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Depletion of the High Plains Aquifer that supplies irrigation water for the semiarid Southern Great Plains may necessitate dryland production of crops like wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] using the wheat–sorghum–fallow (WSF) rotation. Reduced crop productivity without irrigation can be offset by intensifying the WSF rotation with cattle (Bos taurus) grazing. Biomass removal and soil trampling without tillage, however, may reduce rain infiltration and storage during fallow that increases with no-tillage (NT) over stubble-mulch (SM) tillage. Our objective was to quantify grazing and tillage effects on infiltration, sediment transport, and aggregate stability during fallow periods after sorghum and wheat. Using a split plot randomized complete block design, we compared wet aggregate size distribution of a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll; 0.0–0.05 m) and sediment yield in runoff of simulated rain during the fallow-like idle period after wheat and the sorghum fallow. Sediment concentration and yield for both fallows were numerically larger (>40%) with grazing. Sediment concentration from SM tillage increased significantly over NT for either fallow, but soil loss differed only for wheat fallow. Mean final infiltration rate (IRf) and amount (IA60) did not differ significantly with grazing during either fallow, but IA60 was usually 20% lower for grazed than for ungrazed paddocks. Because SM tillage after grazed wheat significantly (P < 0.01) increased IRf and IA60 over NT, occasional SM tillage to disrupt compaction from trampling may increase water conservation for dryland cropping systems combining grazing with NT residue management.

Sorghum ( Sorghum bicolor (L.) Moench), including sorghum-sudan crosses [ S. bicolor subsp. Drummondii (Nees ex Steud) de Wet & Harlan] (SS), represents a broad category of plants that includes those grown primarily for forage or grain. Sorghum cultivars can be further classified as brown midrib (BMR), nonBMR, photoperiod sensitive (PS) and nonPS. The objective of our study was to compare sorghum classes comprised of multiple cultivars in relation to forage and grain yield, agronomic characteristics (i.e. height, lodging, moisture at harvest), nutrient composition and fiber digestibility. Although common properties among different sorghum classes were detected, consistent differences in forage yield and quality factors emerged between classes. The study mean SS-PS forage yield of 19.0 Mg ha −1 was significantly ( P = 0.05) greater than all other non-PS classes and the FS-BMR class consistently yielded less than the corresponding FS class with an average reduction of 2.2 Mg ha −1 . Grain yield varied greatly among the forage sorghum (FS) and FS-BMR cultivars, ranging from 2.30 to 7.54 Mg ha −1 with some FS cultivars yielding as much as those in the grain class. Those sorghum classes with the BMR trait consistently had the lowest acid detergent fiber (ADF) and neutral detergent fiber (NDF), and were lower in lignin content. The BMR trait also increased digestibility of the NDF fraction (NDFD). In vitro-true-digestibility (IVTD) was highest with FS-BMR and grain sorghum (Grain) classes followed by the FS, FS-PS-BMR and SS classes with the SS-PS consistently having the lowest IVTD. Although mean percent IVTD among sorghum classes descended in the same order as was observed for the grain yield, we identified very little correlation ( r = 0.28) between grain yield and IVTD. Lodging was not increased in BMR cultivars compared with the nonBMR cultivars when harvested at the soft-dough stage and there was little correlation between lodging and lignin content, grain yield, or plant height.

Increased precipitation storage as soil water is crucial to dryland production of wheat (L.) and grain sorghum [ (L.) Moench] on the semiarid southern Great Plains. At the USDA-ARS Conservation and Production Research Laboratory at Bushland, TX, surface runoff from a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) is typically greater with no-till (NT) than stubble-mulch (SM) tillage under the 3-yr wheat–sorghum–fallow (WSF) dryland crop rotation. Our objective was to quantify the effects of NT or SM tillage with bare or retained residue on infiltration of simulated rain, sediment transport, and related aggregate stability for continuous wheat (CW) and WSF rotation plots established in 1983. Compared with bare soil, the retained wheat residue cover increased mean 60-min cumulative infiltration across all tillage and rotation combinations by >25 mm and decreased soil loss. Cumulative rain infiltration and total soil loss did not vary significantly (< 0.05) with tillage, but the mean infiltration rate at 60 min was 15.0 mm h less for NT than SM. The CW rotation typically increased infiltration regardless of residue cover or tillage compared with the WSF rotation, which we attributed to greater aggregate stability. The greater aggregate stability for CW may have decreased soil loss compared with WSF, which was greatest for bare SM tilled sites. We conclude that residue cover significantly increases rain infiltration over bare soil conditions independent of any tillage or rotation treatment effects. Nevertheless, increased rain infiltration due to residue cover was not sustained in the absence of soil disturbance for NT.

