Effects of Annual Applications of Low N Nitrogen Fertilizer Rates on a Mixed Grass Prairie

Abstract

Nitrogen (N) fertilizer at rates of 0, 22, and 34 kg/ha was applied annually in the spring or fall over a 5-year period to a mixed grass prairie. Major species present were blue grama (Bouteloua gracilis), western wheatgrass (Agropyron smithii), and dryland sedges (Carex Sp.). Slim leaf goosefoot (Chenopodium leptophyllum) and other annual and perennial forbs were also present. Total herbage production, crude protein content, mineral concentrations, species composition and water use data were collected. Total herbage yields and crude protein from all the fertilizer treatments were significantly greater as compared with the control. Nearly all of the variation in phosphorus (P), calcium (Ca), potassium (K), and magnesium (Mg) concentrations and species composition were associated with the seasonal distribution of precipitation (years) and not with N-fertilization treatments.