A comparison of seven innovative robotic weeding systems and reference herbicide strategies in sugar beet (Beta vulgaris subsp. vulgaris L.) and rapeseed (Brassica napus L.)

More than 40 weeding robots have become commercially available, with most restricted to use in crops or fallow applications. The machines differ in their sensor systems for navigation and weed/crop detection, weeding tools and degree of automation. We tested seven robotic weeding systems in sugar beet and winter oil-seed rape in 2021 and 2022 at two locations in Southwestern Germany. Weed and crop density and working rate were measured. Robots were evaluated based on weed control efficacy (WCE), crop stand loss (CL), herbicide savings and treatment costs. All robots reduced weed density at least equal to the standard herbicide treatment. Band-spraying and inter-row hoeing with RTK-GPS guidance achieved 75%-83% herbicide savings. When hoeing and band spraying were applied simultaneously in one pass, WCE was much lower (66%) compared to the same treatments in two separate passes with 95% WCE. Hoeing robots Farmdroid-FD20 (R), Farming Revolution-W4 (R) and KULTi-Select (R) (+finger weeder) controlled 92%-94% of the weeds. The integration of Amazone spot spraying (R) into the FD20 inter-row and intra-row hoeing system did not further increase WCE. All treatments caused less than 5% CL except for the W4-robot with 40% CL and the combination of conventional inter-row hoeing and harrowing (21% CL). KULT-Vision Control (R) inter-row hoeing with the automatic hydraulic side-shift control resulted in 80% WCE with only 2% CL. Due to the low driving speed of maximum 1 km h(-1) of hoeing robots with in-row elements, treatment costs were high at 555-804 (sic)ha(-1) compared to camera-guided inter-row hoeing at 221 (sic) ha(-1) and broadcast herbicide application at 307-383 (sic)ha(-1). Even though the costs of robotic weed management are still high, this study shows that robotic weeding has become a robust, and effective weed control method with great potential to save herbicides in arable and vegetable crops.