Salinity Effect on Soil Moisture Measurement: Comparison of Different Sensors for two Soil Types.

One of the most challenging problems facing turfgrass managers in the Southwestern United States is addressing the build-up of salts in rootzones as a result of irrigating with available recycled water. To do so requires continuous monitoring of soil salinity and moisture using soil sensors. The salinity level in soils may affect moisture readings, just as moisture levels can affect salinity readings. In addition the accuracy in measuring moisture and salinity depends on the specific type of sensors and on the soil type. A study was conducted at New Mexico State University to compare the accuracy of seven different soil moisture and salinity sensors in 2 soil types. Calibration curves from SDI-12 soil Moisture Transducer, Turf Guard TM Wireless Monitoring System, Watermark Soil Moisture Sensor, ICT 5000-A Soil Salinity Sensor, Sense Wireless Sensor, and IrrolisTM Sense Tx were compared in this study. We measured soil moisture in sandy (sandy skeletal mixed thermic Typic Torriorthents) and clay loams (Typic Torriorthents) with moisture ranging from air dry to near saturation at salinities ranging from 0.5 to 20 dS/m. Generally, the calibration curves showed stronger variation in clay loam suggesting that effects of salinity are more pronounced in clay type soils. Salinity had a negligible effect on moisture readings of Watermark Soil Moisture Sensor. All other sensors must be calibrated for salinity has to be accounted for proper interpretation of readings. Moisture levels, in turn, substantially affected the salinity readings for all the examined sensors.