Green Manure crops are very useful in maintaining soil health by adding organic material. Some add atmospheric nitrogen to the soil, and they help improve soil structure. These crops are best dug under around 1 month before a following crop is planted to allow adequate time for decomposition, or they can be dug in as the plants begin to flower. Feed with manures and fertilisers for best growth and to obtain maximum bulk for turning in or composting. Most will grow at any time, but are usually sown in autumn after summer crops have been harvested.