Cover crops are used in different fields throughout the growing season. If a field is not being used for crop production, that field will have a cover crop for the entire season. This is important because if the field is left with nothing planted in it (bare soil) when a heavy rain comes the topsoil can wash away.
The cover crop will add nutrients that the vegetables planted in the field took out of the soil. For example, crimson clover adds nitrogen to the soil, creates a beneficial habitat, and is beautiful to look at. Cover crops are also used around the fields and in between the beds to distinguish where to walk and to create tractor aisles.
Crimson clover is not only beautiful, it's adding nutrients to the soil as well.
Daikon radish is a cover crop that has a long taproot which goes deep down into the subsoil and brings up nutrients for the next crop to benefit from. Buckwheat is another common cover crop that attracts beneficial bugs. One commonly used cover crop combination at Red Wiggler is hairy vetch/winter rye which creates a living mulch so a crop can be planted into it at a later time. We've planted our tomato transplants as well as our summer squash seeds into this living mulch as a way to reduce the amount of plastic put in the field.
Using cover crops is a part of our crop rotation plan. Crop rotation is used as a way to confuse the pests. Pests are harder to control if the same crop is planted in the same area. If a crop is planted in the same field season after season the pests know where to find it. If the same crop is planted in the same field year after year the yield could be less each season. Rotating crops also helps with the stability of the soil in each field. Changing crops in each field each season allows the ground to remain fertile due to not all nutrients being used in that field. In the same sense, if a field is fallow that season, it allows that field to rest and replenish nutrients.