Analysis of the benefits of green manure returning and its application in ecological farms

Green manure, the traditional practice of burying plant materials in the soil, improves soil fertility and structure. After declining in use since the 1990s, it has been resurgent in China due to green farming policies, with the area planted reaching 3.71 million hectares by 2022. However, its use on organic farms remains limited (42.9%), often due to the use of a single species and suboptimal management. The study conducted a meta-analysis of 15 articles (183 effect sizes) to assess the environmental benefits of green manure. The results show that it generally increases crop yields (78.7% of the data showed a positive effect), with an average increase of 13.8%. The benefits vary by species, crop type, and climate; for example, legume green manure increased wheat yield by 5.1%, while non-legume green manure reduced it. Green manure consistently improved soil microbial health (100% positive effects) and nutrient cycling (82.9% positive), increasing available nitrogen, phosphorus, and potassium. It also increased soil organic carbon (87.5% positive), sequestering carbon with an average increase of 17.3%. There are trade-offs: green manure can reduce soil moisture and increase greenhouse gas emissions by an average of 40.7%. In China, the main models include intercropping (e.g., in corn fields, tea plantations, orchards) and crop rotations (e.g., in rice-wheat systems). For organic farms that require multifunctional technologies, green manure supports soil health and nutrient management. Successful application requires the selection of species adapted to local conditions and integration with practices such as reduced fertilizer use. Challenges to wider adoption include insufficient evidence of direct economic benefits for farmers and a lack of strong policy support. Better policy incentives, improved environmental compensation, and synergistic use with other sustainable practices are needed to realize the full potential of green manure in the green transformation of agriculture.