Shining the light on spectroscopy for sustainable soil management
A giant step: from wet to dry chemistry in soil analysis
Spectroscopy is the study of the interaction between matter and electromagnetic radiation. In recent years, visible near-infrared diffuse reflectance (Vis-NIR) and mid-infrared (MIR) diffuse reflectance spectroscopy has been recognised as a low-cost, efficient, and accurate soil analysis technique and it is becoming increasingly popular.
To support cost-effective, timely solutions for soil analysis and facilitate detailed soil mapping and monitoring, GLOSOLAN launched the soil spectroscopy initiative (GLOSOLAN-Spec) in 2020. Such initiatives, focused on capacity development at country level, through the creation of training materials and by conducting webinars in several languages.
The webinars unpacked the creation and development of national and regional soil spectral libraries and their estimation services as well as the provision of advice and tools. This enables countries to access a wide range of soil data using rapid and cost-effective methods of analysis. Over the long-term, national and regional soil maps can be improved and used to enhance the implementation of sustainable soil management (SSM) practices.
Why spectroscopy is an indispensable tool in soil science
In March 2022, GLOSOLAN-Spec released the first training material on soil spectroscopy for beginners. The publication was the result of the collaboration between soil spectroscopy experts from different institutes including the University of Nebraska, in the United States of America, the University of Sydney, in Australia, and Brazil’s University of São Paulo. It offers an introduction to the use of soil spectroscopy for soil analysis and helps readers understand the basic procedures for using the technology for soil analysis.
The training materials were intended for those new to the data stream wishing to use vis-NIR and MIR spectroscopy in soil analysis. The training manual covers the following topics: (1) the fundamental factors of vis-NIR and MIR and their interactions with soil (2) common lab procedures for vis-NIR and MIR soil analysis, with an emphasis on spectral acquisition, spectral pre-processing, model training and testing, partial least squares regression, and model performance assessment, and (3) vis-NIR and MIR soil spectral libraries available in countries around the world.
Compared to traditional analytical methods, vis-NIR and MIR are easier and quicker to implement and produce more reliable data. Meanwhile, the use of the vis-NIR and MIR instruments follow a set of established and standardized procedures to ensure high-quality spectral measurements. Most importantly, the spectral data contains huge amounts of numerical information, from which statistical models need to be developed to estimate soil properties.
This is a different way of operating by comparison to vis NIR/MIR and other lab analytical methods. Laboratory staff must possess a unique set of skills to interpret results, check errors, and carry out quality control procedures. With the creation of large vis-NIR and MIR spectral libraries at the local, regional, and continental scales, a spatially distributed global network of soil analytical labs based solely on vis-NIR, and MIR is fast becoming practical in agricultural research. Sharing spectral libraries and models among the network will improve the speed and reduce the cost of soil analysis, while making the results easier to compare in and among labs in the network.
This is the first of a series of training materials covering the interpretation of the basic topics in soil vis-NIR and MIR spectroscopy. GLOSOLAN-Spec plans to develop more intermediate and advanced training materials, which will address specific topics related to the use of soil spectroscopy for soil analysis and monitoring.
Today's data-driven agriculture demands access to high-resolution spatial and temporal soil data streams. Soil spectroscopy can help fill this data gap.
Want to brush up your knowledge on spectroscopy? Read the full publication
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Read upon GLOSOLAN-Spec here