Which sensor category would be used to monitor soil moisture?

• A. Weather station
• B. Water quality
• C. Power
• D. Soil moisture

Answer: (D)

Direct measurement of soil moisture relies on soil moisture sensors. These devices sense the water content in the soil, typically provided as volumetric water content or soil moisture tension, and are placed in the root zone to inform irrigation timing. By giving real-time readings, they tell you when to irrigate and when the soil already has enough moisture. Other sensor categories track different things: weather station sensors gather climate data used for ET estimates, water quality sensors monitor salinity and pH in irrigation water, and power sensors track energy or electrical status. None of these directly measure soil moisture, so for monitoring soil moisture specifically, soil moisture sensors are the right choice.