Starting with a Clean Field
Weed control must begin before planting
Planting into weed-free fields helps ensure a strong start for your crop.
By contrast, seeding into established weeds increases risk and supresses yield potential. Once the crop is planted, your weed control options are much more limited. And if weeds are developing resistance, even herbicide mixtures with multiple sites of action may not provide control, weed scientists warn.
Meanwhile, emerged weeds have a big head start and can easily outgrow your crops, stealing sunlight, nutrients and water. “If weeds have already emerged before the crop starts coming up, those weeds are going to have a huge advantage,” says Larry Steckel, weed scientist at the University of Tennessee, in an interview for the United Soybean Board. “There is really no contest.”
To achieve a clean start:
- Scout before planting to ensure an effective burndown treatment before weeds grow too large. Scouting also helps growers evaluate the need for other pre-plant management tactics such as tillage.
- Apply an effective burndown.Spray nonselective herbicides at full recommended rates. Pay attention to planting-restriction intervals to avoid crop injury.
- Consider-plant tillage, if feasible. Tillage, which can be an effective tool to control early flushes of weeds, is also a good resistance-management practice. Tillage is especially effective for destroying winter annuals such as marestail and early emerging summer annuals such as giant ragweed. It is not a good option on erodible soils, however, and must be balanced with soil conservation goals. Pre-plant tillage can increase germination of some problem weeds — such as herbicide-resistant waterhemp — that emerge after planting.
- Include-emergence residual herbicides in your burndown application or after tillage to control weeds that emerge with the crop. You may need to make an additional residual herbicide treatment before the initial residual has dissipated in order to suppress weed emergence until the crop canopy closes.
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