What does ET stand for in ET-based irrigation scheduling?

• A. Evaporation Time
• B. Estimated Time
• C. Evapotranspiration
• D. Erosion Tolerance

Answer: (C)

ET stands for evapotranspiration—the total water lost from a crop and its surrounding soil through soil evaporation plus plant transpiration. In ET-based irrigation scheduling, you estimate how much water the crop has used over a period and replace that amount to keep the soil moisture in the optimal range. ET values change with weather (temperature, humidity, wind, solar radiation) and with crop type and growth stage. In practice, ETc = ETo × Kc is used, where ETo is reference evapotranspiration and Kc is a crop coefficient. This approach aims to match irrigation to actual water use, preventing both overwatering and plant water stress. It’s not just evaporation alone, nor a simple time estimate or erosion-related measure.