Qi Qiuju, Yang Hai, Zhou Quanping, Han Xiaole, Jia Zhengyang, Jiang Yuehua, Chen Zi, Hou Lili, Mei Shijia
Nanjing Center, China Geological Survey, Nanjing 210016, China.
Key Laboratory of Watershed Eco-Geological Processes, Ministry of Natural Resources, Nanjing 210016, China.
Sensors (Basel). 2024 Sep 29;24(19):6323. doi: 10.3390/s24196323.
Soil dielectric sensors have been widely used to obtain real-time soil moisture data, which are important for water resource management. However, soluble salts in the soil significantly affect the accuracy of these sensor measurements. Therefore, it is crucial to select suitable soil dielectric sensors for soil moisture measurements at different salinity levels. Eight mainstream sensors (EC-5, 5TE, Teros12, Hydra-probe II, TDR315L, TDR315H, TDR305H, and CS655) were selected and tested at four different soil salinity levels (EC = 3.0, 1.5, 1.0, and 0.75 dS·m). The measured values using the factory calibration formulas were compared at six soil moisture levels. The results showed that the measured soil moisture values from various sensors exhibited varying degrees of overestimation, which increased with increasing salinity. Only EC-5 did not exhibit distortion at high-salinity levels, with the measured values showing a good linear trend compared to the standard values. Mutational distortion of the measured apparent dielectric permittivity occurred in TDR315L, TDR315H, Hydra-probe II, and 5TE at EC = 3.0 dS·m. Insensitive distortion of the measured apparent dielectric permittivity occurred in Teros12 and TDR305H at EC = 3.0 dS·m as well as in Teros12, TDR305H, 5TE and Hydra-probe II at EC = 1.5 dS·m. All tested sensors performed reasonably well at EC ≤ 1.0 dS·m. Seven sensors (excluding CS655) were calibrated within the distortion threshold. The soil moisture accuracy using the calibrated formulas could reach ±0.02 cm·cm. At EC ≤ 1.0 dS·m, most sensors in this study could be applied with the factory calibration formulas. TDR series, EC-5, 5TE and Teros12 were recommended after calibration for EC > 1.0 dS·m. For extremely high soil salinity levels, the TDR series and EC-5 may be the best choices.
土壤介电传感器已被广泛用于获取实时土壤湿度数据，这对于水资源管理至关重要。然而，土壤中的可溶性盐会显著影响这些传感器测量的准确性。因此，选择适合不同盐度水平土壤湿度测量的土壤介电传感器至关重要。选取了八种主流传感器（EC - 5、5TE、Teros12、Hydra - probe II、TDR315L、TDR315H、TDR305H和CS655），并在四种不同的土壤盐度水平（EC = 3.0、1.5、1.0和0.75 dS·m）下进行测试。在六个土壤湿度水平下比较了使用工厂校准公式得到的测量值。结果表明，各种传感器测得的土壤湿度值均表现出不同程度的高估，且随着盐度增加而增大。只有EC - 5在高盐度水平下未出现失真，其测量值与标准值相比呈现出良好的线性趋势。在EC = 3.0 dS·m时，TDR315L、TDR315H、Hydra - probe II和5TE的测量表观介电常数出现突变失真。在EC = 3.0 dS·m时，Teros12和TDR305H以及在EC = 1.5 dS·m时Teros12、TDR305H、5TE和Hydra - probe II的测量表观介电常数出现不敏感失真。在EC≤1.0 dS·m时，所有测试传感器表现都较为良好。七个传感器（不包括CS655）在校准失真阈值范围内进行了校准。使用校准公式得到的土壤湿度精度可达±0.02 cm·cm。在EC≤1.0 dS·m时，本研究中的大多数传感器可使用工厂校准公式。对于EC > 1.0 dS·m，校准后推荐使用TDR系列、EC - 5、5TE和Teros12。对于极高的土壤盐度水平，TDR系列和EC - 5可能是最佳选择。
