THE VEGAN NEWS  

Ten Good Reasons to Grow a Green Manure Crop!

1. They're cheap and easy to grow.
2. A packet of green manure seeds is easy to carry home - unlike a large sack of animal manure!
3. They can increase soil fertility.
4. They improve soil structure and help prevent soil erosion.
5. They encourage efficient use of land. So why not grow a green manure crop on your unused land this winter?
6. Most green manure crops are very attractive to wildlife.
7. Bare soil encourages weed growth, so green manure bare ground to keep weeds in check.
8. By taking up nutrients from the soil, green manure crops prevent them from being washed away when it rains.
9. Some green manure plants (legumes) are nitrogen fixers.
10. Green manuring increases the humus content of the soil.

How does Green Manuring Work?

Traditionally, green manure crops are sown and allowed to grow, either until the land is needed again or until the plants have reached a certain growth stage. At this point, they are cut down, dug in to the soil and are left to decompose, releasing vital plant nutrients back into the soil which are then used by the next crop. Obviously, if you are using strict no-dig, veganic gardening methods, then digging the crop into the soil is not really an option. But if you don't want to dig, then green manure crops can also be composted or used as a mulching material instead. 

Which Green Manure Plant Should I Use?

There are many varieties of plants which are suitable for use as a green manure crop and some of these are listed in the table below. (Comfrey and sunflowers can also be used for this purpose too.) However, if you do not have enough land left, to devote entirely to growing a green manure crop, it is also possible to sow some green manure crops (e.g white clover) on paths between beds. And crops, such as field beans, can even be sown in between rows of vegetables in your raised bed system if you are short of space. Mixtures of green manure plants can also be used. For example: fieldbeans/mustard; or vetch/clover/rye. 

When selecting the crops that you are going to grow, you should bear in mind the following points:

• Choose either a quick or a slow-growing crop - to fit in with the time that the land will be left vacant.
• The season of the year. (Not all varieties will survive the winter.)
• Whether you want your crop to fix nitrogen or not.
• Your soil type and how much drainage it offers.

Plants marked * are nitrogen fixers

NAME	LATIN NAME	WINTER HARDY	SOWING TIME	WILDLIFE VALUE	GROWING TIME
Alfalfa	Medicago sativa	Yes	Apr-July	Bee	1-2 mths or a few yrs
*Winter Field Beans	Vicia faba	Yes	Sept-Nov	Bee plant	overwinter
Buckwheat	Fagopyrum esculentum	No	March-Aug	Hoverfly nectar	up to 2-3 mths
*Clover, Alsike	Trifolium hybridum	Yes	Apr-Aug	Bee plant	1-2 mths or a few yrs
*Clover, crimson	Trifolium incarnatum	Possibly	March-Aug	Bee plant	2-3 mths
*Clover, Essex red	Trifolium pratense	Yes	Apr-Aug	Bee plant	1-2 mths or a few yrs
Fenugreek	Trigonella foenum graecum	Possibly	March-Aug	Butterfly nectar	2-3 mths
*Lupin, bitter	Lupinus angustifolius	Possibly	March-June	Bee plant	2-3 mths
Mustard	Sinapis alba	Possibly	March-Sept	None	2-8 wks
Phacelia	Phacelia tanacetifolia	Yes	March-Sept	Bee plant	2 mths(summer), 5-6 mths (winter)
Rye, grazing	Secale cereale	Yes	Aug-Nov	Bee/caterpillar food	autumn-spring
*Trefoil	Medicago lupulina	Yes	March-Aug	Bee/butterfly nectar	up to a few yrs
*Tares, winter	Vicia sativa	Yes	March-Sept	Bee/butterfly nectar	2-3 mths or overwinter

There is still time to green manure some land this winter as winter field beans (Vicia faba) and grazing rye (Secale cereale) can still be planted in November. 

When is the Crop Ready for Use?

On the whole it is better not to leave your green manure crop in the ground for too long, as land occupied in this way can not be used for growing other crops. Also, if green manure plants get too old, then they can become tough and will take longer to decompose and be incorporated into the soil by soil organisms. For most green manure crops, it is usually recommended that they are cut and used before they flower.

How to Use Green Manure Crops

Usually, green manure crops are cut down and dug into the top 15-20 cm of soil with a spade. But, veganic gardeners, or anyone else who wishes to avoid digging the soil, can simply hoe off young plants (or chop down older ones) and leave them on the soil surface as a mulch. If plants are chopped down, then to prevent any regrowth of the stubble, cover the ground with a light-excluding mulch (e.g. black polythene/newspaper) until you are sure that the green manure crop is dead. If you are in a hurry to start replanting the ground, then you can of course simply plant through the mulch. In any case, you will need to allow several weeks before planting the next crop in the mulched area, in order to give the mulch some time to decompose and release its nutrients back into the soil. Alternatively, if you do not wish to use your crop as a mulch, then you can compost it instead. Composting is in fact a very good way of using up any crops which have been allowed to get too old and tough!

Further Reading:

• Information Sheet on Green Manures (VON) - This can be downloaded as a PDF file from The Vegan Organic Network web site. 
• Growing Green: Organic Techniques for a Sustainable Future by Jenny Hall and Iain Tolhurst. P. 15 - 19.  This book can be purchased from VON. 

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Suppliers of Green Manure Seeds

Seeds of various green manure crops can be obtained by mail order from the following suppliers:

The 2009 Organic Gardening Catalogue - Offers many types of green manures including: Alfalfa, agricultural lupins, agricultural mustard, buckwheat, five varieties of clover, fenugreek, field beans, phacelia, tares, trefoil and Hungarian grazing rye. 

Suffolk Herbs - Also has a good range of green manures in their 2009 catalogue.

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