Maximizing Efficacy and Economics of Mechanical Weed Control in Row Crops Through Forecasts of Weed Emergence

Abstract

In row crops of the North American Corn Belt two important forms of postplant mechanical weed control are rotary hoeing and inter-row cultivation. Unfortunately, the efficacies of these two control technologies are variable, which leads to high levels of economic risk. We hypothesized that efficacies and profitability of rotary hoeing and inter-row cultivation would increase, and risk would decrease, if the timing of control was based more on weed emergence times, than on rule-of-thumb calendar dates. Field research was conducted in soybean (Glycine max [L.] Merr.) for two years in Minnesota wherein four dates of rotary hoeing and three dates of inter-row cultivation, alone or supplemented by grass or broadleaf herbicides, were examined for weed control, crop yield, and net returns. Results indicate that timing influences the efficacy of mechanical control operations, but blanket optimal calendar windows that are generally applicable cannot be established, as such decisions may be location-specific and/or time-dependent. In contrast, efficacies appear more consistent if emergence percentages are used to decide the time of mechanical operations, e.g., rotary hoe at 30% and cultivate at 60% green foxtail (Setaria viridis [L.] Beauv.) emergence. The results also suggest that while it is possible for exclusive mechanical weed control to be optimal in some instances, consistently profitable weed control strategies will inevitably involve some herbicide usage.