no difference in boll rot or lodging when sprinkler irrigation was compared to-furrow irrigation, Table 8. Widely spaced plants lodged more than thicker plantings, Table 16 ALABAMA AGRICULTURAL EXPERIMENT STATION nit ) ~, FIG. 2. Effect ot voriety on lodging is shown above. Empire variety top hod severe lodging, whereas Stoneville 7 grown under same conditions did not lodge. Boll Size N itr0o4eu h~ad ai mairkedl (flect ill reduc~in~g the ut~ller of bolls' reclirle( to pro)duic a poundw of seedl cottoni unider irrigaited nlajiagelI('1t, but had nio effect wh en mroistrrre w~as limuitinig, TablIe 13. B~oth level's of irrigation produI cedi abouit the samte size bolls. Muchid of the ii erease in 1)o11 weights is the resiult of larger seed. Tl s, the linit perecitacgc is lowered. "Ihere was no) . ic'1( response( to uitrogeu oil the Irlp(eeec MANAGEMENT of IRRIGATED COTTON 17 MANAGEMENT of IRRIGAED COTTON 1 TABLE 13. EFFECT OF NITROGEN AND MOISTURE ON LINT PERCENTAGE AND BOLL WEIGHTS, THORSBY, ALABAMA, 1956-591 Nitrogen applied, lb. per acre Lint percentage Not Pct. Boils per pound of seed cotton Inter-InterHigh e Not High irrigated irrigation irrigation irrigated iigation irrigation Pct. Pct. No. No. No. 94 76 1956 84 37.3 37.9 38.6 120-------.-.-------------------------87 36.0 37.0 240___--__------------------- 38.1 1957 93 38.8 38.1 39.3 --------------------------0-------77 37.7 38.1 38.2 ---------------60-----------------76 36.7 36.6 38.4 120------------------------------------240--_ 96 83 39.7 39.6 ----------- 38.0 o0------------------------85 86 37.6 38.1 38.0 60 ------------------------------------- 72 67 82 75 69 81 -------------------------- 71 66 64 75 69 61 37.1 - 36.4 35.9 72 1958 80 81 38.5 38.5 38.7 120------------------------------------78 78 38.1 37.7 37.9 240 -----------------------------------77 79 37.9 38.3 37.9 360 ---------------------------------1959 95 90 40.0 40.9 40.2 0----------------------------------39.4 38.7 38.8 ----------------------------120---38.7 39.0 38.1 240---------------------------------89 75 84 78 40.4 39.7 40.4 0---------------------------------81 79 77 74 90 70 360------------------------------------480 ------------------------------------ 38.6 39.0 ---- 38.5 97 93 -69 72 70 71 74 ---- 720 -----------------------------------1 Coker ---- 38.4 38.8-69 100A was the variety in 1956-57, Deltapine 15 in 1958-59. soil and likewise no effect of nitrogen on boll sizes, Table 14. Boll size differs widely with varieties under irrigation, Tables 14, 15. This has also been observed under nonirrigated conditions. Boll size was not affected by topping, but was reduced by bottom defoliation, Table 5. Since the defoliant prevented some bolls from reaching maturity, average boll size was reduced. Plant Height Even with ample moisture and fertilizer, there were differences of a foot or more in height from one season to the next with a given variety, Table 10. The Acala varieties were the tallest varieties grown. Auburn 56 variety reached a height of only 50 inches even with irrigation and 300 pounds of N on the Chesterfield soil at Auburn, whereas similar treatments on the Independence soil at Tallassee produced plants 65 inches tall. 18 ALABAMA AGRICULTURAL EXPERIMENT STATION TABLE 14. EFFECT OF VARIETY AND NITROGEN ON LINT PERCENTAGE, BOLL SIZE, MICRONAIRE, AND STAPLE LENGTH, TALLASSEE, ALABAMA, 1958-59 Nitro- Nitrogen plied, Lint percentage Bolls per lb. of seed cotton Micronaire Staple length inch in Variety lb. per 1958 1959 acre Pct. Pct. Auburn 56 60 120 180 240 300 60 120 180 240 300 60 120 180 240 300 60 120 180 240 300 37.6 37.1 36.6 36.7 36.4 35.8 36.8 37.3 36.2 35.8 37.8 36.8 36.9 36.6 36.3 38.0 38.5 37.2 39.0 36.1 39.2 39.4 38.6 39.3 39.4 40.4 39.2 39.6 