Planted cover crops this fall but saw no emergence? Not all is lost!

Victor Gomes, Dickinson REC

Co-author Chandler Gruener, North Central REC

reviewed by Marisol Berti

Many farmers in western North Dakota have planted cover crops like cereal rye or triticale this fall, but with as dry as this season has been, many of them have still to come out of the ground. According to NDAWN, much of western North Dakota has seen over 30 days with less than 0.50-inch of rain, and some areas in the northwest haven't had significant rain in about four months (NDAWN). Under the current drought conditions, not only cover crops but also winter cereals have been struggling to take in some moisture and germinate.

Even cover crops that were drilled or disked in benefit of the seed-to-soil contact will have poor emergence if soil moisture is not adequate. However, most cover crops have the ability to sit dormant in the soil over winter and germinate early in the spring, once it gets enough warmth and moisture. This process is called “dormant seeding”. This process 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. In this case, no germination is better than “a little germination”. If there is enough soil moisture (light rain) to promote imbibition and radicle emergence but not enough moisture for further seedling growth, the crop won’t survive the winter. For successful dormant seeding, farmers need to plant seeds after the ground has cooled (35°F) but before it freezes solid or gets covered in snow for the winter.

If soil temperatures stay below 35°F or the moisture levels are insufficient to start germination, the seed's activity stays low, which prevents it from germinating. Germination kicks in when the soil temperature rises to around 38°F to 40°F 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 don’t see any visible growth in the fall. Nevertheless, a few management practices must be considered:

1.      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.

It is also important to keep in mind what your cash crop will be. The recommendation is to never use cereal rye before a wheat or barley crop.

2.      Incorporate the seeds, do not broadcast! 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.  

3.      Termination timing: Since dormant seeded cover crops will have no growth in the fall, letting them grow as long as possible in the spring will ensure farmers will get the benefits they’re 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 won’t have too 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 10-14 days before planting the cash crop.

Planting green is another choice for termination timing that is adequate when lower biomass is present. This is practice consists on planting your 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 you effectively kill the cover crop. This is a time to ensure you stick to the right rate and adjuvants 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. 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.

Supplementary reads

 Cover Crop Considerations for Dry Conditions

North Dakota Cover Crop Recipe – Starting with Cover Crops