Study on the nitrogen and phosphorus mineralization of livestock and chichken 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 0.29-0.46 mg/(kg·d);rapid release stage from 4 through 10 weeks with MR N 0.60-0.71 mg/(kg·d) and slight decline stage from 10 through 15 weeks with MR N-0.20——0.09 mg/(kg·d).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 Olsen-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 Olsen-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.