To improve next year’s production, sow a cover crop by mid-October.

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TO IMPROVE PRODUCTION in your vegetable garden, sow a fall cover crop, commonly referred to as “green manure.”

There are three types of plants typically used as cover crops: cereal grains (grasses), brassicas (cabbage-family plants) and legumes (pea-family plants).

If you have land that has been left idle, or your soil is heavy clay, cereal grains and brassicas are the most effective.

Planted in fall, oats makes a great cover crop. This grain develops a deep root system that breaks up heavy soils to improve drainage. The vast root system collects and stores nitrogen and minerals from deep within the soil. In spring, the top growth and roots can be turned under to improve soil structure and to release the stored nutrients as fertilizer for the next crop.

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There are a number of cabbage-family cover crops, but if you have heavy, compacted soil, one of the best to sow in fall is ‘Groundhog Daikon Radish’. Daikon means large root, and this strain was bred to form huge tap roots that reach far into the soil to break up hardpan soils and to retrieve nitrogen and other nutrients that have leached deep. This is one cover crop you don’t have to till into the soil. Planted in fall, the radishes grow to up to 20 inches long before dying during the winter, after which they decay to release stored nutrients for spring planting.

For the typical home vegetable gardener, the best cover crops are often legumes such as winter peas, fava beans, clovers or vetches. These members of the pea family germinate and grow quickly enough to form a protective ground cover before winter freezes set in, yet not so fast as to harm late-season or overwintering vegetable crops. Legume cover crops improve the soil by producing thick foliage that prevents pounding winter rains from compacting the soil surface and leaching out nutrients, while at the same time choking out winter and late spring weeds. They improve drainage and soil structure by forming an aggressive root system that breaks up and aerates the soil.

In early spring, a cover crop helps soak up excess moisture, making the soil workable earlier. Most important, cover crops in the pea family host special bacteria that collect nutrients and make them available as fertilizer. Some of the nutrients are used by the legume plants themselves, but the excess is released into the soil and used by neighboring plants. Then, in spring, when the cover crop is worked into the soil, it releases these stored nutrients and provides nitrogen for the next crop.

For this process to occur, however, large populations of nitrogen-fixing bacteria must be present in the soil. Sometimes, there just aren’t enough of these beneficial organisms present to do much good. Luckily, you can buy rhizobacteria at good nurseries and from seed catalogs. There are different types, so make sure you order the right bacteria for the cover crop you’re using.

Moisten the seed slightly with milk or water before sprinkling it with the rhizobacteria to encourage it to stick to the seed. To maximize bacteria survival, sow seed as soon as possible after inoculation, and minimize contact with direct sunlight.

It’s important to plant your legume cover crop between early September and mid-October. Seeds germinate best when soil temperatures are in the 50- to 60-degree range, and sowing the seed by mid-October will allow the plants time to establish deep-enough roots to survive winter cold.

Don’t worry if you still have crops in your garden. Work the seeds into the soil around existing vegetable crops. The cover crop won’t grow tall enough to impede growth on existing plants.

To achieve maximum nitrogen yields, come spring, till in your cover crop when it’s in full bloom, but before it goes to seed. Then save your money to buy a tractor. You’re going to need it to harvest the bumper crops your healthy, fertile soil produces.