Boost Soil Health with Smart Cover Crop Termination

Cover crops are increasing in popularity and adding them into a rotation can offer many benefits when used correctly. They can help build soil organic matter and improve soil structure, while also reducing erosion and suppressing weeds. Many cover crops are terminated as a result of winterkill, but for some, a timely herbicide termination is critical.

In this article, we’ll cover the right termination windows for corn versus soybeans, along with proper herbicide selection to help you optimize your cover crop investment and benefits.

What to Consider When Terminating Before Corn

• Some cover crops produce allelopathic toxins that can hinder germination
• Terminating 2 weeks before planting helps avoid this risk, plus reduces nitrogen tie-up risks
• After termination, soil may not dry out as fast as usual to allow soil conditions to stabilize

What to Consider When Terminating Before Soybeans

There are two main approaches:

1. Traditional: Terminate with a herbicide 2 weeks before planting
2. Plant green, before cover crop gets big enough to interfere with planting, then terminate within a few days after planting, well before the cover crop goes to seed

Important: Monitor soil moisture carefully if planting green

What to Consider When Selecting a Herbicide For Termination

Follow these step-by-step considerations for terminating a cover crop with a herbicide.

1. Keep these optimal application conditions in mind:

   • Spray on a sunny day if possible
   • Aim for daytime temperatures above 60°F
   • Night temperatures should be above 40°F
   • Apply to actively growing crops

2. Match spray volume to herbicide type:

   • Contact herbicides: Use a higher gallons per acre rate for coverage on dense canopies.
   • Translocated herbicides: Standard rates are acceptable, as coverage is less of a concern.
3. Check planting restrictions on what you will plant in the field (e.g., 14–28 days for 2,4‑D before soybeans)
4. Ensure that you understand and follow all label instructions and PPE requirements.

Should I consider Mechanical Termination?

Tillage can be a viable option for certain species, but keep in mind that multiple passes may be needed.

Example: Making the Termination Decision

The Scenario: A cover crop is approaching maturity and corn is planned for the field.

The Risk: Reduced crop performance, cover crop going to seed or robbing nutrients from the crop if termination is delayed, potential for allelopathic toxins to hinder germination.

What to Consider:

• Current growth stage of cover crop
• Upcoming weather forecast
• Available termination methods
• Soil conditions

Possible Plan of Action:

Terminate cover crop 2 weeks before planned planting date using a translocated herbicide at a standard application rate. Ensure that temperatures are between 40°F at night and 60°F during the day and apply on a sunny day if possible.

Common mistake: Waiting too long to terminate, especially when planting corn.

Key Takeaways

The most important elements for successful cover crop termination planning are timing relative to crop needs, selecting appropriate herbicides, and ensuring optimal application conditions. Remember that corn requires earlier termination than soybeans, and always have a backup termination plan in place.

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