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Notes From the Garden

Gardening

Cover Crops

Oct 25, 2001 -- Cover crops are plantings of legumes and grasses that cover soil surfaces, especially in unplanted garden beds. Cover crops offer many benefits to Northwest gardeners. They can be used to reintroduce important nutrients like nitrogen to the soil, to prevent erosion, to inhibit weed growth, to loosen compacted soil and to recycle nutrients from the layers beneath the topsoil. Low-growing cover crops can be undersown alongside existing winter vegetables. Other cover crops should be planted after the harvest is finished and the garden debris has been removed.

Soil testing resources:

U. Mass Soil Test Lab
West Experiment Station
N. Pleasant St.
University of Massachusetts
Amherst, MA 01003
Write for directions on how to do a soil test. No phone calls, please.

A&L Western Agricultural Labs
10220 S.W. Nimbus Ave., Bldg. K-9
Portland, OR 97223
(503) 986-9225

Woods End Research
Box 297
Mount Vernon, ME 04352
(207) 293-2457
info@woodsend.org

Since legumes require adequate supplies of phosphorus, calcium and sulfur, fall is good time to test garden soil for these substances. Soil testing is available through the mail. Most companies require a cup of soil and will send back the results with information on how to interpret them. For a thorough test, several soil samples from different area of the garden can be sent.

The following is from The Maritime Northwest Garden Guide, produced by Seattle Tilth.

"Growing legume cover crops is one of the most important tools for increasing soil fertility in an organic garden. Legumes (peas, vetches, clovers, beans and others) grow in a symbiotic relationship with soil-dwelling bacteria. The bacteria take gaseous nitrogen from the air in the soil and feed this nitrogen to the legumes; in exchange the plant provides carbohydrates to the bacteria. This is why legume crops are said to "fix" or provide a certain amount of nitrogen when they are turned under for the next crop or used for compost.

Annual Winter Cover Crops

Austrian Field Peas (pisum arvense)
Magnus Field Peas (pisum arvense)
Crimson Clover (trifolium incarnatum)
Bell beans/Fava beans (vicia faba)
Lana vetch (vicia dasycarpa)
Common vetch (vicia sativa)

Non-legume Cover Crops for Building Organic Matter and Nutrient Recycling
Mustard (brassica juncea)
Rape (brassica napus)
Arrugula (eruca sativa)
Corn salad (valerianella locusta)

Cover crops that do not fix nitrogen also have a role to play in the vegetable garden. These crops protect the soil from the impact of excessive rainfall and tap nutrients that have leached out of the root zone of crop plants. The result is a recycling of important nutrients back to the biologically rich top layer of the soil, as well as adding organic matter to the soil by increasing carbon reserves. They can be harvested or turned under in February or March before planting the early spring garden."

Reprinted with permission from "The Maritime Northwest Garden Guide, Planning Calendar for Year-Round Organic Gardening" produced by Seattle Tilth Association, Seattle, 1998. Contact them at (206) 633-0451.

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