Horizontal water diffusion model of perlite in a container

Modelling of soil moisture dynamics has attracted attention as a potential solution to lighten the burden imposed on farmers. An accurate soil moisture prediction by the model is necessary to produce an automatic water supply control system, which makes it easy to keep the best soil water conditions for crops. In the case of container cultivation, perlite, which has both suitable water drainage and retention characteristics, is used as soil. However, the water dynamics and distribution in perlite have still unclear. Although there are several models for diffusion dynamics, most of them focus mainly on the direction of gravity. In this work, we study the water dynamics and horizontal distribution of perlite in a container by modelling from experimental data. The experimental results show that the water distribution in perlite over time cannot be expressed as normal diffusion. We propose an extended model that considers the horizontal distribution of the water flux effect and the moisture retention effect. We also discuss the validity of the extended model in terms of water retention and drainage characteristics of perlite.