Dirt, muck, mud — soil is easy to disregard, but it’s invaluable. Soil is home to a quarter of the world’s terrestrial species, just one gram holds 10 billion organisms. And a staggering 95 percent of our food production relies on healthy soil.

Yet that vital resource is limited. Soil forms at a snail’s pace, and more of it is disappearing every year. Since the 1980s, soil erosion has shrunk the area of American farmland by about the size of Ohio. Nearly one-third of soils are degraded globally, threatening food security.

Regenerative agricultural techniques, like cover crops, can counteract these problems. Used to cover soil rather than to be harvested, cover crops provide a variety of benefits — from promoting soil health to attracting pollinators. Yet less than 5 percent of farm fields in the United States are planted with them. Are we missing out on a simple solution to one of our dirtiest problems?

Cover Crops for Soil Health

Cover crops are well-known for benefitting soil health. Along with reduced tillage, these plants increase organic matter in the soil, which boosts its ability to retain moisture.

“We can add as much as half a percent of soil organic matter every year, especially with the large cover crop after wheat, because we have so much sunlight capture that turns into organic matter in the soil,” said Jay Brandt, owner of a regenerative farm growing corn, soybeans and heritage grains in Ohio. He plants a high biomass cover crop during the summer, which means it covers almost all the soil when cut or rolled down.

In addition, cover crops provide impressive erosion control, reducing soil losses up to 100 percent compared to fields without them. But their role in preventing soil loss is less critical under no-till farming since that strategy already reduces erosion, said Kenneth Staver, an associate research scientist at the University of Maryland’s Wye Research and Education Center.

That’s just scratching the surface. Cover crops also mitigate declining soil fertility, an issue that costs U.S. farmers half a billion dollars per year.

For example, cover crops like legumes add nitrogen to the soil, a vital element for plants. They can also make other nutrients like calcium, potassium and phosphorus more available for crops, Brandt said. Due to this effect, he’s reduced his fertilizer use by 50 to 80 percent annually.

While saving money, this also spares the copious amounts of energy needed for fertilizer production and transportation. In turn, this lowers the greenhouse gases emitted by making fertilizer, which are a sizable portion of agriculture’s total emissions.

Cover crops also come in handy with another agricultural problem: pests. They suppress weeds in some locations by competing with them for survival and suppressing sunlight. Cereal rye cover crops inhibit the germination of weeds by giving off compounds through their roots, Brandt said.

As a plus, Brandt also saw a reduction in crop diseases on his farm.

“We have no need to apply fungicide because we get no benefit,” Brandt said. “And we don't experience some of the other soil-borne diseases because of the mulch layer that's left from the cover crop. We don't get any soil splash, which transfers those fungal diseases from the soil to the [crop] leaf.”

By attracting natural enemies, cover crops also limit harmful insects. Altogether, this means the plants can reduce pesticide use, saving farmers money and preventing negative impacts on their health. Fewer pesticide applications also benefit the soil since the chemicals harm the organisms keeping it healthy.

Additional Benefits of Cover Crops

Cover crops shine in other areas too. For instance, they provide food and habitat for beneficial insects and wildlife, and fodder and straw for livestock. They’re also important for environmental health.

“The primary reason we have historically pushed cover crops here in Maryland is because of the nutrient over-enrichment in the Chesapeake Bay,” Staver said. “So we try to reduce the nitrogen loss from crop production.”

Many Maryland farmers plant winter cereal cover crops in fall. These plants uptake nitrate, a form of nitrogen that moves with water, out of the soil. This reduces leaching into waterways in winter and prevents pollution from reaching the Chesapeake Bay. Along with phosphorus, excess nitrogen pollutes the water, damages habitat, fuels algal blooms and triggers fish kills in America’s largest estuary.

Cover crops are gaining attention for their potential to fight climate change, too. By capturing carbon through photosynthesis and adding some of that to the soil, they could be a tool to mitigate global warming.

Despite their plentiful benefits, cover crops have drawbacks — like the time and money needed to plant and terminate them.

“It is more management because you're adding a little bit of complexity in your system,” Brandt said.

Cover crops can also reduce yields for some crops, albeit by a moderate amount. For example, since certain cover crops remove nitrogen from the soil, they can harm crops like corn without proper management, Staver said. And cover crops can compete with cash crops for water, especially in drier areas.

The choice of cover crop can prevent some of these problems, and allowing sufficient time between terminating cover crops and planting cash crops helps.

The Push for Cover Crop Adoption

Given cover crops’ potential, there’s a push for cover crops from the Biden administration. The United States Department of Agriculture’s Natural Resources Conservation Service launched a set of initiatives to promote cover crops and soil health, including its Conservation Stewardship Program and the Environmental Quality Incentives Program.

Individual states also have initiative programs for cover crops, particularly in the eastern half of the U.S. Maryland has a state-wide program for cover crops funded by residents, along with a soil health fund promoting sustainable practices like cover crops.

“We give farmers payments to plant cover crops,” Staver said. “By themselves, it's not in a farmer's financial interest to plant cover crops for the most part … And it's why Maryland is the number one state in the country in terms of the percent of our land that gets cover crops.”

It seems these efforts are paying off. The area of U.S. farmland with cover crops increased by 17 percent from 2017 to 2022.

Healthy Soil for the Future

Cover crops have been used for centuries, but we’re still rediscovering their benefits. With one-third of the world’s farms already using environmentally friendly practices, cover crops are a great addition. Besides their long-term benefits for soil health, they can also cut down on agriculture’s emissions, which are over 10 percent of America’s total emissions.

Soil is one of our most valuable resources. It is critical for food production, filters water, prevents flooding, and is our second-largest store of carbon, after the ocean. Planting cover crops is an easy way to sustain that life-giving dirt.

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