Daugherty Water for Food Global Institute



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Just like fuel gauges monitor fuel levels in a gas tank, soil moisture sensors monitor moisture levels in the soil. Irrigating without using soil moisture sensors is similar to driving without a fuel gauge: you’re likely to be overcautious to ensure you get to where you’re going! Soil moisture probes are designed to estimate soil volumetric water content based on the dielectric constant of the soil. The dielectric constant can be thought of as the soil’s ability to transmit electricity. The dielectric constant of soil increases as the water content of the soil increases, since the dielectric constant of water is much larger than other soil components, including air. So, measurement of the dielectric constant gives a predictable estimation of water content. Like a fuel gauge tells a driver when the tank is full, soil moisture sensors tells crop producers when their crops do not need additional watering.