Simulating the effect of mucilage deposition on rhizosphere rewetting using a morphological pore network model

Water flow dynamics and hydraulic properties of the rhizosphere are influenced by the exudation of mucilage and microbial extracellular polymeric substances (EPS). Upon drying, mucilage becomes hydrophobic and it impacts the rewetting kinetics of the rhizosphere. The effect of deposited mucilage on rewetting depends on the spatial distribution of the hydrophobic structures, which is a result of the drying rate, soil texture and mucilage concentration. To predict the role of deposited mucilage on rewetting, we simulate the deposition and rewetting process using a morphological pore network model that takes into account the spatial distribution of pores sizes and hydrophobic and hydrophilic structures. We show that the simulated water distribution is controlled by the amount, size and connectivity of the deposited material. The simulated water distribution is compared to neutron imaging experiments conducted in soils with different mucilage content. Comparison of simulations and measurements reveals the governing mechanisms of mucilage deposition and its impact on the environmental conditions in the rhizosphere.