{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T17:52:53Z","timestamp":1777571573678,"version":"3.51.4"},"reference-count":32,"publisher":"MDPI AG","issue":"10","license":[{"start":{"date-parts":[[2017,10,19]],"date-time":"2017-10-19T00:00:00Z","timestamp":1508371200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"German Federal Ministry of Education and Research","award":["grant 031A564"],"award-info":[{"award-number":["grant 031A564"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>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.<\/jats:p>","DOI":"10.3390\/s17102387","type":"journal-article","created":{"date-parts":[[2017,10,19]],"date-time":"2017-10-19T11:07:29Z","timestamp":1508411249000},"page":"2387","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":12,"title":["Terahertz Spectroscopy for Proximal Soil Sensing: An Approach to Particle Size Analysis"],"prefix":"10.3390","volume":"17","author":[{"given":"Volker","family":"Dworak","sequence":"first","affiliation":[{"name":"Department Engineering for Crop Production, Leibniz-Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Benjamin","family":"Mahns","sequence":"additional","affiliation":[{"name":"Department Engineering for Crop Production, Leibniz-Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"J\u00f6rn","family":"Selbeck","sequence":"additional","affiliation":[{"name":"Department Engineering for Crop Production, Leibniz-Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4890-9574","authenticated-orcid":false,"given":"Robin","family":"Gebbers","sequence":"additional","affiliation":[{"name":"Department Engineering for Crop Production, Leibniz-Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Cornelia","family":"Weltzien","sequence":"additional","affiliation":[{"name":"Department Engineering for Crop Production, Leibniz-Institute for Agricultural Engineering and Bioeconomy (ATB), Max-Eyth-Allee 100, 14469 Potsdam, Germany"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,10,19]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"367","DOI":"10.1007\/s11119-008-9077-x","article-title":"Soil Heterogeneity at the Field Scale: A Challenge for Precision Crop Protection","volume":"9","author":"Mertens","year":"2008","journal-title":"Precis. Agric."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"237","DOI":"10.1111\/wre.12205","article-title":"Real-time variable-rate herbicide application for weed control in carrots","volume":"56","author":"Dammer","year":"2016","journal-title":"Weed Res."},{"key":"ref_3","unstructured":"Stafford, J.V. (2013). Crop sensor readings in winter wheat as affected by nitrogen and water supply. Precision Agriculture\u201913. 9th European Conference on Precision Agriculture, Wageningen Academic Publishers."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1016\/j.geoderma.2006.03.050","article-title":"High resolution topsoil mapping using hyper spectral image and field data in multivariate regression modelling procedures","volume":"136","author":"Selige","year":"2006","journal-title":"Geoderma"},{"key":"ref_5","first-page":"202","article-title":"Robotic weed monitoring","volume":"61","author":"Bochtis","year":"2011","journal-title":"Acta Agric. Scand."},{"key":"ref_6","unstructured":"Wallor, E., Kersebaum, K.C., Lorenz, K., and Gebbers, R. (2017, January 16\u201320). Connecting Crop Models with Highly Resolved Sensor Observations to Improve Site-Specific Fertilization. Proceedings of the 11th European Conference on Precisin Agriculture (ECPA 2017), Edinburgh, UK."},{"key":"ref_7","unstructured":"Gebbers, R., L\u00fcck, E., and R\u00fchlmann, J. (2013). (2013): 3rd Global Workshop on Proximal Soil Sensing 2013. International Union of Soil Sciences, Working Group on Proximal Soil Sensing. Bornimer Agrartechnische Berichte Heft 82, Leibnitz-Institut f\u00fcr Agrartechnik Potsdam-Bornim e.V."},{"key":"ref_8","first-page":"237","article-title":"Proximal Soil Sensing: An Effective Approach for Soil Measurements in Space and Time","volume":"113","author":"Adamchuk","year":"2011","journal-title":"Adv. Agron."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Gebbers, R., Schirrmann, M., Kramer, E., and Seidel, J. (2011, January 11\u201314). Predicting lime requirements by fusion of proximal soil sensors. Proceedings of the 8th conference on Precision Agriculture, Czech Centre of Science and Society, Prague, Czech Republic.","DOI":"10.3390\/s110100573"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"573","DOI":"10.3390\/s110100573","article-title":"Soil pH mapping with an on-the-go sensor","volume":"1","author":"Schirrmann","year":"2011","journal-title":"Sensors"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"272","DOI":"10.1016\/j.compag.2005.05.001","article-title":"Direct measurement of soil chemical properties on-the-go using ion-selective electrodes","volume":"48","author":"Adamchuk","year":"2005","journal-title":"Comput. Electron. Agric."},{"key":"ref_12","doi-asserted-by":"crossref","unstructured":"Stafford, J. (2005). Evaluation of the penetration resistance along a transect. Precision Agriculture\u2019 05. 