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How Concerned Should I Be About Carryover?

Jan 07, 2013

Question: How concerned should I be about herbicide carryover if I’m planning to rotate from soybeans to corn this spring?

Answer: It’s certainly a concern in those areas where we had dry, hot conditions last year and herbicides weren’t activated and where there’s been little moisture. One of the best ideas we’ve heard for checking on the potential for carryover came to us recently from Kevin Bradley, University of Missouri Extension weed scientist. He offers an easy and inexpensive idea you can use to tell if carryover herbicides will be a problem this coming spring.

Roughly a month prior to planting corn, he recommends that you pull half a dozen or so soil samples from across a field and then place a handful of dirt from each sample in a cup or jar. Plant some corn seed in each cup and watch the corn sprout. In about a week’s time you will know whether any significant herbicide residue is left from the previous year in that soil.

Bradley says if the corn shows signs of injury you’ll know it before you plant and you can keep from making a crop-rotation mistake. He adds that while many agronomic laboratory tests provide an accurate analysis on soils containing carryover herbicides, it’s difficult to know what the test results mean in practical terms.

Notes Bradley: "It’s hard to know whether 15 parts per billion of something in the soil will hurt your corn. A simpler thing is to just do a soil bioassay, and it’s the cheapest thing to do." Read on to learn more about how you might want to address carryover in 2013.

What's the Potential for Herbicide Carryover?
Recent dry soil conditions could make herbicide a bigger threat next year.

Herbicide Carryover Concerns for 2013 Corn and Soybeans Prompted by Drought
Iowa State Univesity agronomists look at the potential impact on corn/soybean rotation. No water, no herbicide breakdown.

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