An experiment was conducted at Ismailia Agric, Res. Station in two adjacent areas, one of them was cultivated with maize crop and the second was cultivated with alfalfa crop permanent all over the year. Maize crop was cultivated for three years, in a time of 114 days each, started from day of year 160 to 274 in 1st year, from 138 to 252 in 2nd year and from 160 to 274 in 3rd year. From maize area crop evapotranspiration (ETC) was calculated and from alfalfa area potential evapotranspiration (ETO) was calculated. Area of maize crop was irrigated by drip regime but alfalfa crop was irrigated by sprinkler regime. The results of (ETC), (ETO), were using calculated (Kc). ETO - FAOPenman-Montieth equation are summarized as follow:  The average of maize coefficients (Kc) on alfalfa, and FAO-penman-monteith of the average of three seasons as well as the average of both was the same. Crop factor depend upon the growth stage of plant, whereas increased in the start period and then decreased in the late period.  ETc , ETo-alfalfa , ETo-FAO , maize-Kc calculated on ETc/ETo-alfalfa , ETc/ETo-FAO and average of ETc/ETo-alfalfa and ETc/ETo-FAO , which they calculated daily or average ten days data, as well as Kc for growth stages, they were subjected to polynomial equations.  Regression equation coefficient R2 of the polynomial equation, the above items were 0.91, 0.36, 0.89, 0.74, 0.86 and 0.83 for daily data and 0.99, 0.67, 0.98, 0.91, 0.96 and 0.95 for ten days average, respectively, also 0.99 for growth stage.