Infiltration Rates on Rootplowed Rangeland

Abstract

Infiltration and runoff from mechanically treated arid Southwestern rangeland were measured. Control plots dominated by creosotebush had greater infiltration rates than the 1972 and 1976 rootplowed and seeded treatments, stressing the importance of cover for reducing runoff and controlling erosion. Infiltration rates on dry soils were significantly higher on the 1972 rootplowed and seeded treatment compared with the 1976 rootplowed and seeded treatment, indicating the lack of soil structure in the 1976 treatment. In the arid and semiarid rangelands in the southwestern United States, rainfall is insufficient and its distribution too uncertain for maintaining vegetation to protect the soil adequately. Attempts have been made to convert sparse desert vegetation, which is often not suited for grazing, to more desirable plant species (Tromble 1976). To establish new species and manage these arid rangelands for maximum productivity, it is important to know which factors control water yield. Rowe and Reimann (1961) listed soil depth and water storage capacity, rainfall amount and distribution, and the type of vegetation, before and after site conversion, as important factors affecting soil water yield. Other factors, such as storm intensity, watershed size, and soil surface characteristics, also affect water yield. Arid and semiarid shrub-covered watersheds can sometimes be converted to grass, increasing onsite forage productivity. Rootplowing to kill the brush and then seeding usable forage species is an important method used in the southwestern United States to improve rangeland. This method disturbs the soil surface, which can enhance water storage, and at the same time prepares a seedbed. Sparsity of vegetation on arid and semiarid rangelands means that soil surface conditions are of prime importance in determining infiltration rates (Duley and Kelley 1939; Horton 1940; Dixon 1966; and Kincaid and Williams 1966). Simple correlations between infiltration rates during the second 30-minute period of 1-hour infiltration tests showed that the soil structure of the uppermost horizon was highly correlated with water intake. Texture of the horizon just below was second in importance, and the nature of the lower Author is hydrologist, Science and Education Administration, Agricultural Research, U.S. Department of Agriculture, Jornada Experimental Range, P.O. Box 698, Las Cruces, New Mexico 88001. Manuscript received August 10, 1979. boundary of the upper horizon was third (Rauzi and Fly