Unexpected Injury — The Impact of Herbicide Carry Over on Cover Crops


The risk of herbicide carry over can sometimes be overlooked when changing cropping plans or trying something new, but herbicide residue can have a drastic impact on susceptible crops, sometimes as long as years after application.

Chemical breakdown times vary, subject to soil temperature and moisture. For some chemicals, susceptible crops can be seeded shortly after application. Others require much longer time periods, and often, carryover considerations are amplified by drought.

RealAgriculture’s Lyndsey Smith spoke with Darren Robinson, associate professor at the University of Guelph Ridgetown Campus, following the SouthWest Agricultural Conference (SWAC) about work he’s doing on measuring the risk to cover crops of common herbicides.

Tillage radish seeded into soybeans at leaf drop. Foresee any issues? Credit: Darren Robinson.
Tillage radish seeded into soybeans at leaf drop. Foresee any issues? Credit: Darren Robinson.

Robinson spoke at SWAC on recent field trials determining how herbicide residual impact cover crops. The crops were seeded four months and one year after various herbicide applications and were assessed for level of visible injury, impact to above ground growth and root growth, their ability to compete with weeds and to improve soil structure.

Of particular interest, Robinson and his team of students not only measured population setbacks, but also gauged whether or not the herbicide injury resulted in loss of use of the cover crop (hint: injury didn’t always mean loss of use).

In this video, Robinson talks about some of the findings, including which herbicide/crop duos the research suggested to avoid, and the greatest determining factor in herbicide breakdown. In addition, Robinson talks about some upcoming research involving cover crops seeded into corn and soybeans.



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