Organic matter is added to the soil as well as the potential for nutrients such as nitrogen.
An added benefit is reducing soil erosion during winter months due to blowing winds. Legumes used as green manure crops can provide a significant amount of nitrogen to gardens the following year. Typically, cover crops are sown in the fall and rototilled under the following spring. However, fallow ground can be covered with plant material for a year or more before plowing under. Crops should be chosen carefully to avoid a potential weed problem down the road.