Guide to planting cover crops in Minnesota
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When crops are harvested early, producers have an opportunity to consider planting a cover crop, which can be an excellent addition to crop rotations. Benefits include:
Improved water infiltration.
Reduced soil erosion.
Ability to scavenge excess nitrogen and phosphorus.
Provide additional nutrients.
Utilize excess moisture.
Extended grazing season.
Improved soil health.
Food source for pollinators.
Trying one to two species of cover crops and planting them in early-harvested fields will set up the fields for long-term success. Particularly good years to try cover crops are when soil moisture is ideal for germination.
How to get started
The best approach is to keep it simple.
In fields where wheat was just harvested, one option is to allow the wheat to reseed itself without tilling the land. As long as the soil is covered, this would be considered a cover crop.
However, this may cause issues by creating a wet mat of plant residue on the soil surface in the spring. A better option may be to seed cereal rye into the volunteer wheat, so the rye can use the extra moisture in the spring.
Choosing a cover crop
When starting out, using one or two cover crops is an excellent way to get acquainted with their benefits.
When commodity prices are lower, expensive seed mixes aren’t necessary. The most popular choices are forage radish and cereal rye. Before choosing a cover crop, consider the following questions:
Do’s and don’ts
If sugarbeets have just been harvested, you don’t need brassicas in the cover crop mix (i.e., turnip, canola or radish) because there isn’t enough time for adequate growth to justify the cost. Instead, plant a small grain or grass.
However, if you’re planning to plant wheat next spring, don’t use cereal rye as a cover crop. Instead, choose oats, so that any volunteers that come up in the wheat crop can be killed.
If cover crops are planted after Aug. 15, use cool season crops. These may include forage pea, barley, wheat and triticale. In Minnesota’s northern climate, there may not be enough time to truly benefit from a legume's nitrogen credit when they’re planted late summer.
When planting cover crops, also consider herbicide carryover and rotation restrictions. Look at herbicide product labels or call your agronomist for exact restrictions. Remember, the label is the final authority.
A cover crop that overwinters will provide the best soil protection through the winter and into spring. However, you’ll generally need to terminate it before planting the cash crop in the spring.
A combination of cereal rye, which will overwinter, and radish (which will winter kill) is an example of a mix where the rye provides added soil protection, while the radish residue decomposes quickly.
For a quick-growing grain that doesn’t overwinter, seeding barley in the fall is a good option. While typically winter-killed, turnips can overwinter, as they did in parts of Minnesota and North Dakota in the 2015-2016 winter. However, if radish is in the mix and there aren’t grazing cattle, then another cover crop that serves the same purpose as radish isn’t needed.
There are several choices for seeding cover crops. They include:
A no-till drill.
Slurry-seeded (keep manure agitated for a more even spreading of seed).
Broadcast and lightly incorporated for seed-to-soil contact.
If the soil is moist, all of these seeding methods are viable options. If the soil is dry, leaving the seeds on the soil surface will reduce germination and coverage during the fall.
Oats are better equipped to be seeded a little deeper if soil moisture is a concern. Peas also need to be seeded deeper than most other cover crops.
In general, when broadcasting or flying on cover crops, smaller seeds are a better choice. These include radish, turnip, flax, dwarf essex rapeseed, cereal rye and barley. Larger-seeded crops, like peas, sunflower, etc., should not be broadcast or flown on.
Consult with your seed dealers and other sources to select the right mix and rates for specific field and crop rotation situations. Consider visiting the following:
Reviewed in 2018