[Long-term effects of imbalanced fertilization with lime and gypsum additions on denitrifying functional genes of an Ultisol at Yingtan, Jiangxi, China].

The abundance of denitrifying functional genes plays a key role in driving the soil nitrous oxide (NO) emission potential. Nitrite reductase genes ( and ) and nitrous oxide reductase genes ( and ) are the dominant denitrifying funtional genes. In this study, real-time quantitative PCR was conducted to evaluate the effects of 32-year imbalanced fertilization and lime and gypsum additions on the abundances of , , and genes in an Ultisol at Yingtan, Jiangxi Province. We further explored the underlying driving factors The results showed that, compared with the balanced fertilization treatment, fertilization without phosphorus (P) signifi-cantly decreased the abundances of , , and genes. Fertilization without nitrogen (N) significantly reduced the abundances of , and , but did not affect the abundance of . Fertilization without potassium (K) did not affect the abundances of all denitri-fying functional genes. Results of stepwise regression analysis and random forest analysis showed that soil pH was a key environmental factor affecting the abundances of and . The application of lime or lime + gypsum significantly increased soil pH, which subsequently increased the abundances of and / by 150%-231% and 127%-155%, respectively. Our results suggested that application of lime or lime + gypsum favored more than in upland Ultisols, which might enhance the relative importance of in NO reduction. Overall, fertilization without P would reduce denitrifying gene abundances, while the application of lime or lime + gypsum enriched and increased ratio of , which might be beneficial for reducing NO emission potential in the Ultisols.