Abstract Accurate soil moisture information helps farmers, ranchers, and land managers make informed decisions, and this information often comes from in situ measurements. In situ sensors operate based on a variety of technologies, and there is an ongoing need to determine the accuracy of these sensors across different soils. Therefore, our objective was to evaluate the accuracy of eight in situ soil moisture sensors across soils of differing texture and bulk electrical conductivities (EC b ) at the Marena, Oklahoma, In Situ Sensor Testbed. Sensors included the Stevens HydraProbe, Delta‐T ThetaProbe, three Campbell Scientific sensors (CS229, CS616, and CS655), Acclima TDR‐315, Sentek EnviroSMART, and the Decagon GS1. Accuracy was quantified by comparing sensor measurements with measurements made using a calibrated neutron probe on 17 days from April to October 2020 at four sites and two depths. The CS616 exhibited the poorest accuracy (mean absolute difference MAD = 0.182 cm 3 cm −3 ) and the TDR‐315 showed the best accuracy (MAD = 0.037 cm 3 cm −3 ), although there were no data for this sensor at the site with the highest clay content and EC b . The CS616, CS655, and HydraProbe demonstrated decreasing accuracy with increasing clay content. Likewise, sensor accuracy decreased with increasing EC b for some sensors, with the order of sensitivity being CS616 > Sentek > CS655 > HydraProbe > GS1. Missing data precluded evaluation of EC b effects on the TDR‐315 and ThetaProbe. The CS229 was insensitive to clay content and EC b . Our results highlight the importance of considering soil properties when selecting soil moisture sensors.
Brown et al. (Fri,) studied this question.