Cattle gain and crop yield for a dryland wheat-sorghum-fallow rotation
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 Mg ha–1 and produced a mean gain of 123 kg ha–1. Wheat grain yield averaged 1.72 Mg ha–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.