Performance of a multi-sensor capacitance probe in estimating soil water content and field capacity

Authors: MEHATA, MUKESH - Oklahoma State University; DATTA, SUMON - University Of Maine; TAGHVAEIAN, SALEH - University Of Nebraska; OCHSNER, TYSON - Oklahoma State University; MIRCHI, ALI - Oklahoma State University; Moriasi, Daniel

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2023
Publication Date: 1/8/2023
Citation: Mehata, M., Datta, S., Taghvaeian, S., Ochsner, T., Mirchi, A., Moriasi, D.N. 2023. Performance of a multi-sensor capacitance probe in estimating soil water content and field capacity. Journal of the ASABE. 66(2):253-261. https://doi.org/10.13031/ja.15416.
DOI: https://doi.org/10.13031/ja.15416

Interpretive Summary: Commercial soil water content (SWC) sensors are one of the technologies used by farmers for irrigation scheduling to optimize water management for sustainable crop production. However, SWC and field capacity (FC; which indicates the upper limit of plant available water retained by the soil) measurement accuracy of these sensors is affected by soil texture, salinity, and manufacturer recommended calibration methods. Therefore, there is a need for rigorous testing of current sensors in different soil types and calibration methods. In this study, we evaluated the SWC and FC measurement performance of a commercially available multi-sensor capacitance probe under irrigated field conditions across western Oklahoma in sites with different soil textures and salinity levels. In general, results showed that the SWC measurement errors increased with increasing clay and salinity for all calibration methods except the heavy clay method. The SWC measurement errors from the least to the largest were 0.05-, 0.08-, 0.11-, 0.14-, 0.18-, and 0.19-cm3 cm-3, for the silty clay loam, combined, silt loam, heavy clay, sand, and default calibration methods, respectively. However, the combined calibration method with the second least SWC measurement error captured a larger range of SWC fluctuations compared to the silty clay loam method and may therefore be more suitable for irrigation management in soils comparable to those in our study area. Overall, the sensor-based approach produced inconsistent and highly variable estimates of FC. These findings can help producers and irrigation planners determine most appropriate sensors for irrigation scheduling.

Technical Abstract: Maintaining the economic and environmental sustainability of crop production requires optimizing irrigation management using advanced technologies such as soil water sensors. In this study, the performance of a commercially available multi-sensor capacitance probe was evaluated under irrigated field conditions across western Oklahoma. Among the six calibrations provided by the manufacturer, the default and silty clay loam calibrations produced the largest and smallest soil water content errors, respectively. In addition, errors generally increased with clay and salinity, except for the heavy clay calibration, which showed improved performance with increasing clay content. The default and sand calibrations were more sensitive to increases in clay and salinity compared to other calibrations. The field capacity (FC) of soil cores collected at study sites was also determined in the laboratory. These laboratory FC values were used to assess the performance of two sensor-based approaches for estimating FC: days to reach laboratory FC after major watering events and the percentile of collected sensor readings that represented laboratory FC. On average 1-3 days were required to reach laboratory FC, with a large range of 1-9 days. The percentiles representing laboratory FC had an average of 56% and a range of 3-97%. Overall, the sensor-based approach produced inconsistent and highly variable estimates of FC.