Soil water sensor performance and corrections with multiple installation orientations and depths under three agricultural irrigation treatments

Authors: CHEN, YONG - Texas A&M University; Marek, Gary; MAREK, THOMAS - Texas A&M Agrilife; HEFLIN, KEVIN - Texas A&M Agrilife; PORTER, DANA - Texas A&M Agrilife; Moorhead, Jerry; Brauer, David

Submitted to: Sensors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2019
Publication Date: 6/28/2019
Citation: Chen, Y., Marek, G.W., Marek, T.H., Heflin, K.R., Porter, D.O., Moorhead, J.E., Brauer, D.K. 2019. Soil water sensor performance and corrections with multiple installation orientations and depths under three agricultural irrigation treatments. Sensors. 19(13). Article 2872. https://doi.org/10.3390/s19132872.
DOI: https://doi.org/10.3390/s19132872

Interpretive Summary: Freshwater resources for irrigation are decreasing worldwide. Effective irrigation scheduling and use of limited irrigation strategies can extend freshwater resources while maintaining profitable yields. The use of soil water sensors for monitoring soil water status for irrigation scheduling is becoming more prevalent in agricultural production systems. However, limited studies explore how sensor type, installation technique, sensor orientation, and soil texture affect sensor accuracy under different irrigation treatment levels. Therefore, researchers from Texas A&M University and USDA-ARS Bushland, TX compared soil water measurements from four commercially available sensors installed at three depths and orientations with collocated neutron probe moisture meter readings. Results indicated that site-specific sensor calibrations are required for accurate estimation of soil water content for three of the four sensors in the clay loam soil. In general, horizontal installations in undisturbed soil outperformed other installation orientations. These results suggest that some factory calibrated sensors may be useful for irrigation scheduling without applying field corrections.

Technical Abstract: Performance evaluations and corrections of soil water sensors have not been studied using different installation orientations under various irrigation treatments in the Texas High Plains. This study evaluated the performance of four sensors using factory calibration and field correction with reference to calibrated neutron moisture meters (NMMs). Sensor performance was determined using horizontal insertion, laid horizontal placement, and vertical insertion at depths of 15.2, 45.7, and 76.2 cm in a clay loam soil with three irrigation treatments. Results indicated the factory-calibrated Acclima 315L sensor performed satisfactorily using the horizontal insertion as compared to the NMMs at depths of 45.7 and 76.2 cm with mean difference (MD) within +/-2% and the root mean square error (RMSE) < 3.5%. The factory-calibrated Acclima 315L using the horizontal insertion can also be directly used with a 75% crop evapotranspiration (ETc) treatment according to the water storage in the soil profile (MD = 0.72% and RMSE = 2.32%). The factory-calibrated Decagon GS1 and Campbell Scientific 655 using the vertical insertion outperformed other installation orientations. There was a significant underestimation of soil water content using the Watermark 200SS. In summary, field corrections were required for the Decagon GS1, Campbell Scientific 655, and Watermark 200SS sensors.