Interface Properties and Droplet Spectra as a Function of Adjuvants and Spray Nozzles

Abstract

The process of droplet formation during spraying is influenced by several factors, including the nozzle type and the use of adjuvants. This study aimed to investigate the effect of adding adjuvants to spray solutions using different nozzles, with a focus on droplet spectra, and to examine the impact of the contact angle and the surface tension on this process. The surface tension and contact angle were evaluated using a droplet shape analyzer. The experiment was conducted in a completely randomized design (CRD) using four treatment solutions: water alone and water mixed with three different types of adjuvants, including fatty acid esters (vegetable oil-based), polyether–polymethyl, and polydimethyl-siloxane. The droplet spectra (volume median diameter, relative amplitude, and droplets smaller than 100 µm) were assessed using a particle size analyzer. A CRD with a 4 × 2 factorial scheme was used to assess the effects of the four treatment solutions and two flat-fan nozzles (ULD 120-02 with air induction and LD 110-02 without air induction technology). The polyether–polymethyl considerably reduced the contact angle and surface tension (226% and 180%, respectively, in relation to water). However, it did not homogenize the droplet spectra or reduce the drift risk. The vegetable oil-based adjuvant increased the droplet size when the standard flat-fan nozzle was used. No significant correlation was found between the surface tension and contact angle regarding the droplet spectra parameters. The effect of adjuvants on the droplet spectra was found to be dependent on the nozzle type, which prevents generalizations about the implications of their use.

Keywords

• agricultural spraying
• air induction technology
• application technology
• contact angle
• droplet size
• droplet shape analysis