Economic Analysis of Nitrogen Fertilization of Smooth Bromegrass for Hay

Abstract

Dry matter yield (DMY) data for smooth bromegrass (Bromus inermis Leyss.) from two N fertilizer experiments on Thin Black Chernozem (Typic Cryoboroll) soils in south-central Alberta were used to determine economic optimum N rates and returns above fertilizer costs for urea vs. ammonium nitrate (AN) using the net present value (NPV) criterion. The N fertilizers were broadcast. In the first experiment, AN was applied annually in early spring at 0, 50, 100, 150, 200, 250, and 300 lb N/acre over 19 yr. In the second experiment, urea and AN were applied annually at 100 lb N/acre in early fall, late fall, early spring, and late spring over 15 yr. The NPVs from N fertilization decreased markedly when the N fertilizer cost to hay price ratio was increased from 7 to 16, but the optimum N rate remained relatively constant at 100 lb/acre. The NPVs were generally greater with AN than urea as the N source. Further, NPV was highest when the N fertilizer was applied in early spring and lowest when it was applied in early fall. The difference in NPV between N fertilizer sources narrowed with late spring application, because AN and urea tended to be equally effective in increasing forage yield. When the market value of protein in forage was considered in the economic analysis, the NPVs increased with use of N fertilizer, and the NPV benefit of AN and urea became greater, particularly for early fall application. We concluded that the application of N fertilizer was profitable, and that AN at 100 lb N/acre rate, was tbe preferred source of N for established grass stands.