Tillage Effects on Infiltration of Simulated Rain and Sediment Transport from Grazed Wheat-Sorghum-Fallow.

Depletion of the High Plains Aquifer that supplies water for irrigation on the semiarid Southern Great Plains is expanding dryland crop production. Stable wheat (Triticum aestivum L.) and sorghum [Sorghum bicolor (L.) Moench] grain yields using the wheat-sorghum-fallow (WSF) rotation require three years for two crops. Intensifying the dryland WSF rotation with cattle (Bos taurus) grazing may offset that reduced crop productivity, but residue removal and soil trampling potentially reduce infiltration of rain stored during fallow. Our objective was to quantify grazing and stubble-mulch (SM) or no-tillage (NT) effects on infiltration and sediment transport during fallow periods after sorghum and wheat harvests. We also measured 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. Although sediment concentration and yield increased by 40% with grazing during both fallow phases, that difference was not significant. SM tillage, however, increased sediment concentration significantly over NT, but soil loss differed only for wheat fallow. Mean final infiltration rate (IR_f) and amount (IA60) for either fallow phase did not differ with grazing treatment despite the 20% lower IA60 with grazing. Because SM tillage significantly (P<0.01) increased IR_f and IA60 over NT after grazed wheat, occasional SM tillage to disrupt compaction from trampling may increase water conservation in dryland cropping systems that combine grazing with NT residue management.