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Terahertz Spectroscopy for Proximal Soil Sensing: An Approach to Particle Size Analysis

Department Engineering for Crop Production, Leibniz-Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany
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Sensors 2017, 17(10), 2387; https://doi.org/10.3390/s17102387
Received: 11 September 2017 / Revised: 13 October 2017 / Accepted: 17 October 2017 / Published: 19 October 2017
(This article belongs to the Section Remote Sensors, Control, and Telemetry)
Spatially resolved soil parameters are some of the most important pieces of information for precision agriculture. These parameters, especially the particle size distribution (texture), are costly to measure by conventional laboratory methods, and thus, in situ assessment has become the focus of a new discipline called proximal soil sensing. Terahertz (THz) radiation is a promising method for nondestructive in situ measurements. The THz frequency range from 258 gigahertz (GHz) to 350 GHz provides a good compromise between soil penetration and the interaction of the electromagnetic waves with soil compounds. In particular, soil physical parameters influence THz measurements. This paper presents investigations of the spectral transmission signals from samples of different particle size fractions relevant for soil characterization. The sample thickness ranged from 5 to 17 mm. The transmission of THz waves was affected by the main mineral particle fractions, sand, silt and clay. The resulting signal changes systematically according to particle sizes larger than half the wavelength. It can be concluded that THz spectroscopic measurements provide information about soil texture and penetrate samples with thicknesses in the cm range. View Full-Text
Keywords: THz; transmission measurement; proximal soil sensing; soil absorption; soil parameters; precision agriculture THz; transmission measurement; proximal soil sensing; soil absorption; soil parameters; precision agriculture
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Dworak, V.; Mahns, B.; Selbeck, J.; Gebbers, R.; Weltzien, C. Terahertz Spectroscopy for Proximal Soil Sensing: An Approach to Particle Size Analysis. Sensors 2017, 17, 2387.

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