Optimum Droplet Size Using a Pulse‐Width Modulation Sprayer for Applications of 2,4‐D Choline Plus Glyphosate

Abstract

Core Ideas Model fit increased by predicting optimum droplet sizes for site‐specific scenarios. Generally, an Extremely Coarse spray would be recommended for a 2,4‐D choline plus glyphosate application. Site‐specific weed management using PWM sprayers was both manageable and effective. Weed control reductions were observed as droplet size increased at several site‐years. Alternative drift reduction efforts must be identified to avoid weed control losses. ABSTRACT The delivery of an optimum herbicide droplet size using pulse‐width modulation (PWM) sprayers can reduce potential environmental contamination, maintain efficacy, and provide more flexible options for pesticide applicators. Field research was conducted in 2016, 2017, and 2018 across three locations (Mississippi, Nebraska, and North Dakota) for a total of 6 site‐years. The objectives were to evaluate the efficacy of a range of droplet sizes (150 µm [Fine] to 900 µm [Ultra Coarse]) using a 2,4‐D choline plus glyphosate pre‐mixture and to create novel weed management recommendations using PWM sprayer technology. A pooled site‐year generalized additive model explained less than 5% of the model deviance, so a site‐specific analysis was conducted. Across the Mississippi and North Dakota sites, a 900‐µm (Ultra Coarse) droplet size maintained 90% of the maximum weed control. In contrast, at the Nebraska sites, droplet sizes between 565 and 690 µm (Extremely Coarse) were almost exclusively required to maintain 90% of the maximum weed control, likely due to weed leaf architecture. Severe reductions in weed control were observed as droplet size increased at several site‐years. Alternative drift reduction practices must be identified; otherwise, weed control reductions will be observed. This research illustrated that PWM sprayers paired with appropriate nozzle–pressure combinations for 2,4‐D choline plus glyphosate pre‐mixture could be effectively implemented into precision agricultural practices by generating optimum herbicide droplet sizes for site‐specific management plans. To fully optimize spray applications using PWM technology, future research must holistically investigate the influence of application parameters and conditions.

Evaluation of optimal droplet size for control of Palmer amaranth (Amaranthus palmeri) with acifluorfen

“…In terms of dry biomass reduction, deviance explained was 1%, indicating that 99% of dry biomass reduction must be explained by factors other than spray droplet size. Similar deviance explained values resulting from prediction models developed across site-years have been reported by Butts et al (2018Butts et al ( , 2019aButts et al ( , 2019c. Weather conditions, geographic location, soil type, fertility levels, weed density, and population genetics should be investigated in future research to implement acifluorfen model assumptions for Palmer amaranth control and dry biomass reduction across multiple locations.…”

“…Smooth-term estimated degrees of freedom (EDF) and deviance explained values are shown in Table 3. A smooth-term EDF of 1 indicates minimum GAM model fluctuation and characterizes a linear model (Butts et al 2018(Butts et al , 2019a(Butts et al , 2019c. Deviance explained values provide a model-fitting estimation between predicted values and actual observations, with greater percentages representing an overall better model fit.…”

“…Prior to herbicide application, 10 plants per plot were tagged at the soil surface for aboveground biomass evaluation. To facilitate evaluation of Palmer amaranth control in response to droplet size, plants were allowed to grow up to 15 cm (Butts et al 2018(Butts et al , 2019a(Butts et al , 2019c. Rulers were used to ensure that tagged plants did not exceed 15 cm in height.…”

“…The development of digital application technology has allowed the implementation of pulse width modulation (PWM) systems into agricultural sprayers (Bode and Bretthauer 2007). PWM sprayers increase application flexibility by delivering a specific droplet size distribution at different driving speeds while variably controlling flow (Butts et al 2018(Butts et al , 2019a(Butts et al , 2019b. In PWM systems, each spray nozzle is equipped with an electronically powered solenoid that typically pulses on a frequency of 10 pulses s -1 (Giles and Comino 1989).…”

The effect of spray solution storage time on nicosulfuron efficacy applied in Urochloa brizantha cv. Marandu

“…However, whether in terrestrial or aerial spraying, success in phytosanitary treatment depends not only on products quality, but also on the technology developed for their application. The need for more economical herbicide applications and environmentally safe is a major concern in agricultural industry (Butts et al, 2019).…”