A green crop is the growing of a crop that will be dug back into the soil. It is a natural method of soil maintenance, when dug into the soil it will boost and replace lost nutrients. This will also encourage earthworms and other beneficial micro organisms to your garden.
There are three main varieties of seed commonly used as green manure crops; Blue Lupins, Barley and Oats and Mustard.
Blue Lupins
This is a good one for maintenance of a soils fertility. Recycling lost nutrients from your subsoil coupled with adding vast amounts of ‘free nitrogen’ which is readily available to your next crops.
Plant in the late summer to autumn. Sow approx 25g per square metre. Let the green crop grow for approx 7-8 weeks, then dig in well.
Although Blue Lupins can have a beautiful flower, to get the best from your green crop you need to dig it back into the soil when the stems are still green and soft
Barley, Oats and Wheat
These produce a large mass of foliage and roots through the winter. They add both protein and organic matter to the soil, in addition to strengthening your soil structure.
Plant late summer to autumn. Sow approx 45g per square metre.
Mustard Seed
This aids in the control of wireworm, nematodes etc, which are often problems associated with root crops. Mustard also reduces the chances of any soil bourne diseases within 40 days of digging in. (Note; If club root is a problem don’t plant brassicas crops after mustard).
Plant late summer to autumn. Sow approx 20g per square metre. Leave the crop for 7-8 weeks then dig in well.
Blue Lupin, Mustard and Grain Mix
Also available are combination packs that are a mixture of all of the above. These mixtures are very effective as they will purify your soil and at the same time build up your soil nutrient. You can also mix up your own using 3 parts Blue Lupins and 1 part of Mustard, sowing at a rate of 12grams per square metre.
This green crop in particular is great as it helps with the prevention of wire worm and adds nitrogen and organic matter to your vegetable garden.
Plant this green crop in late summer to autumn. Sow approx 35g per square metre. Let green crop grow for approx 7-8 weeks, then dig well back into the ground. Approx 2 weeks later re-dig the soil before planting your new vegetables for great results.
For a successful Green Manure Crop, simply apply the seeds at the recommended rates. Then in early spring before the plants flower, (but while the stems are still soft and watery) dig your green manure back into the soil. After digging it in, it is best to leave the ground for up to three weeks before planting your next crop. This is essential with mustard. If you have access to it the addition of animal manure before digging in will hasten the breakdown of your green manure.