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Modelling adhesion and retention processes
A simple technique for describing “leaf roughness” was developed as a universal quantitative parameter (see also advances in applications). This includes effects from leaf surface topography, wax crystal structure and composition. It is based on a static contact angle measurement of acetone:water (20:80 v/v) droplets on leaf surfaces. The advantage of this method is to be able to group leaf surfaces and species by this ‘roughness factor” or to use it for calculating adhesion of droplets of different spray formulations.
A large number of species, including weed and crop plants, fruit and foliage, have been surveyed by this method and grouped into easy, difficult and very difficult to wet categories. It can rank plant surfaces for retention properties and indicate whether the addition of a surfactant is likely to be beneficial. It can predict relative initial spray adhesion on different surfaces and species. Measurement of droplet advancing and receding contact angles can be used in mathematical models of impaction processes (droplet adhesion, bounce or shatter).
Mercer G, et al. 2007. Process driven models for spray retention by plants. Proceedings of 2006 Mathematics in Industry Study Group. Ed. G Wake, Massey University. Pp 57-85.