Cover
crops do an excellent job of controlling soil erosion during the winter
and through the critical high-rainfall months of spring.
The primary risk that winter cover crops pose to the next season’s
crop is moisture depletion. That is why it is important to watch
the weather and kill the cover crop if dry weather sets in.
In the central and lower U. S. Corn Belt, rye is the preferred
nonlegume for a winter cover crop. Advantages of planting grasses
such as rye include:
Rapid establishment of ground cover in the fall
Vigorous growth
Recovery of nitrogen from the soil
Good winter survival
More extensive ground cover
Possible weed control due to allelopathic effect
Legume
cover crops are capable of nitrogen fixation—they can draw nitrogen
from the air and provide it “free” to the following crop.
However, the early growth of legumes can be somewhat slower than that
of grass cover crops, and many of the legumes are not as winter-hardy
as grasses such as rye.
Despite
the limitations, hairy vetch has usually worked well as a winter cover
crop in the southern Midwest. It has fairly good establishment, good
fall growth, and vigorous spring growth, especially if it is planted
early—during late summer.