Submitted to: Journal of Crop Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/15/1997
Publication Date: N/A
Interpretive Summary: Rotary hoeing and interrow cultivation are two important forms of mechanical weed control. Unfortunately, their effectiveness is variable, which leads to high levels of risk for farmers. We found that efficiency and profitability of rotary hoeing and interrow cultivation increased if the timing of control was based more on weed emergence times than on rule-of-thumb calendar dates. Using the important grass weeds, green and giant foxtails, in soybean as examples, effectiveness of mechanical control operations was best and predictable if implemented when weed seedling emergence was estimated to be 30% at the time of rotary hoeing and 60% at time of interrow cultivation. These emergence percentages can be predicted easily by farmers or crop consultants using the ARS-developed WeedCast computer software, which will enable them to increase the effectiveness of mechanical weed control operations.
Technical Abstract: In row crops of the North American "Corn Belt" two important forms of postplant mechanical weed control are rotary hoeing and interrow 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 interrow cultivation would increase, and risk would decrease, if the timin of control was based more on weed biology, especially 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 interrow 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.