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Articles about Compost and Soil Treatments
Aerated Compost Tea, The New Organic Fertilizer
Bark As a Potting Soil Amendment and Mulch
Carbon:Nitrogen ratio of common compost materials
Compost mixtures you can make at home
Composting is Fun for the Whole Family
Green manures and Cover crops in the Organic Garden
Here is Why You Should Use Gypsum in Gardening
How to build a compost heap
How to make loam and leafmould
How to make worm compost
How to solve problems with compost making
How to use organic fertilisers and manures
Mulching - Comparison of costs and results for organic and inorganic mulches
Mulching Benefits - Organic And Inorganic Mulch Types
N:P:K Analysis of common composting materials
Obtaining Free Mulch For Your Garden - Uses And Methods Of Getting It
Soil Basics - Creating Fertile, Healthy Soil
Soil PH And Its Effect On Your Garden
Understanding Soil Nutrients
Using Garden Compost
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Green manures and Cover crops in the Organic Garden
by Frann Leach
The easiest way to add organic material to soil is to grow a green manure and then dig it in - no need to cart stuff to and from the compost heap! Green manures are an inexpensive, convenient source of organic matter, increasing water retention so you don't need to water so often and helping plants to get more out of the soil, so you save on fertiliser. They are often used as cover crops to stop erosion of valuable topsoil by wind and water in bad weather conditions.
You can also dig in grass clippings, which greatly improve the physical condition of heavy textured soils and provide much needed humus and nitrogen, before planting a second crop in a vacant plot. On very acid soil, add a little lime at the same time as you dig in the grass clippings. Give the area a week or two to get back to normal, then plant as usual. Many times, the second crop surpasses the first.
Types of green manure
Green manures basically break down into legumes and non-legumes. Legumes are valuable because they help fix large quantities of nitrogen from the air, making it available to plant roots. They also store moisture and send down deep roots that tap soil minerals, assist soil aeration and drainage and are attractive to bees. Some leguminous crops add anything up to 150 pounds of nitrogen per acre to garden soil, equivalent to approximately five tons of manure. Winter-hardy legumes are also often used in orchards to maintain soil fertility.
Non-legumes are good for short term production of bulk organic matter for the garden. They are usually sown in late summer or autumn and dug in the following spring, so as to clear the land for the growing season.
Mulching with green manures
Although all varieties of green manure can be dug straight into the soil, many can also be used as organic mulching material. Mulches such as rye grass offer nutrition for the soil, attract earthworms and keep the soil moist. And as the mulch decomposes, soil nutrients are released, so you get two effects for the price of one.
Even poor soil can be improved with cover crops. Sandy soils gain moisture from the use of green manures; clay soils are helped by crops with long roots which soften the ground, such as alfalfa; and weedy soils can be cleaned up with fast-growing grasses to choke out unwanted weeds at the same time as adding nutrients. Green manures, treated carefully, will enable the soil to hold its nutrients until they can be used by the crops which follow. Cover crops are also beneficial to soils suffering from erosion or water build-up by providing erosion barriers to hold on to topsoil and absorb excess moisture.
Improving aeration and drainage
Green manures dug into the ground will greatly improve both drainage and air exchange in soils of good structure. The best way to maintain good soil porosity is to add organic matter to the soil by digging in green and farm manures, or adding compost to your soil.
Green manure crops
There are many green manures to choose from. Here are some of the more common ones:
|Crop||Family/Group||Sowing rate||Sowing time||In ground||Notes|
|Alfalfa/Lucerne Medicago sativa||Leguminosae/7||1oz per sq yd||April-July||3-4 months, up to 1 year+||Legume. Very deep rooted. Helps condition the subsoil.|
|Annual ryegrass Lolium multiflorum||Gramineae/9||March||before flowering||Fast growing with good amount of top growth.|
Vicia faba minor
|Leguminosae/7||6" each way||Sept-Nov||c. 5 months over winter||Legume. Can be cut once to regrow. Turn in or allow to seed, harvest, cut and compost.|
|Buckwheat2 Fagopyrum esculentum||Polygonaceae/9||1oz per 4 sq yd||mid March-August||10-12 weeks||Good for acid soil. Attracts bees & hoverflies. Good soil conditioner.|
|Chicory Cichorium intybus||Compositae/4||1oz per sq yd||April-Aug||16 weeks||Deep rooting. Good soil conditioner.|
|Chinese radish Raphanus sativus||Cruciferae/2||1oz per 7 sq yd||May||10-12 weeks||Brassica. Turn in. Do not use after other brassicas.|
|Clover, Alsike3 Trifolium hybridum||Leguminosae/7||1oz per 8 sq yd||April-July||3-12 months||Legume. Good for nitrogen. A good clover for heavy or wet soils.|
|Clover, crimson1 Trifolium incarnatum||Leguminosae/7||1oz per 8 sq yd||March-August||2-3 months in summer||Legume. For farming.|
|Clover, Essex red/Red Merviot Trifolium pratense||Leguminosae/7||1oz per 10 sq yd||April-Aug||3 months-2 years||Legume. Reputed to be a mouse deterrent|
|Cowpea3 Vigna unguiculata||Leguminosae/7||6" each way||April||After harvest||Legume also useful for breaking up hardpans. Crop can be eaten. Harvest and dig in vines.|
|Fenugreek1 Trigonella foenum-graecum||Leguminosae/7||1oz per 4 sq yd||March-August||2-3 months in summer||Not hardy. Cut and compost. Legume, but does not fix nitrogen in the UK.|
|Lupins Lupinus angustifolius||Leguminosae/7||2" apart||March-July
|After 8 weeks
|Legume. Good for light land and after digging in old turf. Dig in before flowering. Adds phosphates.|
|Millet Millium effusum||Gramineae/9||March-April||before flowering||Good for dry or poor soils.|
|Mustard1 Sinapis alba||Cruciferae/2||1oz per 7 sq yd (per 5 sq yd)||March-mid September||3-8 weeks in summer||Brassica. Very quick growing. Turn in before flowering. (Rate to clear wireworm.) Do not use after other brassicas.|
|Phacelia tanacetifolia1,2||Boraginaceae/9||1oz per 10 sq yd||end March-mid Sept||8-16 weeks||Bulks well. Turn in or cut & compost.|
|Rape Brassica napus||Cruciferae/2||1oz per 10 sq yd||July-Aug||Summer 7 weeks, over winter to 6 months||Brassica. Turn in Sept or cut and compost in Oct. Do not use after other brassicas.|
|Rye, Winter grazing Secale cereale||Gramineae/9||1oz per sq yd||mid August-November||24 weeks over winter||Extensive roots and good top growth. Fastest growing winter hardy crop. Turn in early Spring.|
|Spinach Spinacea oleracea||Chenopodiaceae/1||Spring||Cut & lay on soil, leave roots in ground.|
|Winter tare/vetch Vicia sativa||Leguminosae/7||1 oz/80ft row. 1" deep, 4" rows||March-mid September||2-3 months or overwinter||Turn in March/April.|
|Trefoil Medicago lupulina||Leguminosae/7||1 oz per 10 sq yd||mid March-mid August||13-52 weeks||Legume. Also known as Black medic and hop clover. Turn in before flowering. Suitable for undersowing.|
1 May be hit by a hard frost. 2 Attracts hoverflies. 3 Inoculate seed