Informing the operation of intelligent automated intra-row weeding machines in direct-sown sugar beet (Beta vulgaris L.): Crop effects of hoeing and flaming across early growth stages, tool working distances, and intensities

The effective management of intra-row weeds is necessary to preserve crop yields in slow-to-establish directseeded crops like sugar beet, and suitable non-chemical control options are limited. However, the advent of automated intelligent intra-row weeding machines has provided a promising solution. These machines identify individual crop plants and selectively hoe or flame weed the between-crop zone, leaving the intra-row close-tocrop zone untreated. To characterize crop tolerance to intra-row weeding and describe optimal tool working intensities and distances, five pot experiments were performed using sugar beet as the test crop. From cotyledon through the four-leaf stage, hoeing could be implemented as close as 1 cm to the center of sugar beet plants before adverse crop effects were observed. Based on crop injury measured, direct flaming of sugar beet at the cotyledon stage is not advised at any intensity, although flaming tolerance was observed to increase with crop growth stage. Direct flaming did not affect sugar beets when the propane dose was <= 0.74 kg km(-1) at the two-leaf stage, <= 1.49 kg km(-1) at the four-leaf stage, and <= 5.95 kg km(-1) at the six-leaf stage. Sugar beets at the two-leaf growth stage were not damaged by flaming at distances >= 1.5 cm at a propane dose of 3.72 kg km(-1). Field experiments will be necessary to confirm these operational guidelines for next-generation automated intelligent weeders.