Effects of different nitrogen fertilizers on N₂O emissions in a highly acid tea orchard soils

In recent years the long-term application of large amount of nitrogen fertilizers has led to the serious acidification of tea orchard soils with high N2O emission. In this study, different N fertilizers were applied to a highly acid tea orchard soil to evaluate the effects of N fertilizers on N2O emission. The results suggest that all the treatments increase N2O production significantly by the 31 days aerobic incubation. The average N2O emission from the KNO3 treatment is the highest and total emission is 17 times higher than that of the control. The N2O emission of the NH4NO3 treatment is the next. The total N2O productions from the urea［CO（NH2）2］ and (NH4)2SO4 treatments are stimulated but the N2O emissions are significantly lower than that of the KNO3 treatment. The Urea, (NH4)2SO4 and NH4NO3 treatments significantly stimulate soil nitrification activity, while the KNO3 treatment decreases nitrification potential. The results that denitrification is the dominant source of N2O emission in the highly acid tea orchard soil. To find out the microbial mechanism, quantitative PCR of the functional gene of nitrous oxide reductase(nosZ) was determined. The results suggest that nosZ gene copies from the KNO3 treatment are significantly(P0.05) lower than those of the control. Therefore, the inhibition of N2O reductase is one of the important factors to induce the high N2O emission in the highly acid soil.