The Effects of Nitrogen Fertilization on Water Use by Crested Wheatgrass

Abstract

The application of N fertilizer to crested wheatgrass on a dry rangeland site increased yields substantially. In the early part of the growing season when moisture was not limiting, soil moisture was withdrawn from the fertilized site at a higher rate than from the unfertilized plots. At later periods in the growing season the soil water potential curves paralleled each other with the fertilized crop growing under conditions of lower soil water potential. The decreased soil water potential was confirmed when the actual evapotranspiration, as measured by the energy balance method, was examined. The data indicate that for a period following rapid growth in the spring, the evapotranspiration of the fertilized block was less than that of the unfertilized. The soil water potential data indicate that seasonal evapotranspiration was slightly higher on the fertilized plot than on the unfertilized. The water use efficiency, in terms of biomass produced per unit of water used, was much greater for fertilized crested wheatgrass and resulted in increased yields.