Cattle (Bos taurus) grazing intensifies production of the dryland wheat (Triticum aestivum L.)-sorghum [Sorghum bicolor (L.) Moench]-fallow (WSF) rotation in the U.S. Southern High Plains. Stubble-mulch (SM) tillage controls weeds and counteracts soil compaction. No-till (NT) increases soil water at planting and dryland crop yields, but added grazing effects are unknown. Our objectives were to quantify dryland winter wheat and sorghum yield responses to grazing and tillage practices. At the USDA-ARS Conservation and Production Research Laboratory, Bushland, TX, we established all WSF rotation phases in triplicate ungrazed and grazed paddocks beginning 1999 on a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) using SM tillage. During spring 2004, NT or SM tillage were superimposed within grazing main plots. Cattle gain, soil water after fallow, and crop yield were compared during 2005 to 2009 using a split-plot randomized complete block design. Cattle, stocked at 1.8 Mg ha -1 , grazed sorghum stover and growing wheat an average of 29 d for a mean gain of 147 kg ha -1 . Soil water at plantingwas unaffected by grazing, but increased from 14 to 28 mm with NT. Although grazing seldom reduced yield of wheat or sorghum, NT in ungrazed plots increased crop yields sufficiently (0.96-2.6 Mg ha -1 ) in 2008 and 2009 to offset any value added by grazing. We conclude that cumulative grazing effects in NT plots reduced soil water storage and depressed yield. We recommend post-wheat-harvest SM tillage to disrupt soil compaction and restore grazed soil productivity.

Increasing pumping costs and declining well capacities in the U.S. Southern High Plains have led to greater reliance on less productive and inherently riskier dryland cropping systems. Dryland wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] are typically grown in a 3-yr wheat-sorghum-fallow (WSF) rotation that may be intensified by integrating cattle (Bos taurus) grazing. Suitability of grazing dryland crops in the WSF rotation has not been evaluated. Our objectives were to quantify (i) cattle gain during limited grazing of dryland wheat and sorghum stover, and (ii) grazing effects on the growth and yield of the grazed wheat and subsequent sorghum crop. We established, concurrently, all WSF rotation phases in duplicate ungrazed and grazed plots in three replicated paddocks on a gently sloping Pullman silty clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll) at the USDA-ARS, Conservation and Production Research Laboratory, Bushland, TX (35°11' N, 102°5' W). Cattle gain, fallow soil water storage, and the growth and yield of wheat and subsequent grain sorghum were compared from 2000 to 2007 within a randomized complete block. Dryland wheat was grazed an average of 31 d during 7 of 8 test years by cattle stocked at 1.7 Mgha -1 and produced a mean gain of 123 kg ha -1 . Wheat grain yield averaged 1.72 Mgha -1 without grazing and was not different from the 1.57 Mg ha -1 grain yield with grazing. Grazing decreased wheat straw yield, but subsequent soil water storage was unaffected. Sorghum grain yields of 2.26 Mg ha -1 in ungrazed plots were not different from grazed plots averaging 2.20 Mg ha -1 . Overall productivity of the WSF cropping system was increased using limited grazing of dryland wheat forage and sorghum stover with no significant reduction in wheat or sorghum grain yields.

Increasing pumping costs and declining well capacities in regions like the Southern High Plains of Texas are requiring producers to adaptcroppingpracticesforusewithirrigation levelsthatvarybetween complete replacement of crop evapotranspiration (ET) to none (i.e., dryland production). Grain sorghum [Sorghum bicolor (L.) Moench] isacropsuitedtobothdrylandandvariousdeficitirrigationproduction systems. Our objectives were to (i) identify cultural practices (planting date, population, and cultivar maturity) that maximize sorghum grain yield for widely varying irrigation strategies; and (ii) consider effective means to allocate available water among irrigation strategies that maximizes the ratio of yield to ET, that is, water use efficiency (WUE). Using the model SORKAM and long-term (1958–1999) weather records from Bushland, TX, we simulated sorghum grain yields on a Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) under dryland (rain) and three deficit irrigation levels (rain 1 irrigation 5 2.5, 3.75, or 5.0 mm d 21 ) for all combinations of planting date (mid-May, 15 May; early June, 5 June; and late June, 25 June), cultivar maturity (early, 95 d; medium, 105 d; late, 120 d), and plant density (12and16plantsm 22 ).For2.5mm d 21 irrigation level,simulated grain yields were maximized with either early or medium-maturing cultivars planted in early June. In contrast, simulated sorghum yield and WUE increased with a mid-May planting date and later-maturing cultivars forirrigationlevelsof3.75and5.0mmd 21 .Weconcludethatspreading water to uniformly irrigate a field with 2.5 mm d 21 produces |16% less grain than concentrating the same water resources to variably irrigate a field at 3.75 or 5.0 mm d 21 with complementary (2:1 and 1:1) dryland areas.

