Mechanical Side-Deep Fertilization Synergizes with Controlled-Release Fertilizer to Drive Low-Carbon and High-Efficiency Rice (Oryza sativa L.) Production

Against the backdrop of escalating global climate challenges, minimizing carbon emissions while enhancing energy efficiency in rice production has emerged as a core pathway toward achieving agricultural carbon neutrality. A two-year field study conducted in the Yangtze River Delta evaluated three rice cultivation practices: the farmers’ practice pattern (FPP), surface-applied controlled-release fertilizer with machine transplanting (S-CRF), and side-deep applied controlled-release fertilizer with machine transplanting (SD-CRF). Compared to FPP and S-CRF, SD-CRF increased grain yields by 11.3% and 9.2%, respectively, while reducing total energy input by 2.5% and 2.4%. It lowered the carbon intensity of production by 9.7% and 8.2% relative to FPP and S-CRF, primarily through reducing fertilizer/labor-associated carbon inputs and enhancing carbon-use efficiency via higher yield. Economically, SD-CRF outperformed traditional practices, achieving an 81.8% increase in net income and a 37.4% higher benefit-to-cost ratio compared with FPP, respectively, driven by labor cost savings and improved productivity. Notably, SD-CRF reduces labor input by 40.0% compared with FPP, simplifies fertilization operations, lowers farmers’ operational technical thresholds, and effectively boosts their economic income. Data envelopment analysis (DEA) further validated SD-CRF’s superior eco-efficiency, highlighting its dual advantage in balancing yield enhancement and environmental sustainability. Further clarification of SD-CRF application technical indicators, refinement of agronomic practices and machinery efficiency, and promotion of the integrated system’s synergistic benefits and scalable adoption are required to support global sustainable food systems and carbon neutrality goals.