The near infrared (NIR) occurs at frequencies of 1.2x10^14-4x10^14 Hz, with wavelengths between 700 and 2500nm. While fundamental molecular vibrations occur in the MIR range, vibration overtones and combination bands can be detected in the NIR range. NIR instrumentation is field portable and less expensive, and is therefore employed in PSS applications.
NIR can be used to measure soil water content, carbon, texture (clay minerals), iron-oxides and a number of other correlative parameters (e.g. CEC).
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3. Viscarra Rossel, R. A., Cattle, S. R., Ortega, A. & Fouad, Y. (2009) In situ measurements of soil colour, mineral composition and clay content by vis-NIR spectroscopy. Geoderma, 150(3-4), 253-266.