What are cover crops?


In the winter, many fields and garden plots lay fallow. Come spring, those spaces are usually filled with weeds. Cover cropping is an easy and sustainable fix — not only to keep weeds at bay, but also to maintain soil health during the off-season. By knowing what are cover crops and how to use them on your land, small farmers and homesteaders alike can reap long-term economic and environmental benefits.

This photo shows buckwheat and recently tilled buckwheat side by side in a field. Buckwheat is often used as a cover crop -- but what is a cover crop, anyway?
Buckwheat and recently tilled buckwheat. Buckwheat is often used as a cover crop. | Photo by Jason Lilley

Cover crops are sown between seasons after you have harvested your crops and your fields are bare and sapped of nutrients from the growing season. 

“Most cash crops — from the time they’re planted to when they’re harvested — might be growing three to four months, maybe five,” said Dean Baas, sustainable agricultural educator at the Michigan State University Cooperative Extension. “That gives you anywhere from six to nine months where you don’t have anything growing. That makes the soil vulnerable to erosion, and there is nothing there to feed the biological activity in the soil.”

Though some cover crops can be harvested and used, they generally are not used as a cash crop.

“Most cover crops aren’t sold,” Baas said. “That would be another cash crop. The biggest reason you would use cover crops is that you want living plants and living roots in the ground as much of the year as possible.”

By adding roots back into the ground, cover crops hold the soil together and outcompete weeds. Some cover crops also return nutrients to the soil through nitrogen-fixing. 

Cover crops come in many varieties that thrive in different areas and provide specific benefits, but they all promote sustainability and soil health in gardens and fields of all sizes.

A bumblebee on hairy vetch, which is often used as a cover crop. | Photo by Jason Lilley

The benefits of cover crops

Christina Curell, cover crop and soil health educator at the Michigan State University Extension, said that farmers have used cover crops used since the 1950s to prevent erosion and strengthen soil.

“Historically, [cover crops were] used predominantly to build up the soil,” Curell explained. “Living roots in the ground produce [a sort of] glue that holds the soil particles together.”

Curell said that today, farmers generally use cover crops to break up the compaction of soil that comes from seasons of use, which helps with their long term health and sustainability.

“We have healthier soils, so we can invest in things other than fertilizers,” Curell said.

Cover crops have other benefits, including moisture retention and weed control.

“That’s a big benefit of cover crops,” Baas said. “Now, you have something growing to compete and choke out weeds. Particularly on these small farms, anything they can do to reduce the need to weed, especially if they do it by hand, [is beneficial].”

Baas said in lieu of pesticides, organic farmers tend to rely on soil tillage for weed control, which can compromise the health and structure of the soil. Cover crops reduce the need to till and can be especially beneficial on a small scale.

“Even all the way down to the home garden, there are a lot of benefits that can be gained from keeping a plant growing year-round,” said Trenton Roberts, assistant professor and soil fertility extension specialist at the University of Arkansas. 

Homesteaders with grazing livestock can also use cover crops to help feed their animals through the winter.

“By mixing in cover crops, that can help with small livestock grazing in seasons when you typically wouldn’t have green forage for them to eat,” Roberts said. “It adds so many different levels of benefits and opportunities, really.”

Etna-Dixmont Elementary School first-graders spread cover crop seeds in the school garden. | Photo by Gabor Degre

Why cover crops are sustainable

Cover cropping is a sustainable farming practice because it builds the long-term resilience of the land.

“If you think about natural systems that are undisturbed, they rarely have problems with productivity or erosion or nutrient loss,” Roberts said. “What we’re trying to do with the cover crop is to get back to nature or mimic nature as much as we can, [which] leads to a more sustainable production system.”

Building the resilience of the soil will also help protect the land from extreme weather events, which are expected to increase in frequency due to climate change.

“We are seeing increasingly extreme weather patterns,” said Jason Lilley, sustainable agricultural professional at the University of Maine Cooperative Extension. “The roots working their way down through the soil and microbes feeding off of the sugars that are leaking off of the roots are acting as glue and helping to build up the crumbly structure of the soil.”

Bare post-harvest potato field in Presque Isle, Maine. Now, farmers are now trying to manage with cover crops and extended crop rotations. | Photo by Anthony Brino

The challenges of cover crops

Like growing any new crop, starting with cover crops comes with a learning curve. Adding cover crops into the planting rotation can be especially challenging in areas with shorter growing seasons.

“The biggest challenge is planting it: how do I plant this, and when do I plant this?,” Curell said. “In northern climates, it really is prohibitive. Most [cover] crops have to be planted in mid-August, so the biggest concern is how to add the plant into the rotation.” 

You also must know when — and how — you are going to kill and remove your cover crop so they do not become weeds. Some cover crops die during the winter, but others require removal.

“If you get distracted with harvesting and that cover crop matures and sets seed, you’ve created a long-term weed problem,” Lilley said. “Whether it’s using some sort of heavy mower or using a tarp and covering it up, you need to have a plan in place [to remove your cover crop].” 

Even though cover crops are not moneymakers, they need to be cared for like your tastiest and most profitable cash crops.

“It’s really important to have good fertility in the soil,” Lilley said. “These are still plants, so if they’re really limping along, the weeds are going to outcompete the cover crops and you’re not going to get any of that benefits.”

Cover crops also require some upfront cost.

“One of the challenges that people see is the added cost of cover crop seed,” Roberts said. “When you consider the benefits over time, it ends up more than paying for any inputs that you might have put into the cover crop.”

It may take some time to see the benefits of cover cropping, though. 

“The economic side of cover crops is a really hard one to figure out,” Baas said. “They increase the yield but it’s going to take you three to five years at least before you see that.”

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