1. Know and improve your soil | 40 mins
Green Manures
Green manures are plants grown to improve the soil and replace nutrients that have been used by previous years crops. They include clover, ryegrass, vetch and field beans. Growers often miss the opportunity to grow them over the winter as they are pre-occupied harvesting or putting their gardens to bed, but they should be considered an important way of improving your soil to ensure that subsequent plants flourish.
In agriculture green manures are also sometimes called 'cover crops, 'catch crops', 'leys' or 'pasture' and there is no manure involved which can be slightly misleading for beginners! There is actually nothing new about green manures and in fact, until the 1960s, green manures were always grown on fields to improve soil fertility, and it is only with the advent of artificial nitrogen fertilizer that it was no longer thought necessary to grow them although they still play a major role in organic growing.
Green manures bring about lots of benefits for our soil:
- Nitrogen fixing - Legume green manures fix nitrogen in their roots. This is taken up then released back into the soil when plants are cut down.
- Improved soil structure - Green manures have fine roots which help to improve soil structure.
- Added organic matter - When the plant residues of the green manure break down, they add organic matter to the soil.
- Retained nutrients - Growing green manures helps prevent nutrients being washed out of the soil by rain during the winter.
Reflect: What do you think are the environmental benefits of using green manures rather than synthetic nitrogen fertilizer? Could you add green manures into your next crop rotation?