Stored soil water and growing season precipitation generally support early season growth of grain sorghum (Sorghum bicolor L. Moench) in dryland areas but are insufficient to prevent water stress during critical latter growth stages. The objective of this study was to determine if growing plants in clumps affected early season growth and subsequent grain yield compared to uniformly spaced plants. We hypothesized that growing grain sorghum plants in clumps would result in fewer tillers and less vegetative growth so that more soil water would be available during the grain-filling period. Results from 3 yr at Bushland, TX, and 1 yr at Tribune, KS, showed that planting grain sorghum in clumps of three to six plants reduced tiller formation to about one per plant compared to about three for uniformly spaced plants. Grain yields were increased by clump planting by as much as 100% when yields were in the 1000 kg ha 21 range and 25 to 50% in the 2000 to 3000 kg ha 21 range, but there was no increase or even a small decrease at yields above 5000 kg ha 21 . Our results suggest that planting grain sorghum in clumps rather than spaced uniformly conserves soil water use until later in the season and may enhance grain yield in semiarid dryland environments.

Grain sorghum [Sorghum bicolor (L.) Moench] is adapted for use in dryland and irrigated cropping systems on the southern High Plains. Irrigation in this region relies on the declining Ogallala aquifer, and applications are transitioning from full to deficit evapotranspiration replacement. Our objective was to identify optimum planting date, population, row spacing, and cultivar maturity combinations to maximize grain sorghum yield using the SORKAM model and long-term (1958–1999) weather records at Bushland, TX, for a Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) with reduced irrigation. Grain sorghum growth and yield was simulated under dryland and deficit- or full-irrigation conditions (rain 1 irrigation 5 2.5 or 5.0 mm d 21 ) for all combinations of planting date (15 May, 5 June, 25 June), cultivar maturity (early, 95 d; medium, 105 d; late, 120 d), population (12 and 16 plants m 22 ), and row spacing (0.38 and 0.76 m). Simulated grain yield was unaffected by planting population but increased 7% for narrow compared with wide row spacing independent of other treatment effects. Results suggest two alternative management practices to optimize yield for the southern High Plains depending on potential irrigation capacity: (i) where rain plus supplemental irrigation was ,0.2.5 mm d 21 , plant early-maturing cultivars during June and (ii) where rain plus supplemental irrigation approaches 5.0 mm d 21 , plant late-maturing cultivars on 15 May. Earlymaturity cultivars planted on 5 June were better adapted to dryland and deficit irrigation for optimum grain yield on a southern High Plains Pullman soil.

Typical planting recommendations for dryland grain sorghum [Sorghum bicolor (L.) Moench] in the southern High Plains are to delay until soil water is adequate for crop establishment, but no population or cultivar maturity class are specified. Our objectives were to use the SORKAM simulation model, long-term (1958-1998) weather records at Bushland, TX, and known Pullman soil (fine, mixed, superactive, thermic Torrertic Pateustolls) properties to identify an optimum planting date, population, row spacing, and cultivar maturity combination to maximize dryland grain sorghum yield. We simulated sorghum grain yields for combinations of planting dates (15 May, 5 June, and 25 June), populations (3,6, and 12 plants m -2 ), row spadngs (0.38 and 0.76 m), and cultivar maturity class (early, medium, and late). SORKAM consistently (r 2 = 0.69, RMSE = 792 kg ha -1 ) simulated grain yields that averaged about 5% more than measured values and correctly simulated row width and population effects on yield. Simulated grain yields increased with narrow row-spacing ∼9%, independent of planting date or cultivar. Increasing plant population significantly decreased panicle seed number, seed mass, and plant tillers; however, the simulated grain yield was unchanged (3996-4106 kg ha ') by plant populations. Mean simulated grain yields were greatest for the 5 June planting dates with early and medium maturity cultivars that avoided late summer heat or water deficit stresses and matured before freezing weather. Our results show early or medium maturity cultivars, planted 5 June, in 0.38-m row widths, using 3 or 6 plants m -2 , achieve the greatest dryland grain yield on a southern High Plains clay loam soil.

Seedling emergence is the crucial first step in crop establishment; however, crops frequently must penetrate or lift a thin, dense, soil layer called a crust, which is formed by drop impact or aggregate slaking during rainstorms and sprinkler irrigation. Shaping the soil surface into a small ridge or cap above the seed row may decrease crust strength and improve seedling emergence. Our objectives were to quantify the effects of surface soil geometry (25 mm high by 50 mm wide soil cap without removal) on (i) crust formation and strength, (ii) seedling emergence of selected crops, and (iii) seed zone soil temperature. Sieved (

Greater infiltration of precipitation increases water available for cotton (Gossypium hirsutum L.), wheat (Triticum aestivum L.), and sorghum [Sorghum bicolor L. (Moench)] production on the semiarid Texas South Plains. The objective of this study was to determine the short-term effects of tillage and crop residues on water infiltration into an Olton clay loam (fine, mixed, thermic Aridic Paleustoll), a Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll), and an Amarillo loamy fine sand (fine-loamy, mixed, thermic Aridic Paleustalf). Cropping treatments included (i) conventional tillage of continuous cotton (CVT), (ii) no-tillage, limited residue, of continuous cotton (C-NTL), and (iii) no-tillage of cotton grown in rotation with limited grain sorghum (S-NTL), or (iv) wheat (W-NTL) residues [...]