When properly managed, cover crops, such as cereal rye or winter wheat, can help address many challenges you are facing in your cornfields. That list includes everything from reducing nutrient loss and soil erosion to improving water filtration rates and adding valuable organic matter to the soil.
They can also serve another important purpose: suppressing herbicide-resistant weeds. To be sure, planting cover crops isn’t a stand-alone weed control program. You’ll still need to use spring residuals and fall-applied herbicides to get season-long weed control in your corn fields. But where cover crops can play a role is in helping reduce weed population density and keeping them smaller and easier to control with herbicides.
Actively growing cover crops and the resulting layer of cover residue they produce block sunlight and take up water and nutrients from emerging weeds. For winter annuals like marestail, sowing appropriate cover crops in fall when marestail typically emerges will help block its establishment and then slow its growth rate the following spring. With certain cover crops, there is even the opportunity for allelopathy. This process occurs after the crop dies and begins breaking down in the soil. Chemicals are released from the plant matter that act as a preemergence herbicide of sorts, further prohibiting weeds from germinating and growing.
But choosing to add cover crops for weed control requires careful consideration. First, it’s imperative to carefully read all residual herbicide product labels. This will determine if desired fall-seeded crops are listed in the included rotational crop guidelines.
For example, the label for Resicore® herbicide contains the following instructions:
“Rotation to Non-food Winter Cover Crops
Following harvest of corn treated with Resicore, only non-food or non-feed winter cover crops (with the exception of winter wheat) may be planted. Do not graze or harvest rotational cover crops for food or animal feed for 18 months following the last application of Resicore. This prohibition does not apply to winter wheat, which may be planted 4 months following the last application of Resicore, or to nongrass animal feeds, which may be planted 9 months after the last application of Resicore.”
Also, you’ll need to decide which crop or crops will meet the needs of your fields. To help with that, the Midwest Cover Crops Council developed its Cover Crop Decision Tool. With it, you can select multiple inputs to generate a customized list of potential cover crop options that best match your needs — even ranking them in terms of weed control.
With a plan in place, you’ll want to scout fields to monitor the impact the selected cover crops have on weed populations. But with careful planning, you could give your weed control program a boost.
Resicore is not registered for sale or use in all states. Resicore is not available for sale, distribution or use in Nassau and Suffolk counties in the state of New York. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.