A Novel Electromagnetic Soil Moisture Sensor for Automated Irrigation Scheduling

J.M Blonquist Jr., S.B. Jones, D.A. Robinson, Utah State University.

“Instrumented weather stations are often used for evapotranspiration (ET) determination in order to estimate crop water use for irrigation scheduling. A direct measurement of crop water use by subsurface measurements of soil water content has been limited by the high cost of reliable soil moisture sensors. Recent advances in electromagnetic (EM) sensor technology coupled with improved analysis and communications capabilities has made automated irrigation scheduling based on state-of-the-art soil moisture sensing capability a reality. Our objective was to compare ET-based irrigation scheduling with a novel time domain transmission (TDT) soil moisture sensor. The TDT sensor is designed to directly connect to custom irrigation controllers and conventional irrigation timers and controls irrigation via an easily set threshold soil water content value. A nearby weather station provided estimates for ET for comparison. The Acclima system under-irrigated relative to ET-based irrigation recommendations when a lower flow rate sprinkler head was used, thus conserving water and saving money. The grass did not show signs of water stress. Field observations of the grass in the plot showed a green, healthy lawn.”

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