Influence of Fertilization and Supplemental Runoff Water on Production and Nitrogen Content of Western Wheatgrass and Smooth Brome

Abstract

Simulated water spreading and nitrogen fertilization were studied on soils developed from Pierre Shales in western South Dakota. When both supplemental water and nitrogen fertilizer were applied, forage yields increased almost nine-fold. Western wheatgrass and smooth brome yields ranged from about 1,000 lb/acre on the untreated control to about 8,700 lb/acre with optimum supplemental water and 320 lb/acre nitrogen fertilizer. Forage yields increased with April and June supplemental water as compared with annual application in either April or June. Nitrogen content of harvested hay increased as nitrogen application rate increased above 80 lb/acre. Percent nitrogen decreased with increased supplemental water and ranged from about 1.2 to 2.2% in western wheatgrass and from about 1.0 to 2.3% in smooth brome. Least squares analysis, considering all nitrogen and water treatments, indicated that each lb/acre of nitrogen fertilizer applied increased the forage yield by about 19 lb/acre, and that each inch of additional water increased forage yields by about 50 lb/acre.