ll-‘Qkl Bulletin 838 September I956 flidcs in BUTTON IRRIGATION an the fliy/l Plains . I-v g - ‘s: < r 15 ‘P’ in cooperation with the UNITED STATES DEPARTMENT OF AGRICULTURE TEXAS AGRICULTURAL EXPERIMENT STATION R. D. LEWIS. DIRECTOR, COLLEGE STATION, TEXAS Summary and Recommendations This bulletin gives the results of studies conducted for several years at Lubbock a; Tulia on the use of irrigation water by cotton. JP Cotton yields in pounds of lint per inch of water were about the same for all moist i levels studied. s. In general, the high moisture levels are the most profitable. If the supply of water is short, no significant loss will occur in yield per acre-inch water by following any one of the treatments studied. Cotton uses varying amounts of water efficiently, which makes it an easier crop irrigate than grain sorghum. The preplanting irrigation is the most important one. Definition oi Terms Transpiration: The water absorbed by the crop and evaporated from plant surfaced It does not include soil evaporation. It is expressed as acre-feet or acre-inches per act or as a depth in feet or inches. Consumptive Use (evapo-transpiration) : The sum of the volumes of water used by t vegetative growth of a given area in transpiration and building of plant tissue and that eva; orated from adjacent soil, snow or intercepted precipitation on the area in any specified ti divided by the given area. If the unit of time is small, the consumptive use is expressed acre-inches per acre or depth in inches; but if the unit of time is large, such as a crop-gro ing season or a 12-month period, the consumptive use is expressed as acre-feet per acre a. depth in feet or inches. .~ Water Requirement: The quantity of water, regardless of its source, required by; crop in a given period of time for its normal growth under field conditions. It includes s ‘ face evaporation and other economically unavoidable wastes. It usually is expressed in dep (volume per unit area) for a given time. i Irrigation Requirement: The quantity of water, exclusive of precipitation, required f1 crop production. It includes surface evaporation and other economically unavoidable wast It usually is expressed as depth in inches or feet for a given time. » Irrigation Efficiency: The percentage of irrigation water delivered to the farm i field that is available in the soil for consumptive use by the crops. When measured att field or plot, it is called field-irrigation efficiency. ’ :1 Moisture Percentage: The percentage of moisture in the soil, based on the weight i the ovendry materiaL. c- Field Capacity: The moisture percentage, on a dry-weight basis, of a soil after ra drainage has taken place following an application of water, provided there is no water wit _ capillary reach of the root zone. This moisture percentage usually is reached in 2 to 4 after an ordinary irrigation, the time interval depending on the soil type. ’ Permanent Wilting Percentage: The percentage of water in the soil when plants w; permanently. S MAKING STUDIES OF THE UNDER- ter 0f the High Plains estimate there 'mately 150 million acre-feet of water ' e sands which underlie this region. ificient use of water from this water- 'd, in a supplemental form, has made to increase production as much as 300 .-- normal dryland crop production dur- I: few years. More than 40,000 irriga- §are being pumped to supply water to 3 million acres. This represents an 5 of more than 100 million dollars in .plants and equipment alone. igh Plains produces about one-tenth of . nited States cotton crop and one-third p Texas crop. The terrain is level and, i’. is suited to large-scale, high-speed, I operation. The soils have a high de- erent fertility and produce good yields .3: d other crops with minimum expense. Climate 'gh Plains are in the northwestern cor- 1s and are well over 3,000 feet in eleva- rds from the Lubbock station show “annual rainfall has averaged slightly ches for a 44-year period (Table 1). ‘tely 82 percent of this rainfall occurs J through October. Distribution is more than the total amount of rainfall re- ' e two rainfall peaks of the year are in ptember. In 4 years out of the 10 the i rainfall is more than 3 inches. 