Short-Term Straw Return Combined with Nitrogen Fertilizer Alters the Soil Nitrogen Supply in Rice–Rapeseed Planting Systems

Abstract

This study aimed to assess the influences of short-term straw return combined with nitrogen (N) fertilizer on crop yield, soil properties, the bacterial community, and soil nitrogen cycling gene abundance in a rice–rapeseed planting system. A two-year field experiment was conducted in a paddy field from 2019 to 2021. There were four treatments in the experiment: −N−S, no N applied with no straw return; −N+S, no N applied with straw return; +N−S, N applied with no straw return; and +N+S, N applied with straw return. The results showed that short-term straw return combined with N fertilizer could increase crop yield and N use efficiency. N fertilizer application had a positive effect on Gemmatimonadota and Desulfobacterota abundance. Straw returning had a positive effect on Desulfobacterota and Proteobacteria abundance. N fertilization significantly increased the abundance of amoA-AOA, amoA-AOB, and nxrB in agricultural soils. Straw return and N fertilization were not conducive to denitrification. We conclude that short-term straw return combined with N fertilizer in rice-growing areas not only increase crop yield and improve crop N uptake but also increase SOM, total N, and NH4+ and improve the soil microbial activity and N use efficiency.