Planting Cover Crops Still Beneficial in Fall, Even Under Dry Conditions

By Chandler Gruener and Victor Gomes

Many farmers in western North Dakota have planted cover crops like cereal rye or triticale this fall, but as dry as this season has been, many of the plants have yet to emerge, say North Dakota State University Extension specialists.

According to the North Dakota Agricultural Weather Network, much of western North Dakota has seen more than 30 days with less than one-half inch of rain, and some areas in the northwestern region of the state have had no significant rain in about four months. Under the current drought conditions, cover crops and winter cereals have been struggling to take in moisture and germinate.

“Even cover crops that were drilled or disked in, and benefited from the seed-to-soil contact, will have poor emergence if soil moisture is not adequate,” says Victor Gomes, NDSU Extension cropping systems specialist at the Dickinson Research Extension Center. “However, most cover crops have the ability to sit dormant in the soil over winter and germinate early in the spring, once they get enough warmth and moisture.”

This process is called dormant seeding and is different from frost seeding, which happens late in the winter after the soil freezes.

“One of the concerns that often comes up when cover crop seedlings do not emerge in the fall is that the “dormancy” won’t be broken in due time with moisture imbibition by the seed, and therefore the seed will die in the ground over winter,” says Chandler Gruener, NDSU Extension soil health specialist at the North Central Research Extension Center near Minot, North Dakota. “In this case, no germination is better than some germination.

If there is enough soil moisture (light rain) to promote seed sprouting but not enough moisture for further seedling growth, the crop will not survive the winter. For successful dormant seeding, farmers should plant seeds after the ground has cooled (35 degrees Fahrenheit) but before it freezes solid or is covered in snow for the winter, recommend the specialists.

If soil temperatures stay below 35 degrees Fahrenheit or the moisture levels are insufficient to start germination, the seed's activity will stay low, preventing it from germinating. Germination kicks in when the soil temperature rises to around 38 to 40 degrees Fahrenheit and enough moisture is present.

Farmers will still be able to reap the benefits of having a cover crop emerge early in the spring even if they do not see any visible growth in the fall. Nevertheless, a few management practices should be considered:

• Cover crop choice is crucial for successful emergence in the spring. Appropriate cover crops like cereal rye, winter camelina, hairy vetch, triticale and winter wheat are winter hardy and have better chances of surviving the winter dormant in the soil and then emerging to protect the soil in the spring. Farmers should determine what to use as their cash crop. The recommendation is to never use cereal rye before a wheat or barley crop.
• It is important to incorporate seeds into the ground, not broadcast them. If the goal is improving soil health, then simply getting the seed in the ground is the most important factor to consider. Make sure seeds have good soil contact by drilling, not broadcasting, to avoid losing them to snow runoff.
• Termination timing is important. Because dormant seeded cover crops will have no growth in the fall, letting them grow as long as possible in the spring will ensure farmers get the benefits they are seeking. If planting a summer crop like corn or soybeans, the cover crops will likely benefit from a longer growth period. If planting a spring crop, like a small grain cereal, it is likely that the cover crops will not have much time to produce biomass. Still, some ground cover early in the spring is better than no ground cover. Overall, the recommendation is to terminate the cover crop 10 to 14 days before planting the cash crop.
• Planting green is another choice for termination timing that is adequate when lower biomass is present. This practice consists of planting the cash crop into a living cover crop. If this is done, it is best to terminate within a few weeks after planting to help prevent soil moisture from tying up. When terminating, the selection of the right chemical product is key to make sure the cover crop is effectively killed. It is recommended to follow the product and adjuvant guidelines required to ensure the cover crop is fully terminated.

“All things considered, dormant seeding still represents a risky choice and like any other planting event it takes careful planning and attention to weather patterns,” says Gomes. “While good cover crop emergence and establishment in the fall is preferred, when not enough moisture is available, having some ground cover available early in the spring is still better than no ground cover, and could help with soil dry-down, allowing for an earlier planting of the cash crop in flood-prone areas in the spring.”