Plot Scale Soil Diffusivity Measurement System - PedoDiff

• Applicants: Dr. Detlef Lazik; Professor Dr. Stephan Peth, since 6/2023
• Subject Area: Soil Sciences
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 470880829

Soils play a crucial role in the global cycle of greenhouse gases and gas exchange between soil and atmosphere is of central importance, but its spatial and temporal dynamics are not yet understood sufficiently. Several small-scale methods exist to determine gas concentration and soil diffusivity (Ds) under laboratory conditions and in the field. However, due to the natural spatial heterogeneity of soils and the temporal dynamics of soil structure, it is hardly possible to transfer these results to the field scale.Our goal is to develop a system for measuring gas diffusivity (PeDiM) in arable soils. The new measuring system averages over local heterogeneities, and measures Ds at the field scale. It has already been shown that gas concentrations can be measured in porous media using tubular, nonporous, gas-selective membranes. The underlying measuring principle is based on the selective diffusion of the individual gas components of soil air into an arrangement of membrane tubes, which can be installed into the soil in defined length. Based on this principle, we will develop an in-situ measuring and monitoring system for Ds. Therefore, the following steps are planned: i) The new measuring principle developed in this project for quasi-continuous determination of Ds is implemented for a PeDiM prototype on laboratory scale. ii) For precise positioning of the PeDiM system in the soil, an installation device that causes minimum soil disturbance will be developed. iii) The PeDiM prototype will be tested in 2D and 3D mesocosm experiments for various substrates under controlled conditions. Parallel diffusion measurements with established measurement techniques allow the configuration of PeDiM to be optimized. iv) The optimized, final PeDiM systems will be installed in an arable field soil, and Ds will be measured in the topsoil for several months. The results will be interpreted in the context of weather-dependent soil water content changes and the dynamic changes of soil structure. Direct comparison of the PeDiM results with established, small-scale lab and profile scale diffusivity measurements will allow the investigation and confirmation of scale effects experimentally.In the end, our project will provide an innovative long-term stable measuring and monitoring system that allows the quasi-continuous measurement of Ds on the field scale for the first time. This captures an essential parameter for transport processes with respect to atmospheric boundary conditions on a scale relevant for soil-atmosphere interaction. Particularly interesting for arable soils is the completely new approach to assess the interaction between temporal dynamics of soil structure and Ds. Furthermore, continuous monitoring of Ds allows the linkage of turnover processes in soils with greenhouse gas emissions, which finally supports the development of predictive models.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr. Jürgen Böttcher
• Ehemalige Antragstellerin: Dr. Nina Stoppe-Struck, until 6/2023