P23 - Physics & Mechanics

Localization and quantification of physical and mechanical rhizosphere properties using X-ray microtomography and micro-sensing techniques

Grafik P23
Phase 2

In the second phase we are going to study the evolution of mechanical soil parameters in a combination of field- and lab-based experiments with a special focus on penetration resistances (PR), including in-situ measurements with a customized micro-penetrometer and relating PR values to spatial root data. Our soil column experiments will comprise different moisture contents and bulk densities in accordance with the approaches of other PP members and aim to quantify the contribution of PR on root growth, as well as the impact physical boundary conditions have on root geometries. The continuing development of pore space will be studied by employing image analysis of pore networks, including an assessment of particle movement with state-of-the-art software (ToolIP-MAVI and LaVision-DaVis). The distribution and transport of oxygen in the rhizosphere has a great impact on microbial activity and bio-chemical reactions and will be monitored by using oxygen and redox micro-sensors during root growth. Stabilization processes of rhizosphere aggregates will be surveilled over an incubation period and be evaluated via dry crushing and wet sieving approaches. In cooperation with the Technical University of Munich and Thünen Institute Braunschweig we are planning to procure spatial information on single macro-aggregates in their function as microbial habitats.

Phase 1

The aim of this project is to non-invasively image and study the evolution of structural patterns in the rhizosphere using soil column experiments (SCE) via X-ray computed tomography and quantitative image analysis. Two textures and genotypes from the central experimental platform will be used to investigate hydraulic and mechanical processes during root growth in a series of experiments. Aim is to use two different moisture contents: an “ideal” and a water-stressed treatment. The water content of this treatment will be determined with a pre-test and should allow sufficient, yet distinctly modified root growth. Our hypothesis is, that the resulting root structure under drought conditions, will be specific to soil texture and maize genotype. Tool-IP will be used for image analysis of pore and root system. Furthermore, deformation patterns will be identified using DaVis, a specialized software based on digital image correlation.
The distribution and transport of oxygen in the rhizosphere has a great impact on microbial activity and bio-chemical reactions and will be analysed by using micro-sensors after the harvest of the plants of the SCE. In collaboration with the working group at the University of Bayreuth the effect of mucilage and soil moisture on micro-mechanical processes during root penetration will be studied. For this workpackage a series of mechanical tests is planned, including penetration resistance, compression and shear vane tests. Another cooperation is planned with the Technical University of Munich regarding rhizodeposition and its effect on structure formation in the rhizosphere by applying novel staining techniques to visualize micro-scale soil organic matter distribution.

Link to English scientific abstract

Link to German scientific abstract