Limits on Western Range Forage Production—Water or Man

Abstract

Water is generally regarded as the limiting factor in forage production on arid rangeland. If 800 lb. is taken as the water requirement for a pound of range forage, 12 inches as the average precipitation, and 400 lb. as the average forage production/acre, only 12.5% of the precipitation, or 1.5 inches, is used in producing the forage crop. If we estimate that in addition, 1/2 inch is lost to deep percolation, 1 inch to over-the-surface runoff, and 1 inch to undesirable vegetation, we account for 4 inches. Thus, the remainder, two-thirds of the total precipitation, is lost by evaporation, without benefit to man. The importance of the resource lost by evaporation is discussed in relation to the potential productivity of arid lands.