Cover Crops
Cover Crops build soil health and take up nitrogen left over at the end of the growing season. They also add diversity to your crop rotation, keep your soil covered over the winter and help to maintain living roots in the soil. Cover crop management strategies should be tailored for your farm to support your goals and objectives.
What should I expect?
- Performance that lines up with your goals and desired benefits- Individual cover crop species and mixes offer a variety of benefits for your operation, from improved nutrient cycling to weed suppression.
- Improved soil health- By increasing diversity in your cropping system, keeping the soil covered and maintaining living roots in the soil, you’re helping to feed the soil ecosystem through the winter. Cover crops also help to increase organic matter, which helps to retain water and nutrients in the soil profile.
- Managing your cover crops like your cash crops- Your soil is a valuable asset. Investing time to plan and implement a cover crop management strategy will pay dividends to the economic and environmental sustainability of your farm.
What are the benefits?
The following table shows how different cover crop species offer a variety of benefits depending on the needs of each of your fields. Cover crop management is also an important part of the equation. For example, planting early encourages increased cover crop growth and nitrogen uptake in the fall, while later termination supports higher biomass and weed suppression.
Mixed species cover crops can increase management complexity, but also offer multiple benefits compared to the use of a single species. Careful management helps to maximize benefits and ensure that cover crops don’t interfere with early growth and development of the following crop.
Cover Crops in Action
Cover crop management strategies involve a broad range of components, including species or mixes, seeding rates, and timing and methods of establishment and termination. Cover crop research in the Mid-Atlantic region has been conducted for more than three decades, and the body of research on the impacts of these different management strategies continues to grow. Research highlights include:
- Queenstown, MD- Cereal Rye reduced nitrate loss to groundwater by 80% when planted after no-till corn harvest (Staver & Brinsfield, 1998).
- Salisbury, MD- Hairy vetch (a legume) fixed about 1.8 lb N/acre/day from April 10 to May 5, resulting in an additional 60 lb N/A in aboveground biomass that becomes available to the next crop. (Clark, et. Al., 1995)
- Beltsville, MD- A mixed species cover crop took up an intermediate amount of nitrogen compared to a pure stand of rye or hairy vetch. Similarly, the mixed-species stand released nitrogen back into the soil more slowly than hairy vetch but faster than a stand of pure rye. (Poffenbarger, Mirsky, et. Al., 2015)
- Two sites in MD- Forage Radish can take up 100 – 150 lb of N if planted in August or early September. Radish usually winter-kills and decomposes rapidly, which may reduce the need for fertilizer, but also makes N vulnerable to leaching early in the season. (Dean & Weil, 2009) Combining radish with another winter-hardy species will ensure that a cover crop is present into the spring.
Just getting started with cover crops?
This quick quiz can point you in the right direction to find a cover crop species or mix that works for your operation:
What is your main goal for planting cover crops?
When is your planting window?
Do you prefer to plant a single species or a mixed-species cover crop?
Is it desirable for your cover crop to winter kill?
Cover Crop Finder
Brassica
Cover crops from the brassica family include radishes (sometimes called tillage radish or forage radish), as well as kale, mustard, rapeseed/canola and even turnips. Radishes are the most well-known in this group, and are ideal for nutrient uptake, reducing compaction and weed and pest suppression. Some species need to planted planted earlier in the season (by mid-September), but radishes also terminate in low winter temperatures, making them an option that's (usually) easier to manage in the Spring.
SARE is a great resource for more detail about the benefits and management considerations of different cover crop species. Here's a link to their web page on Brassicas and Mustards: https://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition/Text-Version/Nonlegume-Cover-Crops/Brassicas-and-Mustards
Legume
Legume cover crops include species of clover, vetch and peas. These cover crops fix nitrogen from the atmosphere and convert it into a form that's available to the following crop. They also help to prevent erosion and- if they're planted early enough in the fall or terminated late enough in the spring- can produce enough biomass to suppress weeds. Legumes need to be planted earlier in the season than most grass species, but can be planted later than radishes.
