Water dynamics in two rockwool slab growing substrates of contrasting densities

It is important to determine the dynamics of water and nutrients in the growing substrate used for soil-less cultivation because this allows better time and space management of the water and nutrient supply according to plant needs during each step of the crop cycle. In this study, we focus on the motion of water in rockwool slabs used as growing substrate for a sweet pepper crop. The transport equation is first quoted and root absorption described by a sink term for which the absorption law was experimentally determined. Control volume methods by means of commercial computer fluid dynamics (CFD) software were used to solve the water movement equations numerically in three dimensions. However, as Richards’ equation describing water movements in the substrate is quite different from the Navier–Stokes equations used by the CFD, considerable modifications of the standard transport equations were required. The numerical results were then compared with experimental results and, once validated, the model was reused for a sensitivity analysis with respect to various physical parameters of the substrate. Based on this study, we propose an alternative substrate design more suitable for closed systems.