Got a bare patch of garden space where you want to protect or even enhance the soil? Cover crops and green manures are one way to do this.

Cover crops are plants that are grown to protect soil from erosion and protect existing nutrients in the soil from leaching during rains and snow melt. They may or may not be incorporated into the soil later. Green manures are incorporated into the soil while they are still green, or shortly after flowering, in order to improve the soil. Cover crops and green manure crops can overlap in their uses.

Now, in spring, for example, you might sow a mix of field peas and oats. This is a quick-growing mix, with the upright-growing oats supporting the peas, like a living trellis. You can even harvest some of the pea shoots to enjoy in salads, steamed or stir-fried; and make a tea with some of the oat straw to nourish your nervous system. Cut the oat-pea crop in June or July (with a scythe, for instance, or mow it), turn it under or use it as a mulch.

Both peas and oats will add organic matter to the soil, and peas should add some nitrogen (especially if you inoculated them with nitrogen-fixing bacteria and did not remove much of the plant for edible pea shoots). Once the cover crop is turned under or pulled aside for use as mulch, plant a vegetable crop in the cleared space — such as tomatoes in early June or fall broccoli in July.

If you have a particularly weedy spot that you’re trying to reclaim for gardening, you might plant peas and oats in April, cut and incorporate them into the soil in June, and follow up with one or two plantings of buckwheat, which can be grown after the last spring frost. Cut the buckwheat when it starts to flower (about six weeks after sowing), turn it under, and plant another crop of buckwheat. Cut that crop after about six weeks, turn it under and follow it with a mix of oats sown in September. The oats will be killed over winter, but will have put on enough growth to make a nice mulch to protect the soil. Pull back that mulch or till it under in spring, and you’re ready to plant. By growing and cultivating this succession of cover crops, you should have reduced much of the weed problem.

If you have a bare spot in the garden in summer but don’t necessarily have a weed problem, buckwheat is still a good choice to fill that spot temporarily, rather than leaving it bare and subject to erosion or nutrient leaching in heavy rains.

A combination of hairy vetch and winter rye, sown in late summer, is a favorite for preventing erosion and adding organic matter and nitrogen (from vetch) to the soil. As with peas and oats, the winter rye provides support for the legume — vetch, in this case. Both vetch and rye will stay alive over winter and will grow again in spring, except in northern Maine, where vetch is not reliably hardy.

This cover crop combination is a favorite of organic farmers but can put on so much growth that it is difficult for gardeners to cut and incorporate it into the soil. If you have a quality scythe, you can cut the crop in the spring and use it for a summer mulch. Some growers just cut strips of the rye-vetch mixture and transplant crops such as tomatoes into the strip, leaving alternating strips of rye and vetch to grow until the vetch flowers, then cutting that growth to use as mulch for the tomatoes. This works well for growing potatoes, too, especially since mulch cuts down on potato beetle problems significantly.

Some growers sow hairy vetch (without rye) between rows of winter squash plants in early July. The vetch is shaded by the squash over the summer; once the squash plants die back in the fall, the vetch takes off and provides a good winter cover.

Likewise, hairy vetch and winter rye can be sown between rows of corn in late summer.

Oats, sown alone in September, are a good choice for gardeners who don’t want a large amount of organic material to deal with in the spring. They’ll be killed by a hard frost, but the dead stalks will mulch and protect the ground over winter. They’re easy to pull aside in the spring for planting early vegetable crops, such as spinach or lettuce.

The Fedco catalog has good information about cover crops, as does the video “Farmers and Their Innovative Cover Cropping Techniques” ($15 for the DVD from uvm.edu/vtvegandberry/Videos/videoorderform.html) and the online publication, “Overview of Cover Crops and Green Manures” (http://attra.ncat.org/attra-pub/covercrop.html).