Factors affecting the behaviour of soil salinity sensors

Summary

The stability of 22 commercially available soil salinity sensors was studied: 23% were considered to be stable under the imposed experimental conditions during a period of 14 months. During the same time period, accuracy of sensors decreased from ±0.32 to ±0.98 mmho cm⁻¹. Time response is adequate under saturated conditions (Fig. 3) but it may be extremely long for unsaturated soils (Fig. 4 and Table 2). Measurements of the soil solution electrical conductivity with salinity sensors and by the suction probe extraction technique demonstrated that the soil matrix affects the salt distribution near soil surfaces and within the pore space. Time response (63% of total change) of sensor thermistor is 0.9 min, with an estimated accuracy of ±0.3 °C.