Effects of combined application of manure and chemical fertilizer on the nitrification in acid vegetable soil

A laboratory soil incubation experiment with moisture content of 60% water holding capacity (WHC) at 25℃ was conducted to study the effect of combined application of manure and chemical fertilizer on the nitrification in acid vegetable soil. The results show that the time dependent NO-3-N accumulation was in exponential mode with a delay of 10 days for all treatments. Potential nitrification rate and ammonia oxidizing rate decreased significantly with treatment of adding fresh pig manure plus NPK fertilizer (FPM+NPK) and treatment of compost pig manure plus NPK (CPM+NPK) compared to NPK treatment. The soil microbial biomass carbon and soil microbial biomass nitrogen increased significantly with CPM+NPK treatments compared to NPK treatment in field condition. There was no significant difference with N2O emissions from nitrification incubation between FPM+NPK and CPM+NPK treatments, however the N2O emissions from nitrification incubation with FPM+NPK treatment was significant lower than that with NPK treatment in incubation condition, and the N2O emissions with CPM+NPK treatment was significant lower than that with NPK treatment in the field experiment. There were significant positive correlations between soil pH values and potential nitrification rate in the incubation end, as well as cumulative N2O emissions from nitrification incubation and potential nitrification rate. Combined application of manure and chemical fertilizer significantly changed soil nitrification and N2O emissions from nitrification incubation and field soil.