39.8 40.0 38.0 37.4 35.3 36.1 36.7 38.4 36.9 36.3 37.2 36.9 38.3 38.3 38.0 38.6 39.0 39.6 38.6 37.7 37.0 38.9 Av. 19581959 Av. 1958 1959 Pct. No. No. No. 37.4 36.7 36.1 37.1 36.0 37.9 37.1 36.1 36.4 36.5 38.2 37.7 36.8 38.1 36.5 38.8 38.9 38.3 39.0 39.2 40.0 38.9 38.7 38.4 39.5 72 70 73 70 74 64 65 63 71 65 73 73 68 68 70 75 71 72 75 76 75 76 78 74 80 71 77 74 82 79 74 77 80 77 83 80 76 74 79 73 82 80 90 80 77 83 73 79 85 92 72 74 74 76 77 69 71 72 74 74 77 75 71 74 72 79 76 81 78 77 79 75 79 80 86 4.1 3.7 3.8 3.9 3.7 3.9 3.8 3.4 3.7 3.5 3.9 3.9 3.8 3.8 3.7 3.9 3.9 3.6 3.7 3.9 3.9 3.6 3.6 3.7 3.5 4.6 4.8 4.7 4.6 4.7 4.6 4.5 4.3 4.3 4.2 4.3 4.6 4.3 4.0 4.6 4.5 4.7 4.4 4.5 4.5 4.7 4.9 4.9 4.3 5.0 Av. 19581959 Av. No. No. No. 4.4 4.3 4.3 4.3 4.2 4.3 4.2 3.9 4.0 3.9 4.1 4.3 4.1 3.9 4.2 4.2 4.3 4.0 4.1 4.2 4.3 4.3 4.3 4.0 4.3 33 33 33 33 33 33 33 33 33 33 34 33 33 33 33 33 33 33 33 33 33 34 33 33 33 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 35 36 35 35 36 35 34 34 34 34 34 34 34 34 34 34 34 34 35 34 34 34 34 34 34 34 35 34 34 35 34 34 34 Plains Coker 100A Stoneville 7 60 Deltapine 15 120 180 240 300 Cotton planted a month late was more vegetative in the fall than cotton planted at the recommended time. The late cotton was always as tall or taller at frost than the early cotton. Picking all the fruit of Coker 100A to simulate complete loss of fruit to insects had no effect on plant height until after August 1. Defruited plants in 1957 reached heights of 68 and 73 inches at frost for the early and late planted cottons at Thorsby. Corresponding heights without fruit picking were 51 and 54 inches. Similarly, all the varieties listed in Table 6 for 1957 were defruited. All reached heights about 1 foot taller than the normal plants. This may not be an accurate measure of the effect on plant size when insects destroy the fruit, because hand picking the fruit may have had some dwarfing effect. There was no evidence of lodging with any of the varieties MANAGEMENT of IRRIGATED COTTON 19 MANAGEM.ENT of IRRIGATED COTTON 1 TABLE 15. LINT PERCENTAGES AND BOLL SIZES OF COTTON GROWN WITH IRRIGATION AND 300 POUNDS OF NITROGEN, THORSBY, ALABAMA, 1957-59 Lint percentage Variety Boils per pound of seed cotton Auburn 56 Plains- Empire Coker lGAStoneville 7 Deltapine 15 Stoneville x Acala- Empire Dixie 3202- Plains 491-2.--Deltapine S.L.-All-in-One---_Pope -------- Hi-bred ------Rex --------Acala 4-42----Acala 44----- King----_ 1957 Pct. _36.6 _37.6 36.8 _36.6 _37.6 .39.2 -38.7 _35.5 -38.3 _38.4 _37.6 35.2 39.2 _39.4 1958 Pet. ___ 36.1 35.2 35.7 38.5 39.0 1959 Pet. 35.3 36.5 36.0 36.6 38.8 38.0 Av. Pet. 36.0 36.7 36.0 36.3 38.3 38.7 36.0 37. 1 38.2 1957 No. 61 59 49 63 68 72 69 50 57 73 52 55 68 54 37.6 37.4 37.4 37.8 1958 No. -_64 56 66 -79 ---------62 56. 54 1959 No. 65 65 54 67 74 72 -------54 Av. No. 63 63 53 65 71 74 -------55 52 53 where the fruit was removed. boils causes plants to lodge. straighten upright unless they are so severely lodged that they become matted. Lint Percentage This, indicates that weight of gr-een After the boils open, plants tend to Nitrogen caused a decrease in the lint percentage, Table 13, because of an increase in seed size. With ample moisture this effect on lint percentage was most evident when yield responses from nitrogen were obtained. All varieties had satisfactory lint percentages, even with exceptionally high rates of N, Tables 14, 15. Stoneville 7 and Deltapine 15 had the highest lint percentages, but boils were small. The Acala varieties, on the other hand, had intermediate lint percentages but extremely large boils. Empire also had a low percentage but produced large boils. Spacing no effect on lint percentage, Table 7. lint had Micronaire Micronaire