Short Duration Grazing in Central New Mexico: Effects on Infiltration Rates

Abstract

The objectives of this study were to determine the infiucnce of short duration grazing, continuous grazing, and grazing exclusion on infiltration rates on 2 range sites in southcentral and eastcentral New Mexico. Short duration grazing had no beneficial effect on the hydrology of 2 different range sites. The terminal infiltration rates of both short duration grazing systems, after the cattle had grazed the area, were about one-half the terminal infiltration rate of the same area before the cattle grazed the area. Cattle distribution within the different grazing treatments had no effect on infiltration rates at 0.4,0.8, and 1.2 km away from water for a moderate continuous, heavy continuous, and a short duration grazing system. Moderate continuous grazing was superior to heavy continuous grazing and short duration grazing, based on the hydrologic variables evaluated. Grazing systems impact range watersheds by altering vegetation and soil variables. The objectives of most grazing systems are to increase forage production while, at the same time, increasing livestock and wildlife production. In the past several years, researchers have studied several different grazing systems and their effect on surface water runoff and sediment production. However, little is known about the effect of short duration grazing on rangeland watersheds. A short duration grazing system is defined here as having a stocking density index greater than 2 (Kothmann 1974), but is distinguished from a high intensity, low frequency grazing system by grazing periods of less than 2 weeks. Aldon and Garcia (1973) studied the effects of changing from heavy continuous to moderate continuous grazing with summer deferment on a 190-ha watershed. They reported sediment yields decreased 71% over a 4-year period. Smith (1980), working at the Ft. Stanton Experimental Ranch in southcentral New Mexico, noted moderate continuous grazing was superior to either heavy continuous grazing or a Cpasture l-herd rotation grazing system. Smith (1980) concluded that reduced vegetal cover on the heavy continuous and 4-pasture l-herd systems was the predominate reason for decreased infiltration rates and increased sediment production. Wood and Blackburn (198 I), in the Rolling Plains of Texas, reported a 4-pasture 3-herd grazing system (Merrill system) approached the optimum infiltration rate of a 20-year old exclosure. On the basis of analyzing infiltration rates, Wood and Blackburn concluded the deferred-rotation system was superior to moderate continuous; high intensity, low frequency (HILF); or heavy continuous grazing. McGinty et al. (1979), working in Sonora, Texas, reported infiltration rates of midgrass interspace areas were highest in a livestock exclosure and a deferred-rotation pasture. The heavy continuous grazing treatment significantly reduced terminal infiltration rates. McCalla et al. (1984) initiated another study at the Sonora Research Station to evaluate the influence of mixed livestock grazing on the hydrologic variables in moderate continuous; heavy continuous; and a high-intensity, low frequency grazing system stocked at a moderate level. The pastures were 5 ha each and were grazed at a ratio of approximately 50:25:25% for cattle, goats, and sheep, respectively. In general, he concluded there was no signifi