Ammonia volatilization during aerobic and anaerobic manure decomposition

Ammonia volatilization, nitrogen immobilization, carbon decomposition and formation of volatile fatty acids was investigated in a laboratory incubation experiment with fresh poultry manure, to which increasing amounts of straw were added. Less than 1% of the manure nitrogen was volatilized as ammonia during anaerobic decomposition due to low pH values. In aerobic manure alkaline conditions prevailed and between 9 to 44% of the nitrogen was volatilized as ammonia. The volatilization courses could be described by a parallel first-order model. Increasing straw additions reduced ammonia volatilization during aerobic decomposition. Straw caused no immobilization of nitrogen under anaerobic conditions. In aerobic manure, nitrogen was mainly bound in organic forms whereas in anaerobic manure about two-thirds of the nitrogen was in ammonium form. C/N ratios in the organic matter of anaerobic manure were higher (33.1–87.5) than in the aerobic manure (9.5–18.0).