Spraying big sagebrush with 2,4-D [2,4-dichlorophenoxyacetic acid] reduced the rate of soil moisture withdrawal. About 75% of the difference in total moisture depletion occurred within the 3- to 6-foot soil depth; an opposite effect in the 2nd-foot indicated that the increase in grass herbage production is most strongly reflected in that zone. Total evapotranspiration losses from the 0- to 6-foot soil profile were reduced about 14% over the 4-month growing period the 2nd year after spraying.