Green manures are any crop high in nutriments that can be tilled back into the soil. Like all plants Green Manures capture CO2 and transforms it into sugars. Many have nitrogen fixing bacteria living around there roots which convert Nitrogen from the air to a form that plants can absorb The soil food web quickly decomposes Green Manure so the nutriments in the leaves and roots can be taken up by the next crop. Cover crops can also be inter-planted with other crops.
Cover crops add organic material to your soil. They make the soil easier to work. Cover crops help the soil hold water and nutriment for easy absorption by plants. Many cover crops have deep root structure that improves soil aeration and when the deep roots decay improve the soil structure. The deep roots loosen the soil and mine minerals which are made available to the garden. Cover crops are cheaper than buying commercial grades of compost and soil amendments. They protect soil from compaction and erosion by softening the impact of rain. Cover crops reduce weed crops. They prevent the leaching of soil nutriments by absorbing them.
Determine your soil building goals. Is it nitrogen fixing, creating heavy biomass or breaking down compacted soil. Choose green manure crop for time of year and your soil building goals from the planting guide that follows. Mixing more than one crop together is a good idea. Consider a strategy to under sow green manures under maturing crops.
It is best to harvest green manures right after they have started to bloom. Harvesting earlier is fine but plants will not have reached their maximum nutritional storage and bio mass. After flowering green manures become woody and after they seed and take longer to break down.
Bury them as you turn you soil or cut them off and chop them up. If you chop them up mix cover crop with the two inches of soil and treat as a mulch or use them in a side mulch. If you remove the chopped cover crop from your garden you will have missed out on its biggest benefit,
feeding your soil. Allow buried crops to decompose before planting (one to three weeks depending on crop, soil and weather.