Droplet Size characterization of agricultural sprays using laser diffraction

Abstract

Accurate spray characterization helps to better understand the pesticide spray application process. The goal of this research was to present the proof of principle of a droplet size and velocity measuring technique for different types of hydraulic spray nozzles using laser diffraction method. Control of agricultural spray deposition is vital if pesticides and other agrochemicals are to be delivered safely and effectively to the intended target. One of the most significant parameters in controlling the behaviour of these sprays is the droplet size. Research has shown that the spray droplet size, and the factors which affect it, is one of the most important variables affecting spray deposition levels downwind of the application area (spray drift). The droplet size also defines how the spray is accumulated by the target species. A variety of different particle sizing techniques have been used to characterise agricultural sprays in the past. Of those available, laser diffraction provides a flexible and rapid method for the assessment of the delivered particle size. Modern laser diffraction equipment allows data acquisition rates of up to 2500Hz to be achieved (one measurement every 0.4ms), permitting both the average particle size delivered by the spray system and the spray dynamics to be assessed. This allows for an increased understanding of the atomisation process and the effect of formulation changes on the delivered particle size, leading to improved efficiency of delivery to the intended target.