Herbicide Micro-Dosing for Weed Control in Field-Grown Processing Tomatoes

Weeds within the seedline area and in close proximity to crop seedlings are highly competitive and reduce cropyield. When chemically selective herbicides are unavailable or ineffective, spatially selective removal is required and is oftena manual operation. Automation of selective weed removal requires sensing and actuation systems. Image and spectralanalysis can discriminate weeds from crop plants while precise dosing methods are required for automated treatment of small,distinct weeds. A pulsed-jet, micro-dosing actuator was developed to apply liquid herbicide treatments. The biologicalperformance of micro-dosing was evaluated in field-grown processing tomatoes with a nonselective herbicide (glyphosate)in mixtures including surfactants and splash-inhibiting polymers. Liquid dose rates were 37 .L/cm2 for treatment areas of6.3 . 12.5 mm. Pulse durations were 6 to 10 ms. A formulation including a surfactant and a polymer provided efficacy whilereducing splash, i.e., micro-drift that caused phytotoxicity to adjacent crop plants. When treated with the micro-dosingsystem, splash-related phytotoxicity produced greater yield suppression than competition from escaped weeds. The resultsestablished that use of non-selective herbicides for micro-scale dosing of weeds during early crop growth is a feasiblealternative to broadcast application of chemically-selective herbicides. The optimal point of crop and weed growth for usinga weed-sensing, one-pass post-emergent control system requires understanding of crop development, weed competition, andthe ability of the crop to recover from inadvertent splash of micro-dosed materials.