Coupling Dynamic Root Growth with a Water and Solute Transport Model to Estimate Water and Nutrient Uptake by Maize Plants.

Plant roots are at the interface between the soil and the atmospheric domain. They are taking up water from the soil and deliver it to the plant, which evaporates it over the leaf stomata into the atmosphere. We are interested in investigating maize root traits which are beneficial for water and nutrient uptake under suboptimal soil conditions. Roots traits of interest for example include branching angles, gravitropism, and relative sink strength of the primary root. These traits determine the soil volume explored by a single plant and competition among roots. Assumption of equal or layered root distribution in the soil profile would not account for root competition. Thus we are creating different root architectures in three dimensions with the dynamic root growth model SimRoot, which has been developed in the Lynch lab since 1994. SimRoot is coupled with SWMS_3D, a three dimensional finite element model for estimating water and solute transport in porous media. Water and nutrient transport in the soil is estimated by SWMD_3d, and water and nutrient uptake by the roots is estimated by SimRoot. Knowledge on root architecture (obtained by laboratory and field experiments) and nutrient uptake kinetics (obtained by laboratory experiments) are used in SimRoot as input parameters. With the coupled program we test different root growth scenarios of single plants and estimate their water and nutrient uptake behavior in space and over time. Results are presented for selected root architectures and varying environmental factors like soil properties and climate conditions.