Comparative analysis of four soil water sensors for irrigation water management

Abstract With the increasing availability of soil water sensing technologies for irrigation management, it is essential to compare sensor options in production field settings. In this study, four soil water sensors—CropX, FieldNet with Watermark sensors, Valley Aqua Trac Lite using Sentek probe, and Aqua Trac Pro with Watermark sensors—were compared with Acclima TDR‐310H (where TDR is time domain reflectometry) at four depths during the 2021–2023 growing seasons in three production fields in southeastern North Dakota. The Acclima sensor was calibrated in the same fields where the sensors were installed and was considered the reference standard for comparison with the other sensors. Soil water characteristic curves were developed to convert soil water potential from Watermark sensors from FieldNet and Valley Aqua Trac Pro systems to volumetric water content for comparison to other sensors. Overall, Aqua Trac Lite and CropX had mixed results at all depths (root mean square error [RMSE] typically above 0.05 cm 3 cm −3 ). Lindsay and Aqua Trac Pro had better (smaller) RMSE across depths at sites 1 and 3 compared to CropX and Aqua Trac Lite. As expected, measured soil water contents varied over time for all sensors (i.e., significant main effect for timestamp [ p < 0.05]). However, the sensor type's effect on θ v was consistent across all 3 years (i.e., main effect for sensor type [ p < 0.05] but there was no interaction with timestamp [ p > 0.05]). These results will help farmers and crop consultants understand sensor performance when selecting soil water sensors for irrigation management.