Effect of Adjuvants on Physical–Chemical Properties, Droplet Size, and Drift Reduction Potential

Adjuvants alter the physical–chemical properties of pesticide formulations, influencing either the droplet size or drift phenomenon. Selecting the appropriate adjuvant and understanding its characteristics can contribute to the efficiency of Plant Protection Product (PPP) application. This reduces drift losses and promotes better deposition on the crop. The objective of this study was to evaluate the effects of four commercial adjuvants based on mineral oil (Agefix and Assist), vegetable oil (Aureo), and polymer (BREAK-THRU) on the physical–chemical properties (surface tension, contact angle, volumetric mass, electrical conductivity, and pH), droplet size, and drift, using pure water as the control treatment (no adjuvant). Surface tension and contact angle were measured with a DSA30 droplet shape analyzer, while droplet size measurements were determined through a laser diffraction particle analyzer (Malvern Spraytec), using a single flat fan spray nozzle (AXI 110 03) operating at 0.3 MPa. Drift reduction potential was evaluated inside a wind tunnel with an air speed of 2 m s⁻¹. All adjuvants reduced surface tension and contact angle compared to water. volumetric median diameter (VMD) increased for Aureo, Assist, and Agefix, generating coarse, medium, and medium droplets, respectively, while BREAK-THRU formed fine droplets, similar to those generated by water. Aureo had the greatest reduction in Relative Span Factor (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>R</mi><mi>S</mi><mi>F</mi></mrow></semantics></math></inline-formula>), with a reduction of 30.3%. Overall, Aureo, Assist, and Agefix adjuvants significantly reduced the percentage of droplets <100 µm and increased those >500 µm. Drift reduction potential was achieved for all adjuvants, with Aureo showing the highest reduction of 59.35%. The study confirms that selecting the appropriate adjuvant can improve PPP application and promote environmental sustainability in agricultural practices.