Sunflower (Helianthus annuus L.) crop has been cultivated during the last years by the producers in Rio Grande do Norte, after the increase in demand due to National Program for Production and Use of Biodiesel. Being a non traditional crop in the region, there are no studies about the water management, so this work aimed to determine the crop evapotranspiration (ETc) and the crop coefficients (Kc) for the different development stages of the sunflower, cultivar Catissol I, in the plateau of Apodi - RN. Daily measurements of ETc were performed using two similar weighing lysimeters, with useful area of 2.7 m².The reference evapotranspiration (ETo) was estimated using the method of Penman-Monteith FAO.The crop cycle was of 90 days and the total ETc and ETo during this period were, respectively, 442.0 and 580.6 mm.The phenological stages were defined with the duration of 28, 15, 27 and 20 days for the initial phase (Phase I), vegetative development (Phase II), flowering (Phase III) and physiological maturation (Phase IV), respectively.The crop coefficients obtained for the different stages of development were 0.52, 0.74, 0.98 and 0.81 for the phases I, II, III and IV, respectively.
irrigation management; weighing lysimeter; evapotranspiration
