Herbage Yields in Relation to Soil Water and Assimilated Nitrogen

Soil water, herbage assimilated nitrogen, and herbage were measured in the field and used to estimate the effectiveness of nitrogen fertilization to increase yields in cheatgrass communities. The application of regression analysis to estimate the amount of nitrogen fertilizer needed to increase herbage in relationship to available soil moisture is presented. When herbage nitrogen is in the range of 0.5 to 0.7% at the end of the spring growing season, nitrogen rather than soil water appears to limit herbage production.