A Coupled Modeling Approach for Root-Soil Interaction Processes Using DuMuX

Abstract:

The water and nutrient uptake of plant roots in soils have a crucial influence on soil physical processes. The interacting processes between plant roots and soil are important for several agricultural problems, for example water management or leaching of pesticides. However, the coupled mechanisms of local soil and root water flow, transport of dissolved substances, root growth, and root uptake are difficult to measure and thus experimental data are rare. Numerical models can be used to understand these complex soil-root systems and help to analyze and interpret experimental measurements. The model approach presented here couples a root system and a soil model. Crucial for this approach is the 1D-3D grid coupling which combines a 1D network grid (root system) with the 3D soil grid. Based on that grid coupling, local processes are defined, for instance the local water uptake of a single root segment. Here, the interface conditions between roots and soil play a major role and we use local grid refinement strategies to better resolve these interface processes. This grid refinement of the 3D soil grid is based on the root network (1D grid) and adapts if root growth occurs. It offers the possibility to describe processes in the soil-plant continuum in a more physical manner avoiding empirical descriptions of root water uptake as a function of bulk matric potential, osmotic potential, root length density, and transpiration rate. Our coupling approach is included into the framework of DuMu^x, an open-source simulator for flow and transport processes in porous media. This implementation combines biological, chemical and physical processes in soil, inside roots, and at root-soil interfaces, and is contained in a sustainable and consistent framework for the implementation. We will show example simulations describing water flow, solute transport and root growth in a soil-root system.