Nutrient Balance and Straw Recycling Efficiency in Paddy Fields of Southern China

Rice production systems play a critical role in promoting agricultural circular economy and mitigating climate change. However, the absence of reliable coefficient data remains a major constraint for comprehensive evaluation and policy formulation. Under the growing imperative to enhance resource efficiency and environmental sustainability in agriculture, this study investigates the material inputs, nutrient flows, and recycling potential of three major rice types (early indica, continuous late indica, and single-season japonica) cultivated in Taizhou, China. Taking 1 mu (≈ 666 m²) as the functional unit, we integrate Life Cycle Assessment with Material Flow Analysis to quantify per-mu inputs and outputs throughout the entire rice-growing cycle. Data were acquired through a combination of field surveys, laboratory testing, and literature review, enabling detailed characterization of fertilizer application patterns, biomass yields, and embedded nutrient content (N, P₂O₅, K₂O). The results reveal that nitrogen fertilizer is significantly overapplied, particularly in single-season japonica rice, with an overuse rate reaching 237%. Straw return demonstrates potential to substitute 13.6%–48.2% of required nutrients, yet its seasonal effectiveness remains limited. Overall nutrient loss per mu ranged from 13.4 kg to 17.7 kg across rice types, accounting for 36.9%–56.3% of total nutrient inputs. The study contributes a foundational dataset and analytical framework for evaluating input–output efficiency, nutrient cycling, and sustainable fertilizer substitution in traditional rice systems, supporting region-specific policy formulation and low-carbon agricultural transitions. These findings underscore the urgent need to optimize nutrient management strategies to reduce environmental risks and promote circularity in rice-based agroecosystems.