» wfiv-F-q‘, B—1428 February 1983 orghum for Grain: Production Strategies in the Rolling Plains Contents INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 METHODS AND MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Subsoiling and Diking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Yield Potential for Sorghum in the Rolling Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Management Effects on Soil Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Subsoiling and Diking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Yield Potential for Sorghum in the Rolling Plains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Management Effects on Soil Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 RECOMMENDATIONS AND CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . 10 LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 SUMMARY With proper management, dryland production of grain sorghum seems feasible and desirable on the Rolling Plains of Texas. Profitable production of dryland sorghum requires that growers plant a high-yielding, medium-maturing hybrid in ]une. Management strategies of grain sorghum include furrow diking and, if needed, deep tillage or subsoil- ing. Runoff often can be prevented and additional water captured by furrow diking to produce an aver- age of 3,000 pounds of grain per acre. Plant residues play an important role in soil productivity and crop production. KEYWORDS: Grain sorghum/furrow diking/subsoiling/plant residues/fine sandy loam/clay loam/yield/Central Rolling Red Plains ‘ Sorghum for Grain: Production Strategies in the Rolling Plains C. I. Gerard, P. Sexton, L. E. Clark, and E. C. Gilmore, ]r.* INTRODUCTION The two most important cash crops in the Rolling Plains are cotton and wheat. Grain sorghum ranks a poor third behind wheat, which provides only about half the cash receipts produced by cotton. Water is the dominant factor for yields in the Rolling Plains (5), and under present cultural methods water fre- quently is not sufficient to produce economical yields of dryland sorghum in the Rolling Plains. Production systems are needed in the Rolling Plains which return a significant amount of residue to the soil. Because of poor structural stability related to low organic matter, soils in the Rolling Plains are subject to compaction and runoff and have low per- meability to rainwater. High temperatures common in the Rolling Plains contribute to rapid decomposi- tion of plant residues and low soil organic matter. In the High Plains of Texas, Bilbro and Hudspeth (1), Hudspeth (6), and Lyle and Dixon (8) have used basin tillage or diking to reduce runoff and increase crop yields. In 1977, Bilbro and Hudspeth (1) report- ed that furrow diking increased cotton yields by 10 to 15 percent. Hudspeth (6) reported dryland cotton yields from 1975-1978 were increased from 30 to al- most 70 pounds per acre (lb/A) by furrow diking. Furrow diking appears to be a possible way of re- ducing runoff and erosion while increasing the yields of dryland grain sorghum in the Rolling Plains. Stephens and Quinby (13) have been credited with development of hybrid grain sorghum at the Chillicothe Research Station in the Rolling Plains. Increased yields of hybrid sorghum caused it to be- come a profitable crop and by 1960 it occupied 95 percent of the acreage of sorghum for grain (10). Sorghum produces large amounts of residue which should be beneficial to soils in the Rolling Plains; however, in 1979 and 1980 only 30,000 to 40,000 acres of sorghum were harvested in the northern Low Plains (14, 15). The Rolling Plains is often plagued by drought periods; sorghum, being a determinant plant, is susceptible to drought during critical stages of its growth. These studies were conducted to determine if cultural practices to conserve water could be used effectively to increase yields of grain sorghum in the Rolling Plains. The effects of subsoiling and furrow diking on sorghum yields, and incorporating of plant residues on soil conditions, were studied. METHODS AND MATERIALS Subsoiling and Diking The influence of subsoiling and diking on yields of sorghum was evaluated in 1979, 1980, and 1981. This experiment was conducted on an Abilene clay loam soil (properties