Green manure refers to crops specifically grown for the purpose of being ploughed back into the soil while still green, to enrich it. Common examples include legumes like sunn hemp, cowpea, or alfalfa. It benefits the soil by: 1) Increasing organic matter content, which improves soil structure and water retention. 2) Adding nitrogen and other nutrients, especially when leguminous plants are used due to their nitrogen-fixing capabilities. 3) Suppressing weeds and preventing soil erosion. It contributes to sustainable agriculture by reducing the reliance on synthetic fertilizers, improving soil health naturally, and fostering a healthier ecosystem, making farming more environmentally friendly and resilient.