Healthy soil and sustainable growing

["TradingPostPaul" <tradingpost@riseup.net>]

This came up before  but it's worth saving, considering the need for
humus-producing root mass in home and market gardens. This is a Rodale
Institute site. See the charts on the link page.
http://www.newfarm.org/features/0104/no-till/chart.shtml

Choosing the best cover crops for your organic no-till vegetable system
A detailed guide to using 29 species

By Mark Schonbeck and Ron Morse

Posted January 29, 2004: In no-till cover crop systems, the known benefits
of cover crops are maximized by allowing them to grow until shortly before
planting the vegetable or other cash crop, and by managing the cover crop
without tillage. The best cover crops for this purpose have the following
characteristics:

    * They produce a lot of biomass, at least 3 tons above-ground dry
matter per acre.
    * They are readily killed by mowing, rolling or other mechanical means,
forming a mulch or
    * they are reliably winter-killed, leaving a mulch for spring no-till
planting, or
    * they die down naturally in time to plant summer vegetables.
    * Their residues are sufficient to provide effective weed control in
the subsequent vegetable crop.
    * They provide habitat for natural enemies of vegetable crop pests.
    * They have favorable (or at least neutral) effect on levels of
available soil N, P and K.
    * They do not suppress the vegetable through chemical (allelopathic) or
microbial effects.
    * They do not present serious weed, pest, disease or other management
problems.

Often, a combination of a grass and a legume is used, since this enhances
biomass production and therefore mulch thickness, weed suppression and
organic matter inputs. The combination also offers a balanced carbon to
nitrogen (C:N) ratio, which gives a gradual release of plant available N,
in contrast to the N-immobilization (tie-up) by an all-grass cover, or the
rapid N release and potential leaching losses from an all-legume cover. The
higher diversity of a two-species cover crop can also enhance allelopathy
(suppression of weeds by natural chemical substances from the mulch),
diversity of beneficial soil microbes, and nutrient effects. For instance,
legumes tend to enhance availability of phosphorus (P), while grasses,
especially rye, enhance availability of potassium (K).

The most widely-known and extensively researched organic no-till systems
are those based on hardy winter annual cover crops, mostly combinations of
cereal grain rye (or winter rye), hairy vetch, crimson clover and Austrian
winter peas. These crops are planted in early fall, and mowed or rolled
after they flower the following spring, usually in May. Summer vegetables
like squash, cucumber, pepper, tomato, eggplant, okra, sweet corn, beans,
or (in cooler regions) mid-season brassicas, are then transplanted or
direct-seeded no-till into the cover crop mulch.

In recent years, growers and researchers have begun experimenting with a
much wider range of annual cover crop species for no-till vegetables
planted at other seasons. Other cool-season annuals like oats and fava
beans can be planted in early spring, then killed in mid summer for late
plantings of cucumber, bean or summer squash. Summer annual (frost-tender)
cover crops like millets, cowpeas or soybeans can be planted after the
spring frost date, then knocked down at the end of summer to plant fall
brassicas or other fall crops. Finally, cover crops that are not
winter-hardy in a given location can be planted in mid to late summer and
allowed to winterkill, forming a mulch for no-till spring vegetables.

One of the basic tenets of sustainable agriculture is that greater
diversity yields greater agro-ecosystem stability, more beneficial
organisms, fewer pests and diseases, more sustained crop yields, and more
opportunities for farmer innovation. We feel that this is true also of
cover crops, and one of the objectives of ongoing research is to develop a
larger cover crop “toolbox” from which growers can select cover crops
most suited to their regions and production systems. The following table
gives some basic information on a number of cover crops, some
tried-and-true, and some less-known experimental species. The table is
organized into legumes and non-legumes, listed in order of cold-hardiness.
The table is intended not as a cover crop prescription for organic no-till
vegetables, but as an information resource for farmers and other
experimenters to use in selecting cover crop combinations for their
specific vegetable crop rotations and cropping systems.

Cover Crop Information Sources:

The information in the table is based on the written references listed
below and on the first-hand experience with cover crops of the three
researchers at the end of this list.

Managing Cover Crops Profitably, 2nd Edition, Sustainable Agricultural
Network, Handbook Series No. 3, National Agricultural Library, Beltsville,
MD 20705-2351. 212 pp.

Peaceful Valley Farm Supply, P.O. Box 2209, Grass Valley, CA 95945; tel
888-784-1722; www.growingorganic.com. Products and Seed Catalog.

Overview of Cover Crops and Green Manures, Fundamentals of Sustainable
Agriculture series bulletin, 16 pp. Available through Appropriate
Technology Transfer for Rural Areas web site or by phone order. ATTRA, P.O.
Box 3657, Fayetteville, AR 72702; tel. 1-800-346-9140; www.attra.ncat.org.

Pursuing Conservation Tillage Systems for Organic Crop Production, Organic
Matters series bulletin, 28 pp. Available through ATTRA web site or phone
order.

Summer Cover Crops, by N.G. Creamer and K.R. Baldwin, North Carolina
Cooperative Extension Service, Horticulture Information Leaflet 37, 1999, 8
pp.

Professor Ron Morse, Department of Horticulture, Virginia Tech, Blacksburg,
VA 24061. Tel. 540-231-6724; e-mail morser@vt.edu.

Dr. Keith Baldwin, P.O. Box 21928, North Carolina A&T State University,
Greensboro, NC 27420. Tel. 336-334-7957; e-mail kbaldwin@ncat.edu.

Dr. Mark Schonbeck, 439 Valley Drive NW, Floyd, VA 24091. Tel.
540-745-4130; e-mail mark@abundantdawn.org.

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see also
http://www.newfarm.org/depts/notill/index.shtml

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