Green Manure Cropping Systems and Their Ecological Functions: Current Knowledge, Mechanisms, and Future Perspectives

Green manure can improve soil fertility by influencing the structure of the soil microbial community and enzyme activity, which in turn affects the main cropping system, and can reduce the use of chemical fertilizers and pesticides, thus reducing environmental pollution. In this study, we reviewed the literature on different green manure cropping patterns, focusing on the effects of different green manure cropping patterns on soil microbial communities, soil enzyme activities, soil physicochemical properties, and the main crop diseases, pests, weeds, and agronomic traits, etc. The positive effects produced by green manure are mainly reflected in the following aspects: (1) improving soil physicochemical properties and soil enzyme activities; (2) influencing soil microbial diversity; (3) improving the overall health of the main crop; (4) increasing the yield of the main crop. This study systematically summarizes the green manure planting patterns and their effects on the main crops, and provides a theoretical basis for green manure planting to solve crop succession barriers and enhance soil fertility; in addition, green manure has a positive effect on the conservation of soil microbial diversity, improves soil quality, and enhances agricultural production, which contributes to the sustainable development of agriculture. Accordingly, this review systematically summarizes green manure cultivation patterns and synthesizes available literature concerning the ecological functions of green manures, including their modulating impacts on soil physicochemical characteristics, microbial assemblages, pests, pathogens, weeds, and crop productivity. Moreover, it identifies key research challenges in this field and proposes outlooks for the sustainable utilization and prospective development of green manures within agroecosystems.