5th European Conference on Precision Agriculture, Wageningen Acadamic Publishers.","DOI":"10.3920\/978-90-8686-549-9"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"15","DOI":"10.3997\/1873-0604.2008031","article-title":"Electrical conductivity mapping for precision farming","volume":"7","author":"Gebbers","year":"2009","journal-title":"Near Surf. Geophys."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"2","DOI":"10.1016\/j.geoderma.2012.11.009","article-title":"Resistivity mapping with GEOPHILUS ELECTRICUS\u2014Information about lateral and vertical soil heterogeneity","volume":"199","year":"2013","journal-title":"Geoderma"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"1015","DOI":"10.2136\/sssaj1992.03615995005600040003x","article-title":"Depth Profiles of Electrical-Conductivity from Linear-Combinations of Electromagnetic Induction Measurements","volume":"56","author":"Cook","year":"1992","journal-title":"Soil Sci. Soc. Am. J."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Singh, G., Williard, K.W.J., and Schoonover, J.E. (2016). Spatial Relation of Apparent Soil Electrical Conductivity with Crop Yields and Soil Properties at Different Topographic Positions in a Small Agricultural Watershed. Agronomy, 6.","DOI":"10.3390\/agronomy6040057"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"949","DOI":"10.2136\/sssaj2013.07.0264","article-title":"Sensing of soil organic carbon using VIS-NIR spectroscopy at variable moisture and surface roughness","volume":"78","author":"Rodionov","year":"2014","journal-title":"Soil Sci. Soc. Am. J."},{"key":"ref_18","first-page":"51","article-title":"Soil parameters maps in paddy field using the real time soil spectrophotometer","volume":"63","author":"Shibusawa","year":"2001","journal-title":"JSAM J."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"64","DOI":"10.1016\/j.geoderma.2012.09.007","article-title":"Using a mobile real-time soil visible-near infrared sensor for high resolution soil property mapping","volume":"199","author":"Kodaira","year":"2013","journal-title":"Geoderma"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"31","DOI":"10.1016\/j.geoderma.2016.05.005","article-title":"An assessment of model averaging to improve predictive power of portable VIS-NIR and XRF for the determination of agronomic soil properties","volume":"279","author":"Stockmann","year":"2016","journal-title":"Geoderma"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"9973","DOI":"10.3390\/s111009973","article-title":"Application of Terahertz Radiation to Soil Measurements: Initial Results","volume":"11","author":"Dworak","year":"2011","journal-title":"Sensors"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"799","DOI":"10.1007\/s10762-017-0384-z","article-title":"Invited Review Terahertz Transmission, Scattering, Reflection and Absorption\u2014The Interaction of THz Radiation with Soils","volume":"38","author":"Lewis","year":"2017","journal-title":"J. Infrared Millim. Terahertz Waves"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Li, M., Dai, G., Chang, T., Shi, C., Wei, D., Du, C., and Cui, H.-L. (2017). Accurate Determination of Geographical Origin of Tea Based on Terahertz Spectroscopy. Appl. Sci., 7.","DOI":"10.3390\/app7020172"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Takeya, K., Muto, K., Ishihara, Y., and Kawase, K. (2016). Monitoring Theophylline Concentrations in Saline Using Terahertz ATR Spectroscopy. Appl. Sci., 6.","DOI":"10.3390\/app6030072"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Kuroo, K., Hasegawa, R., Tanabe, T., and Oyama, Y. (2017). Terahertz Application for Non-Destructive Inspection of Coated Al Electrical Conductive Wires. J. Imaging, 3.","DOI":"10.3390\/jimaging3030027"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Lu, Q., and Razeghi, M. (2016). Recent Advances in Room Temperature, High-Power Terahertz Quantum Cascade Laser Sources Based on Difference-Frequency Generation. Photonics, 3.","DOI":"10.3390\/photonics3030042"},{"key":"ref_27","doi-asserted-by":"crossref","unstructured":"Robertson, P.G., Coleman, D.C., Bledsoe, C.S., and Sollins, P. (1999). Standard Soil Methods for Long-Term Ecological Research, Oxford University Press.","DOI":"10.1093\/oso\/9780195120837.001.0001"},{"key":"ref_28","unstructured":"White, R.E. (2006). Principles and Practice of Soil Science. The Soil as a Natural Resource, Blackwell Publishing. [4th ed.]."},{"key":"ref_29","first-page":"81","article-title":"On the electromagnetic theory of light","volume":"5","author":"Strutt","year":"1881","journal-title":"Philos. Mag."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"377","DOI":"10.1002\/andp.19083300302","article-title":"Beitr\u00e4ge zur Optik tr\u00fcber Medien, speziell kolloidaler Metall\u00f6sungen","volume":"25","author":"Mie","year":"1908","journal-title":"Ann. Phys."},{"key":"ref_31","unstructured":"Bohren, C.F., and Huffman, D.R. (1983). Absorption and Scattering of Light by Small Particles, Wiley."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"103","DOI":"10.1016\/j.jqsrt.2017.05.010","article-title":"CELES: CUDA-accelerated simulation of electromagnetic scattering by large ensembles of spheres","volume":"199","author":"Egel","year":"2017","journal-title":"J. Quant. Spectrosc. Radiat. 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