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A comparison of laboratory and field calibration of the ECH2O EC-20 soil moisture probe for soils in the Middle Rio Grande Valley




Kinzli, Kristoph-Dietrich, author
Manana, Nkosinathi, author
Oad, Ramchand, author
U.S. Committee on Irrigation and Drainage, publisher

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Throughout the American West irrigated agriculture has been targeted to increase water use efficiency. Soil moisture sensors offer a method to achieve efficiency improvements but have found limited use due primarily to high cost and lack of soil specific calibration equations. In this paper we examine the ECH2O EC-20 soil moisture sensor, a low cost capacitance sensor and develop a unique laboratory calibration method. Field and laboratory calibration equations were developed for 6 soil types in the Middle Rio Grande Valley. The average absolute error in volumetric water content for field calibration was 0.43 m3/m3, and 0.012 m3/m3 for the laboratory calibration. The factory calibration equation for the EC-20 was also evaluated and found to yield an average absolute error of 0.049 m³/m³. We found that the EC-20 is a reliable, cost effective, and accurate sensor, and recommend that the laboratory calibration method presented here be used to obtain maximum accuracy. We also recommend that the field calibration of the EC-20 soil moisture sensor be foregone, as this type of calibration exhibits large error rates. Additionally, it was found that the field calibration method was time consuming, covered a small range of moisture content values and was destructive to the area around installed sensors, which could lead to measurement errors.


Presented at Irrigated agriculture responds to water use challenges - strategies for success: USCID water management conference held on April 3-6, 2012 in Austin, Texas.

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