Dworak Volker, Mahns Benjamin, Selbeck Jörn, Gebbers Robin, Weltzien Cornelia
Department Engineering for Crop Production, Leibniz-Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany.
Sensors (Basel). 2017 Oct 19;17(10):2387. doi: 10.3390/s17102387.
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.
空间分辨土壤参数是精准农业中一些最重要的信息。这些参数，尤其是粒度分布（质地），通过传统实验室方法测量成本高昂，因此，原位评估已成为一门名为近程土壤传感的新学科的焦点。太赫兹（THz）辐射是一种很有前景的无损原位测量方法。258吉赫兹（GHz）至350 GHz的太赫兹频率范围在土壤穿透以及电磁波与土壤化合物的相互作用之间提供了良好的平衡。特别是，土壤物理参数会影响太赫兹测量。本文介绍了对与土壤特性相关的不同粒度级分样品的光谱传输信号的研究。样品厚度范围为5至17毫米。太赫兹波的传输受到主要矿物颗粒级分（砂、粉砂和黏土）的影响。根据大于波长一半的颗粒大小，所产生的信号会系统地变化。可以得出结论，太赫兹光谱测量可提供有关土壤质地的信息，并能穿透厘米级厚度的样品。
