Area treated and waterhemp control in soybean with ONE SMART SPRAY™ technology

Abstract Emerging targeted herbicide application technologies, such as the ONE SMART SPRAY™ system (Bosch BASF Smart Farming, Cologne, Germany), enable postemergence herbicide application only where weeds are detected. Field studies were conducted at four site-years in Seymour, IL, and Janesville, WI, during 2023 and 2024 to compare area treated and waterhemp control between broadcast and targeted herbicide applications in soybean. In Seymour – 2023, early postemergence application (V2 growth stage) resulted in less area treated (26%) than the standard time but required inclusion of a layered residual herbicide to reach 89 to 93% waterhemp control and biomass reduction ≥94% at 28 days after standard application time (DASAT). The standard time (V4 growth stage) in Seymour – 2023 provided 87 to 97% waterhemp control and ≥94% biomass reduction at 28 DASAT but resulted in more area treated 76% at postemergence application. In Seymour – 2024A and Seymour – 2024B, where waterhemp densities were low (≤5 plants m -2 ), treatments had >96% waterhemp control and biomass reduction 28 DASAT, and targeted applications resulted in 17 to 34% area treated, regardless of application time. In contrast, in Janesville – 2024 (high waterhemp density; > 30 plant m -2 ), waterhemp control and biomass reduction did not exceed 90% at 28 DASAT, where area treated was ≥97% at postemergence application, indicating that targeted spraying essentially functioned as a broadcast application and would have required additional postemergence application(s) for effective season-long control. Under high waterhemp densities, frequent nozzle activation reduced potential herbicide savings and diminished differences from broadcast applications, clearly indicating that targeted systems are best suited for fields where effective foundational management practices, including robust preemergence herbicide programs and other integrated weed management tactics, reduce weed density during postemergence application season.