The key to fertile, moisture retentive, friable soil - full of organic life.

This is a crop grown to add organic matter and nutrients to beds that are empty for a period of time. It is sown specifically for digging in to the soil to provide organic matter and plant food. It is also able to make nutrients available, so that when it is dug in, they are nearer the surface and accessible to the next crop of plants. Deep rooting plants bring up available minerals from the sub-soil. The root systems of these plants break up the soil and make it easy to work.

Nitrogen Fixers
The legumes (clovers, tares, vetches, etc.) have the ability to ‘fix’ the nitrogen in the soil through bacteria living in tiny nodules in their roots. When the plants are dug in, the nitrogen becomes available for the next crop.

Sowing
Sow a winter crop in late summer or early autumn and dig it in before planting or sowing vegetables the following spring. Some crops of green manures are fast growing enough to allow sowing between ordinary crops in the growing season. Choose a plant that will mature in the time available, preferably unlike the crop just harvested or the one you intend to sow. The soil needs to be in good condition. If low in nutrients, apply a fertiliser before sowing.

Green manure crops provide shade and competition for water and soil nutrients that will discourage all but the most tenacious weeds. A winter cover crop keeps nutrients, especially nitrogen, from being leached from the soil. After a winter crop the soil is beautifully friable in the spring. Never leave your precious soil bare for any length of time but grow a green manure covering to protect from the baking sun and rain. The manure crops will not cause a nuisance by re-growing after being dug.

Working green manures in to the soil.
Do not let the crop flower or become too woody before you dig it in or the rotting process will take nitrogen from the soil. It can be mown before flowering if you are not ready to use the ground. Alfalfa and clovers can be mown for a season or more leaving the mowing to rot into the soil.

If the crop is fairly large, it may be best to cut it up finely with a mower before cultivating the soil. Allow a period of wilting before digging the material under. Low growing crops can simply be cut down with a spade and allowed to wilt for a few days, then dug in, while taller plants can be worked in to the surface with  rotary cultivator then, after a few days, rotavated more deeply. When digging in, do not bury the material deeper than 15cm (6 inches).

IMPORTANT: Green Manure will never provide all the fertility in the soil required by vegetables and good compost and manures must be added in conjunction.