in Table 1) and was a ran- domized block design with three replications. All treatments, described in Table 2, were 12 rows wide and about 200 feet (ft) in length. The locations of all treatments were the same throughout the time of the experiment. The slope of the field down the rows ranged from 0.1 percent on the lower half to 0.4 percent on the upper half. The lower 50 ft of the field had a low place which tended during significant rainfall to accumulate water from the upper side of the field. Land on which the experiment was installed was planted to cotton in 1978. In 1979 land preparation consisted of bedding and re-bedding prior to or dur- ing installation of the subsoiling and diking treat- ments. Treatments 1 and 2, the check treatments (Table 2), had no other tillage operations until beds were cultivated with a rolling cultivator immediately prior to planting in 1979. In 1980 treatment 2 was changed to evaluate diking interval, and in 1981 it was changed to evaluate diking alternate middles (half diked). Subsoiling treatments were installed March 8, 1979, during the bedding and re-bedding operation. Treatments 3 and 5 were subsoiled on 20-inch inter- vals parallel with rows. After the first bedding opera- tion furrows were subsoiled to a depth of 16 inches; re-bedding was accomplished and furrows were again subsoiled to the same depth. Dikes 6 to 8 inches in height were installed by hand 50 ft apart in all furrows of treatments 4 and 5 on March 9. All beds were cultivated, and Pioneer hybrid 8501 was planted at a rate of about 3 seed per foot (seed/ft) of row Iune 21. Propazine was applied broadcast on ]une 22 at a rate of 1.2 lb/A. Dikes which were broken for planting were reinstalled July 24. Plant height measurements were taken late Au- gust after anthesis. Grain yield was obtained by har- vesting three center rows with a combine on October 12. Four samples were taken at 50-ft intervals down the row to correspond with diking intervals and to measure the effect of slope on yield. "Respectively, professor, technician, associate professor, and professor and resident director, Texas Agricultural Experiment Station, Vernon, Texas 76384. TABLE 1. THE pH, PERCENT ORGANIC MATTER, AND PARTICLE SIZE DISTRIBUTION OF ABILENE CLAY LOAM AND MILES FINE SANDY LOAM AT DIFFERENT SOIL DEPTHS Soils Abilene Clay Loam Miles Fine Sandy Loam organic organic Soil depth pH matter* sand silt clay pH matter sand silt clay Inches % % 0-6 6.9 1.00 45 26 29 5.8 0.40 76 13 11 6-12 6.9 1.05 45 28 27 6.4 0.33 73 13 14 12-24 6.9 0.91 45 25 30 6.7 0.38 58 15 27 ‘Standard error = i 0.05 TABLE 2. DESCRIPTION OF TILLAGE TREATMENTS IN 1979, 1980, AND 1981 Treatment N0. a Description 1979 1. Check No treatment 2. Check No treatment 3. Subsoiled Land was subsoiled 16 inches deep below beds and furrows 4. Diked Rows were diked 50 ft apart Rows were diked and subsoiled as described under Treatments 3 and 4 5. Subsoiled and Diked . Subsoiled and Diked 1980 . Check No treatment . Diked Rows were diked 8 ft apart . Subsoiled Land was subsoiled 16 inches deep below beds and rows in 1979 . Diked Rows were diked 4 ft apart Rows were diked and subsoiled as described under Treatments 3 and 4 1981 . Check No treatment 2. V; Diked Every other row was diked 6 ft apart . Subsoiled” Subsoiled 16 inches deep below beds and rows in 1979 4. Diked Rows were diked 6 ft apart 5. Subsoiled and Diked“ Rows were diked and subsoiled as described under Treatments 3 and 4 ‘Treatments were 12 rows wide and about 200 ft in length and replicated three times. "The subsoiled plots were split in 1981. In 1981 six rows were subsoiled 14 inches deep in the furrow. The other six rows were not subsoiled in 1981. In 1980, land preparation consisted of shredding sorghum stalks from the previous crop and discing with a tandem disc on April 7. Beds were re- established in their original location and dikes estab- lished April 8. Dikers manufactured in Lockney, Tex- as, were mounted behind lister sweeps and adjusted to establish dikes about 6 to 8 inches high on 4- or 8- ft intervals in the furrow. The tripping mechanism which determined intervals between dikes was a 3-ft- diameter wheel. Beds were plowed June 13 and Pioneer hybrid 8501 was planted June 18 at a