Robert Hartzler, Professor, Agronomy
As farm size continues to increase Iowa farmers continue to seek ways to minimize labor requirements for production of corn and soybean. In terms of weed management, this involves placing greater reliance on a few highly effective herbicides. While these systems can provide short-term control of weed populations, they are vulnerable to rapid shifts in weed communities that result in significant devaluing of important herbicides.
Increase adoption of integrated weed management systems that maximize profits and reduce the likelihood of weed shifts.
The objectives of this program were achieved through an integrated research and extension program. Field research, both at ISU Research Farms and on cooperating farmer fields) was conducted to evaluate the benefits of both cultural and chemical weed management strategies in corn and soybean production. Two primary areas of emphasis were promoting the use of preemergence herbicides in glyphosate-resistant crops to reduce reliance on glyphosate, and enhancing the competitiveness of the crop through row spacing and plant populations. Promoting the benefits of these integrated approaches was achieved through a combination of presentations at Extension meetings (winter crop clinics and summer field days), newsletter articles, and articles placed on the internet.
Iowa farmers have made changes in their cultural practices over the past decade that have enhanced the competitiveness of both corn and soybean, therefore reducing the requirement for chemical weed control. In soybean, the % acres planted in 15-20” row spacing has increased by more than 10% in the past five years (Iowa Ag Statistics Services). In corn, average plant populations have increased approximately 425 plants/acre/year since 2001. While other factors are involved in these management changes, they both enhance the competiveness of the crop with weeds. Another example of the adoption of integrated weed management systems is a doubling in the number of glyphosate-resistant soybean treated with preemergence herbicides from 2007 to 2008.
100 Corn and Soybean Production and Protection
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August 25, 2008
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