Benefit To Soybean Farmers
Starting clean or weed-free is the key to any good weed control program, especially when dealing with herbicide-resistant weeds such as Palmer amaranth. Many conventional, soil-active (residual) herbicides are available that effectively control many of these weeds. However, control is more complicated in organic systems: 1) where effective residual herbicides are not an option, and 2) when weeds may germinate at different times throughout the growing season.
Flame weeding is a non-chemical tactic that has previously been evaluated to control several grass and broadleaf weed species (Cisneros and Zandstra 2008; Sivesind et al. 2008) in multiple cropping systems including corn (Stepanovic et al. 2016a) and soybean (Stepanovic et al. 2016b). The majority of this research has evaluated the effects of flame weeding on emerged weeds. However, Gallant (2013) reported that flaming “popped” redroot pigweed seeds post-dispersal. Furthermore, certain seeds such as those of horseweed (marestail) and Palmer amaranth tend to germinate from shallower depths in the soil profile, and may be more readily controlled by flaming on or near the soil surface.
Cultivation/tillage is a tactic used in both conventional and organic farming to prepare a seedbed for planting. It too can be effective in controlling emerged weeds, but this tactic can also bring weed seeds to the soil surface and stimulate weed germination. Growers may use this aspect to their advantage by implementing the stale seedbed tactic - a weed management practice in which weed seeds just below the soil surface are allowed to germinate only to be killed by repeated cultivation prior to planting the cash crop. However, additional cultivation often leads to additional weed emergence and cannot be used when the soil is too wet. Flame weeding may aid in this practice by eliminating emerged weeds when cultivation is not an option. In general, flaming will only burn the top couple millimeters of soil leaving weeds buried deeper in the soil intact.
We hypothesize that integrating flame weeding with the stale seedbed approach will improve control by 1) stimulating weed emergence for early flaming postemergence, 2) burning weed seed on or near the soil surface, and 3) minimizing soil disturbance and additional weed germination.