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COMPUTATION OF EVAPOTRANSPIRATON BY FIELD EXPERIMENT

COMPUTATION OF EVAPOTRANSPIRATON BY FIELD EXPERIMENT. PRESENTED BY D.GANAPATHI. Evapo - transpiration (ET).

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COMPUTATION OF EVAPOTRANSPIRATON BY FIELD EXPERIMENT

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  1. COMPUTATION OF EVAPOTRANSPIRATON BY FIELD EXPERIMENT PRESENTED BY D.GANAPATHI

  2. Evapo-transpiration(ET) The quantity of water transpired by plants during their growth or retained in the plant tissue, plus the moisture evaporated from the surface of the soil and the vegetation

  3. Field experimental plots.

  4. WR = seasonal water requirement, cm • IR = total irrigation water applied, cm • ER =- seasonal effective rainfall, cm • Mbi = moisture percentage at the beginning of the season in the ith layer of the soil • Mei = moisture percentage at the end of the season in the ith layer of the soil • Ai = apparent specific gravity of the ith layer of the soil • Di = depth of the ith layer of the soil within the root zone, cm • n = number of soil layers in the root zone D

  5. Sunken Colorado pan

  6. The principle of the evaporation pan is the following: • The pan is installed in the field • The pan is filled with a known quantity of water (the surface area of the pan is known and the water depth is measured) • The water is allowed to evaporate during a certain period of time (usually 24 hours). For example, each morning at 7 o'clock a measurement is taken. The rainfall, if any, is measured simultaneously • After 24 hours, the remaining quantity of water (i.e. water depth) is measured • The amount of evaporation per time unit (the difference between the two measured water depths) is calculated; this is the pan evaporation: E pan (in mm/24 hours) • The E pan is multiplied by a pan coefficient, K pan, to obtain the ETo.

  7. Formula • ETo = K pan × E pan ETo: reference crop evapotranspirationK pan: pan coefficientE pan: pan evaporation

  8. THANK U

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