Authors:
Dr. Maxime Phalempin | UFZ Helmholtz Centre for Environmental Research | Germany
Ulla Rosskopf | Leibnitz Universität Hannover | Germany
Dr Steffen Schlüter | UFZ Helmholtz Centre for Environmental Research | Germany
Prof. Doris Vetterlein | UFZ Helmholtz Centre for Environmental Research | Germany
Prof. Stephan Peth | Leibnitz Universität Hannover | Germany
In the literature, studies focusing on the interactions between root growth and soil physical properties usually assume soil properties to be “bulk properties” and disregard discontinuities and microscale heterogeneity. So far, soil physical properties with respect to root growth has mostly been addressed as a bulk or artificially, e.g., with the creation of artificial macropores. Structured soils, however, consist of a multitude of loose and dense soil particles, of which their complex arrangements create paths of least resistance for root growth. To address the heterogeneity of soil strength at the microscale, 3D penetration resistance data would be excellent tools. In this work, we provide the very first proof of concept on how to generate such data. To do so we carried out co-located measurements of gray value obtained with X-ray CT and penetration resistance measured with cone penetration test. We investigated two soil textures, i.e., loam and sand. To carry out the GV measurements, we developed a new approach which considers an adaptive volume of the zone of influence of the penetrometer tip as a function of soil density. By fitting an empirical relationship to the pairs of points of penetration resistance and gray value, we could convert gray values of the X-ray CT images into penetration resistance values, at a spatial resolution equal to that of the shaft diameter of the penetrometer tip we have used. In our contribution, we will present some methodological considerations for the generation and adequate use of 3D penetration resistance data. We will also demonstrate how such data can be used to derive quantitative information on root-soil interactions processes.