Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 4, 1998
Publication Date: N/A
Interpretive Summary: Recent public concern over environmental pollution from farming practices has stimulated discussion and research on methods to reduce herbicide use in crop production. Decision-support models are beginning to provide tools to improve farm profits while holding the promise of reducing herbicide use. Bioeconomic models integrate biological processes of weed-crop interactions with economic factors to give farmers more comprehensive information to guide weed control decisions. While several decision-support models have been developed, field testing has been limited. The goal of our research was to evaluate a bioeconomic weed management model for corn and soybean under a range of field conditions. Results of our research showed that model-generated treatments reduced herbicide use compared with a standard farmer practice in the initial year of the study. However, in succeeding years, weed densities increased in model-generated treatments resulting in greater herbicide use and reduced crop yields compared with standard practices in some instances. The results of this research suggested that short-term reductions in herbicide use may have longer-term consequences if weed control levels are not maintained. The bioeconomic model showed potential to control weeds with less herbicide and at a lower cost to farmers. However, the research also pointed out it will be important to integrate bioeconomic models in the broader context of weed management to prevent weed population increases that may increase herbicide use or reduce crop yields.
Technical Abstract: Selecting effective weed management options requires biological and ecological as well as economic information. This study compared model-based to standard-herbicide weed control in a corn/soybean rotation that had a long-term history of different tillage and weed management practices. The model integrates weed population dynamics, herbicide efficacies, and economic information to evaluate preplant incorporated or preemergence weed control options based on weed seed bank size and postemergence strategies based on weed seedling densities. Weeds were fewer in standard-herbicide compared to model-based treatments. No-tillage plots had the greatest numbers of weeds in 3 out of 4 years. Soybean yield was reduced the first year of the study and the third year in all model-based treatments. Corn yields were greatest in reduced tillage plots. Results of using model recommendations to control weeds were mixed, with preemergence recommendations being insensitive to a common cocklebur infestation. Our conclusions agree with those of others that the nature of the weed pressure may be a prevailing influence on the outcome of using weed control recommendations of bioeconomic models.