Cover Crop Mixtures: Choosing Species for a Mix
Cover crops protect soil, air, and water when incorporated into crop rotations and including a mixture of multiple species can enhance the benefits they provide. Individual crop species often have different functions and growth periods and it is important to optimize the individual attributes that each species provides when included in a mixture.
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- [Instructor] Cover crop mixtures are increasing in popularity across the farming landscape, but it is important to understand specific features that each species of cover crops contributes in order to create a mixture that is most appropriate to meet your farm's goals.
After watching this video, you will have a better understanding about the functions of different cover crop species and some tips on making a cover crop mixture.
The numerous benefits of cover crops are well understood and farmers across the country are observing improvements in air, water, and soil quality on their farms when including cover crops in their rotations.
They're also finding that these benefits positively impact crop yields and their overall bottom line, which likely explains the increase in popularity of cover crops.
With all of these benefits accounted for, it is important to note that certain species of cover crops are more adept at functions than others.
Therefore it is important to identify goals associated with the specific needs on your farm and to use cover crops that are appropriate for meeting these goals.
Similar to most agronomic crops, cover crops typically fall under three general categories, each of which have different features and functions.
Grasses like annual ryegrass require great amounts of biomass and are known for scavenging nitrogen, preventing erosion, and suppressing weeds.
Brassicas and mustards like radish are broadleaves and are known to prevent erosion, but also reduce soil compaction and suppress weeds.
And finally, the legume crops like crimson clover are also broadleaves, but are mainly recognized for their ability to increase soil nitrogen.
Individually, cover crop species can excel at providing separate functions.
However, they also have their own drawbacks when it comes to providing multiple functions.
For example, forage radish suppresses weeds in the fall, and breaks up soil compaction, but because it is a winter-killed species, it can contribute to nitrogen leaching in the spring.
Clover fixes nitrogen but the minimal amount of biomass it produces is not very effective in suppressing weeds.
Cereal rye prevents nitrogen leaching from the soil, but immobilizes N for the following cash crop.
Incorporating different numbers of species into a mixture therefore allows the farmer to maximize multiple benefits that cover crops provide.
More comprehensive information about this topic can be found in the bulletin, making the most of cover crop mixtures.
Here are a few tips for making a mixture.
First, identify the desired cover crop services that you wish to achieve in a certain area on your farm.
These could include things like reducing erosion, or building nitrogen, or suppressing weeds.
Two or three top priorities is a good place to start.
Talk to other nearby farmers too to learn what they use.
Second is very important to know what time of year you need the cover crop to fit into your rotation, and choose species that will be productive in that growth window.
Third, pick a set of cover crops that provide the desired services and fit into the adapted growth period that you identified in steps one and two.
It isn't necessary to go overboard with species in a mix.
It is okay to only have two species if that's what works for your farm.
Typically two to three species is a good starting point, but growers will sometimes plant up to eight to 10 crops in a mix, so do what is best for you.
Fourth, select species that are complementary with each other and work together well in a mix.
And finally identify any drawbacks or missing services and replace species as necessary to amend any missing features.
Many printed online publication are available to help you way through this information and make the right choices, including the making the most of cover crop mixtures bulletin that I mentioned earlier.
Also see Managing Cover Crops Profitably, which is available at the learning center and the USDA SARE website.