measures a factor related to both fiber fineness (diameter of the fiber) and maturity (degree of filling of the fiber). Thus, it is a mathematical figure that is influenced by both fineness and maturity. It is one of most widely used measures of the milling properties of cotton. the 20, 20 ALABAMA AGRICULTURAL. EXPERIMENT STATION ALABAMA AGRICULTURLEP IMN ST IO TABLE 16. EFFECT OF NITROGEN AND MOISTURE ON MIGRONAIRE AND FIBER LENGTH OF COTTON, THORSBY, ALABAMA, 1956-591 Nitrogen applied, lb. per acre. Micronaire Not rrigated Fiber length (upper-half H o Hmiate iig tig In. 1 mean) In. Inter- Inter- rgationirrigationigadrgatioii In. 1956 60------------------------------------120------------------------------------240------------------------------------1957 0------------------------------------60 ------------------------------------120------------------------------------240----------------------------------1958 0-----------------------------------120------------------------------------240 ------------------------------------360------------------------------------1959 0 ------------------------------------120-------------------------------240----- ------------------360------480----------------------------------- -720-- - ------ ------------1 o------------------------------------- 3.9 3.7 3.8 3.6 3.9 4.2 3.9 3.7 3.5 3.3 3.2 3.2 3.6 3.5 3.8 3.8 3.5 3.7 3.6 3.6 4.4 4.3 4.3 4.1 3.5 3.1 3.3 3.3 3.5 4.2 4.2 4.1 4.1 3.7 3.4 3.2 3.3 1.13 1.10 1.11 1.10 1.13 1.16 1.11 1.19 1.12 1.06 1.07 1.12 1.10 1.06 1.16 1.07 1.13 1.14 1.16 1.08 1.19 1.18 1.09 1.13 1.16 1.15 1.09 3.3 3.4 3.5 3.8 3.6 3.7 3.7 -- 1.10 1.08 1.08 1.09 1.10 1.08 1.08 1.02 1.01 1.04 1.10 1.12 1.09 1.06 1.07 1.08 1.08 _--------------------------- 3.8 1.01 3.9 .99 3.8 1.01 3.8 1.01 3.7-1 3.6-1.08 .06 Coker 100A was variety in 1956-57; DPL 15 in 1958-59. Fiber analyses for the experiments were made by the Fiber Testing Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Knoxville, Tennessee. Micronaire values varied with season, location, and variety, Tables 7, 14, 16. Neither nitrogen nor spacing had an effect on micronaire. The effect of irrigation on micronaire depended on the season. When dry weather occurs during the fiber maturation period, fibers fail to mature, which results in low micronaire values. Under such conditions irrigation will produce cotton with more mature fibers. If moisture is adequate to cause the fibers to mature, irrigation will cause no change in micronaire even though yield may be increased considerably. Staple Length The upper half mean length is a measurement made on a machine called a fibrograph. This measurement corresponds closely MANAGEMENT of IRRIGATED COTTON 21 to the length of staple as measured by commercial cotton classers. There was usually a slight increase in fiber length with increasing rates of nitrogen on the Greenville soil, Table 16. On the Independence soil at Tallassee where no yield response was obtained from added N, there was no, effect of rates of N on fiber length, Tables 7, 14. Other Fiber Properties Other fiber properties measured were strength and elongation. There was no effect of nitrogen, moisture, or plant spacing on these fiber properties. Seed Germination Germination percentage was highest with seed produced at the lowest rate of nitrogen at Tallassee in 1958, Table 17. Although this was apparent in all five pickings, it was most prominent in the first picking where there was a reduction of 7.3 per cent as the rate of N was increased from 60 to 120 pounds per acre. The cause of this effect observed in this 1 year's results is not known. TABLE 17. GERMINATION OF SEED FROM FIVE VARIETIES OF COTTON GROWN WITH FIVE RATES OF NITROGEN, TALLASSEE, ALABAMA, 1958 Variety60 Variety