Infiltration and interrill erosion responses to selected livestock grazing strategies, Edwards Plateau, Texas

Abstract

Understanding the temporal response of infiltration rate and interrill erosion to selected livestock grazing strategies is necessary for the continued soil and water conservation of rangeland. Infiltration rate and interrill erosion were sampled bimonthly from 1978-1984 on pastures grazed continuously (MCG) and moderately stocked (8.1 ha AU-1); continuously (HCG) and heavily stocked (4.6 ha AU-1); high-intensity, low-frequency (HILF) and moderately stocked (8-1; 17:119 day, stocked at 8.1 ha AU-1); short duration (SDG) and heavily stocked (14-1; 4:50 day, stocked at 4.6 ha AU-1). The MCG and HILF pastures were able to recover from droughts and maintain initial infiltration rates and interrill erosion. In contrast, infiltration rates decreased and interrill erosion increased on HCG and heavily stocked SDG pastures. The trend of infiltration rate and interrill erosion deterioration in the heavily stocked SDG and HCG pastures was not gradual; rather, it followed a stair-step pattern typified by decreasing condition during drought and an inability to recover to pre-drought level during periods of above-normal precipitation. The heavy stocking rate and climate rather than grazing strategy were the primary factors influencing the hydrologic responses. Infiltration rates were seasonally cyclic in the SDG and HCG pastures, but no significant seasonal trend could be identified in the MCG pasture. This was attributed to greater midgrass cover and litter accumulation in the MCG pasture which provided cover stability compared to less litter accumulation and a greater dominance of seasonal shortgrasses and forbs in the SDG and HCG pastures. Total organic cover was the most important factor determining infiltration rate. The midgrass bunch growth form and litter accumulation were the most important factors influencing interrill erosion. Both factors increased microrelief, and obstructed sediment transport and interrill erosion.