COMPARISON OF DIFFERENT AGRONOMIC ACTIVITIES ON PHYSICOCHEMICAL PROPERTIES AND N-CYCLING GENE ABUNDANCES IN FARMLAND SOIL NEAR COPPER TAILINGS AREA

To evaluate the impact of different agronomic activities on soil physicochemical properties and Ncycling gene abundances in farmland soil near copper tailings area.The pot experiments were performed from September 11 to December 5 in 2023, soil physiochemical properties, abundance of nifH, AOA-amoA, AOB-amoA, nirS, nirK and nosZ, and variation of N-cycling bacterial population were investigated.Results showed that combined application of Chinese milk vetch and N fertilizer significantly decreased soil pH while increasing the levels of total nitrogen, organic matter, available nitrogen, nitrate nitrogen, urease activity, alkaline proteinase activity, and abundances of nifH, AOA-amoA, and AOB-amoA.Results of multiple regression analysis suggested that the abundance of nifH, AOA-amoA, AOB-amoA, nirS and nosZ negatively correlated with pH (p < 0.05), and positively correlated with available N, nitrate nitrogen and alkaline proteinase activity (p < 0.01), and the abundance of nosZ correlated positively with available nitrogen and nitrate nitrogen.The main driving factors for N fixation, nitrification and denitrification, were Hyphomicrobium, Nitrospira and Nitrosospira, respectively.Combined agronomic practices had a better role in improving the cadmium-containing soil properties than the unitary Chinese milk vetch planting or N fertilizer alone.Therefore, pH, available nitrogen and nitrate nitrogen were crucial environmental factors for the abundances of nitrogen cycle genes.