Know how to select the right cover crop species for you

The cover crops you pick go a long way in determining your success so choose the one that best fits your operation.

 

What do we know about cover crops?

Implementing cover crops is a great way to improve the soil health on your farm, but knowing which species to consider can be tricky. Understanding the traits of each species will help guide your purchase decisions.

There are three main categories of cover crops that give general information about the expected traits of those cover crops including grasses, brassicas, and legumes. Typically, legumes and brassicas will have a lower C:N ratio compared to grasses, but grasses tend to be easier to establish and hardier. Now that we’ve refamiliarized ourselves with the importance of cover crops, let’s dive into some of the species that have helpful traits for your cover crop management:

• Grasses. All grass species of cover crops are not created equal. There are cereal grains and there are forages, both of which influence how and when the crop matures. Grasses are competitive, generally easy to seed, and the most cost-effective.
  • Examples of grain species: cereal wheat, rye, barley, oats, and triticale.
  • Examples of other grass species: annual rye grass and sorghum-sudan grass.
• Broadleaves (Brassicas). Brassicas are the most common cover crop in the broadleaf category. They are fairly cold tolerant, can increase biodiversity, and have a low C:N ratio with a high seed/lb density.
  • Examples: turnips, radishes, kale, mustard, Dwarf Essex rapeseed, camelina.
• Broadleaves (Legumes). Legumes are typically separated from the broadleaves category because of their unique ability to fix nitrogen. It takes until the cover is flowering to establish enough biomass to get a nitrogen credit with this species. Many broadleaves have larger seeds and need to be planted deeper.
  • Examples: peas, clovers, vetches, sunhemp, etc.
• Other covers. This would include cover crops such as buckwheat and pennycress. There are also new cover crop species being developed with unique traits as this space evolves. 

So, where should you start? Keep it as simple as possible as you begin considering cover crop species. This might mean keeping your acres to a manageable number and picking out fields that are more forgiving when it comes to planting covers. Below are some key questions you should dig into before you begin purchasing seed:

What is your goal?

How you approach your cover crop management strategy will depend on the goal that you are trying to achieve. 

• Are you looking to reduce your soil erosion? You’ll most likely want fast-growing cover crops with extensive root systems. This goal will direct you towards species like grasses and brassicas.
• Do you have issues with compaction? You’ll want to find cover crops with longer tap roots or deep fibrous roots that can provide pores for water and air to move through. 
• Do you want to reduce your nitrogen fertilizer usage? Establishing a legume cover crop, which is able to fix nitrogen, will be critical.

If you’re looking for inspiration, check out some common soil health goals that we’ve compiled here. 

What are the plant growth characteristics? 

Understanding growth characteristics will give you most of the information you need to know, such as winter hardiness, C:N ratio, biomass growth, nitrogen fixation, and potential for disease carry-over etc. Understanding some of these basic concepts can help guide you through the rest of the following questions. I also recommend checking out Sustainable Agriculture Research and Education - Managing Cover Crops Profitably

What is the ideal application method and timing?

If you have an overwintering cover crop you will need to get it in the ground before the soil is too cold. Generally, cereal grains as cover crops are the most cold-hardy and will germinate and grow best. A second option would be to consider some of the leafy brassicas like kale, rapeseed, and turnips.

If you need to get cover crop seed on earlier for better growth, there are three main options for you: apply seed after an early harvested crop like wheat, shorten your maturity for your corn or beans, or, lastly, aerially apply your cover crop.

Check out some of our additional articles about application timing:

• Factors you should consider when planting a corn cover crop
• Looking to get more out of your cover crop? Try interseeding.
• Farming methods to consider when implementing regenerative ag programs

What are the watch-outs for the species you're considering?

Not all cover crop information is straight forward and different species have different management strategies. Sometimes cover crop species have certain traits to watch out for. An example of this type of watch-out is the termination of annual ryegrass. Growers have had great success with an annual ryegrass cover crop but it does have very specific termination considerations. This is due to its growth being closely related to air temperature. If temperature is below 50 degrees Fahrenheit, herbicide takeup is extremely limited. Another example would be hairy vetch as a legume cover crop. It has the potential to create large amounts of biomass and nitrogen but can also have a “hard seed” which is seed that doesn’t germinate in the first year. This tends to cause it to come back and surprise you in unexpected spots. Grazing your cover crop will mean you need to understand the nutritional value of the feed and be aware of any issues with toxins. 

Do you have a termination plan in place?

Cover crop termination can dictate the health and success of your main cash crop. Managing it at the right time for what your goals are and having a good backup plan can go a long way. Dive deeper with our termination article. 

When should you buy your seed and from who?

Who you purchase your seed from is not dictated by the Cargill RegenConnect® program, but you should work with someone who can help you answer some of the questions listed above. Do not wait until the last minute to purchase your seed as this puts you at risk for price hikes and lack of availability.  

Ultimately, asking yourself and your support network these questions will help you decide what species makes the most sense for your operation. If you are unsure of who to work with and what question you should ask, feel free to reach out to your Cargill agronomist, we are happy to help you work through these decisions. 

 

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Additional Resources:

Midwest Cover Crops Council - Cover Crop Decision Tool

Northeast Cover Crops Council - Cover Crop Decision Support Tools