Dr Maria Knadel presented selected studies from the Soil Physics and Hydropedology section, at the Dept. of Agroecology, Aarhus University.

The use of near-infrared spectroscopy (NIRS) at the Department was initiated with a project dedicated to in-situ mapping of agricultural soils using a mobile sensor platform. Shortly after, a need for a development of a national soil spectral library was recognised.

The development of today’s Danish soil spectral library (SSL) was launched by a national collaborative project between Aarhus University, an advisory service and FOSS Analytical. The project was dedicated to implementation of soil spectra in the assessment of soil quality, with the university providing soils with meta data, expertise and knowledge on soils and SSLs.

The company FOSS Analytical providing spectral instrumentation, and the advisory service disseminating project results to farmers and advisors. The success of the project and the establishment of the SSL served, and still serves, as a base for further research work at the university and facilitates a solid foundation for ongoing collaboration within the university, other scientist in Denmark and abroad, and the company.

The development of the SSL is an ongoing process where new samples are added and the library is updated. Since its first creation, a wide range of projects on laboratory-based spectroscopy rolled out. The results of studies presented by Dr Knadel cover not only the estimation of basic soil properties but also functional soil properties, such as structural, surface or engineering properties, or properties related to contaminants transport and binding.

At present, the application of field spectroscopy is less common than laboratory investigations in studies from Denmark, but also worldwide. That is due to the challenges related with uncontrolled field conditions and external factors having degrading effects of on soil spectra. To address these issues Aarhus University is co-leading a joint European project - ProbeField (in the framework of the H2020 EJP SOIL programme) which has been recently funded. The aim of the project is to develop a novel protocol for robust in-field monitoring of carbon stock and soil fertility based on among other techniques: soil spectroscopy and existing soil spectral libraries*.

Spectroscopy-based soil characterisation is also used by the researchers in modelling and digital soil mapping. In practice the investigated methods and approach proposed can be also employed by farmers and agricultural consultancy companies in the regulatory decision-making process. 

Dr Nicola Bork presented the activities within NIRS to soil at FOSS and introduced the solution for analysis of basic soil properties based on a bench NIR sensor.

The company developed a soil application package with a NIR instrument, digital services for data management, calibration development, maintenance, and distribution. The package includes also digital training, a dedicated application guide covering the performance and step by step guid for sample handling and calibration. Dr Bork shared further examples from a project with major soil laboratory reporting similar error for soil organic carbon to the reference wet chemistry technique and a better repeatability than the reference method. Finally, a demonstration of the instrumentation and how it operates was given.

After an hour of presentations, the speakers got the chance to address a total of 45 questions from the audience facilitating a vivid discussion. A total of 266 participants representing 77 countries joined live session.  

Photograph. Caption: Soil NIRS laboratory at Aarhus University. ©Aarhus University/Maria Knadel

*Apart from the research activities dedicated to soil spectroscopy, the Department offers a PhD course in this topic. The course is designed to provide an in depth theoretical and practical knowledge of NIRS and its application to soil science. The objectives of the course are to develop the participants’ ability to use NIRS sensors and provide the basic skills to analyse soil spectra. The overall goal is to show the possibilities of NIRS and contribute to innovative soil analysis that can provide fast and accurate estimates of soil properties illustrating the potential alternative to current traditional wet chemistry analysis. The application of spectroscopic techniques in the Departments has proven the possibility of a determination of a wide range of soil characteristics in a cheaper and faster manner. This approach can provide more insight on fundamental understanding of soil and its functions.