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Cover Crops are Essential to Organic Farming
By (uncredited)

An essential part of organic farming is the use of cover crops. These are special crops specifically to benefit the soil. As the name implies, cover crops are grown to cover and protect the soil from erosion.

Another important use of cover crops, or green manure crops, as they are often called. is to provide organic matter for the soil. Organic matter is the lifeblood of the soil. There are two ways to get organic matter into the soil: haul it in, as with manure or compost, or grow it in place, as with a cover crop.

Cover crops provide plant nutrients. Legumes such as clover, alfalfa, and beans fix nitrogen from the air into nitrates which can be used by the plants. Deep rooted cover crops such as alfalfa. if allowed to grow long enough, bring up nutrients from deep in the soil.

One can divide cover crops into o 4 groups according to when they are planted and how long they grow.

1) Fall seeded over winter crops. Winter rye, wheat and hairy vetch are planted in the fall after the row crops are harvested. They provide writer cover and continue growth in the spring. Then they can either be tilled in before planting or, in the case of rye and wheat, harvested for grain and straw later. For best winter cover, plant early in September or early in October. If the previous crop will not be harvested soon enough, the cover crop can be seeded into some standing row crops. This can be done in August before the last cultivation, which will then cover the seed.
2) Short term cover crops. Soybean and buckwheat are examples of cover crops planted in early summer and tilled in about 2 months or less. Soybean is a good nitrogen fixer. Buckwheat makes fast, lush growing and is good at suppressing weeds.

3) Longer term perennials. Alfalfa and the various clovers are biennials or perennials which should be grown at least a whole season, or longer if possible, to get the maximum nitrogen fixing and soil building effects. One common practices is to over seed them into rye or wheat in the spring. After the grain is harvested or just cut for straw, the legume cover crop comes on.

4)Living Mulch. Low growing white clover can be seeded into standing crops such as corn or tall vegetables in the middle of the sea=son after early cultivation.

Cover crops should be tilled into the soil at least 2 weeks before the next crop is planted. The soil organisms breaking down the cover crop can tie up available soil nitrogen. After breakdown is about completed the organisms start dying back and release nitrogen for soil use.