The Green Manuring Process
The Green Manuring Process
First decide when you want to sow theand when you will want to use the ground again. Then choose a suitable variety to suit the period, the type and your where appropriate.
Sow the green manure seed in rows or broadcast over the ground. The former method is preferable when conditions are dry, or where birds are likely to take the seed. Broadcasting is quicker and gives a more even cover but tends to use up more seed.
Leave the green manure to grow until a few weeks before you want to use the ground again, or until the plants are beginning to mature, whichever comes first. Green manure foliage must be young and sappy when it is dug into the ground. For mustard, buckwheat, crimson clover, lupin, fenugreek, phacelia, winter tares and field beans, this means at or before flowering. If the plants go past this stage, remove them to the compost heap rather than digging them in.
Grazing rye should be dug in when you can feel the flower stem forming in the base of the plant. If it reaches this stage before you are ready to dig it in, simply cut the foliage down and leave it on the ground.
Alfalfa, clover and trefoil can be dug in whenever the foliage is fresh green and growing. If they are to be grown for more than one season, cut them down when flowering to encourage fresh new growth.
To dig in, take a sharp spade and turn the green manure into the top 15-20cm (6-8in) of soil, chopping the plants with the spade as you go. If there is a great bulk of foliage, this process may have to be repeated after a day or two. Alternatively, cut down the foliage and allow to wilt before digging in.
Alternatives to digging
Annual green manures can also be hoed, cut or mowed down, the foliage being left on the surface as a mulch.
Perennial green manures can be covered with a light-excluding mulch which can either be planted through or removed once the green manure is dead.
Sowing/planting after a green manure
If the soil is warm and the plants young and chopped, the land should be ready for use 2-3 weeks after incorporating the green manure. If the plant material is rather tough, and/or the soil is cold, leave 3-4 weeks. A fine tilth may take slightly longer to achieve.
Undersowing a green manure
Trefoil, a green manure that will tolerate some shade, can be sown under tall crops such as sweetcorn and Brussels sprouts. It will grow slowly until the crop is removed, when it will grow away strongly. This technique, known as undersowing, is useful for fitting a green manure into a tight rotation.
Sow the trefoil seed when the crop plants are 5-7.5cm (2-3in) high.