RESUMEN
The experiment was conducted on sunflower (variety BARI Surjomukhi-2) crop during the month of mid-November, 2014 to mid-March, 2015, in a lysimeter (dimension:1 m X 1 m X 1 m size) to measure crop evapotranspiration (ETc) and determine crop coefficient (kc) values at Irrigation and Water Management Division, Bangladesh Agricultural Research Institute, Gazipur. The study was examined by applying four irrigation at an interval of 10, 15, 20, and 25 days allowing drainage within and adjacent the tank. Results reveals that irrigation at 15 days interval produced the highest yield and was considered suitable for estimating ETc and kc. Seasonal total ETc was found as 270.89 mm. The kc values of sunflower under different ET0 methods for initial, development, mid-season and late season ranged from 0.34 to 0.48, 0.80 to 1.10, 1.06 to 1.55, and 0.27 to 0.36, respectively. Among different methods, P-M method gave relatively higher value than those of other methods and also FAO recommended value. Therefore, this information would be a helpful tool for crop water requirement and irrigation scheduling for similar semi-arid climates.