rate of about 3 seed/ft of row. Propazine was applied broad- 2 cast June 18 at a rate of 1.2 lb/A. Sorghum was cultivated with a rolling cultivator July 9 and dikes were re-established in appropriate treatments July 18. Residual effects of subsoiling were evaluated in 1980 (Table 2). Because of low yields in 1980, sorghum was not harvested in 50-ft increments down the row as in 1979. Instead, three center rows 200 ft long were harvested for yield determination November 13. Land preparation for the 1981 crop consisted of shredding stalks and moldboarding January 20 and 21. This was followed by tandem discing and land planing the area to make the slope more uniform and fill some low areas where water accumulated. Beds were re-established in their original location, and appropriate treatments were diked January 28. In treatment 2 (Table 2), alternate furrows were diked (half diked). All furrows in treatments 4 and 5 were diked; diking intervals for all treatments were about 6 ft. Subsoiling was accomplished for treatments 3 and 5 during the bedding operation. Half of each of the 12-row plots was subsoiled to a depth of about 14 inches; the other six rows were not subsoiled. Weeds became a problem in the test area, so beds were cultivated for weed control, and Propazine was applied at a broadcast rate of 1.2 lb/A and incor- porated with a rolling cultivator on April 13. Dikes were re-established in appropriate treatments the same day. Beds were cultivated and Pioneer hybrid 8501 was planted July 6 at a rate of about 3 seed/ft of row. Dikes were re-established in appropriate treat- ments on August 3 after satisfactory stand establish- ment. Yield determinations were made by combine harvesting three center rows on October 26. Three 60- ft increments were harvested down the slope for each treatment to evaluate effect of slope on yield. In 1981, dikers were modified to trip by means of a hydraulic motor-driven mechanism described by Lyle and Dixon (8). This replaced the 3-ft diameter wheel used in 1980 and provided a more uniform diking interval. Removing the wheel also allowed shortening of the dikers by about 3 ft, which allowed easier handling of less weight. Sorghum in these experiments was uniformly fertilized with 250 lb/A of 16-20-0 each year. Soil moisture at 1 to 4 feet at 6-inch increments was determined using neutron scattering technique. In 1979, moisture use was determined about 75 ft from the upper side of slope. In 1980 and 1981 moisture use by sorghum was measured on the upper, middle, and lower part of slope. Distance of access pipes with respect to slope for monitoring soil moisture were about 30, 90, and 150 ft down slope for upper, mid- dle, and lower part of slope, respectively. Test weight and grain moisture were determined for combined grain samples each year, and grain yield was adjust- ed to 13 percent moisture. Yield data was subjected to analysis of variance. Regression analysis of yield and water use was used to determine the relationship of yield and total water use as well as yield and water use in inches per day for the 30- to 60-day period of growth (panicle development stage of plant growth). Yield Potential for Sorghum in the Rolling Plains Pan evaporation and dryland yield data at Chil- licothe and Munday were used to determine the relationship between water deficit and grain yields for 1976 to 1981. The water deficit was defined as pan evaporation in inches from a Class A Weather Bureau pan minus the rainfall received. The relationship of water deficit and grain yields was used with water deficit data from 1914 to 1981 to estimate the probabil- ities of various levels of sorghum grain yield in the Rolling Plains. The necessary calculations used to make these estimates are given below. Class A Weather Bureau pan evaporation data for Chillicothe have only been measured since 1976. However, evaporation from a 2-ft sunken pan was measured for the years 1914-1981. Estimates of water deficit from a Class A pan for the years 1914-1981 for months May through September were obtained from the‘ regression of measurements of water deficits from a Class A pan and water deficit from a 2-ft sunken pan for the period 1976-1981. The equation for water deficits for months May