Winter Cover Crops: Timing Cover Crop Planting in Corn-Soybean Short-Season Rotations

Establishing winter cover crops after or between harvests can be a great way to preserve soil structure, protect against erosion and produce biomass that feeds the soil ecology. However, if you’re in a region where corn or soybeans are harvested later in the year, planting cover crops in your rotations can be challenging.
Let’s look at a few factors that will determine if and when planting cover crops is beneficial in your short-season climate and which winter cover crops will work best for your area.

Season length for winter cover crops

In short-season regions, the window between harvest and first frost is tight. That makes it critical to know when to plant a cover crop. If winter cover crops are planted too late, they won’t have time to establish, and you won’t get the soil erosion control or maximum biomass your cover crops should provide.

Pay attention to your region’s first killing frost date, which is typically when temperatures hit 28 F.¹ You’ll want to plant your cover crops 6-8 weeks before that date, so you can maximize the amount of biomass grown. This is especially true for legume cover crops, such as vetch. However, the ideal time to plant winter cover crops can vary depending on the type of cover crop you want to use and how you will terminate it.

Variety selection for winter cover crops
There are numerous options available to you when selecting the right cover crop. Not all species are created equal, and each species offers distinct benefits.

In short-season regions, winter-hardy species like cereal rye and triticale are often the most reliable options for cover cropping. These grasses tolerate cold temperatures and can establish even when planted late, making them ideal for narrow post-harvest windows. However, while they may survive the winter, limited fall growth can reduce their biomass production and overall benefits to soil health and erosion control. Brassicas and legumes generally need a longer establishment period and are better suited to earlier planting or interseeding.

Getting the most out of your cover crop investment begins with selecting species that align with your available planting window. The right match can mean the difference between a thriving cover crop that improves your soil and one that struggles to establish before winter.

Seeding method for winter cover crops

There are two ways you can establish a winter cover crop. Either drill after harvest or interseed before harvest. Broadcasting cover crops before harvest allows them more time to grow and develop biomass above and below ground. Even with lower fall stands, preharvest broadcasting often results in greater overall biomass than drill-seeding late in the season.² However, your seeding method choice will depend on your available planting window and rotation schedule.

To buy extra time for fall growth, many farmers interseed cover crops into standing corn or soybeans. This early start boosts fall biomass and coverage, especially when harvest delays push seeding later than ideal.³

For interseeding into corn, plan to broadcast cover crops around V4-V6, or wait until R5.⁴ Soybeans do better with cover crops being interseeded between R5 and R7.⁵ This typically occurs when soybeans are starting to mature and their leaves are turning yellow.
If those options aren’t available, planting cereal rye late in the season may be a better decision. You won’t get the benefits of a cover crop in the fall or winter, but you’ll see it pop up in the spring.

Experts are available to help you make your winter cover crop decisions. Reach out to your seed retailer, a nearby extension office agent, or a seed company professional like your regional BASF representative.

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Endnotes

1. Nielsen, R. L. (Bob), and Ellsworth Christmas. “Early Season Frost & Low Temperature Damage to Corn and Soybean.” Corny News Network, Purdue University Department of Agronomy, Corny News Network, May 2002, www.agry.purdue.edu/ext/corn/news/articles.02/frost_freeze-0520.html.
2. Koehler‑Cole, Katja, Nate Dorsey, Katie Pekarek, and Jenny Brhel. “Seeding Rates for Broadcasting Cover Crops Into Late‑Season Corn and Soybean.” CropWatch, Institute of Agriculture and Natural Resources, University of Nebraska–Lincoln, revised 31 Aug. 2022, cropwatch.unl.edu/2020/seeding-rates-broadcasting-cover-crops-late-season-corn-and-soybean.
3. Bongard, Phyllis. “Strategic Farming: Let’s Talk Crops! Focused on Cover Crops.” Minnesota Crop News, University of Minnesota Extension, 14 Feb. 2022, blog‑crop‑news.extension.umn.edu/2022/02/strategic‑farming‑lets‑talk‑crops_14.html.
4. Bongard. “Strategic Farming: Let’s Talk Crops! Focused on Cover Crops.”
5. Bongard. “Strategic Farming: Let’s Talk Crops! Focused on Cover Crops.”