Influence of Nozzle Type, Speed, and Pressure on Droplet Size and Weed Control from Glyphosate, Dicamba, and Glyphosate Plus Dicamba

Abstract

Improper or suboptimal application techniques can cause decreased weed control and increased environmental contamination. Droplet size is a key factor in pesticide applications in regard to both drift and efficacy. Droplet size can be altered by several application parameters, such as nozzle type, pressure, orifice size, and spray solution. The objective of this study was to evaluate the influence of nozzle type, application speed, and pressure when using glyphosate, dicamba, or glyphosate plus dicamba on droplet size and control of common lambsquarters, velvetleaf, kochia, and grain sorghum. The study was conducted with two herbicides, glyphosate at 0.77 kg ae ha-1 and dicamba at 0.56 kg ae ha(-1), tested alone and in combination. The application rate was 94 L ha-1 at three different speeds (8, 16, and 24 kph), and the pressures used were low, medium, and high for each speed and orifice size combination. The pressures were combined with the appropriate orifice size to deliver a fixed spray volume. An XR, AIXR, and TTI nozzle were used (two of which are venturi nozzle designs). The droplet size ranged from 219 to 232 gm for the XR nozzle across the three solutions, 440 to 482 tm for the AIXR nozzle, and 740 to 828 gm for the TTI nozzle. Solutions using dicamba resulted in the largest droplet size, followed by glyphosate and then the combination. There were no significant interactions for nozzle x herbicide across all species.