Research on cover crops started in the 1940’s.  The book,
Managing Cover Crops Profitably, 3rd Edition, which is published
by Sustainable Agriculture Network, discusses how and why cover
crops work and provides an extensive listing of cover crops.
There are a number of benefits to planting cover crops.  Cover
crops provide soil cover which helps prevent soil erosion by
wind and water and reduces leaching (nitrogen and phosphorus)
into surface water and groundwater.   Cover crops improve soil
fertility by adding organic matter to the soil and furnish
moisture conserving mulch.   Legume cover crops (e.g. red
clover) have tap roots that can penetrate hard pans and reduce
soil compaction.    Certain cover crops can supply nutrients to
cash crops and thus reduce purchased fertilizer inputs.
Sometimes the cash crop does not use all the available nutrients
(e.g. nitrogen, phosphorus, potassium, etc.) in the soil at the
end of a growing season.   Non-legume species (e.g. barley,
cereal rye, wheat) absorb existing a