Straw incorporation significantly enhanced rice yield via regulating source–sink balance

Abstract In recent years, rice ( Oryza sativa L.) yield in China has significantly increased, resulting in a substantial amount of straw residue and a low utilization rate. In situ straw returning is the most convenient and efficient method for utilizing straw. However, the long‐term effects of straw returning on rice yield and the optimal straw returning method remain unclear in the double‐cropping rice regions of South China. This study investigated the effects of straw mulching (SMR) and straw incorporation (SIR) on rice yield, nutrient absorption, and the source/sink, using straw removal as a control (CK). The findings indicated that, compared to the CK, rice yield under SIR was 6.6%–24.8% higher. Furthermore, SIR significantly enhanced nitrogen (N) accumulation in rice plants. At maturity, the total N accumulation and distribution ratio were highest under SIR, with total N accumulation increased by 5.6%–26.8% compared to SMR, and by 13.0%–57.8% compared to CK. Compared with CK, the grain‐leaf ratio (GLR) and harvest index (HI) under SIR increased by 5.4%–20.7% and 11.6%–15.6%, respectively. Similarly, compared with SMR, GLR and HI under SIR increased by 2.2%–15% and 6.5%–17.8%, respectively. Overall, SIR not only enhances nitrogen accumulation in rice plants but also boosts the net assimilation rate, ultimately maximizing the GLR. Therefore, the SIR strategy represents the most effective approach for sustainable crop production in the double‐cropping rice regions of South China.