Modelling the influence of rhizodeposits on root water uptake

The chemical compounds produced by plant roots, referred to generally as rhizodeposits, affect several soil hydraulic properties. For example, the surface tension of soil water, and the contact angle between menisci and the pore surface. What remains less clear is how these effects manifest when considering soil water infiltration and retention, and the consequent impact on the availability of water for uptake by plant roots. By modifying the Richards equation, a novel model for soil water transport was developed which incorporates the influences of rhizodeposits. The finite-element method was used for simulations of model equations and calibration against experimental data was achieved through Bayesian optimisation. Numerical simulations from the calibrated model were used to investigate the effects of rhizodeposits on root water uptake under various precipitation regimes. It was found that the impact of rhizodeposits on the availability of water to the roots can be either positive or negative depending on precipitation regime and root system maturity. This, therefore, suggests that rhizodeposit characteristics require careful consideration when developing crops for improved water use efficiency and stress-resilience.