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Cover Crop Basics

How to Grow a Cover Crop

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Buckwheat growing.
Photo © Flickr user TANAKA Juuyoh

What is a cover crop? Cover crops are also called "green manure" and sometimes, "living mulch." They are plants that are grown to suppress weeds, help build and improve soil, and control diseases and pests.

Step 1: Choose Your Cover Crop

First you must decide which cover crop is right for your needs. Choices vary depending on the season, the growing conditions, and what you would like to achieve with your soil. Some crops are better than others for putting organic matter into the soil, others fix nitrogen, adding fertility to the soil, and still others are best at smothering weeds.

A winter cover crop is planted in fall or late fall to provide ground cover over the winter months. If a legume is chosen, it will also fix nitrogen. In northern climates, a hardy cover crop that can withstand cold winters is often chosen. Hairy vetch and rye are two common northern winter cover crop choices. In southern climates, there are many more choices as more plants can survive the temperate winter.

A summer cover crop is often called a "green manure." Summer cover crops can fill a niche in crop rotations, improve conditions in soil too difficult to grow in,or to add organic matter.

A living mulch is used for weed suppression and interplanted with another crop. For example, hairy vetch is often interplanted with corn to provide protection against weeds. Ryegrass can be broadcast into vegetables to prevent weed invasion.

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    Step 2: Plant Your Cover Crop

    After you've chosen the location of your cover crop and which type of cover crop meets your needs, it's time to plant.

    Specific tools used will vary depending on the size of your cover crop bed. A tractor will suit a large area, but urban farmers or those with a smaller area to cover can use hand tools.

    The basic steps are the same no matter the technique:

    • Rake the area smooth.
    • Remove any debris or large stones.
    • Broadcast seed according to the seeding rate for your particular cover crop choice.
    • Lightly rake in the seed.
    • Water with a fine mist.

    Step 3: Care for Your Cover Crop

    The beauty of cover crops is that they don't need special care. After all, their purpose is to reduce weeds, increase organic matter, and cover the ground well. But you should mow crops periodically to keep them from getting out of hand, and water them during times of drought.

    Step 4: Kill Your Cover Crop

    Cover crops must be killed before they set seed: at flowering or, for grains, as soon as the seedheads emerge.

    Usually, cover crops are mowed down. Then, after several days of drying, till the cover crop into the ground.

    After tilling, wait two to three weeks before planting the cover crop site with vegetables or flowers. This allows the green material to fully decompose, a process that binds nitrogen. And some cover crops, such as rye, actually prevent seeds from germinating. Great for weed suppression, but not so great when you want to grow something. After several weeks, these germination-preventing compounds are no longer present in the soil.

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