Evaporation rate of droplets of aqueous solutions containing agricultural adjuvants

Abstract

In this work, the impact of three commercial adjuvants on physical properties, spray droplet formation, evaporation kinetics, and post-deposition persistence is evaluated. Spray measurements revealed that surfactant-type adjuvants increased the proportion of small droplets, while the more viscous formulation produced a coarser spray with fewer driftable fines. Using a coupled evaporation–flight model, it was shown that only the smallest atomized droplets experienced substantial shrinkage or complete evaporation before deposition. After impact, droplet lifetime was governed by both deposited droplet size and wettability: stronger spreading led to faster evaporation, whereas larger and more spherical droplets exhibited extended persistence. Overall, the results demonstrate that adjuvant effects on evaporation and drift potential arise primarily from modifications to spray droplet size distributions during atomization, while the effect on intrinsic evaporation kinetics is weak. These findings support formulation-driven strategies to mitigate spray drift and optimize foliar coverage in agricultural applications.