Cattle Manure Application Strategies Effects on Bahiagrass Yield, Nutritive Value, and Phosphorus Recovery

Animal manure application based on crop N requirements often leaves excess P in the soil because of the differences in the N/P ratio in manures and that required by the plants. This experiment was designed to evaluate the effects of cattle (Bos taurus) manure applied alone or in combination with ammonium nitrate (AN) on bahiagrass (Paspalum notatum Flugge) dry matter (DM) yield, nutritive value, tissue P concentration and recovery, and soil P concentrations. Treatments consisted of a control, two N rates (200 and 400 kg ha(-1)), two N sources [manure alone or manure plus AN (50/50% combination)], and two application frequencies (single vs. split). Bahiagrass was harvested at 28-d intervals and evaluated for DM yield, crude protein concentration (CP), in vitro digestible organic matter (IVDOM), and tissue P concentration. Soil samples were analyzed for Mehlich-1 extractable P. Bahiagrass DM yield, nutritive value, and P recovery were greater for the manure Plus AN treatments when compared to the control and manure alone. Although greater N rates increased DM yield and CP, bahiagrass P recovery was reduced as the N rate increased. Approximately 20 and 53% of the applied P was recovered by bahiagrass when manure was applied alone and in combination with AN, respectively. Soil-test P (0-15 cm depth) was greater for the treatments receiving manure alone compared to manure plus AN treatments. Our results demonstrated that applying manure in combination with an inorganic N source can increase forage yield and nutritive value while reducing the risks of soil P accumulation.