Which data inputs are used by weather sensors in modern controllers to adjust watering?

• A. Soil moisture and soil type.
• B. Rainfall and wind speed.
• C. Rainfall, temperature, and ET data.
• D. Water hardness.

Answer: (C)

Weather-based irrigation controllers adjust watering by using data that reflect current and expected plant water demand. Rainfall data tell the system when it has recently received water, so it can skip or cut back irrigation after rain. Temperature helps estimate how quickly the landscape will lose water, influencing how much watering is needed. ET data, short for evapotranspiration, represents the actual water demand of plants under the current conditions, combining factors like temperature, humidity, wind, and sun. Together, rainfall, temperature, and ET data allow the controller to schedule irrigation to meet plant needs while avoiding waste.

Soil moisture and soil type are soil properties, not weather inputs, and water hardness has no bearing on irrigation timing. Rainfall and wind alone don’t capture plant water demand as effectively as including ET data.