A UNIVERSAL SPRAY DROPLET ADHESION MODEL

Abstract

Initial spray droplet adhesion is a consequence of dynamic interactions of formulants within the spray dropletduring flight and on impact, physical properties of the droplet, leaf surface morphology, and leaf orientation. The objectiveof this study was to produce a more robust universal spray droplet model using simple parameters (factors) that are easilymeasured. This was achieved by combining the data from two existing models for adhesion, thereby increasing the numberof both species and formulations studied within one model. Plant species and formulations chosen provided a range of leafsurface characters and droplet impaction surface tensions. The velocity model was also improved in order to removeanomalies in the adhesion model. The new universal adhesion model can predict the percentage adhesion of spray droplets(ranging from 109 to 912 .m) impacting any typical leaf surface (providing that it is not excessively hairy) at velocitiesranging from 1 to 3.5 m s-1. The universal adhesion model can also predict adhesion of any aqueous formulation (pure waterthrough to emulsifiable concentrates) with dynamic surface tensions of 20 to 72 mN m-1. Overall, observed and predictedadhesion values were in good agreement, with 72% deviance explained by the new universal model.