Conservation tillage reduces nitrous oxide emissions by regulating functional genes for ammonia oxidation and denitrification in a winter wheat ecosystem

Abstract Conservation tillage is considered a promising strategy for the reduction of farmland nitrous oxide (N2O) emissions. Soil microbial ammonia oxidation and denitrification are key factors in N2O emissions. However, studies on the effects of tillage practices on soil ammonia oxidation and denitrification by microbes are scarce. This study was based on a 7-year fixed-site field experiment on different tillage practices, including conservation [chisel plough tillage (CPT) and zero tillage (ZT)] and conventional tillage [ploughing tillage (PT)]. Compared with PT, CPT and ZT significantly reduced cumulative soil N2O emissions by 45.82% and 73.58%, respectively. The abundance of functional genes in soil microbes was quantified by real-time PCR, revealing that the archaea amoA, nirK, and nirS genes were less abundant in conservation tillage than in conventional tillage soils, while nosZ gene abundance was greater in conservation tillage than in conventional tillage soils. A significant positive correlation was found between N2O emission flux and archaea amoA, nirS, and nosZ gene copy number under agricultural soil conditions for ammonia oxidation and denitrification. This finding will improve the methods used for mitigating N2O emissions from agricultural soil.