Gardening: Want to improve soil health? Try planting cover crops

In order to improve soil heath and organic matter, vegetable gardeners should aim to have actively growing plants in the garden for 10 or eleven months each year. This is desirable because organisms needed for healthy soil live primarily around the roots of actively growing plants, and these organisms are an important source of organic matter in the soil.  

Although we often focus only on soil fertility as a measure of productivity, organic matter is just as critical. Increasing organic matter in the soil by just 1% can lead to a 12% increase in crop yields.

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We can grow cool-season vegetable crops in the early spring and fall, and our favorite warm-season vegetable crops throughout the summer, but that still leaves the potential for bare soil without actively growing plants for several months of the year. Cover crops can fill the void of actively growing plants when we do not have vegetable crops in the ground.

What are cover crops?

Cover crops are plants grown in a vegetable garden to improve the soil’s physical structure, fertility and health. Cover crops also help prevent soil erosion, suppress weeds, regulate soil temperatures and provide habitat for beneficial insects. Just like vegetable crops, there are cool-season cover crops and warm-season cover crops.  

Cool-season cover crops planted in late summer and fall will grow during fall and winter and can be especially useful with improving soil structure and increasing soil organic matter. 

Cover crops are sometimes called green manures as they add nutrients and organic matter when they are tilled into the soil and decompose. 

Choosing a cover crop

There are many different plants that can be grown as cover crops, including grasses, grains and legumes. Gardeners can also choose to plant cover crop mixes that are blends of two or more different crops. 

• Legumes such as clover and field peas will add nitrogen to the soil. These cool-season crops can be planted in either spring or late summer or early fall. Oats can be an excellent cover crop that typically dies over the winter, making it a good choice for garden areas that will be worked early in the spring for planting cool-season vegetable crops such as peas and greens.

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• Oilseed or tillage radish is a cover crop with a deep taproot that is useful in breaking up heavy or hardpan soils to allow for greater water infiltration and air movement in the soil.

• Winter rye is a grain that is an excellent cover crop as it grows quickly, adapts to different soil conditions, and can be planted later into the fall.

• Buckwheat is a warm-season cover crop that can be planted in spring and summer as well as after cool-season crops and in areas of the garden that will be left fallow.

You can find a chart showing the different plants used as cover crops and their characteristics as well as seeding rates at: go.osu.edu/covercropsgarden.

Managing cover crops in the spring

To prevent cover crops from self-seeding and utilize them to their full potential, cut cover crops just before they start to flower.  

Cover crops may be cut by hand, with a trimmer or a lawn mower. Plants should then be incorporated into the soil with a tiller, pitchfork or broad fork so that they will decompose. Allow a few weeks for the cover crop to decompose before planting.

Mike Hogan is an associate professor at Ohio State University and an educator at the OSU Extension.

hogan.1@osu.edu