through September from a Class A pan as a function of a 2-ft pan was y = 24.4 + 0.70X (r = 0.96) where y = water deficits from Class A pan in inches and X = evaporation from 2-ft pan in inches. The frequencies of years with water deficits of 3O to 35, 35 to 40, 45 to 50, and 55 to 6O inches from May through September were calculated. The dry- land sorghum yield for each water deficit category was estimated from a regression of yield on water deficit described above. Rainfall, pan evaporation from Class A Weather Bureau pan, and temperature data for 1979-1981 are shown in Tables 3 and 4. The implications of these data for potential dryland grain sorghum production in the Rolling Plains are dis- cussed in "Results." Management Effects on Soil Properties The effects of different cropping systems on selected chemical and physical properties of a Miles fine sandy loam soil were determined. The cropping systems compared include continuous sorghum, cot- ton, and wheat; a cotton-guar rotation; and a wheat- guar double crop system. This study was initiated in TABLE 3. RAINFALL AND PAN EVAPORATION DATA FROM A CLASS A PAN FOR 1979-1981 AT CHILLICOTHE, TEXAS Rainfall Evaporation Months 1979 1980 1981 1979 1980 1981 Inches Inches January 1.49 2.14 0.04 * 2.80 4.75 February 0.43 0.71 0.80 1.76 3.51 5.98 March 2.37 0.42 1.55 6.95 7.59 6.01 April 2.10 0.72 3.19 8.01 10.40 8.78 May 6.23 7.43 5.20 10.46 7.05 8.88 June 4.16 1.17 3.87 13.94 15.13 13.07 July 3.03 0.00 0.69 12.43 20.63 16.58 August 5.31 0.44 0.83 12.33 17.02 12.15 September 0.01 2.42 0.74 10.21 9.42 11.10 October 1.97 0.78 2.28 11.07 8.55 7.07 November 1.36 0.60 0.66 4.56 4.30 5.37 December 1.21 1.18 0.28 3.25 3.68 3.65 Total 29.67 18.01 20.13 94.97 110.08 103.39 *Pan remained frozen. TABLE 4. TEMPERATURE DATA AT CHILLICOTHE FOR 1979, 1980, AND 1981 Mean Mean Mean Minimum temperature Maximum temperature Mean temperature Months 1979 1980 1981 1979 1980 1981 1979 1980 1981 OF 0F OF January 20.5 29.4 30.6 39.7 51.5 56.7 30.1 40.4 43.6 February 25.3 28.8 33.2 38.6 57.5 60.7 38.6 43.1 46.9 March 39.3 36.5 43.2 67.3 67.1 67.2 53.3 51.8 55.2 April 47.2 44.6 54.7 73.8 78.6 81.1 60.5 61.6 67.9 May 54.5 56.7 59.9 83.4 84.5 84.6 68.9 70.6 72.3 June 64.2 71.5 69.0 92.4 100.0 94.9 78.3 85.8 82.0 luly 70.2 76.4 75.1 96.6 105.5 100.2 83.4 91.0 87.6 August 67.5 74.8 70.2 93.4 100.7 95.3 80.4 87.7 82.7 September 61.6 68.1 65.1 90.5 90.0 92.1 76.0 79.0 78.6 October 52.9 51.1 55.2 84.4 79.6 75.6 68.6 65,4 60.7 November 34.7 39.9 41.4 61.7 64.6 68.1 48.2 52.3 54.8 December 31.4 34.6 33.7 55.7 60.1 58.6 43.5 47.3 46.2 1975 and is ongoing at the Chillicothe Research Sta- tion. Selected properties 0f the Miles soil at Chil- licothe are reported in Table 1. Bulk densities and organic matter determinations under different cropping systems were evaluated by taking cores of the 0-6, 6-12 and 12—24-inch soil depths with a Giddings sampler in December, 1980. The organic matter was determined according to the Walkley method (16). The saturated hydraulic con- ductivity (KS) of the 0-3- and 9-12-inch soil depths under different cropping systems was evaluated by taking undisturbed soil cores with the Giddings sam- pler in December, 1980, Iune, 1981 and November, 1981. Polyvinyl chloride (PVC) cores were 3 inches in height and 4 inches in diameter. The cores were transferred to the laboratory and analyzed for Ks according to the method described by Klute (7). Laboratory studies evaluated the roles of residue and antecedent moisture on KS of Miles fine sandy loam and Abilene clay loam soil. Soil properties of Miles and Abilene soils used in these studies are reported in Table 1. For these evaluations sections of PVC pipe 6 inches in height and 4 inches in diameter were filled with surface Miles and Abilene soils to a depth of 3 inches. The soil was broken up and mixed to simulate a discing operation. The soil was divided into three equal samples. Sorghum residue equiva- lent to 5,000 and 10,000 lb/A was added to each of two samples. The third sample received no residue. The sorghum residue was ground to pass through a 20 mesh sieve (0.8 mm opening). The residue was added to the soil and thoroughly mixed. Three inches of these soils amounted to about 1.8 lb (800 grams) of oven dry