Abstract: Different land use patterns can substantially alter the structure and function of agricultural ecosystems. The impacts of land use on the abundance of nitrite reducing genes, which are critical in producing nitrous oxide, at a regional scale remain largely unclear. We collected dryland soils that grow peanut and paddy soils from sixteen counties or cities in Jiangxi Province to determine the abundance of nitrite reducing genes nirS and nirK using real-time quantitative PCR. Results showed that nitrate and available phosphorus contents in dryland soils were significantly higher than those in paddy soils, while total carbon, total nitrogen and ammonium contents showed opposite trends. There were no significant differences in pH and dissolved organic carbon content between dryland and paddy soils. The abundance of nirS was two order of magnitudes higher than that of nirK in both dryland and paddy soils, indicating that nirS dominated in the acidic agricultural soils. Moreover, the abundance of nirS and nirK was significantly higher in dryland soils than that in paddy soils, indicating that nitrite reducing microorganisms might prefer dryland soils. Soil total nitrogen (TN) and NH₄⁺-N contents were the best predictors for the abundance of nirS and nirK genes in dryland soils and paddy soils, respectively. Taken together, soil nitrogen forms and contents were the most important abiotic factors controlling the abundance of nitrite reductase genes in acidic agricultural soils of Jiangxi Province.

Key words: land use pattern, nitrogen cycle, nirS, nirK