Cover cropping with specific cash crops: corn, soybeans, and wheat

Check out the video above as well as this article to learn about cover cropping with different cash crops. For more on cover crops and carbon farming, explore Carbon College’s free video courses.

While your specific goals and regional growing conditions will have the most influence on your cover crop decisions, cover cropping methods and techniques can also change depending on your cash crop. Let’s look at cover cropping with three major cash crops: corn, soybeans, and wheat/small grains. 

For corn, the best cover crop options are generally legumes like red cover, winter peas, and hairy vetch and brassicas, like radish, turnip, forage collards, and winter canola. However, make sure the brassicas are less than 25% of the mix. Grasses, like oats, triticale, and annual ryegrass, are also a good option, but they can have a high C:N ratio if they reach maturity so aim for them to be less than 50% of the mix. 

Corn growers will have three major considerations for deciding when to terminate: 

• moisture management

• weed management

• nitrogen management

Corn growers often terminate their cover crops 10-14 days ahead of cash crop planting. Growers with a few years of experience of cover cropping typically have soils with more active soil biology, allowing later termination, up to the same day as planting or prior to emergence, as long as you have adequate soil moisture and nitrogen availability. The biggest factor for determining termination timing is moisture management. In heavy moisture conditions, the early season soil moisture can be at least partially managed by terminating the cover crop later to transpire more soil moisture. If soil moisture is limited, it’s often better to terminate earlier.

For soybeans, brassicas will help make phosphorus more available, but they shouldn’t make up more than 50% of the mix. The mix can be supplemented with grasses, like cereal rye and triticale, which are great for weed control in beans, as well as legumes, like red clover, as long as they’re not more than 25% of the mix. Soybean growers will want to consider moisture and weed management when choosing termination timing. 

Compared to other cash crops, soybeans have little issue emerging through thicker residue or competing with cover crops that might still be slightly green. For first-time cover crop use ahead of soybeans, herbicide is the easiest termination strategy. However, roller crimping is also very effective if available in your climate. If you decide to terminate with roller crimping, make sure the cover crop has reached adequate maturity so the crimping will be effective. 

For wheat and small grains, legumes like red clover planted with the wheat are a good cover crop option because they’ll both supply nitrogen and help control weeds. Brassicas, especially winter-killed ones like radish and forage collards are another good option ahead of wheat. This is because wheat doesn’t like the competition of being planted into living plants or thick residue. 

With wheat, the termination strategy will depend primarily on moisture and nitrogen competition for the main crop. With wheat, the termination date you choose will vary greatly depending on where you’re located. If you’re in a Western state, you may need to terminate cover crops as early as 90 days before planting based on RMA guidelines. It’s also critical to manage the nitrogen tie up from the cover crop by adjusting application timing. To do this, you’ll need to consider the C:N ratio of the cover crop residue and apply nitrogen closer to cash crop planting and support the microbial community with additions of humic acid, sugar, and/or molasses. If you’re able to, we also recommend using biologicals combined with soil microbial food to boost germination and early crop vigor. 

For more crop-specific cover crop information, regional and local info is available through Extension, Indigo agronomists, and Regional Cover Crop Councils. You can also connect with an independent agronomist trained in carbon farming practices through Indigo’s independent agronomist locator. Additionally, check out Indigo’s Cover Crop selector to learn about the best cover crop options for your fields.