Challenges in rapid soil quality assessment and opportunities presented by multivariate chemometric energy dispersive X-ray fluorescence and scattering spectroscopy

- Evaluation of current mainstream spectrometric techniques for soil analysis.
- Practical solutions for rapid soil quality assessment (SQA) via chemometrics.
- Development of miniaturized spectral soil sensors for in situ SQA.

There is, especially in precision agriculture, an increasing demand world over for affordable sensors for in situ (field deployable) soil quality assessment (SQA) applicable at an ecological scale due to the interplay between soil quality and environmental degradation. Although spectrometric (particularly optical) techniques offer the opportunity to meet this demand due to their high analytical versatility, their utility in rapid SQA is limited by the complexity of the soil matrix, and the interpretation of the resulting spectra and (usually) multivariate quality assurance (i.e. SQA) data. In this paper, we examine the utility of spectrometric techniques for soil analysis and critique their applicability to rapid SQA; in particular, we appraise their potential for development towards intelligent portable SQA systems for in situ application. We then evaluate in this perspective the applicability of a new method we have recently developed namely chemometrics energy dispersive X-ray fluorescence and scattering spectrometry (EDXRFS) for SQA, emphasizing its potential for realizing rapid intelligent sensor architecture for in situ SQA. We conclude that a point of care soil sensor that infers soil properties, and intelligently modulates precision agriculture may be realized by integrating the EDXRFS spectroscopy method to a portable XRF spectrometer.