'ent use of irrigation water to supple- annual rainfall helps insure a good yield gality cotton. The Lubbock vicinity has frost-free season of 211 days. The av- of killing frosts are April 6 in the "d November 4 in the fall. The short i ason is a constant threat to the cotton Because other climatic conditions, such hts, wind, high-intensity rains and hail, i practical to plant cotton before early I 50 of the 211 frost-free days are lost. ‘to 170 days are left for maturing the -.p0int where there is a minimum damage ' . Any practice that tends to delay ma- iuld be avoided. ly, assistant irrigation engineer, Substation bock, Texas; and irrigation engineer, Soil and servation Research Branch, Agricultural Re- i ‘ce, U. S. Department of Agriculture, Lincoln, . and formerly of the Amarillo Experiment Sta- and, Texas. ides in COTTON IRRIGATION on the fliy/l Plains ~E. L. THAXTON, JR. and N. P. SWANSON* High Plains Cotton Soils Pullman clay loam, Amarillo fine sandy loam and Amarillo loam make up the largest part of the area farmed to cotton on the High Plains of Texas. Three million acres may be planted in ir- rigated cotton on the three soil types. Most of the Pullman clay loam soil is on the northern edge of the cotton belt in the Texas Panhandle. The Amarillo loam is the transition soil between the Pullman clay loam and the Ama- rillo fine sandy loam. Pullman clay loam is a deep, fine-textured, slowly permeable soil, often 5 to 6 feet in depth and capable of holding a large amount of water. The greatest problem encountered in irrigating these soils is getting adequate water into the soil. Infiltration rates may be as low as one-tenth inch of water per hour. Amarillo "fine sandy loam is a freely perme- able, medium-textured soil. It is about 3 to 4 feet deep and is underlain by a rock-like accumulation of highly calcareous material. The infiltration rate is often 2 inches per hour. Cotton is grown on about a million and a half acres of this soil type. Amarillo loam is an intermediate or transition type. It is fine to medium-textured, permeable and averages 4 _to 5 feet in depth. Infiltration rates average 1 to 1% inches per hour. Cotton is grown on about 300,000 acres of this soil type. Contents Summary and Recommendations __________ -- 2 Definition of Terms _________________________________ __ 2 Introduction .... -_ _- 3 Climate ............... -- 3 High Plains Cotton Soils _________________________ 1 3 Previous Work at Lubbock ____________________ __ 4 Test Near Tulia _________________________________________ -- 4 Water Management ................................... -- 5 Cultural Practices ....................................... _- 7 Methods of Irrigation _______________________________ __ 8 Fiber Quality 8 Acknowledgment ________________________________________ -_ 8 Figure 1. Water applications were measured carefully onto level borders in the water management study near Tulia in 1954. Previous Work at Lubbock Pump irrigation studies at the Lubbock sta- tion by D. L. Jones and Frank Gaines (Progress Report 667) pointed out the need of a preplanting irrigation on the fine sandy loam soils of the area (Table 2). Two preplanting irrigations gave good results in these early tests, primarily because of the ad- ditional water stored in the root zone. Summer irrigation was profitable, but the preplanting ir- rigation was the most valuable from the yield of lint per acre-inch of water. Similar irrigation tests W e r e continued through 1951-54, but the dates of irrigation were revised to conform with certain stages of plant development. Table 3 indicates that a preplanting irrigation again gave the greatest yield of in- crease, but that two summer irrigations were prof- itable. Summer irrigations were applied at the time of the first flowering and again at the peak fruiting stage. No attempt was made to keep the plants out of stress between irrigations although Forinal summer rainfall usually corrected this de- 1c1 . TABLE 1. A 44-YEAR SUMMARY OF NORMAL PRECI- PITATION BY MONTHS, LUBBOCK STATION. 1911-54 Years a Years within Years of Mm‘ ilfiiéil .3333’. oinféiiifill gfiifllis percent percent percent Ianuary .53 . 