|a bed of summer buckwheat before garlic goes in early October|
Some cover crops like clover, vetch, and field peas fix nitrogen in the soil. They do this by participating in a symbiotic relationship with bacteria capable of converting nitrogen in the air into a form that the plant can use. These bacteria live in nodules on the roots of the plant, which are formed as a result of the bacteria taking up residence.
Lots of growers use these crops to add nitrogen to the soil while allowing the area to be fallow. Before planting the area again in vegetables or grains, they cut the crop down and then turn the soil, allowing the plants to compost in place.
Here are four good reasons to do this:
One, the nutrient most necessary to plants (nitrogen) is replaced in the soil. Two, the population of beneficial soil microorganisms is encouraged. Three, weed seeds are out-competed while the soil is not being cultivated for crops. Four, the soil is not bare during the time it is fallow. This in turn has several benefits. Erosion is controlled, the soil surface isn't likely to form a crust during a rainy period, and the roots of the plants help form soil macropores, important for water infiltration. I talk about water infiltration more here.
During winter in areas that don't support year-round production, cover crops are essential to the health of the soil by again protecting from conditions such as rain. In summer, a quick cover crop can be used to help the soil before a rotation goes in, to grow greens for compost, to feed farm animals, or to provide forage flowers for insects.
No matter the reason or season, using a cover crop on your farm or garden beds is an important part of creating an organic system.
Here are some links to companies that sell cover crop seed: