Management and environmental conditions: Factors such as soil salinity,poor land fertility, limited application of fertilizers,the absence of control of diseases and pests and poor soil management may limit the crop development and reduce the evapotranspiration. Other factors to be considered when assessing ET are ground cover,plant density and the soil water content
Management and environmental conditions: • Factors such as soil salinity, poor land fertility, limited application of fertilizers, the absence of control of diseases and pests and poor soil management may limit the crop development and reduce the evapotranspiration. • Other factors to be considered when assessing ET are ground cover, plant density and the soil water content
Management and environmental conditions The effect of soil water content on ET is conditioned primarily by the magnitude of the water deficit and the type of soil.On the other hand,too much water will result in waterlogging which might damage the root and limit root water uptake by inhibiting respiration
Management and environmental conditions • The effect of soil water content on ET is conditioned primarily by the magnitude of the water deficit and the type of soil. On the other hand, too much water will result in waterlogging which might damage the root and limit root water uptake by inhibiting respiration
Management and environmental conditions Cultivation practices and the type of irrigation method can alter the microclimate,affect ET of crop. Soil evaporation in a young orchard,where trees are widely spaced,can be reduced by using a well- designed drip irrigation system.The drippers apply water directly to the soil near trees,thereby leaving the major part of the soil surface dry,and limiting the evaporation losses
Management and environmental conditions • Cultivation practices and the type of irrigation method can alter the microclimate, affect ET of crop. • Soil evaporation in a young orchard, where trees are widely spaced, can be reduced by using a welldesigned drip irrigation system. The drippers apply water directly to the soil near trees, thereby leaving the major part of the soil surface dry, and limiting the evaporation losses
Management and environmental conditions A windbreak reduces wind velocities and decreases the ET rate of the field The use of mulches,especially when the crop is small,is another way of reducing soil evaporation. Anti-transpirants,such as stomata-closing, reduce the water losses from the crop and hence the transpiration rate
Management and environmental conditions • A windbreak reduces wind velocities and decreases the ET rate of the field • The use of mulches, especially when the crop is small, is another way of reducing soil evaporation. • Anti-transpirants, such as stomata-closing, reduce the water losses from the crop and hence the transpiration rate
4.Reference crop evapotranspiration (ETo) The evapotranspiration rate from a reference surface,not short of water,is called the reference crop evapotranspiration The reference surface is a hypothetical grass reference crop with specific characteristics
4. Reference crop evapotranspiration (ETo) • The evapotranspiration rate from a reference surface, not short of water, is called the reference crop evapotranspiration • The reference surface is a hypothetical grass reference crop with specific characteristics