  The agricultural industry requires improved efficacy of sprays being applied
to crops and weeds to reduce their environmental impact and increase financial
returns. One way to improve efficacy is by enhancing foliar penetration. The
plant leaf cuticle is the most significant barrier to agrochemical diffusion
within the leaf. It has been noted that a comprehensive set of mechanisms for
ionic active ingredient penetration through plant leaves with surfactants is
not well defined and oils that enhance penetration have been given little
attention. The importance of a mechanistic mathematical model has been noted
previously in the literature. Two mechanistic mathematical models have been
previously developed by the authors, focusing on plant cuticle penetration of
calcium chloride through tomato fruit cuticles. The models included ion binding
and evaporation with hygroscopic water absorption, along with the ability to
vary the active ingredient concentration and type, relative humidity and plant
species. Here we further develop these models to include lipophilic adjuvant
effects, as well as the adsorption and desorption of compounds on the cuticle
surface with a novel Adaptive Competitive Langmuir model. These modifications
to a penetration model provide a novel addition to the literature. We validate
our theoretical model results against appropriate experimental data, discuss
key sensitivities and relate theoretical predictions to physical mechanisms.
The results indicate the addition of the desorption mechanism may be one way to
predict increased penetration at late times and the sensitivity of model
parameters compares wells to those present in the literature.
