Which statement about ET-based irrigation control best describes its benefit?

• A. It uses rainfall data to decide irrigation without ET.
• B. It only reduces watering during droughts.
• C. It measures soil color to decide watering.
• D. It uses ET data to estimate plant water use, enabling more precise watering and water savings.

Answer: (D)

The main idea is that ET-based irrigation control uses evapotranspiration data to gauge how much water the crop is actually using and needs. By combining weather information (like temperature, humidity, wind, and solar radiation) with crop type and growth stage, the system estimates crop evapotranspiration (ETc). The controller then schedules irrigation to replace that precise amount of water, leading to more accurate watering and real water savings.

This is why the option that describes using ET data to estimate plant water use and enable more precise watering and water savings is the best fit. Rainfall data without ET doesn’t reflect how much water the plant requires, watering adjustments only during droughts can’t capture typical crop demand, and measuring soil color isn’t a reliable method for determining plant water needs. ET-based control directly ties irrigation to the crop’s actual water use, delivering the benefits.