Cover crops make so much sense – they cut fertilizer costs, improve soil health and condition, prevent soil erosion, improve water holding and infiltration capacity, produce nitrogen, and much more. Many cover crops are ALLELOPATHIC, which means they exude chemicals from their roots that suppress the growth of other plants (weeds!) around them.
Cover crops are either LEGUMES (clover, hairy vetch, peas, alfalfa), which convert nitrogen in the air to a form that plants can absorb, or NON-LEGUMES (buckwheat, cereal/small grains, and crucifers like radish, turnip, and mustard) that contribute added organic matter and suppress weeds. Both groups are useful tools in a crop rotation line-up. Often you don’t have to choose one type over the other type but you can use a mixture of different types of cover crops. Peas & oats, rye & vetch, winter peas & triticale, and oats & radish are particularly useful combinations.
When planning which cover crop to plant in the fall, it is also helpful to divide the available species: (1) those that will WINTER-KILL, and not re-grow in the spring, and (2) those that will produce some growth in the fall, go dormant during the winter, and then grow back in the spring.