Currently, Laramie-McGuire says growers in her area are relying on a combination of crop rotation and chemical group rotation to manage waterhemp. Sikkema’s research builds on these basic weed management strategies and expects the results to enhance the effectiveness of these practices. INTEGRATED MANAGEMENT TOOLS “Depleting waterhemp seeds in the soil seed bank is integral to reducing the spread and impact of this weed,” says Sikkema. His research, using integrated weed management tactics, is focused on finding the most effective management strategy for Ontario growers. The study includes five crop rotations: continuous soybean, corn/soybean, soybean/ wheat, corn/soybean/winter wheat, and corn/ soybean/winter wheat plus a cover crop. Early results indicate the most effective crop rotation for reducing waterhemp seeds in the soil seed bank is corn/soybean/winter wheat plus a cover crop. Using this rotation, the soil seed bank counts after only three years into the research study show a reduction from 165 million to 30 million seeds per acre. Other weed management strategies being studied include two soybean row widths, 37.5 cm and 75 cm, and using a combination of up to eight multiple herbicide modes of action in the three-crop rotation. After three years into the research project, Sikkema is intrigued by the results. He says he expected it would take more time to see promising results, and with six more years left in the study he’s optimistic he can meet his goal of depleting the number of waterhemp seeds in the soil seed bank by 95 per cent. “We’ve confirmed that a more complex weed management strategy is needed for waterhemp,” says Sikkema. “And while we’re focused on waterhemp, the principles of what we’re learning can be applied to all weed species.” l ONTARIO GRAIN FARMER 23 APRIL/MAY 2022 This research project has received funding from Grain Farmers of Ontario
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