Effectiveness of Hot Water, Infrared and Open Flame Thermal Units for Controlling Weeds

Abstract

ABSTRACTThermal weeding in Eastern Canadian agriculture is relatively new and being considered as a viable tool in organic food production. Hot water (HW), infrared (IR) and open flame (OF) thermal units were compared in terms of energy efficiency and effectiveness (percentage of weeds killed). The units were operated at ground speeds of 1.5, 2.5 and 3.5 km h−1, and were tested on Amaranthus retroflexus L. (redroot pigweed), Chenopodium album L. (common lambsquarters), Persicaria maculata L. (ladysthumb), and Sinapis alba L. (white mustard) at growth stages of > 6, 6–8 and < 8 leaves. HW was also operated at 1 km h−1. The energy consumption of IR was determined to be more than four times that of HW and OF, which consumed similar amounts per unit area. All units showed peak energy efficiency at 2.5 km h−1 speed; with the OF attaining the highest energy efficiency followed by IR, and then by HW, which was the least energy efficient. HW was also the least effective in controlling weeds, killing less than 48% of all four species. IR at speeds of 1.5 and 2.5 km h−1 killed 100% of all weed species that were at growth stages of > 6 leaves. OF at 1.5 and 2.5 km h−1 killed 100% of young redroot pigweed, common lambsquarters, and ladysthumb, but not white mustard. OF at 2.5 km h−1 speed had the highest energy efficiency and effectiveness for most weed species that were at their early growth stage. Although IR at 3.5 km h−1 used higher energy input and had lower energy efficiency, it showed a potential for controlling a good number of the weed species as effectively or more effectively than OF at 1.5 km h−1.