August
2004
By
B. Rosie Lerner
Extension Consumer Horticulturist
Purdue University
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Feed Garden Soil With Cover Crops
Many gardeners have used cover crops to help keep soil from blowing away
over winter. An added benefit of raising cover crops is that the foliage
and root growth can be tilled under in late winter to help loosen heavy
soils and improve overall soil structure and fertility. Also known as
"green manure," these cover crops can be especially valuable
in preparing a new site for gardening or for rehabilitating a heavy or
compacted site.
Cover crops are generally sown in late summer or early fall. In established
gardens, wait until after summer vegetables are harvested. The type of
crop to grow will depend on the desired function, as well as availability.
Winter rye, buckwheat, hairy vetch and winter wheat are ideal for use
as cover crops and are among the most commonly available through garden
centers and mail-order catalogs.
The amount of seed to plant will vary with the species, but, in general,
winter cover crops are seeded at a rate of 2-3 pounds per 1,000 square
feet. Till or spade the soil, and scatter the seed over the area to be
covered at a depth corresponding to the size of the seed. Large seeds
should be covered with one-fourth to one-half inch of soil or compost.
Small seeds can be left on the surface and lightly raked. Apply a thin
layer of loose straw to protect the area from wind and runoff from heavy
rains.
Fertilizing is generally not necessary, especially for established garden
beds. Some members of the Legume family of plants, most notably alfalfa
and hairy vetch, actually facilitate the fixing of nitrogen in association
with certain soil-borne bacteria. The bacteria colonize in nodules of
the legume's roots.
The root growth of the cover crops will help loosen heavy or otherwise
compacted soils, and the addition of the dead foliage later in winter
or spring will improve aeration, water-holding capacity and nutrient status.
The cover crop should be plowed under several weeks prior to spring planting
time to allow the vegetation a chance to break down a bit. For plants
that have a large volume of top growth that tends to get tangled in the
tiller tines, mow the tops first, then till under.
8-19-04
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