ECONOMIC-FEASIBILITY OF USING COMPOSTED MANURE ON IRRIGATED GRAIN-SORGHUM

The economic feasibility of using composted manure from western Kansas feedlots in combination with commercial N in the production of irrigated grain sorghum [Sorghum bicolor (L.) Moench] was evaluated. Effective disposal of large quantities of manure from large scale feedlots has been a concern. Yield data from a west central Kansas experiment station study was used to estimate a quadratic production function where grain sorghum yield is a function of compost and commercial N application rates. Four rates of commercial N (0, 55, 110, and 165 lb/acre) and five rates of composted feedlot manure (0, 0.9, 1.8, 3.6, and 7.2 tons dry matter per acre) in a factorial arrangement were applied to irrigated grain sorghum. The production function estimate was used to determine the combination of composted manure and commercial N, which maximized net returns. The results suggest that a compost application rate of 1.5 tons/acre with 110 lb/acre of commercial N would be economically feasible when the price of commercial N, including application charges, is $0.15/lb and the price of compost is $7.68/ton. Once the price of compost reaches $9.50/ ton compost use is no longer economically feasible.