soil per core. Soils in cores with different amounts of residues were dried for 3, 6, and 9 days at 90 to 95° F. The antecedent volumetric moisture contents of the Miles soil after 3, 6, and 9 days averaged 6.9, 1.1, and 0.2 percent, respectively. Antecedent moisture refers to moisture content of cores after drying and prior to saturation in distilled water for evaluation of KS. The antecedent volumetric moisture contents of the Abi- lene soil after 3, 6, and 9 days were 12.7, 5.4, and 1.7 percent, respectively. Each drying interval and resi- due treatment was replicated three times. The Ks of each treatment were determined, according to a method described by Klute (7), initially and after each interval of wetting and drying. The number of wet- ting and drying cycles for cores dried 3, 6, and 9 days were 11, 6, and 6, respectively. These studies suggest that the cores approached an equilibrium (Ks) value after four to six wetting and drying cycles. The equilibrium Ks of soil as functions of antecedent mois- ture and added residue are reported and discussed in ”Results.” The effects of subsoiling on soil compaction and sorghum production were evaluated. Soil strength, an index of compaction, refers to resistance of the soil to penetration by a metal probe called a soil pene- trometer. Resistance to penetration by a penetrome- ter varies with soil moisture and density and is ex- pressed in atmospheres. The strength of the top 24 inches of a Miles soil when wet, at about field capaci- ty, was determined using a recording penetrometer mounted on a Giddings soil sampler. The tapered steel rods used for strength measurements were about 1/2 and 3/4 inches in diameter depending on the strength of the soil. The shafts of the rods were about 1/4 inch smaller than the maximum diameter of these tapered rods. These rods were mounted in a load button of a 300-lb transducer. The millivolt (mv) output, which is a linear function of soil resistance to penetration at different soil depths, was continuously monitored with a mv recorder. RESULTS Subsoiling and Diking Yields of sorghum grown under different tillage practices in 1979, 1980, and 1981 at Chillicothe are shown in Tables 5, 6, and 7, respectively. The overall averages for years 1979-1981 are represented in Table 8. During these years, yields of the check treatment ranged from a low of about 550 to a high of 4,350 lb/A. High rainfall in May through August (Table 3) provided high yields in 1979, and yields of treatments TABLE 5. INFLUENCE OF SUBSOILING AND DlKlNG TREATMENTS ON YIELD OF SORGHUM HYBRID (PIONEER 8501) IN 1979 Distance Down Slope, In Feet 0-50 50-100 100-150 150-200 Average % of % of % of % of % of Treatments lb/acre check lb/acre check lb/acre check lb/acre check lb/acre check 1&2 No treatment 2939 68 4184 96 4973 114 5298 122 4353 100 (check) 3 Subsoiled‘ 4153 95 5237 120 5244 120 5111 117 4941 114 4 Dikedz 4384 101 4855 112 4947 114 5256 121 4865 112 5 Subsoiled and 4898 113 4999 115 5255 121 5372 127 5136 119 diked Average 386663 94 4696b 111 5084ab 117 5272a 122 lLand was subsoiled 16 inches deep below the beds and furrows. ZDikes were 50 ft apart (put in manually). 3Average values for distance down slope followed by same letter are not significantly different at 5% probability level. Average yields of treatments 3, 4, and 5 were significantly higher yielding than check at 5% probability level. ranged from 2,900 to almost 5,400 lb/A. The average yield increases, due t0 subsoiling and diking, were14 and 12 percent, respectively. Even though the dikes were 5O ft apart the effects of location with respect to the slope on yields were highly significant. Visual observations and plant height measurements, as indi- cated in Table 9, showed a growth gradient between dikes. Plants close to the dikes on the upper side of the slope were 36 percent taller and appeared more productive than plants 25 and 50 ft from the dikes. These results indicated the need for shorter intervals between dikes and the need for determining plant response and moisture use with respect to the loca- tion down the slope. As shown in Table 5, the effect of distance down slope had a highly significant effect on sorghum yields. Yields for treatments either diked or