Combined use of laboratory-based and portable infrared and x-ray fluorescence spectroscopy approaches for the spatial-vertical characterization of samples of selected soil groups

• Applicants: Professor Dr. Bernard Ludwig; Professor Dr. Michael Vohland
• Subject Area: Soil Sciences
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 459985119

Sensor-based soil monitoring, which uses infrared spectroscopic (IR) approaches (Vis/NIRS, MIRS) and energy dispersive X-ray fluorescence spectroscopy (XRF), can quantify soil properties that are essential to derive and evaluate soil functions in high spatial and temporal resolutions. However, collection and evaluation in laboratory-based and portable sensor-based methods have not yet been optimised, making it difficult to critically assess possibilities and limitations of these methods.This proposal aims at optimising the IR and XRF data collection for spectrally-active soil properties using laboratory-based and portable methods for representative soil type complexes of selected soil landscapes. The individual methods are optimised with regard to measuring modes (diffuse reflectance infrared Fourier transform vs. attenuated total reflection for MIRS, powder vs. pellets for XRF), sample preparation (in-situ, dried, dried and sieved, dried and ground), measuring conditions and required sample numbers. Specific depth functions for the different soil properties will be defined in the studied sample profiles.A systematic comparison of calibration algorithms for the quantification of spectrally-active soil properties by Vis/NIRS, MIRS and XRF will be performed. Linear and non-linear calibration approaches and spectral deconvolution will be employed as functions of different sample sizes in multiple partitions. Spectral variable selection and spiking using existing databases will be used. The accuracy of soil profile characterisation by portable and laboratory-based spectroscopic methods as well as a potential transferability of calibrated estimation models will be systematically investigated on individual profiles of the studied soil type complexes. The analysis of site-specific relationships between spectrally-active and spectrally-inactive or spectrally poorly-defined soil properties will be performed both chemometrically and by regression analyses using the spectrally-active soil properties as predictors. The synergistic IR and XRF data analysis using the laboratory-based and mobile approaches will be based on low-, mid- and high-level as well as hybrid data fusion approaches with an emphasis on outer-product analysis, low-level fusion with subsequent automatic wavelength range selection, mid-level fusion using the principal components and high-level fusion using the approaches of Bates-Granger and Granger-Ramanathan.This project provides the tools with which to optimize the data collection of sensor-based soil monitoring, to improve the determination accuracy of differently complex soil properties by data fusion approaches, and to evaluate the applicability of a spatial and profile-related sensor-based monitoring for selected soil type complexes.

• DFG Programme: Research Grants