Water Management in Horticultural Crops

1.Blaney-Criddle method

The original Blaney-Criddle prediction method for determining ETo was modified to improve the accuracy.



Where,

ETo = reference evapotranspiration (mm day-1) for the month considered
C = adjustment factor depending on RH min, daytime wind velocity and ratio of actual sunshine hours to maximum possible sunshine hours.
T=mean daily temperature (⁰C) for the month under consideration
P=mean daily percentage of total annual daytime hrs.

The ETo may be computed with any one of the empirical formulae proposed by Blaney – Criddle, modified Penman, radiation and pan evaporation methods using mean climatic data for the period desired. To find out the crop ET (ET crop) the ETo values calibrated by the relationship called crop coefficient (Kc).