subsoiled were from 1,214 to 1,959 lb/A higher diking produced about 250 lb/A more than the check treatment. Their response may have been due to a small increase in moisture captured and stored by diking. Yields in 1981 (Table 7) ranged from a low of about 300 to a high of 2,550 lb/A. As shown in Figure 1, sorghum response to diking on the upper and middle section of the slope was dramatic. Diking, location with respect to slope, and the interaction of diking location with respect to slope significantly influenced yields. The average yield of the diked treatments was more than double that of the check. TABLE 6. YIELDS OF GRAIN SORGHUM HYBRID (PIONEER 8501) UNDER DIFFERENT CULTURAL TREATMENTS OF SUBSOILING AND DIKING IN 1980 T t t Ib/ % f h k than the check at the top of the slope, but there was rea men S acre 0 c ec essentially no difference among the treatments at the 1 N9 trfatment l¢he¢l “t: o 1/2 DIKED DIIGD CHECK Figure 1. Bar graph showing the effects of slope and diking on grain sorghum yields in 1981. as shown in Figure 2, meant approximately 1,600 lb/A. Assuming the relationship between yield and water use holds between 4 and 8 inches, water uses of 4.5, 6, and 8 inches of water produced about 0, 1,200, and 2,780 lb/A in 1981 (Figure 2). Yield response to available soil water is influ- enced by climatic or evaporative conditions. In 1977 the relationship between water use and sorghum yields at Munday indicated that more than 5.0 inches of water were needed before any grain was produced (5). As shown in Figure 3, in 1981 the relationship between sorghum yield and water use in inches per day by sorghum during the 30- to 60-day period was highly significant. Diking, as shown in Figure 4, increased the water use during this critical panicle development stage in upper and middle part of slope from about 0.06 inch per day to almost 0.10 inch per day. Many plants on the upper and middle part of the slope on check and subsoiled treatments (1 and 3, Table 2) which used only 0.06 inch per day failed to produce any grain. This difference in water use dur- ing the critical growth stage apparently resulted in sorghum yielding an average of 2,200 instead of about 400 lb/A. The average water use in inches for 1979 and 1980 is shown in Table 10. In 1979 the average water use was measured about 75 ft down slope. The pounds of sorghum produced per inch of water was high, ranging from 350 to 424 (Table 10). In 1980, water use averaged about 7.0 inches and the sorghum produced per inch of water was extremely low, rang- ing from 80 to 110 lb/inch (Table 10). As shown in Table 11, 1981 water use ranged from 5.5 to 7.7 inches of water and production ranged, depending upon treatment and site with respect to slope, from 66 to 351 lb/inch of water. The average response by dil- s00 0 0.02 0.04 0.06 0.0a 0.10 0.12 WATER USE - INCHES/DAY Figure 3. Relationship between yields of sorghum under difierent tillage treatments and moisture use in inches/day by sorghum during the 30- to 60-day period of plant development in 1981. significant rainfall before planting, diking can more than double grain sorghum yields (Table 7). Max- imum yields with ideal climatic conditions and pre- sent varieties would probably range from 4,000 to 5,000 lb/A. Estimated yields in Table 12 based on water deficits over 68 years show that one could expect yields greater than 2,100 lb/A 69 percent of the time. Half of the time yields would range from 2,100 to 4,400 lb/A and 31 percent of the time yields would be less than 2,100 lb/A. These yields were estimated for grain sorghum grown with conventional tillage systems. Planting at the proper time plus diking and subsoiling, if needed, would increase the probability of producing yields near 3,000 lb/A. UPPER SIDE 0F stops R MIDDLE PART OF SLOPE E LOWER END OF SLOPE I 0. 10 — : — : I __- 0.0a : g g - 3 _ _ 3 0.00 —- Q (I) LLI I 2 0.04 0.02 0 1/2 01x50 01x20 Figure 4. Bar graph showing effects of slope and diking on water use in inches/day during the 30- to 60-day period of growth for sorghum in 1981 at Chillicothe. 