Abstract In this study, four textural classes of soil (Clay, Clay Loam, Loam, and Loamy Sand) were used to investigate the dielectric properties of soils, using a vector network analyser with an open-ended coaxial probe kit at room temperature (25 ± 2°C) in the 700–7000 MHz microwave frequency range. Four levels of soil moisture content (oven dry, 33% field capacity, 66% field capacity and 100% field capacity) were maintained to perform the experiment with three replication and three observation each. The results showed that, with increasing soil moisture, from oven dry conditions to 100% field capacity, both the real (Dielectric Constant) and imaginary (Loss Factor) components of the dielectric properties increased; however, the responses were not linear. The dielectric properties of oven dry soils were very low compared with the soils with higher moisture content. Therefore, soil moisture was the major contributor to the dielectric behaviour of soil. The dielectric properties of sandy soil were much lower than the other soils; however, the dielectric loss factor of the Dookie clay soil was higher compare with the other soils. Models were developed to explain the dielectric properties of soils as a function of frequency and moisture content. The goodness of fit (r2) for these models varies between 0.952 for the Dookie Sandy Soil to 0.997 for the Dookie Loam Soil, suggesting that these models were adequate to describe the dielectric properties of these soils over the range of frequencies and moisture contents assessed in this study. Another model was developed to estimate the expected penetration depth of electromagnetic waves in these soils, based on the model of the dielectric properties. It was clear that penetration decreases with both frequency and moisture content. Low frequencies penetrate further into the soils than higher frequencies. Similarly, dry soils allow further penetration than moist soils.

中文翻译：

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作为土壤类别和水分含量的函数的土壤介电特性的测量和建模

摘要 在这项研究中，四种质地类型的土壤（粘土、粘土、壤土和壤土砂）用于研究土壤的介电特性，使用矢量网络分析仪和开放式同轴探针套件在室温下 (25 ± 2°C) 在 700–7000 MHz 微波频率范围内。维持四个水平的土壤含水量（烘箱干燥、33% 田间持水量、66% 田间持水量和 100% 田间持水量）以进行实验，每个重复 3 次，观察 3 次。结果表明，随着土壤湿度的增加，从烘干条件到 100% 的田间容量，介电特性的实部（介电常数）和虚部（损耗因子）分量均增加；然而，反应不是线性的。与含水量较高的土壤相比，烘干土壤的介电性能非常低。因此，土壤水分是土壤介电行为的主要贡献者。砂质土壤的介电特性远低于其他土壤；然而，Dookie 粘土的介电损耗因子高于其他土壤。开发了模型来解释土壤的介电特性作为频率和水分含量的函数。这些模型的拟合优度 (r2) 在 Dookie Sandy Soil 的 0.952 到 Dookie Loam Soil 的 0.997 之间变化，这表明这些模型足以描述这些土壤在频率和水分含量范围内评估的介电特性这项研究。基于介电特性模型，开发了另一个模型来估计电磁波在这些土壤中的预期穿透深度。很明显，渗透率随着频率和水分含量而降低。低频比高频更深入土壤。同样，干燥的土壤比潮湿的土壤更容易渗透。