Recent concerns regarding herbicide spray drift, its subsequent effect on the surrounding environment, and herbicide efficacy have prompted applicators to focus on methods to reduce off-target movement of herbicides. Herbicide applications are complex processes, and as such, few studies have been conducted that consider multiple variables that affect the droplet spectrum of herbicide sprays. The objective of this study was to evaluate the effects of nozzle type, orifice size, herbicide active ingredient, pressure, and carrier volume on the droplet spectra of the herbicide spray. Droplet spectrum data were collected on 720 combinations of spray-application variables, which included six spray solutions (five herbicides and water alone), four carrier volumes, five nozzles, two orifice sizes, and three operating pressures. The laboratory study was conducted using a Sympatec laser diffraction instrument to determine the droplet spectrum characteristics of each treatment combination. When averaged over each main effect, nozzle type had the greatest effect on droplet size. Droplet size rankings for nozzles, ranked smallest to largest using volume median diameter (D_v0.5) values, were the XR, TT, AIXR, AI, and TTI nozzle with 176% change in D_v0.5 values from the XR to the TTI nozzle. On average, increasing the nozzle orifice size from a 11003 orifice to a 11005 increased the D_v0.5 values 8%. When compared with the water treatment, cloransulam (FirstRate) did not change the D_v0.5 value. Clethodim (Select Max), glyphosate (Roundup PowerMax), lactofen (Cobra), and glufosinate (Ignite) all reduced the D_v0.5 value 5, 11, 11, and 18%, respectively, when compared with water averaged over the other variables. Increasing the pressure of AIXR, TT, TTI, and XR nozzles from 138 to 276 kPa and the AI nozzle from 276 to 414 kPa decreased the D_v0.5 value 25%. Increasing the pressure from 276 to 414 kPa and from 414 to 552 kPa for the same nozzle group and AI nozzle decreased the D_v0.5 value 14%. Carrier volume had the least effect on the D_v0.5 value. Increasing the carrier volume from 47 to 187 L ha⁻¹ increased the D_v0.5 value 5%, indicating that droplet size of the herbicides tested were not highly dependent on delivery volume. The effect on droplet size of the variables examined in this study from greatest effect to least effect were nozzle, operating pressure, herbicide, nozzle orifice size, and carrier volume.

Nomenclature: Clethodim; cloransulam; glufosinate; glyphosate; lactofen.

Recientemente ha habido preocupación por la deriva producto de la aplicación de herbicidas, su subsecuente efecto en el ambiente de los alrededores, y la eficacia del herbicida, lo que ha obligado a los aplicadores a enfocarse en métodos para reducir el movimiento de herbicidas a zonas fuera del objetivo deseado. Las aplicaciones de herbicidas son procesos complejos, y como tales, se han realizado pocos estudios que consideren múltiples variables que afectan el espectro de gotas producto de la aspersión del herbicida. Los objetivos de este estudio fueron elucidar los efectos del tipo de boquilla, el tamaño del orificio, el ingrediente activo del herbicida, la presión, y el volumen de aplicación sobre el espectro de gotas de la aspersión del herbicida. Los datos del espectro de gotas fueron colectados para 720 combinaciones de variables de aplicación-aspersión, las cuales incluyeron seis soluciones de aspersión (cinco herbicidas y agua sola), cuatro volúmenes de aplicación, cinco boquillas, dos tamaños de orificio, y tres presiones de operación. El estudio de laboratorio fue realizado usando un instrumento Sympactec de difracción láser para determinar las características del espectro de gotas para cada combinación de tratamiento