Green manure
From Allotments4All
Contents
Introduction
Most green manures are sown in spring to be dug in during the autumn, or planted in the autumn to over winter. Also After green manure has been dug in, the ground may need to be left for a couple of weeks before planting. This is to allow time for the top growth to begin rotting down.
In most circumstances green manure should be harvested before it flowers, to avoid problems with seeds growing while you are trying to plant your next crops and avoid nutrient loss from your soil.
This website is quite useful in sowing times: http://www.btinternet.com/~bury_rd/green.htm and scroll down to the table. It's helpful, but not extensive, there are many more green manures, have a google for it.
Green manure can help to keep moisture in the ground, preventing a 'dust bowl' effect where surface winds dry bare earth making it very dusty on the surface.
Green manure can provide good habitats for wildlife as it tends to prodcus a "total cover" as opposed to rows with gaps between. This will act as valuable ground cover for all reptiles and amphibians (such as slow-worms, newts, toads and frogs).
When dug in it will produce humus which will act as a long term spongy layer, makingthe soil more water retentive.
Alfalfa
Alfalfa is quite a quick growing green manure and very deep rooted. This means it has the ability to draw up nutrients from a long way down in the sub-soil to add to your allotment.
Can be combined with fenugreek to germinate in October for good ground cover and control of weeds. Easy to dig in in spring.
Broad beans
You can fill any gaps, as soon as they occure, with broad beans spaced about 6 inches.
Pull the beans and either compost them or dig them in elsewhere at whatever stage. The young tops are quite tasty! If they're sown at the end of the season they stay until ground is needed in Spring. 6 inch spacing is good for weed suppression, but not for harvesting, although a good many do crop. I then use the beans for more GM sowing! The food crop is kept in place in the rotation, at 12 inch spacing, always from new seed. I grow far more than we need and use the spare beans to keep the GM going.
To avoid the potential for disease it is advisable not to use broad beans as your only source of GM but it contributes to ensuring every bit of ground is always covered, and as much nitrogen as possible is going back into the soil or into the compost heap.
Buckwheat
Buckwheat can be sown between March - August. It has pretty pale pink flowers that attract hoverflies.
Mustard
Mustard is terrifcally fast, 2-8 weeks
Phacellia
Fast growing and produces considerable bulk during the summer and so suppresses weeds. Has a blue flower that attracts insects and butterflies (assuming you leave it to flower) and is not difficult to dig in even after flowering.
Red Clover
Can be sown in the spring to be dug in during Autumn or sown in Autumn for digging in during the spring. Sweetens and also helps to lighten heavy soils and provide a great deal of humus. 100g for 400sq. ft.
Poached Egg Plant
Can be sown in September to 'over winter' and then skimmed off the soil with a sharp spade in late March. Harvesting and composting in late March will allow the sun to warm the soil for seed sowing several weeks later.
Limanthus normally flowers in late May and then die off during the summer months. Its worth planting small amounts in an area where they can be left to flower and the seeds gathered for resowing later the same year. Simply spread a narrow sheet of fine netting underneath the plants just before they flower to catch the seeds. Sheeting makes a significant difference to the amount of seed you are able to collect, since ordinarily seeds are not held in pods and do not spend a great deal of time maturing on the plant. Seeds fall to the ground individually and are difficult to collect because of this.
Limanthus is also a particularly useful low growing companion plant for fruit bushes.
Becuase Limanthus is an over wintering crop, you can use it as an easily available 'slug bait' to trap slugs under pieces of wood and carpet during winter and early spring months.
The open faced yellow and white flowers provide easily accessible nectar for hover flies, whose larvae are significant greenfly preditors.
