Comparing of Different Equations for Calculate Reference Evapotranspiration under Condition Tikrit City and Its Relation with Potato Crop Factor


A field study was conducted to compare different methods for Reference evapotranspiration calculation at different growth stage of potato crop with drip irrigation , sprinkler irrigation and furrow irrigation in College of Agriculture, Tikrit University. Combination method including : modified Penman-Menteith radiation method ( Jensen- Haise ). temperature methods (Hargreevs equations , Blaney-Criddle, kharrofa and evaporation pan) . results indicate pan evaporation gives the highest Reference evapotranspiration (ETo) values followed by kharrofa, Hargreevs and Penman-Menteith. equation, while pan evaporation gave the lowest Reference evapotranspiration (ETo) values. Blaney-Criddle gives the highest Kc values were (0.97, و 0.93 , 0.87) for three irrigation system respectively while evaporation pan gave the lowest Kc values were (0.61 ,0.60 , 0.57) for three irrigation system respectively. drip irrigation (DI) gave the highest kc values (0.97-0.63) as compared with sprinkler irrigation (SI) and furrow irrigation (FI) for all growth stage crop followed by SI (0.60-0.93) and FI (0.57-0.87).