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• Application of green manure and/or rice straw increased rice yield compared with F. • The FMS combined the advantages of FM and FS in improving soil fertility. • The FMS had the greatest effect on soil microbial community and enzyme activities. • Straw had more lasting effects on soil properties and rice yield than green manure. The cultivation of green manure or rice straw returns in southern China increases crop yields and soil fertility. Few studies have reported the effects of combining both management techniques on rice performance and soil fertility. A 3-year field study was carried out to analyse the impacts of the co-incorporation practice on soil microbial and biochemical parameters as well as crop yield. Five treatments were tested: (i) no-fertilizer (CK); (ii) chemical fertilizer (F); (iii) F plus green manure (FM); (iv) F plus rice straw (FS); (v) F plus green manure plus rice straw (FMS). The results showed that incorporation of green manure and/or rice straw increased double rice yields by 4.1% (FM), 4.7% (FS) and 9.6% (FMS) compared with F. The FMS treatment enhanced soil organic C (SOC), total N (TN), mineral N (N min), and available K (AK) levels by combining the advantage of FM in increasing TN and N min and the advantage of FS in increasing SOC and AK in comparison with F. The incorporation of green manure and/or rice straw stimulated microbial growth (total phospholipid fatty acids, PLFAs) and altered the soil microbial community structure relative to F, in which FMS had the greatest effect. The enzyme activities of β-glucosidase, β-cellobiosidase, N -acetyl-glucosaminidase, L-leucine aminopeptidase and phosphatase were higher in the green manure and/or rice straw application treatments than in the F treatment in the order FM ≈ FS < FMS. The partial least squares path model (PLS-PM) analysis indicated that green manure mainly influenced the abovementioned indices in the early rice season, while the effects of rice straw lasted until the late rice season. Our results suggest that co-incorporation of green manure and rice straw is a more effective practice for improving soil fertility and rice yields. [ABSTRACT FROM AUTHOR]

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. • Long-term green manure substitution significantly improves soil mineral N. • Long-term green manure substitution enhances crop N uptake and reduces N losses. • The WHCNS_LIXIM model performed well in simulating soil mineral N and crop N uptake. • Milk vetch application of 15–30 t ha−1 was recommended to improve crop N uptake and reduce N losses. [ABSTRACT FROM AUTHOR]