Fractionating Rainfall into Vegetative Interception and Soil Infiltration in Perennial Grassland.

With the recent drought and decreasing Ogallala Aquifer, livestock producers on Texas High Plains grasslands and native rangeland appreciate the critical transfer points in the hydrologic cycle of rainfall infiltration of soil and soil water storage. Predicting how much water actually penetrates the soil necessitates estimating the interception of rain by the plant canopy and soil-surface plant residue. This study aimed to determine the fractions of rainfall interception caused by a pasture canopy and residue throughout the growing and dormant seasons. It was conducted on three non-grazed paddocks of WW-B.Dahl Old World bluestem [Bothriocloa bladhii (Retz) S.T. Blake] (Bdahl) near Lubbock, TX. Bdahl is an introduced, highly water-efficient and grazing-tolerant perennial C4 grass, making it a feasible candidate for converting annual row-crop land to perennial grassland in the face of declining water supply. Measurements included soil water content changes, interception rates of vegetation, and evaporation rate from leaf blades and residue. Six measurements per paddock were made under different rain intensities and different post-event weather conditions. Results are used to develop a hydrologic sub-routine for use in a pasture decision-support program to advise producers on the intensity of grazing in relation to soil water supply.