Department of Physics, University of Malta, MSD2080 Msida, Malta.
Department of Environmental Engineering DIAM, University of Calabria, 87036 Cosenza, Italy.
Sensors (Basel). 2023 Jun 5;23(11):5357. doi: 10.3390/s23115357.
Agriculture is a major consumer of freshwater and is often associated with low water productivity. To prevent drought, farmers tend to over-irrigate, putting a strain on the ever-depleting groundwater resources. To improve modern agricultural techniques and conserve water, quick and accurate estimates of soil water content (SWC) should be made, and irrigation timed correctly in order to optimize crop yield and water use. In this study, soil samples common to the Maltese Islands having different clay, sand, and silt contents were, primarily, investigated to: (a) deduce whether the dielectric constant can be considered as a viable indicator of the SWC for the soils of Malta; (b) determine how soil compaction affects the dielectric constant measurements; and (c) to create calibration curves to directly relate the dielectric constant and the SWC for two different soil types of low and high density. The measurements, which were carried out in the X-band, were facilitated by an experimental setup comprising a two-port Vector Network Analyzer (VNA) connected to a rectangular waveguide system. From data analysis, it was found that for each soil investigated, the dielectric constant increases notably with an increase in both density and SWC. Our findings are expected to aid in future numerical analysis and simulations aimed at developing low-cost, minimally invasive Microwave (MW) systems for localized SWC sensing, and hence, in agricultural water conservation. However, it should be noted that a statistically significant relationship between soil texture and the dielectric constant could not be determined at this stage.
农业是淡水的主要消耗者，通常与低水资源生产力有关。为了防止干旱，农民往往会过度灌溉，这给日益减少的地下水资源带来了压力。为了改进现代农业技术和节约用水，应该快速准确地估计土壤含水量（SWC），并正确安排灌溉时间，以优化作物产量和用水效率。在这项研究中，主要研究了马耳他群岛常见的具有不同粘土、沙子和淤泥含量的土壤样本，以：（a）推断介电常数是否可以作为马耳他土壤 SWC 的可行指标；（b）确定土壤压实如何影响介电常数测量；（c）为两种不同密度的土壤类型创建校准曲线，直接将介电常数与 SWC 相关联。在 X 波段进行的测量是通过一个实验装置实现的，该装置由一个两端口矢量网络分析仪（VNA）连接到一个矩形波导系统组成。从数据分析中可以发现，对于每个研究的土壤，介电常数随着密度和 SWC 的增加而显著增加。我们的研究结果有望有助于未来的数值分析和模拟，旨在开发低成本、微创的微波（MW）系统，用于局部 SWC 感测，从而实现农业节水。然而，应该注意的是，在现阶段，还不能确定土壤质地和介电常数之间存在统计学上的显著关系。
