Evapotranspiration: The sum of evaporation from the land surface plus transpiration from plants. It is a crucial metric in precision agriculture used to determine exactly how much water a crop has lost and needs to be replenished.
In VarshaKrishi's Edge-AI systems, simulated evapotranspiration rates are calculated locally based on soil moisture and ambient temperature without needing cloud connectivity. This prevents overwatering and nutrient leaching in critical crops like wheat and sugarcane.
Evapotranspiration (ET) combines two water losses: evaporation from the soil surface and transpiration through plant leaves. Reference evapotranspiration (ET0) is computed from weather data — temperature, humidity, wind speed and solar radiation — using the FAO-56 Penman-Monteith equation, then multiplied by a crop coefficient (Kc) that changes with growth stage to give actual crop water use (ETc).
ET is the scientific basis of irrigation scheduling: it tells you how much water the crop actually consumed since the last irrigation, so you replace exactly that amount. Farms irrigating on fixed calendars typically over-water by 30-45% — pumping cost, nutrient leaching and disease pressure all rise with the excess.
VarshaKrishi gateways compute FAO-56 ET0 locally from on-farm weather sensor data — not from a district forecast — and pair it with root-zone soil moisture readings. The result is a daily irrigation advisory calibrated to the specific field's microclimate, generated fully offline.
Directly measuring ET needs research equipment (lysimeters, eddy covariance), so practical systems estimate it: weather sensors feed the FAO-56 Penman-Monteith equation for reference ET0, which is adjusted by a crop coefficient. Soil moisture sensors then verify the water balance the estimate predicts.
ET quantifies exactly how much water the crop used, so irrigation can replace that amount and no more. This typically cuts water use 30-45% versus calendar-based schedules while maintaining or improving yield.
See also: Volumetric Water Content, Microclimate — or browse the full smart farming glossary.
Discover how VarshaKrishi utilizes this technology in our offline-first systems across rural India.
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