61 11 2 February .65 70 11 5 March .78 59 20 5 April 1.37 59 10 14 May 2.72 64 27 30 I une 2.25 59 20 27 IulY 2.03 59 18 23 August 1.96 52 34 16 September 2.60 59 14 36 October 2.18 64 5 30 November .55 57 14 0 December .69 64 16 0 Yearly average 18.37 4 Tests Near Tulia An irrigation test on cotton was set 1953 to determine seasonal and average dai- sumptive use of water on Pullman clay 10a near Tulia. s Irrigations were measured carefully onr a e1 borders so that accurate moisture figure be obtained (Figure 1). There were no lot rainfall or irrigation water by runoff. gage was located on the site to measure tation. Soil moisture samples were taken p times during the season to depths of 6 feet. i ings were taken three times a week duriq irrigation season from Bouyoucos blocks. A plot had blocks in each foot of soil to a dept feet, with an additional location in each p measuring moisture in the 0 to 2-foot dep, calibration curve made on Pullman clay l the Amarillo Experiment Station was used . Tulia location following early comparisons 0 ture values obtained by gravimetric and resistance methods. Some modifications ' bration were made for the lower depths of Tulia following further comparisons durig 1953 season. Consumptive use data obtained for t rious moisture levels used in these tests are. in Tables 4 and 5. Moisture use approach inch per day on the cotton plots during th use period in both 1953 and 1954. Figure 3 show moisture depletion during the seaso creased water use started near the firs l, stage and continued as long as there was c available water in the profile. ' The general pattern of moisture ex ~- consisted of removal first near the surfa subsequent withdrawals at deeper depths available moisture in the 5 to 6-foot zop utilized. There was essentially no difference i utilization efficiency regardless of i , treatment. The pounds of lint per acre- TABLE 2. SUMMARY OF COTTON IRRIGATI? AT THE LUBBOCK STATION. 1937-41‘ Lint Lint Total ield per or _ Treatment annual Y r inch c' irrigation cfcere of ' _ water pr Inches Pounds Pounds No irrigation 0 309 15.7 2 preplantings 6 457 18.8 1 preplanting 3 387 17.6 1 preplanting and _ 1 postplanting 6 442 18.0 1 preplanting and 2 postplantings 9 464 16.9 ‘Rainfall ranged from 11.71 to 40.55 inches. T ranged from 17.4 to 21.5 in 1953 and from “to 21.9 in 1954. This indicates that cotton water effectively over a wide range of avail- T , thus providing some latitude for the time application to cotton on the High Plains. . he data on consumptive use during 1953-54 2 years of very low rainfall. In a normal ‘ cotton probably would use water at about me rate during peak-use periods, but the ll during the growing season would make er irrigations less frequent. Even though ted rainfall occurred, it still would be neces- to apply 3 to 4 inches of water to the cotton .1 the growing season, in addition to the pre- ' g irrigation, to be assured of better than ge production. In years of more than aver- Y infall and higher relative humidity, lower iration rates would be expected, thereby ing the consumptive use. In this case, rain- “distribution will be as important as the amount. nfrequent, heavy rains would not be as ben- _ to the plants as moderate Weekly or semi- V‘: rains, even though the total amount of ll was the same. ‘This is because of possible "by deep percolation and runoff. Rainfall p, ess of the moisture deficit in the root zone ' t be useful to the crop. On the other hand, lrains falling on the air-dry surface of a clay {soil often fail to bring the moisture content p- surface above wilting point. The moisture $81168, or partially replenishes, the deficit t» by evaporation, but little or no moisture Zes available to the plants. Water Management " hen Pullman clay loam soils are wet to a of 6 feet, moisture storage provides almost "ches of available water. Water-use studies 's soil show that enough Water is withdrawn FIELD CAPACITY -_________EI=ANIIU§_ _QA_IE________ _ ___ __ AMAY I JUNE I JUlLY ' AUG. I SEPT. 1 lameeuunnc omx l-nmmmu sox AVAILABLE MOISTURE m o TO 24-mcn on-zrm TO ans -- re 2. Available moisture in soil storage in 0 to depth of soil. cotton. Tulia. 