Effects of Topdressed Compost, Manure, and Urea on Yield and Forage Quality of an Irrigated, Perennial Grass Mix.

Significant quantities of animal manures are generated by livestock and equine facilities along the Front Range of the Rockies. Topdressing raw manure on perennial forage is not recommended due to high potential losses of N into the atmosphere and surface water. Composted manure contains significantly less ammonium-N than raw manure. A two year field study was conducted at the Agricultural Research, Development and Education Center (ARDEC), Fort Collins, CO to determine the effects of topdressing composted manure, raw manure and urea on the yield and forage quality of irrigated, perennial, cool season grass forage. Composted horse manure and raw manure at 136 t ha^-1 and 272 t ha^-1 and raw manure 136 t ha-1 with wood shavings were topdressed once on established grass forage. Urea at 204 kg ha^-1 was topdressed each spring for two years. Forage yield and quality were measured in the first and second hay cuttings in each year. No yield differences were apparent in the first year after application. In the second year, yield from urea applied annually was greater (P=0.05) than all other treatments. In three out of the four harvests over two years relative feed value resulting from the application of compost applied at 272 t ha^-1 was greater (P=0.05) or not different from 204 kg ha^-1 urea topdressed annually or 272 t ha^-1 manure applied once. Topdressed compost shows promise to sustain forage quality while limiting losses of N. Future research is needed to determine whether applying more than 272 t ha-1 compost will increase yield while maintaining forage quality.