Preferential flow & the effect of soil sensors’ geometry

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True soil sensing means accurately measuring natural water flow through soil. However, Installation of all commercial soil sensors has been scientifically proven in many published papers to disturb the natural soil structure and affect water flow. In 1997 Rothe et al. published a paper in the leading soil science journal, suggesting that water content measurement is “highly sensitive to installation effects”. Tube-shaped sensors (e.g. Sentek, Aquaspy or traditional tensiometers), are inserted into a drilled hole directly or with a lubricating slurry of mixed soil. The geometry of the hole and tube allows water to flow along the shaft of these sensor rapidly; quicker than it would take for it to reach the same depth through undisturbed soil. Fork-shaped sensors (e.g. Decagon and Acclima) require digging a pit, inserting the sensors horizontally in the side walls and filling back the pit with soil. The disturbed soil changes its hydraulic properties and causes preferential flow pathways to form near the sensors. Therefore, in most cases, the sensors’ readings will not accurately represent the actual soil moisture that is available to the plants in the soil, but will rather report a biased soil moisture value depending on the magnitude and nature of the disturbance. The biased readings may lead to ill-advised irrigation decisions, typically resulting in under-irrigated fields and loss of yield. When integrating such inaccurate data into big-data systems, the output would be completely off, and meaningless. To solve this problem, CropX have developed a revolutionary soil sensor with a patented spiral geometry that allows a fast and easy installation, unprecedented accuracy and unbiased results due to the prevention of water flow around the sensor. CropX conducted a study showing that probe geometry may significantly affect the accuracy of the soil moisture sensors. Probes with a geometry that that minimally disturb soil structure, such as the spiral design of CropX probes, are found to be superior to other commercially available probes and provide more accurate readings that closely represent the moisture content of the soil. To view & download the study, visit pref flow whitepaper
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