The Midwest Cover Crops Council, the Northeast Cover Crops Council and the Southern Cover Crops Council have created tools to help producers in their regions decide on the right cover crops based on their goals, soil types, growing season lengths and locations.
USDA-funded Sustainable Agriculture Research and Education program and other experts say that if used correctly, cover crops can provide the following benefits in certain conditions:
- Carbon sequestration: Farmers who use the right cover crops in conjunction with a no-till system can trap an extra 750 to 800 pounds of carbon per acre per year in the soil, says Rattan Lal, a soil scientist at The Ohio State University. Similarly, a study analyzing data from 131 different studies found that cover cropping increased soil carbon by 15.5% near the surface. Lal cautions that the soil must be left unplowed to retain the carbon. Biomass also could be lost through haying and grazing, he says. Carbon sequestration rates depend on temperature, latitude, soil texture and other environmental and management factors.
- Reduced fertilizer costs: Cover crops such as hairy vetch, medium red clover, Austrian winter peas and fibrous-rooted cereal grains can contribute nitrogen to the following cash crops. Reducing nitrogen usage, in turn, can reduce emissions of nitrous oxide from fields, the largest source of greenhouse gas emissions from U.S. agriculture.
- Reduce soil erosion: With enough stalk and leaf growth, many cover crops can help prevent soil loss, particularly in winter months when nothing else will grow in fields.
- Suppress weeds: Cover crops use water and nutrients and block light that is needed by weeds. Cover crops also change the soil surface temperature or possess herbicidal compounds in their roots that can effectively prevent weeds. Cereal rye, barley, oats and mixtures can be effective for keeping weeds at bay, SARE says.
- Improve soil health and nutrient cycling: According to SARE, there are several ways that cover crops can improve soil health. For example, rye can add organic matter to the soil, sorghum sudangrass has deep roots that can help relieve soil compaction, and ryegrass can “stabilize field roads, inter-row areas and borders when soil is wet.”
- Conserve soil moisture: Cover crops can help increase water infiltration and reduce evaporation. Rye, wheat and sorghum-sudangrass hybrids can effectively cover the soil surface, while legumes like medic and Indianhead lentils may conserve more moisture than conventional bare fallow in dryland areas.
- Protect water quality: Cover crops can reduce pollution from sediments, nutrients and chemicals by taking up excess soil nitrogen, reducing erosion and slowing runoff. Authors of the SARE report cite a study conducted on Georgia corn fields that found a rye cover crop “scavenged” between 25% and 100% of residual nitrogen.
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