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United States Department of Agriculture

Agricultural Research Service

Research Project: Development of Water Management Technologies for the Mid-South

Location: Crop Production Systems Research Unit

Title: Evaluation of soil moisture sensors

Authors
item SUI, RUIXIU
item Pringle, Horace -
item Barnes, Edward -

Submitted to: International Irrigation Show
Publication Type: Proceedings
Publication Acceptance Date: October 18, 2013
Publication Date: November 6, 2013
Citation: Sui, R., Pringle, H.C., Barnes, E.M. 2013. Evaluation of soil moisture sensors. International Irrigation Show. pp. 11.

Interpretive Summary: One of the methods for irrigation scheduling is to use soil moisture sensors to measure soil moisture levels in plant root zone and apply water if there is water shortage for plants. USDA-ARS Scientist at Crop Production Systems Research Unit in Stoneville, MS, working with his collaborators, tested measurement accuracy and repeatability of sixty-six soil moisture and soil temperature sensors with six types of Mississippi Delta soil. The sensor calibration was conducted for measuring soil water content. Results of this study showed the soil moisture sensors were capable of detecting general trend of the soil moisture changes. However, the accuracy of sensor measurements varied by sensors and soil types. For accurate measurements, the soil moisture sensor requires soil-specific calibration. The temperature sensors performed very well in the test. Soil temperature could be consistently and reliably determined using the sensors. Information obtained from this work can be used to develop sensor-based irrigation scheduling methods for crop production.

Technical Abstract: This study evaluated the measurement accuracy and repeatability of the EC-5 and 5TM soil volumetric water content (SVWC) sensors, MPS-2 and 200SS soil water potential (SWP) sensors, and 200TS soil temperature sensor. Six 183cm x 183cm x 71cm wooden compartments were built inside a greenhouse, and each compartment was filled with one type of soil from the Mississippi Delta. Sixty-six sensors with 18 data loggers were installed in the soil compartments to measure SVWC, SWP, and soil temperature. Soil samples were periodically collected from the compartments to determine SWVC using gravimetric method. SVWC measured by the sensor was compared with that determined by the gravimetric method. SVWC readings of the sensors have a linear correlation with the gravimetric SVWC (r2=0.82). The correlation was used to calibrate the sensor readings. The SVWC and SWP sensors were capable of detecting general trend of soil moisture changes. However, their measurements varied significantly among the sensors and were influenced by soil property. To obtain accurate soil moisture measurements, the sensors require soil-specific calibration. Their repeatability also should be taken into consideration in the applications. The 5TM, MPS-2, and 200TS sensors performed well in soil temperature measurement test. Their temperature measurements were consistent and reliable with all types of soils.

Last Modified: 8/19/2014
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