Photo courtesy of Greg Roth, Penn State Penn State's cover crop interseeder at work last summer on the Dan King farm in Milheim, Pa.

“Cover crops are amazing crops we don’t grow for putting money in our pocket but for the sake of our soil health,” said Vicki Morrone, an organic field crop specialist with Michigan State University Center for Regional Food Systems, as she kicked off the recent webinar, “Cover Crop Types and Uses on Your Farm.”

Morrone explained that cover crops benefit the soil as they are allowed to grow and break down in it and are subsequently turned into the soil. That improves crop health, as the plants can draw more nutrients and moisture from the soil.

Marrone also said that cover crops can hold onto soil during events such as heavy rain or wind.

“The roots provide food for soil microbes,” Marrone added. “Legumes make nitrogen for later crop use and roots hold onto nitrogen.”

Clover is one example of a nitrogen-fixing cover crop.

“Let’s say you had a drought year,” Marrone said. “All the nitrogen sits in the soil without anything to hold it there. You lose that investment unless you have roots to hold it there. When we turn a cover crop into the soil, it turns nitrogen into the soil.”

Cover crops with deep, thick roots help break up hardpan and crusted soil that could have otherwise impeded water from soaking into the soil.

“Even heavy rains can cause compaction, not just tractors driving over it or walking on it,” Marrone said.

She added that cover crops also provide heavy amounts of organic matter to feed soil microbes. Some of them can even help reduce soil pests. For example, mustards breaking down can act as biofumigants and rye deters weeds from germinating.

“Rye is the perfect beginner if you’ve never grown a cover crop,” she said.

With diverse cropping systems and vegetable operations, it can challenge growers to know what type of cover crop they should use. The seasons for many types of vegetables vary, for example. Their cash crops can also have widely varying nutrient needs.

Marrone said that the cover crop “families” include legumes, grasses and brassicas.

Legumes, such as clovers, peas and vetch, improve soil fertility by adding nitrogen, but are poor weed suppressors. Brassicas, like mustard, reduce compaction, but are also poor weed suppressors. Grasses, such as rye, oats and wheat, suppress weeds well and help conserve soil nutrients but they tie up nitrogen.

Marrone said that farmers need to look at the whole plant, including the root.

“If the roots turn pink when you pinch them, you have healthy nodules,” she said.

Some covers, such as alfalfa, may be cut and fed to their animals, but growers should check with their nutritionist to make sure it’s not too rich for them.

She said that for all cover crops, farmers receive the best benefit if they cut them at about 30% flowers.

“Otherwise, the plant puts too much energy into the flowers from the roots,” she said. “You’ll lose that nitrogen opportunity.”

After mowing and turning over the soil, farmers should wait for 10 days to two weeks before planting.

“That’s very important so the microbes have time to do their job,” Marrone said. “Once it starts breaking down, some of the microbes are available to your plants.”

Deborah Jeanne Sergeant is a freelance writer in central New York. Email her at

Lancaster Farming