Soybean School: How wide is your spring burndown window?

If you have weeds pop up prior to planting soybeans you can control them with a burndown herbicide application. But what happens when rain and wind conspire to prevent you from applying a burndown and you have to control weeds after planting?

In this episode of the Soybean School, OMAFRA weed control specialist Mike Cowbrough takes us to the Elora Research Station where he set up an experiment to examine what happens when different burndown herbicides are applied after the label-recommended timing, which restricts application three days after soybean planting.

Cowbrough says growers should always follow recommended application timings and rates, but he believes there may be situations where spraying a little late may be worth the risk if growers need to control glyphosate-tolerant Canada fleabane or giant ragweed.

Cowbrough concludes that different herbicides pose different levels of risk when applied up to six or nine days after planting. Based on this trial, he says applying both metribuzin and saflufenacil up to six days after planting is a reasonable risk to take if you are rewarded with better control of troublesome glyphosate-tolerant weeds that could be even more problematic the following year.

Based on his research, Cowbrough says these two products give you more “wiggle room.” In both cases, he saw no reduction in stand, no significant crop injury and no yield loss with either metribuzin or saflufenacil .


Bernard Tobin

Bernard Tobin is Real Agriculture's Ontario Field Editor. AgBern was raised on a dairy farm near St. John's, Newfoundland. For the past two decades, he has specialized in agricultural communications. A Ryerson University journalism grad, he kicked off his career with a seven-year stint as Managing Editor and Field Editor for Farm and Country magazine. He has received six Canadian Farm Writers' Federation awards for journalism excellence. He's also worked for two of Canada's leading agricultural communications firms, providing public relations, branding and strategic marketing. Bern also works for Guelph-based Synthesis Agri-Food Network and talks the Real Dirt on Farming.


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