lb. Pct. Seed germination from five nitrogen rates 120 lb. 180 lb. 240 lb. 300 lb. Average Pct. 77 79 81 81 72 78 Pct. 80 73 78 72 74 75 Pct. 81 78 82 77 79 79 Pct. 77 72 79 79 73 76 Pct. 80 77 81 78 75 78 Auburn 56 Plains-Coker 100A-........... Stoneville 7 Deltapine 15 -----------Average 85 83 83 82 76 82 SUMMARY and CONCLUSIONS 1. Yields in excess of 5,000 pounds of seed cotton per acre were produced in the State when adequate moisture and fertilization were combined with other good management practices. Although this illustrates the potential for cotton yields, such production is not necessaxily practical farm goals at present. 2. Cotton has shown yield responses to nitrogen rates as high as 360 pounds of N per acre. However, with present varieties 22 ALABAMA AGRICULTURAL EXPERIMENT STATION and insect control, about 120 pounds of N is a more practical rate for irrigated cotton. 3. To obtain yield responses from high rates of nitrogen or high rates of moisture, both must be used with other good management practices. 4. Topping cotton to a height of 42 to 48 inches controlled lodging and did not reduce yields. 5. Defoliation of the lower 2 feet of plants with magnesium chlorate when three-fourths of the bolls were of mature size reduced the 3-year average yield by 491 pounds of seed cotton per acre. 6. Planting 1 month later than the recommended date reduced the 3-year average yield by 752 pounds of seed cotton per acre. 7. Cotton with plant populations of 30,000 and 10,000 lodged less than populations of 5,000 plants per acre. 8. With high rates of nitrogen and moisture, serious lodging problems were often encountered. 9. There were marked differences in lodging among cotton varieties when grown with high rates of nitrogen and moisture. Some varieties lodged almost completely, whereas others practically none when 300 pounds of N per acre was applied. 10. No lodging was observed with any of the varieties tested when all fruit was removed from the plants. 11. The severity of boll rot was dependent upon the kind of season as well as the amount of rank growth and lodging. 12. Even with the same nitrogen and moisture rates, some varieties differ a foot or more in plant height from season to season. 13. Nitrogen decreased the lint percentage, but increased boll weights and seed weights, and had no effect on micronaire values. 14. Irrigation increased the fiber length and had a variable effect on micronaire depending on the season. MANAGEMENT of IRRIGATED COTTON 23 LITERATURE CITED (1) O. L., SCARSBROOK, C. E., Doss, B. D., AND PEARSON, R. W. Interrelations of Nitrogen Fertilization and Irrigation of Cotton. International Congress of Soil Science Proc. (In Press). BENNETT, HAMILTON, J., STANBERRY, C. O., AND WOOTON, W. H. Cotton Growth (2) and Production as Affected by Moisture, Nitrogen, and Plant Spacing on the Yuma Mesa. Soil Sci. Soc. Amer. Proc. 20:246-252. 1956. (3) SCARSBROOK, C. E., BENNETT, O. L., AND PEARSON, R. W. The Interac- tion of Nitrogen and Moisture on Cotton Yields and Other Characteristics. Agron. Jour. 51:718-721. 1959. (4) SPOONER, A. E., BROWN, D. A., AND WADDLE, B. A. Effects of Irriga- tion on Cotton Fiber Properties. Ark. Agr. Expt. Sta. Bul. 601. 1958. (5) STURKIE, D. G. Effects of Some Environmental Factors on the Seed and Lint of Cotton. Ala. Agr. Expt. Sta. Bul. 263. 1947. (6) WADLEIGH, CECIL H. Growth Status of the Cotton Plant as Influenced by the Supply of Nitrogen. Ark. Agr. Expt. Sta. Bul. 446. 1944. ACKNOWLEDGMENT The authors acknowledge the assistance of J. K. Boseck, superintendent of the Tennessee Valley Substation, and J. W. Langford, superintendent of the Plant Breeding Unit, in carrying out the cotton irrigation experiments reported in this publication.