4000 E 3000 O i‘ U) Q Z A 3 2000 Y-13743—233JX 2 n--004 I Q _l E 1000 >- 30 as 40 45 so ss so WATER DEFICIT - INCHES Figure 5. Relationship between water deficits and dryland sorghum yields from conventional tillage at Chillicothe and Munday from 1976 to 1981. TABLE 11. WATER USE AND PRODUCTION OF GRAIN SORGHUM PER INCH OF WATER AS INFLUENCED BY DIKING AND DISTANCE DOWN SLOPE IN 1981 Distance Down Slope, In Feet 0-60 60-120 120-180 Ave rage water use lb/in water use lb/in water use lb/in water use lb/in Treatment inches of H2O inches of H2O inches of H2O inches of H2O Check 5.5 66 5.9 113 7.5 298 6.3 159 v2 Diked 6.0 240 5.9 303 7.7 307 6.5 283 Diked 6.9 273 7.1 351 7.5 312 7.2 312 Average 6.1 193 6.3 256 7.6 306 Management Effects on Soil Properties data show that sorghum tends to increase organic Effect of Cropping Systems on Selected soil prop matter in the soil surface more than the other crop- erties are shown in Tables 13, 14, and 15. The find- P1115 SyStemS Peeukamp (9) V1Sua11Zeu SO11 S1rue1u1e_ ings, though not conclusive, do show certain trends. aS a funeuOn O1 Orgame maueu He SuggeSted 111111 SO11 The data in Table 13 indicate that soil from the wheat Structure ue1er1O1a1eS Yapuuy u111eSS 111e Orgauue mat‘ and Sorghum Cropping Systems had Significantly ter is replenished PGIIOCLICEIIIY. _A modified diagram higher organic matter contents than soil from other frOm Pee111 o p- A w 2000 ¢ Y-—549.5+1.03X ' R-O.94 0 0 2000 4000 e000 e000 YIELD — POUNDS/ACRE Figure 7. Relationship between grain yield and air dry stover yields at Chillicothe in 1981. ‘ 5-0 MILES F s L , 3.0 VOL H 2o ea == o 6.9a 2.0 > 1.1 I 0.2 1.5 . A _ I 10 ‘ 0 0.5 h 0 0 5000 10000 POUNDS/ACRE i Figure 8. Effects of antecedent percent moisture and plant residues on KS 0f a Miles fine sandy loam soil. 2.0 1.5 1.0 KS - INCHES/HR 0.5 ABILENE C L VOL H2O % O 12.7 A 5.4 I 1.7 I I ' __} O 0 5000 10000 RESIDUE - POUNDS/ACRE Figure 9. Influence of antecedent percent moisture and plant residue 0n KS of an Abilene clay loam. 12 SOIL DEPTH — INCHES 2O 24 BED A SUBSOILED I NOT SUBSOILED —_:_- ‘=11 ATMS Figure 10. The effect 0f subsoiling 0n soil strength in atmospheres 0f top 24 inches of a Miles fine sandy loam. weeds. Under these conditions it may require one or two field operations for control of weeds and replace- ment of dikes. After harvesting in some years it may be possible to use dikes already in place to catch water for the next crop. In the event of an earlier planting or harvesting, consideration should be given to killing or plowing out stalks. If this is not done, considerable moisture may be extracted by the remaining green stubble. Obviously, this moisture could be used by the next crop. The stubble also may be used for grazing, and if yields are quite low, the entire crop might be grazed out. In summary, sorghum returns more residue to the land than present dryland cropping systems. This is certainly true of the main cash crop, cotton (12). Use of dikes would not only increase grain but stover yields as well. Studies have shown that the permea- bility of many soils as measured by saturated hydrau- lic conductivity is a function of a number of factors including the amount of residue returned to the soil by crops. Return of sorghum residues should favor- ably influence the yields of subsequent crops. The precise amount or degree of increased productivity of the land is not yet known. Minimum tillage might make the effectiveness of sorghum as a residue crop even greater than suggested by the soils data. Further studies are presently underway to clarify the benefits and problems, if any, of minimum or reduced tillage. Sorghum production in the long run probably will mean significantly higher yields of other crops such as wheat and cotton. . It is the purpose of this publication, using past climatic data and recent yield records, to provide an estimate of potential sorghum yields for the Rolling Plains. It should be possible from these parameters to estimate the economic feasibility of sorghum produc- tion systems. These data emphasize that runoff often can be prevented and additional water captured for crop production by furrow diking and subsoiling where required. Plant residues can play important roles in soil productivity and in the production of crops such as sorghum, cotton, and wheat in the Rolling Plains of Texas. 11 12 LITERATURE CITED . Bilbro, C. I. and E. B. Hudspeth. 1977. Furrow dil