Cover crops are not a new or novel concept, but their traction has grown in recent years across the prairies. They’re not cash crops — they simply cover the soil to provide a number of agronomic benefits to the land. A cover crop’s purpose is to protect bare, erosion-prone land and to better the soil health. A cover crop is typically seeded after harvest or in the spring to protect the soil.
Before venturing down the path of cover crops, the first question to ask is why do it? What goal do you aim to achieve with seeding a cover crop?
The timing, species, seeding, evaluation, and eventual termination of your cover crop will depend on your overall goal. You first need to establish what your immediate, short-term, or long-term goal of the crop is. Most cover crop goals are linked directly to soil health:
- minimizing soil erosion
- managing soil moisture
- increasing organic matter
- improving soil structure
Other goals for cover crops may be focused on livestock, such as providing a high-quality forage for grazing.
Plant Species to Include
Once you’ve set your goals, you can establish your seeding window and choose which crop you’ll be seeding. Plant characteristics and overall crop diversity need to be coordinated to help you reach your cover cropping goals. A mixture of species is recommended to ensure establishment and ground cover can be gained early on. Benefits of each species are:
- grasses: readily available seed, provide rapid ground cover, and are nitrogen scavengers
- legumes: ability to fix nitrogen
- other broadleaves: some species have a taproot (which are drought tolerant), and some are nitrogen scavengers
- warm season plants: need warm temperatures and full growing season
- cool season plants: prefer cooler temperatures and can be seeded later in the summer
The 2020 Prairie Cover Crop Survey identified clover, oat, pea, hairy vetch, radish, and ryegrass as the top species used in cover crops across the Prairie region.
“Canola growers should be cautious of using brassica species within their cover crops mix, as they act as a green bridge for brassica disease inoculum to build in the soil,” said Justine Cornelsen, Agronomic and Regulatory Services Manager with BrettYoung.
Pathogens that cause blackleg, clubroot, and verticillium stripe in canola also affect other brassica species like radishes and turnips. Cornelsen added that sclerotinia stem rot is another disease to be cautious of as it affects all broadleaf plant species.
Cover crops can provide some additional challenges when it comes to seeding, weed management, and crop termination. Some of the first few challenges are the variation of seed size, how best to get all the seed into the ground, and at which rates to do so. Seeding rates for cover crops are not a well researched topic so the recommendation of rates can be vague, but they’re typically reduced from monocrop recommendations and divided by the number of species within the mix. Seed size needs to be taken into consideration here as larger seed will take up more overall weight in the mix to achieve the same target plant population as other, smaller species. Cost and seed availability also influence the seeding rate and seed mix used in the end. The environment and predicted forecast should also influence which species you use and your seeding rate.
The general rule of thumb is to terminate your cover crop two to four weeks prior to when you plan to seed your cash crop.
The survey mentioned above found the top methods of crop termination to be winterkill and grazing. Another method you can use is a herbicide application, but plant mix will influence which herbicide product you use and the timing of application for the best efficacy.
The benefits of cover crops are not easily seen, and it can be tough to measure a return on investment. Because of that, it’s important to come back to your original goals and assess if the cover crop achieved them. You can see many of the benefits in future crops through improved soil health, nutrient balance, and weed suppression.
Legumes, grasses, premixed blends, and custom blends can all be sourced from BrettYoung to help achieve your cover crop goals. Talk to your local BrettYoung Regional Account Manager (RAM) for more information.