By Bob Hartzler, Department of Agronomy
The late arrival of spring has everyone ready to hit the fields running when fields finally dry out. Some will be tempted to forgo applying herbicides prior to planting to ensure fields get planted in case another wet period arrives. This is an exceptionally risky proposition for no-till fields because it provides weeds a head start on the crop and a competitive advantage for the rest of the season. If everything falls in place perfectly, this practice can be successful. But any delay in getting back into the field to apply the burndown and residual herbicides can have a big impact on the success of weed control and, therefore, profits.
Selection of an appropriate burndown treatment is the first step in a successful no-till weed management program. Fields should be scouted to determine what weeds are present. The addition of 2,4-D to glyphosate improves control of many winter annual weeds and any glyphosate-resistant weeds such as horseweed/marestail. A seven-day interval between application and planting is required with 0.5 lb ae/A (0.5 pt/A of a 4 lb/gal product) for both corn and soybean. Growers wishing to plant immediately following the burndown application can substitute Sharpen (or other Kixor product) for 2,4-D to maintain effectiveness of horseweed control. An MSO and N source is required when using Sharpen for burndown purposes.
Bob Hartzler is a professor of agronomy and weed science extension specialist with responsibilities in weed management and herbicide use. He can be reached at 515-294-1164 or hartzler@iastate.edu
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