Infiltration and interrill erosion responses to selected live- stock grazing strategies, Edwards Plateau, Texas

Understanding tbe temporal response of infiltration rate and interrill erosion to selected livestock grazing strategies is necessary for the continued soil and water conservation of rangeland. Inflltration rate and btterrill erosion were sampled bimontbly from 1978-1984 on pastures grazed continuously (MCG) and moderately stocked (8.1 be AU-r); continuously (I-ICC) and heavily stocked (4.6 ha AU-r); bigb-intensity, low-frequency (IIILF) and moderately stocked (8-l; 12119 day, stocked at 8.1 ha AU-t); short duration (SDG) and heavily stocked (14-l; 4~50 day, stocked at 4.6 ha AU-r). The MCG and HILF pastures were able to recover from drougbts and maintain initial btflltration rates and btterrill erosion. In contrast, Miltration rates decreased and btterrlll erosion increased on HCG and heavily stocked SDG pastures. Tbe trend of infiltration rate and interrill erosion deterioration in tbe heavily stocked SDG and HCG pastures was not gradual; rather, it followed a stair-step pattern typified by decreasbtg condition durbrg drought and an inability to recover to pre-drougbt level during periods of above-normal precipitation. Tbe heavy stockbrg rate and climate rather than grazing strategy were the primary factors btiluencing tbe hydrologic responses. Infiltration rates were seasonally cyclic in the SDG end HCG pastures, but no significant seasonal trend could be identified in tbe 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 dombtance of seasonal sbortgrasses 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 accumuiation were the most important factors brfbrencing interrill erosion. Both factors increased microrelief, and obstructed sediment transport and interrill erosion.