There was a lot of prep work for next season in Midwest fields after a dry fall, but the latest blast of Arctic air may cause some problems for farmers with cover crops.

Iowa State Extension field agronomist Meaghan Anderson said that combination may make for a few interesting decisions in the coming weeks as farmers prepare for the 2021 planting season.

With many cover crops planted into dry soils, particularly in western Iowa, Anderson said there may not have been ideal germination or growth before winter. With the addition of sub-zero temperatures, she said fields will need to have enough snow cover for the cover crop to survive.

“Soil temperatures in the uncovered areas could be quite a bit colder than they are in snow-covered areas,” she said. “Hopefully we have a good snow cover out there.”

Anderson said when spring comes, decisions on when to terminate the cover crops will largely depend on how quickly the warmup occurs.

“It all depends on what things look like as we head into March and how quickly we shed the snow,” she said. “I really wouldn’t be too surprised to see things get kind of a sluggish start as far as coming out of dormancy and growth.”

Anderson said there isn’t much deep-soil moisture for cover crops to tap into currently. Some farmers may consider leaving their cover crops in the ground to see additional growth. On the other hand, she said with the lower moisture levels, farmers may not want to gamble and save that moisture for their corn and soybeans.

If the cover crop is smaller, the crop would be easier to terminate in theory, Anderson said.

The timing of termination is the key, according to Kevin Bradley, University of Missouri Extension plant sciences specialist.

“Proper spring termination of cover crops is important in order to be able to plant your cash crop successfully, and also to prevent any of the surviving cover crop from competing with the cash crop,” Bradley said.

In his research, he said a residual herbicide can be included in the burndown process without any adverse effects when terminating cover crops two to three weeks before planting or when cover crops are less than 12 to 18 inches in height.

If termination is delayed for any reason, he said additional biomass may not allow the residual herbicide to reach the soil surface.

“Our results would encourage you to leave the residual herbicide out if you have to wait,” Bradley said. “You might have to include it at the time of post-emergence herbicide applications.”

Anderson said some of the decisions on termination will be made based on what cover crops a farmer is dealing with, especially if they are going into a soybean crop.

She added that cover crops might be used to limit weeds if a farmer decides to go with late termination.

“We know soybeans can tolerate a lot of that residue,” Anderson said. “The fascinating thing about cover crops is that you seed it and terminate it. There are about a million different ways to do it in between those two points.”