1. It creates a mass of succulent growth that can be easily converted, either in situ or sometimes via the compost heap, into soil fertility, nutrient, humus and gives a boost to the microorganisms.
2. Soil texture is improved either directly by releasing soap forming compounds like saponins, which bind the soil into a crumbly texture. Or indirectly through the action of organisms, especially worms, who munch on the decaying plant material and add it to the soil as vermicast.
3. Green manuring can be done between autumn and spring when the soil is likely to be less busy with crops.
4. Green manures can take up nutrients into their bodies that otherwise might be leached away when the winter rains arrive.
5. Green manures take up the water during these wet periods. once dug in or covered over the water being retained in their decaying bodies.
6. winter cover crops protect the soil from erosion, keeping the temperature and moisture more equable and even. It also providing food and habitat for countless critters.
7. A good green manure will also exclude weeds, either by preventing them germinating or by choking them out at a later stage.