Ecological Effects and Fate of N Following Massive N Fertilization of Mixed-Grass Plains

Abstract

The response of range herbage and soils on mixed-grass range in southeastern Wyoming to single massive applications of N fertilizer was studied from 1969 to 1973. Herbage yields and N content of herbage were increased by fertilizer in all years of study. Peak responses occurred in 1970 and 1971. Most of the applied N was accounted for in 1970 in top growth and in mineral form. However, a substantial portion could not be accounted for in 1972-73. In early April, 1973, a significant part of the applied N was concentrated below the zone of main root activity in the soil and may be unavailable for future plant use. Several undesirable plants were increased by massive applications of N, and some desirable plants decreased. Massive applications of N on this rangeland produced both desirable and undesirable responses.