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 irriga ted grain sorghum [Sorghum bicolor (L.) Moench] was evaluated. Effecti ve disposal of large quantities of manure from large scale feedlots ha s been a concern. Yield data from a west central Kansas experiment sta tion study was used to estimate a quadratic production function where grain sorghum yield is a function of compost and commercial N applicat ion rates. Four rates of commercial N (0, 55, 110, and 165 lb/acre) an d five rates of composted feedlot manure (0, 0.9, 1.8, 3.6, and 7.2 to ns dry matter per acre) in a factorial arrangement were applied to irr igated grain sorghum. The production function estimate was used to det ermine the combination of composted manure and commercial N, which max imized net returns. The results suggest that a compost application rat e of 1.5 tons/acre with 110 lb/acre of commercial N would be economica lly feasible when the price of commercial N, including application cha rges, is $0.15/lb and the price of compost is $7.68/ton. Once the pric e of compost reaches $9.50/ ton compost use is no longer economically feasible.