Modeling Effects of Subsoil Structure On Water and Nutrient Uptake By Plant Roots.

The non-tilled subsoil has generally a higher bulk density than the tilled top soil layer. The stronger compaction of the subsoil may therefore have an important impact on root development and consequently on root water and nutrient uptake. Biopores in the subsoil, either created by roots of previous crops or by earthworms, are often preferential zones of root growth. In order to evaluate the impact of this preferential root growth in biopores on root water and nutrient uptake by means of model simulations, water flow and nutrient transport towards individual roots and within the plant’s root system need to be implemented in the simulation model. In this contribution, we present the potentials of such a soil-root simulation model R-SWMS [Javaux et al., 2008] to address these questions. Scenarios with different degrees of preferential root growth into biopores, different biopore densities in the subsoil, and different properties of biopore walls in terms of their compaction, discontinuity, and local enrichment in nutrients are considered. The construction of biopore geometries and biopore wall properties, which are used to define the structure of the soil domain, is based on X-ray CT scans of soil cores taken from field plots with different pre crops. The development of root structures in biopores and soil matrix is based on field data from the same field plots. The simulated water and nutrient uptake for the different scenarios may then be used as parameters to evaluate the effect of subsoil structure. Although the model simulations do not provide direct experimental evidence, comparison of scenarios may be useful to identify crucial parameters, to quantify potential effects of subsoil structure, and to design future experiments that allow a quantification of the effect of subsoil structure on water and nutrient uptake by crops.

Javaux, M., T. Schröder, J. Vanderborght, and H. Vereecken (2008), Use of a three-dimensional detailed modeling approach for predicting root water uptake, Vadose Zone Journal, 7(3), 1079-1088  doi: 10.2136/vzj2007.0115.