Study on the nitrogen and phosphorus mineralization of livestock and poultry manure in red soil

A laboratory incubation experiment was conducted using composted chicken and pig manures and red soil which derived from Quaternary red clay. The dynamic changes in mineral nitrogen (NO-3-N and NH+4-N) and soil available phosphorus (Olsen-P) were studied under different manure application rates. Results showed that the mineralization of N and P significantly differed. .The N mineralization phases were: slow release stage in the initial 4-week with mineralization rates (MR) N 0.290.46 mg/(d?kg); rapid release stage from 4 through 10 weeks with MR N 0.600.71 mg/(d?kg) and slight decline stage from 10 through 15 weeks with MR N -0.09-0.20 mg/(d?kg). The release of available P mainly occurred in the third week. The application of chicken and pig manures could markedly increase soil mineral N and available P. However, the impacts of application amount on N and P release processes were negligible. Through 15-week incubation, the release ratio of mineral N for chicken manure ranged from 15.6% to 18.3%, which was close to that of pig manure by 14.8% to 16.9%. As respect to the release ratio of available P, the values of 34.0%41.6% for pig manure were greater than those of 30.2%37.8% for chicken manure. This suggested that 60%80% of the applied manure N and P, which have not been mineralized or re-fixed in soil, were remained in the soil after 15-week application.