Species and Varieties

Many types of plants can be used as cover crops but you can broadly split them into four classes: grasses such as ryegrass and barley; legumes such as alfalfa or clover; brassicas such as radishes or turnips; and non-legume broadleaves such as spinach or flax. Each type has its own distinct benefit.

Use Penn State Extension’s vast resources to help you decide the best species and varieties of cover crops. Find tips on cover crop mixtures, legal considerations in seed use, and extending the grazing season using brassicas.

Common Cover Crop Types

There is a wide variety of cover crops to choose from, but the most commonly used are canola, cereal rye, red clover, and hairy vetch.

Winter canola, a genetically altered rapeseed, is an ideal crop to follow small grains. Benefits include better grassy weed management and extension of the grazing season.

Cereal rye is an important cover crop because of its ability to consume excess nutrients and release them the following spring. It is also an excellent cover crop when rolled and crimped to control weeds.

Red clover is a short-lived perennial that is winter hardy throughout Pennsylvania. When used as a cover crop, it fixes nitrogen to meet the needs of the following crop, protects soil from erosion, improves soil tilth, competes with weeds, and supplies forage needs.

Hairy vetch is an annual leguminous cover crop that’s also winter hardy throughout Pennsylvania. It brings a number of benefits such as fixing large amounts of nitrogen, reducing soil erosion, and improving soil health. It also provides weed control when left as a mulch on the soil surface.

What Mixture of Cover Crops Should I Plant?

You can divide cover crops into four main types: grasses, legumes, brassicas, and broadleaves. Deciding which one to plant depends on the planting goal.

If soil improvement, prevention of erosion, and extra forage are your goals, grasses, broadleaves, and legumes work very well. Grasses and broadleaves are also very effective nitrogen scavengers. Legumes, on the other hand, are excellent nitrogen fixers.

Brassicas are cover crops that work well as weed suppressants. They also prevent erosion, alleviate soil compaction, scavenge nutrients, and suppress soil-borne pests.

To maximize the benefits of planting cover crops, it is common practice to use cover crop mixtures. Researchers at Penn State Extension, as well as producers using cover crops, provide practical advice on choosing cover crop mixtures. You can also get insights from other producers if cover crop mixtures are really cost-effective, based on their experience.

There are many things to consider when planting cover crops. A burndown program is one way of controlling them, although there are special cover crop control considerations. Whether to buy cover crop seed from a dealer or use bin-run seed is another important consideration. Rotations, seed depth and rate, and no-till considerations also affect the final decision of what cover crop to plant. A certified crop adviser can offer advice.

Planting Fall Cover Crops

Timing plays a fundamental role in any cover crop management plan. Cover crops planted in the early fall have much deeper root penetration and produce more biomass than cover crops planted later. A spinner spreader can be a very effective way to seed rye and other cover crops.

Not all cover crops are suitable for fall planting. Use Penn State Extension’s Cover Crop Species to Plant Mid-September guide. The Crops Day series of workshops also introduce up-to-date information for the upcoming season and can be used to get pesticide applicator recertification credits.

Winter Cover Crops

When planting winter cover crops, you must keep in mind cover crop strengths and weaknesses, complementary growth periods and growth forms, nitrogen acquisition strategies, and consider beneficial insects and pollinators, too.

Summer Cover Crops

Summer cover crops include sudangrass, pearl millet, buckwheat, and sun hemp. All can deal with drought and heat while still providing benefits such as suppression of certain nematodes and soil-borne pathogens, nitrogen fixing, suppression of summer annual weeds, and provision of substantial biomass.