Accurate soil moisture measurements are key for optimising field irrigation and for the precise monitoring of water flow in soil profiles or large watersheds. In recent decades, various soil moisture sensors (SMSs) have been widely used, and several studies have been conducted to evaluate the performance of the SMS technologies under different soil and field conditions. The soluble salt content in soil can affect the sensitivity of SMSs because of their influence on soil permittivity. In this field study, we evaluated different types of SMSs in gypsiferous and salt-affected soils located at two agricultural sites in western Iraq. Two WaterScout capacitance sensors, SM100 and SMEC300, were evaluated in addition to the Watermark granular matrix sensor. Soil moisture measurements by the gravimetric method were compared with SMS readings. Bulk electrical conductivity (ECb) ranged between 3.3–8.1 and 5.6–10.3 dS m⁻¹ for sites 1 and 2 respectively, during the experiment. The results showed that site-specific calibration of the sensors significantly increased their accuracy. At Site 1, the RMSE values for the Watermark, SM100, and SMEC300 sensors changed from 3.48, 2.68, and 1.96 before calibration to 1.25, 0.91, and 0.90, respectively. For site 2, the RMSE values changed from 3.78, 3.09, and 2.34, to 1.37, 1.03, and 0.95, respectively. After the site-specific calibration, the capacitance sensors were sufficiently accurate for scientific measurements. The granular matrix sensors should only be used for field irrigation management if a high-accuracy level is not required and only after site-specific calibration.

准确的土壤湿度测量是优化田间灌溉和精确监测土壤剖面或大型流域中的水流的关键。近几十年来，各种土壤湿度传感器 (SMS) 得到了广泛应用，并且已经进行了多项研究来评估 SMS 技术在不同土壤和田间条件下的性能。土壤中的可溶性盐含量会影响 SMSs 的灵敏度，因为它们会影响土壤介电常数。在这项实地研究中，我们评估了位于伊拉克西部两个农业地点的含石膏和受盐分影响的土壤中不同类型的 SMS。除了 Watermark 颗粒矩阵传感器之外，还评估了两个 WaterScout 电容传感器 SM100 和 SMEC300。通过重量法测量的土壤水分与 SMS 读数进行了比较。在实验过程中，位点 1 和位点 2 分别为^-1。结果表明，传感器的特定地点校准显着提高了它们的准确性。在站点 1，Watermark、SM100 和 SMEC300 传感器的 RMSE 值从校准前的 3.48、2.68 和 1.96 分别变为 1.25、0.91 和 0.90。对于站点 2，RMSE 值分别从 3.78、3.09 和 2.34 更改为 1.37、1.03 和 0.95。在特定地点校准之后，电容传感器对于科学测量来说已经足够准确了。如果不需要高精度水平且仅在特定地点校准后，颗粒矩阵传感器应仅用于田间灌溉管理。