EVAPOTRANSPIRATION


WHAT IS EVAPOTRANSPIRATION?


Evapotranspiration is the combination of evaporation and transpiration. Evaporation is water loss from surrounding soil surfaces and plant surfaces. Transpiration is the natural process by which water is extracted from the soil by the root system and moves through the plant carrying nutrients and is eventually changed to water vapor escaping to the atmosphere through the stomata in the plant leaves.


ET is important to a grower because it represents the amount of irrigation water that must be supplied to ensure that there is sufficient water to meet the needs of the plant.


WHAT AFFECTS ET?


Five basic factors influence a plant’s need for water. Because all of these factors vary from day to day, there are daily variations in the amount of water used by plants. Measuring these factors provides information that can be used to estimate the amount of water needed. It is important to remember that these conditions are not constant but are continually changing. The five factors are sunlight, wind, air temperature, humidity and soil water.


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• sunlight — This is an important part of photosynthesis. The majority of plants transpire during daylight hours and can be affected by the intensity of the sunlight, duration, altitude and shading from other plants, terrain or structures.


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Evapotranspiration is the combination of evaporation and transpiration.


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