Simple sensors to achieve fine spatial resolution in continuous measurements of soil moisture and salinity

摘要

It is increasinglynecessary to be able to measure, simultaneously, continuously and at finespatial resolution, the salinity and water content ofsoil. This paper reports the design, construction, calibration and laboratorytesting of two simple but robust instruments that enable this to beachieved. Salinity in solution was measured reliably, at 10-mm spacing, bymulti-electrode resistivity probes up to saturation with NaCl (c. 6 mol l–1), though these probes requiredindividual calibration and were unable to detect precipitated salt. Volumetricwater content was measured with great sensitivity over awide range, from air-dryness (0.06 m3m–3) to saturation (0.55 m3m–3) in a sandy loam, using thermal-conductivity probesthat used a common calibration and were unaffected by the salinity of the soilsolution, by temperature and by ageing. style="line-height: 20px;">Keywords: soil moisture, soil salinity, thermal-conductivity moisture probe, four-electrode salinity probe