The question was raised about the use of cover crops.
A lot of the references really have in mind the use of
cover crops as an alternate crop on farms that is also
good for the soil. "The New Organic Gardener" by Eliot
Coleman, ISBN 0-930031-22-9,is a good reference on the
practical use of cover crops in gardens.
Coleman makes the point that cover crops are seldom used
in the garden because they are labor intensive and because
their use requires a measure of patience. It's simply easier
and faster to put down a layer of compost or composted manure
as a mulch and turn the job of enriching the soil and
preventing weeds over to Mother Nature.
Coleman points out, however, that the use of cover crops also
adds diversity to the ecosystem of the garden and I think
he makes a good point.