1953. TABLE 3. SUMMARY OF COTTON IRRIGATION TESTS AT THE LUBBOCK STATION, 1950-54‘ Total Lint annual Total Yield inch of Lint per Compared Treatment with pre- irrigation water per acre water planting Pounds Inches Inches Pounds Pounds oi lint per acre None 13.2 165 12.5 255 April only 8.2 21.4 420 19.6 ' April. Iune 12.2 25.4 451 17.8 —I— 31 April. Iuly 12.0 25.2 470 18.7 + 50 April. Aug. 12.5 25.7 517 20.1 —I— 97 April. lune. Iuly 12.9 26.1 468 17.9 + 48 April. Iune, Aug. 16.2 29.4 588 20.0 +168 April. I uly, _ Aug. 15.5 28.7 590 20.6 +170 April. I une. I uly. Aug. 19.5 32.7 518 15.8 + 98 ‘Irrigations were made near these dates each year: April 20. Iune 25. Iuly 15 and August 5. zlncluding rainfall. at 6 feet to justify storing water for crop use at that depth. It is possible for the farmer to store a large part of the water required for maximum crop production in the soil prior to planting by a preplanting irrigation. About 9 inches of available water can be stored in Amarillo fine sandy loam when the soil profile is wet to field capacity to a depth of 6 feet. In many places, it is feasible to wet the soil profile to depths of 4, 5 or even 6 feet with one summer irrigation. Pullman clay loam, which takes water slowly, cannot be irrigated effectively more than 3 or 4 feet deep with a summer irrigation. Refilling the entire profile of the Pullman clay loam with a sum- mer irrigation might temporarily wetlthe soil to a point where the cotton roots would suffer from lack of oxygen. Water stored 4 to 6 feet IO“ i | : i i FIELD CAPACITY ______________ _- =1 a- ' I 8 l l l'\ x z g _g ix |\!\\ " __ ‘y! '\_ I . l: 6 \l\\l l l l\\\'\ E ' \ ll i \ '\ | \ ‘1 n‘ < I \ _ 3 w, u N w 4‘ zl 5i ° ‘i: °: en ... g. lI-l _II | I 2L a.l 9| Q I 0| Z I | - : w i s! MAY l JUNE l JULY l AUG. l SEPT. l iPREPLANTING ONLY ——-MAINTAIN 25% AVAILABLE MOISTURE IN O TO 24-lNCH DEPTH TO 8/15 ----- -- MAINTAIN 50X AVAILABLE MOISTURE IN O TO 24-lNCH DEPTH TO B/l ‘"—MAINTAIN 50% AVAILABLE MOISTURE "IN O TO 24-lNOH DEPTH TO WIS Figure 3. Available moisture in soil storage in 0 to 60-inch depth of soil. cotton. Tulia. 1954. 5 l953-'-— 1954- -' ' INCHES OF WATER USED | l I I I I I I I I J ,ooo,ooooo,o,ooo MONTH JUNE JULY AUGUST ssetzvcra Figure 4. Consumptive use of cotton by l0-day periods on Pullman clay loam soil, Tulia. Daily water use for Iuly 31 and August 31 has been included in the last 10-day periods. deep in Pullman clay loam soil usually is adequate to meet the seasonal withdrawalby the cotton crop from those depths without replenishment after planting. In general, the preplanting irrigation on the three important cotton-producing soil types of the High Plains should be adequate to bring the soil profile to field capacity to a depth of 6 feet on deep soils and 4 feet on soils of medium depth. Each summer irrigation should be sufficient to store about 4 inches of water in Pullman clay loam and 4 to 5 inches in Amarillo fine sandy loam. In dry years, when little or no rainfall occurs, irrigation will be needed every 14 to 18 days. Al- lowing for losses in application, as much as a 6-inch application may be required, depending on the efficiency of the irrigation system. Table 6 shows there is a great variation dur- ing the summer in consumptive use from one 10-day period to the next, depending on weather conditions and the availability of water in the TABLE 4. CONSUMPTIVE USE AND WATER UTILIZA- TION EFFICIENCY DATA FOR COTTON, TULIA, 1953 . Lint Lint per Moisture Number of Total . . treatment irrigations water- pgxzlge aofirgéicg? Inches Pounds Pounds Preplanting only 2 12.7 273 21.5 25 percent available water maintained in 0-24-inch depth to August 15 4 20.0 361 18.1 50 percent available water maintained in 0-24-inch depth to August 1 4 19.6 341 17.4 50 percent available water maintained in 0-24-inch depth to August 15 ' 5 23.2 476 20.5 soil. Consumptive use by cotton was measured‘ high as 0.42 inch per day during extremely I dry periods. Normal use should be about L fourth inch per day during August. Moisture g increases as the plant grows until the maxim . fruiting period is reached (Figure 4). This pe, od normally starts during late July and may I» tinue into September. Cotton uses less water wi a decreasing