Factory calibrated soil water sensor performance using multiple installation orientations and depths

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

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2019
Publication Date: 2/26/2020
Citation: Chen, Y., Marek, G.W., Marek, T.H., Heflin, K.R., Porter, D.O., Moorhead, J.E., Schwartz, R.C., Brauer, D.K. 2020. Factory calibrated soil water sensor performance using multiple installation orientations and depths. Applied Engineering in Agriculture. 36(1):39-54. https://doi.org/10.13031/aea.13448.
DOI: https://doi.org/10.13031/aea.13448

Interpretive Summary: The amount of freshwater available for irrigation is decreasing worldwide; and therefore application of irrigation water needs to be more efficient if crop yields are to be maintained. The use of soil water sensors is commonly advocated to aid irrigation management in crop production systems. However, limited studies explore how sensor type, installation technique, sensor orientation, and soil texture affect sensor accuracy. 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 (NMM) readings. Results from paired comparisons indicated that sight-specific sensor calibrations are required for accurate estimation of soil water content for the clay loam soil. However, soil profile water content values integrated from one sensor compared well with values integrated using NMM readings. These results suggest that some factory calibrated sensors may be useful for irrigation scheduling, provided the implications of installation techniques are understood.

Technical Abstract: The use of soil water sensors is commonly advocated to aid irrigation management in crop production systems. However, there are many questions concerning how sensor type, installation technique, sensor orientation, and soil texture may affect sensor accuracy. A field study was conducted to compare the performance of four commercially available soil water sensors (Acclima 315L, Campbell Scientific 655, Decagon GS1, and Watermark 200SS) using different installation orientations with horizontal insertion, laid horizontal placement, and vertical insertion at depths of 15.2, 45.7, and 76.2 cm in an irrigated field of clay loam soil. Results indicated all four soil water sensors demonstrated similar trends of soil water contents in response to wetting events at the 15.2 cm depth following a four-month settling period prior to the start of the growing season. In addition, comparatively, the Acclima 315L performed well using horizontal insertion compared to the calibrated neutron moisture meter (NMM) at depths of 45.7 and 76.2 cm with an R2 of 0.73 and 0.96 and slope of 1.36 and 1.47, respectively. Overall, site-specific calibrations for each sensor are required for accurate soil water content estimations with this clay loam soil. Overall, however, soil profile water storage integrated using the Acclima 315L at the three depths compared reasonably well with profile water storage determined by the NMMs. These results suggest that irrigation management may benefit from soil profile water estimations derived from factory calibrated sensors, provided sensor type and installation orientation at specific depths are adequately understood.