SARE is a great resource for more detail about the benefits and management considerations of different cover crop species. Here's a link to their web page on Legume Cover Crops: https://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition/Text-Version/Legume-Cover-Crops
Grass
Grass and cereal species of cover crops include rye, barley, oats, and annual ryegrass. These species of cover crops are good at taking up nitrogen left over at the end of the growing season, preventing erosion and producing biomass that can help with weed suppression and building soil organic matter. Many species, especially rye, can be planted later into the fall, making them a good option for crops that are harvested late in the season. Oats are an option if you're looking for a species that will likely terminate in the winter.
SARE is a great resource for more detail about the benefits and management considerations of different cover crop species. Here's a link to their web page on Non-Legume Cover Crops: https://www.sare.org/Learning-Center/Books/Managing-Cover-Crops-Profitably-3rd-Edition/Text-Version/Nonlegume-Cover-Crops
Grass-Legume Mix
A mixed-species cover crop may require a higher level of management to ensure successful establishment and termination, but can also offer benefits of multiple cover crop species at once.
Grass and cereal species of cover crops include rye, barley, oats, and annual ryegrass. These species of cover crops are good at taking up nitrogen left over at the end of the growing season, preventing erosion and producing biomass that can help with weed suppression and building soil organic matter. Many species, especially rye, can be planted later into the fall, making them a good option for crops that are harvested late in the season. Oats are an option if you're looking for a species that will likely terminate in the winter.
Legume cover crops include species of clover, vetch and peas. These cover crops fix nitrogen from the atmosphere and convert it into a form that's available to the following crop. They also help to prevent erosion and- if they're planted early enough in the fall or terminated late enough in the spring- can produce enough biomass to suppress weeds. Legumes need to be planted earlier in the season than most grass species, but can be planted later than radishes.
Mixing the two kinds of cover crops together can result in a cover crop stand that takes up nitrogen in the fall and releases it to the next crop in the spring. This mix can also produce significant biomass and help to prevent erosion.
SARE is a great resource for more detail about the benefits and management considerations of different cover crop species. Here's a link to their article, "Making the most of cover crop mixtures": https://www.sare.org/Learning-Center/SARE-Project-Products/Northeast-SARE-Project-Products/Making-the-Most-of-Cover-Crop-Mixtures
Grass-Brassica-Legume Mix
A mixed-species cover crop may require a higher level of management to ensure successful establishment and termination, but can also offer benefits of multiple cover crop species at once.
Grass and cereal species of cover crops include rye, barley, oats, and annual ryegrass. These species of cover crops are good at taking up nitrogen left over at the end of the growing season, preventing erosion and producing biomass that can help with weed suppression and building soil organic matter. Many species, especially rye, can be planted later into the fall, making them a good option for crops that are harvested late in the season. Oats are an option if you're looking for a species that will likely terminate in the winter.
Cover crops from the brassica family include radishes (sometimes called tillage radish or forage radish), as well as kale, mustard, rapeseed/canola and even turnips. Radishes are the most well-known in this group, and are ideal for nutrient uptake, reducing compaction and weed and pest suppression. Some species need to planted planted earlier in the season (by mid-September), but radishes also terminate in low winter temperatures, making them an option that's (usually) easier to manage in the Spring.
Legume cover crops include species of clover, vetch and peas. These cover crops fix nitrogen from the atmosphere and convert it into a form that's available to the following crop. They also help to prevent erosion and- if they're planted early enough in the fall or terminated late enough in the spring- can produce enough biomass to suppress weeds. Legumes need to be planted earlier in the season than most grass species, but can be planted later than radishes.
Mixing the two kinds of cover crops together can result in a cover crop stand that takes up nitrogen in the fall and releases it to the next crop in the spring. This mix can also produce significant biomass and help to prevent erosion.
SARE is a great resource for more detail about the benefits and management considerations of different cover crop species. Here's a link to their article, "Making the most of cover crop mixtures": https://www.sare.org/Learning-Center/SARE-Project-Products/Northeast-SARE-Project-Products/Making-the-Most-of-Cover-Crop-Mixtures
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Resources
- Book (Free online): Managing Cover Crops Profitably (SARE)
- Website: Cover Crops and Soil Health (USDA NRCS)
- Factsheet: Cover Crops (Delaware-Maryland 4R Alliance)
- Search for additional resources here:
Related Practices
Nitrogen Modeling, Split Nitrogen Application