availability of soil moisture, pa n; _ ularly on clay soils. Cotton can survive for m . days with very low water use, but norm i} growth and production are not achieved (Fig 5 and 6). Average rainfall for July and August is abet‘ 2 inches per month. Consumptive use measu. ments show that cotton is capable of using inches of water during July and over 9 inches d ‘I ing August (Table 7). These amounts, less - pected rainfall, leave a deficit of 6 inches of wa to be supplied by irrigation and from depletion =1 soil-moisture storage during July, and 7 inch to be supplied similarly during August, if f, crop has all the water required to make n‘ growth. A total moisture deficit of 15 inches hf; be expected for July and August (Figure 7 ). moisture storage is inadequate to supply uf amount and the storage possibly will have b depleted by deficits in May and June. The lower consumptive use in midseason, indicated in Figure 4, was caused by rains in latter half of July 1953 and by a few days of i; atively cool weather in early August 1954. The consumptive use for September wl somewhat lower, less than 6 inches. The expec Q September rainfall is 2.6 inches, therefore, t required withdrawal from soil moisture story would be about 3.4 inches. Sound irrigation pl ' ning insures that this amount of readily availa water will be stored in the soil profile at the f, ginning of September, eliminating late-season' rigations. This will allow the plants to beco hardened as the season ends and prevent a I crop of immature cotton that might result fro, late irrigation (Figure 8). TABLE s. CONSUMPTIVE use AND WATER u | r TION EFFICIENCY DATA FOR COTTON. TULIA, 1954 Moisture Number oi Total G133: ‘A treatment irrigations water p; acre oiw-r. . , Inches Pounds Po ,3 Preplanting only 1 14.5 302 20.3’- 25 percent available water maintained in 0-24-inch depth to August 1s s 22.s 442 19.5 50 percent available water maintained in 0-24-inch depth to ‘ 7 August 1 4 . 22.0 481 21.3 50 percent available water maintained in 0-24-inch depth to August 1s 4 26.0 s21 ‘ 20.1 6 There were no runoff losses from the irriga- gii. and rainfall measured in these studies. The piigations were adequate, with uniform moisture fribution and penetration, and there were no p percolation losses. Losses by evaporation were 510W as could be expected under the conditions rienced. Since most farm-irrigation systems not as efficient as the one used for these stud- greater applications of water will have to be e to compensate for the higher losses on less ‘cient systems. Summer irrigations should begin about the 1 of first bloom and terminate by the end of ,ust. The size of the area selected for sum- . irrigation should not be too large for irriga- on an 18-day schedule with the water avail- Timely rainfall in some seasons will per- extending the irrigated acreage. f The depth of water to be applied at an irriga- depends on the moisture content and storage R city of the soil. Enough water should be ‘lied to replenish the moisture deficit in the root or to obtain field capacity to a desired depth. Experience and the use of a sharpshooter inted shovel), soil tube and a soil auger or to determine depths of water penetration to estimate moisture content are invaluable. r-irrigation wastes valuable water and time i is detrimental to the crop. Under-irrigation "yuires more frequent applications with higher poration losses and labor costs. See your local Extension Service or Soil Con- ; atlon Service personnel for assistance in es- t1ng moisture cond1t1ons 1n the SOllS on your Cu|tura| Practices y. Cotton should be planted between May 10 a 1 20 to obtain a good stand and yield. Studies lathe Lubbock station show that little gain in "Figure 5. Yields were considerably lower on the borders j, iving only a preplanting irrigation in the test near Tulia. TABLE 6. CONSUMPTIVE USE OF COTTON BY 10-DAY PERIODS ON PULLMAN CLAY LOAM SOIL WITH 50 PER- CENT AVAILABLE MOISTURE MAINTAINED IN 0-24-INCH SOIL DEPTH UNTIL AUGUST 15. TULIA Period 1953 1954 — — — Inches of water — — — Iune 1-10 .4 .2 11-20 .4 .8 21-30 .4 1.0 Iuly 1-10 .6 .9 11-20 2.7 3.8 21-30‘ 2.6 3.2 August 1-10 4.2 3.3 11-20 .3 3.4 21-30‘ 2.6 3.4 September 