The efficacy of sulfosulfuron on spontaneous barley as affected by the type, size, and outlet design of flat fan nozzle.

Sulfosulfuron, when applied at a label-increased rate, can control spontaneous barley (Hordeum spontaneum K. Koch) in wheat. For optimization, a dose-response bioassay was conducted on three-leaf spontaneous barley plants treated with six sulfosulfuron doses (0, 6.75, 13.5, 27, 40, and 80 g a.i. ha⁻¹) under the wind speed of 0 and 6 m s⁻¹. Each of the doses was sprayed with three nozzle types (standard, anti-drift, and air induction), each with three outlet designs (single, dual, and triplet flat fan) at three nozzle sizes (02, 03, and 04, delivering 210, 315, and 420 L ha⁻¹, respectively). Moreover, at 0 m s⁻¹ wind, vertically and horizontally oriented water-sensitive papers (WSP) were treated with a dose of 40 g a.i. ha⁻¹ sulfosulfuron. The horizontally-oriented WSP wetted less as the droplet size produced by the nozzles increased. The vertically-oriented WSP wetted more as the outlet number of nozzles increased. When the ED 90 values averaged over the nozzle type at 0 m s⁻¹ wind, the standard nozzle type had the best performance, followed by the anti-drift nozzle type and then the air induction nozzle type, while this ranking reversed at 6 m s⁻¹ wind. Moreover, the optimized rates were achieved by increasing the spray volume and the outlet number of all nozzle types at both wind speeds. At 0 m s⁻¹ wind, the standard triplet flat fan nozzle delivering 420 L ha⁻¹ was the best with a low endo-drift. At 6 m s⁻¹ wind, the air induction triplet flat fan nozzle delivering 420 L ha⁻¹ was the best nozzle having a low exo-drift. • Here is a nozzle selection guide to optimize sulfosulfuron efficacy on wild barley. • The larger the droplet size, the more the spray endo-drift. • Increased outlet number of flat fan nozzle, a method to decrease spray endo-drift. • The larger the droplet size, the less the efficacy of sulfosulfuron. • Increased spray volume mitigates droplet size effect on sulfosulfuron efficacy. [ABSTRACT FROM AUTHOR]