Economic performance of crop rotations in the presence of herbicide-resistant giant ragweed

Economic assessment of alternative crops and crop rotations helps farmers determine those most appropriate for their farms. The objective of this research was to evaluate the economic net return and associated financial risk for crops and crop rotations common to the midwestern United States, based on two 3-yr experiments in southern Minnesota where herbicide-resistant giant ragweed (Ambrosia trifida L.) was present. Crop rotations included corn (Zea mays L.), soybean [Glycine max L. (Merr.)], wheat (Triticum aestivum L.), and alfalfa (Medicago sativa L.). Crop rotations were continuous corn (CCC), soybean–corn–corn (SCC), corn–soybean–corn (CSC), soybean–wheat–corn (SWC), soybean–alfalfa–corn (SAC), and alfalfa–alfalfa–corn (AAC). Average crop yields during the study period were utilized along with average prices received and estimated production costs for each crop in Minnesota during this period to evaluate economic net return. Average net return of the SWC, SCC, CCC, CSC, SAC, and AAC rotations was US$11, $170, $247, $258, $368, and $919 ha^–1 yr^–1, respectively. The AAC rotation was stochastically dominant to all other crop rotations for risk-averse decision makers. One or 2 yr of alfalfa stochastically dominated corn, soybean, and wheat, regardless of crop rotation, largely due to more stable alfalfa prices over the study period coupled with above-average yield and lower production costs. These results confirm that rotations containing alfalfa have the potential to provide a substantial economic net return to farmers while mitigating the risk of herbicide-resistant giant ragweed (Ambrosia trifida L.) infestations.