1-10 2.5 1.6 11-20‘ .7 .8 21-302 .5 .4 Water used by plants 17.9 19.4 ‘Daily water use for Iuly 31 and August 31 has been included in the last 10-day periods. “Low availability of moisture in 0-24-inch depths. maturity is obtained by earlier planting. Early- planted cotton often has to be replanted, or a poor stand is obtained with some decrease in yield as a result of cold ground, disease and weather con- ditions. The planting rate should be 20 to 30 pounds of seed per acre. Normally cotton is planted in 40-inch rows to facilitate the use of the cotton TABLE 7. MONTHLY CONSUMPTIVE USE BY COTTON WHEN NOT LESS THAN 50 PERCENT AVAILABLE MOIS- TURE WAS MAINTAINED IN THE 0-24-INCH SOIL DEPTH UNTIL AUGUST 15. TULIA Year Month 1953 1954 Average — — — — ——Inches—————— Iune 1.0 2. 1.5 Iuly 5.9 7.9 6.9 August 7.1 9.2 8.1 September 3.7 2.8 3.3 Total 17.7 21.9 19.8 Figure 6. Yields were high on borders kept at not less than 50 percent available moisture to August 15 in the test near Tulia. 1954. 7 Figure 7. Plants receiving only a preplanting irrigation had exhausted most of the water in the soil profile before September Z9 on the irrigation tests near Tulia. 1953. stripper. The cotton should be planted in shallow furrows and covered 11/2 to 2 inches deep. Cultivation should be made only when needed for weed control. Cultivations to maintain a dust mulch do not conserve moisture. High residue crops and minimum tillage operations, however, help maintain adequate intake rates. E ven Figure 8. Sound irrigation practices allow plants to become hardened as the season ends and prevent a crop of “bolly" cotton. These stormprooi bolls were well matured by frost, 1954. 8 though hand harvest is still used by many fa A ers, economic studies conducted on the High Pla' show that the stripper harvester is more econo ical and nets the farmer the most money. ‘ Methods of Irrigation The furrow method of water application most commonly used on the High Plains. A tem of graded furrows .has been most popul although little consideration has been given to’ ' efficient design. A few farmers using level f 1 rows find that more uniform crops and hig g yields with less water are possible, but more la‘ may be required than with the graded furr Some cotton is being produced on the bench-love. slopes with level borders, graded borders, leg furrows or graded furrows. These benches, p ually 8 to 12 rows wide, are farmed with conv‘ tional equipment. Small streams of water :5 able on most of the farms in the area make i border method of irrigation impractical. Sprinkler irrigation has become popular is more efficient than the furrow method of 3p; cation on the very sandy and rolling land found part of the cotton-producing areas. A well signed sprinkler system is recommended Wh the soils take water rapidly or the terrain is suitable for furrow irrigation. Most growers find that the furrow method distributing water is the most satisfactory cheapest on the finer textured soils. The usei underground tile and portable aluminum pipe, portable aluminum pipe only, has been satisfi tory, especially where the farm has steep slo Fiber Quality The quality of cotton may be’ affected gr, ly by summer irrigations. Fiber tests made ' cotton from the irrigation tests at Lubbock s that the highest quality cotton was produced only a preplanting irrigation. Largest yields made with two summer irrigations but the q p ity of the cotton produced was low. Three s mer irrigations reduced both the yield and qf ity. A good compromise between quality and ', came from a late July irrigation which produ less lint per acre but better fiber quality. irrigations, after August 30, are likely to p, poor quality fiber and also may reduce yieldsf The fiber qualities most adversely affe by late irrigations are micronaire fineness maturity. If these two tests are not made, i, poor quality will be reflected by the cotton er’s grade. Other factors of quality which t, be affected are strength, uniformity and t; Acknowledgment These studies were conducted cooperati by the Texas Agricultural Experiment Station. Soil and Water Conservation Research Bra Agricultural Research Service, U. S. Departm; of Agriculture. ' i}