Green manuring is a potential method for reducing chemical N fertilizer input and reactive N losses to the environment that can achieve dual goals of food security and green development of agriculture. In this study, three long-term field experiments in south China and process-based model (WHCNS_LIXIM model) were combined to examine effects of long-term green manure substitution on soil N supply, crop N uptake, and N losses in rice production system. Results showed that green manure substitution significantly improves soil mineral N by 27.4–94.9% and 1.0–45.0% at jointing and maturity stages, respectively, compared with the use of chemical N alone. Moreover, 18.4–62.2% of crop N uptake increased at the maturity stage at Xinyang and Yujiang sites. The model demonstrated satisfactory performance in modeling dynamics of soil mineral N, crop N uptake, crop dry matter, and grain yield of the rice–green manure system with a determination coefficient (R²) > 0.967 and slope of linear regression equation (β) close to 1.0. Simulated N budgets presented that green manure reduces 20–40% of the chemical N fertilizer input and decreased 5.5%, 25.1%, and 30.6% of N losses by ammonia volatilization, leaching, and runoff, respectively, when green manure application rates (fresh matter) are less than 30 t ha⁻¹. However, the total N loss increased with the increase of green manure application amounts when application amounts are larger than 30 t ha⁻¹. These findings indicated that the further reduction of chemical N fertilizer was needed when the application amount of milk vetch was higher than 30 t ha⁻¹. A milk vetch application of 15–30 t ha⁻¹ was recommended to substitute 20–40% of chemical N fertilizer to improve crop N uptake and reduce N losses, and develop green rice production system in the study areas.

绿肥是减少化学氮肥投入和活性氮对环境损失的潜在方法，可以实现粮食安全和农业绿色发展的双重目标。本研究将华南地区的三个长期田间试验和基于过程的模型（WHCNS_LIXIM 模型）相结合，考察了长期绿肥替代对水稻生产系统土壤氮供应、作物氮吸收和氮损失的影响。 . 结果表明，与单独使用化学氮相比，绿肥替代在拔节期和成熟期分别显着提高了土壤矿物质氮 27.4-94.9% 和 1.0-45.0%。此外，在信阳和余江地区，成熟期作物氮吸收量增加了 18.4-62.2%。该模型在模拟土壤矿物质 N、作物 N 吸收、² ) > 0.967，线性回归方程( β )的斜率接近1.0。模拟氮预算表明，当绿肥施用量（新鲜物质）小于 30 t ha ^-1。^{然而，当施用量大于30 t ha -1}时，总氮损失随着绿肥施用量的增加而增加。这些研究结果表明，当紫云英的施用量高于30 t ha ^-1时，需要进一步减少化学氮肥。^{15–30 t ha -1}的紫云英应用建议替代 20-40% 的化学氮肥，以提高作物对氮的吸收，减少氮的流失，并在​​研究区发展绿色水稻生产体系。