Dynamics of spray deposition pattern with UAV-based herbicide application for effective weed management in sugarcane...

Sugarcane productivity is severely constrained by weeds, which reduce yield by 12.0-83.0%, impair crop quality, and harbour pests and diseases. This study was designed to analyze the dynamics of spray deposition pattern of a UAV-based herbicide spraying system for efficient weed management in sugarcane compared to manual knapsack sprayer as a control. The experiment was conducted using a split-plot design with two herbicide combinations as main plots, and evaluating three UAV flight speed and three heights of spray application as sub-plots with three replications.

UAV flight height, flight speed and droplet size significantly influence spray deposition pattern. Optimal conditions for herbicide application were UAV flight speed of 3.0 m s^-1 and a flight height of 1.0 m above the crop canopy using halosulfuron methyl + metribuzin. The spray deposition parameters included a coverage range of 15.9-17.1%, droplet density of 45.4-46.4 droplets cm^-2, number median diameter and volume median diameter of 107.6-109.7 μm and 273.7-276.0 μm, respectively, resulting in a spray drift potential indicator of <15.0%. Transformed data indicated that weed density ranged from 10.5 to 11.9 plants m^-2 with weed dry matter between 4.9 and 5.4 g m^-2.

Under optimized conditions, UAV-based spraying achieved 80.2% weed control efficiency compared to the unweeded plot and was on at par with the control. The UAV-based spraying system operated with a field capacity of 2.6 ha h^-1 and incurred a cost of operation of US$4.37 ha^-1, with water savings of 89.0% and reduced operational cost of 81.6% compared to control. UAV-based spraying thus provides an efficient, economical and sustainable weed management strategy in sugarcane cultivation. © 2026 Society of Chemical Industry.