Residual Herbicides and Cover Crop Establishment

By Sean Jordal

For all the benefits corn and soybean growers are seeing associated with Cover Crop applications, the number of acres being planted to Cover Crops continues to rise.

At the same time, with more persistent weeds showing tolerance to glyphosate herbicide programs in recent years, another rising trend involves growers adding tank mix partners and other modes of action that provide some residual weed control for their Cash Crops.

When these two trends converge, it can be problematic, leaving growers wondering about the effect that any related herbicide residue might have on Cover Crop establishment.

Herbicide Restrictions Require More Careful Consideration

In general, most herbicide labels usually include information regarding the restrictions for rotation of crops. However, many of these restrictions do not include Cover Crops. Or, if they do include Cover Crops, they’re probably staged at the very safest time period available—because, when those labels were written, Cover Crops were not overly prevalent in the market.

Expert recommendations call for looking at the most current tolerance information, and the plant backed restrictions, to get a good Cover Crop stand establishment.

Cover Crops planted for conservation practices allow for greater flexibility, depending on the mix formula and the risk of herbicide interaction. But those planted heavily, as part of a row crop situation, might be limited to that information as well.

Start Planning Months Ahead

When it’s clear that a residual herbicide program might impose on a Cover Crop program, the time to develop a plan is in the fall, the preceding year, versus the summer of the year in which the programs will be implemented. This is essential to making certain an herbicide application will provide good weed management to maximize Cash-Crop yield potential, without detracting from the benefits of a Cover Cropping system.

For more information, growers can do an Internet search using the keyword phrase: Herbicide Rotation Restrictions in Forage and Cover Cropping Systems.

This report, published by the University of Wisconsin, reviews different Cover Crop species against various herbicide programs and their active ingredients, identifying the best choices growers can make to maximize success in terms of both their Cover Crop establishment and preservation of a weed-free environment for their row crop.

The Winner is. . .

September 15

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