Among the oil used in the Brazilian Biodiesel Program (Pro-Biodiesel), the castor bean stands out due to high adaptability to adverse weather conditions and the multitude of industrial applications of its oil.The objective of the present work was to evaluate the effects of increasing doses of nitrogen, applied by fertigation, in the castor oil plant (Ricinus communis L.) cultivar IAC-Guarani. The experiment was implemented in an investigation site within the Federal University of Ceará, in the city of Fortaleza (03º44'S, 38º33'W, 19,5 m). The sowing of was made in holes with a depth from 3 to 5cm, in the spacing of 1,0 m x 1,0 m. The foundation manuring was composed of micronutrients (15 g of FTE BR-12) and phosphorus, in the form of MAP (1.740g). The macronutrients nitrogen and potassium were applied by fertigation on a weekly basis. During the cycle of the culture, the plants were irrigated daily using a drip irrigation system, where the water depths were quantified starting from 75% of the (ECA) evaporation measured in the class "A" pan. The experimental delineation was in blocks at random with five treatments: 0, 50, 100, 150, and 200% of the nitrogen recommended in the soil analysis, with four repetitions. The application of different doses of nitrogen through fertigation, influenced the following productive factors: weight of 100 seeds of the racemes of 2nd and 3rd orders, the productivity of the racemes of 3 rd order and total productivity of the plant. The estimated dose of nitrogen of 131% of the recommended by the soil analysis, was the one that provided the highest total productivity.