Mitchell et al. conducted a two-year lamb grazing trial, at the University of California Imperial Valley Research and Extension Center near El Centro, California, to test the effects of lamb grazing by measuring alfalfa (Medicago sativa) yield for the first harvest following grazing, and the soil parameters of penetration resistance and infiltration rate. Authors used a severe degree of grazing, after 600 hd d/acre, only bare ground and grazed alfalfa crowns remained. Despite this severity, yields were 5.4% greater at the first spring cutting in comparison to mowed, ungrazed alfalfa. Although sheep trampling increased soil penetration resistance at the surface, there was no injurious effect on water infiltration rates or on subsequent yield of alfalfa. The results for water infiltration rates contradict other literature for arid rangeland, which they believe is a consequence of the nature of water flow in cracking clay soil. They concluded that intensive winter grazing of alfalfa by lambs was not detrimental to subsequent hay yield, nor to the soil of an irrigated pasture in the Sonoran Desert.
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