Reference crop evapotranspiration (ETo) Only factors affecting ETo are climatic parameters.Consequently,ETo is a climatic parameter and can be computed from weather data. The FAO Penman-Monteith method is recommended as the sole method for determining ETo
Reference crop evapotranspiration (ETo) • Only factors affecting ETo are climatic parameters. Consequently, ETo is a climatic parameter and can be computed from weather data. • The FAO Penman-Monteith method is recommended as the sole method for determining ETo
5.Crop evapotranspiration under standard conditions (ETc) Crop evapotranspiration under standard conditions (ETc)refers to the evaporating demand from crops that are grown in large fields under optimum soil water,excellent management and environmental conditions,and achieve full production under the given climatic conditions
5. Crop evapotranspiration under standard conditions (ETc) • Crop evapotranspiration under standard conditions (ETc) refers to the evaporating demand from crops that are grown in large fields under optimum soil water, excellent management and environmental conditions, and achieve full production under the given climatic conditions
climate grass reference ET crop Radiation Temperature Wind speed Humidity well watered grass Kc factor ETc X well watered crop optimal agronomic conditions
Crop evapotranspiration under standard conditions In the crop coefficient approach the crop evapotranspiration,ETc,is calculated by multiplying the reference crop evapotranspiration,ETo by a crop coefficient,Ke: ETe =KcETo where ETe crop evapotranspiration [mm d-1]. K crop coefficient [dimensionless], To reference crop evapotranspiration [mm d-1]
Crop evapotranspiration under standard conditions
Crop coefficients (Kc) Experimentally determined ratios of ETc/ETo,called crop coefficients (Kc),are used to relate ETc to ETo ETc=Kc ETo
Crop coefficients (Kc) • Experimentally determined ratios of ETc/ETo, called crop coefficients (Kc), are used to relate ETc to ETo ETc = Kc ETo