Weed Management in Corn

January-March 2002

Jim Fawcett , crop specialist

Crop producers are faced with new weed management decisions each year with the introduction of new products, new herbicide resistant crops, and changing weed problems. In the more competitive environment, it is crucial for farmers to find the most cost-effective ways to manage weeds in corn and soybeans in order to maintain profitability. After several years of using Roundup Ready Soybeans, weed populations have declined in some fields, providing an opportunity to decrease herbicide costs in the following year of corn by reducing herbicide rates.

Greg Brenneman and I conducted weed management demonstrations in corn by the Kirkwood Community College Campus near Cedar Rapids , on the SE Iowa Research and Demonstration Farm near Crawfordsville, and on the Tom Wall farm in Johnson County . The demonstration at Kirkwood was conducted in cooperation with the Linn County Natural Resources Conservation Service, Kirkwood Community College , and the PURE water quality project. The demonstration in Johnson County was conducted in cooperation with Monsanto Chemical Company. About 20 herbicide systems in corn were demonstrated in side-by-side comparisons that emphasized low-cost alternatives as well as new products on the market.

Tours were conducted at all three sites with a total of 135 in attendance. Several chemical companies, as well as the Linn County Soil Conservation District, donated money which paid for a meal and helped with cost recovery. ISU Extension signs were placed in front of each plot showing the treatment as well as the cost. Results from the demonstrations were used at private pesticide applicator re-certification sessions and were made available to others in ISU Extension.

Impact :
Several hundred crop producers learned of ways to cut costs and mistakes to avoid in cutting herbicide rates for corn production at the private pesticide applicator re-certification sessions. One producer commented on the pesticide applicator evaluation form that it was important to have someone to get unbiased weed control information from rather than having to rely on chemical company recommendations. Information on reduced rates of herbicides would not generally be available anywhere else.

Nitrogen (N) is an important nutrient for achieving optimum corn yields, but too much N can lead to environmental problems. There are also environmental concerns about the carbon dioxide levels in the atmosphere. One proposed method for reducing the carbon dioxide levels in the atmosphere is for farmers to store carbon in the soil.


Page last updated: July 11, 2006
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