Oil Yield of Sunflower Cultivated With Different Water Depths and Nitrogen Doses

Sunflower is adapted to different soil and climate conditions, but its water and nitrogen requirements are not well defined. This study was carried out in Apodi, Rio Grande do Norte, Brazil, to evaluate the oil yield of sunflower in response to irrigation depth and nitrogen dose. A randomized block experimental design was used with a factorial scheme with four replications. The factors tested were irrigation depths corresponding to 58, 80, 100 and 120% of crop evapotranspiration (water-use efficiency variable), and nitrogen doses corresponding to 40, 100, 200 and 370% of the standard dose. Data were submitted to analysis of variance by the F-test, followed by the Tukey test of means and regression analysis. The increase in the water depth until 100% ETc and in the nitrogen dose until 260 kg ha-1 promoted increase in the values of all variables, but at higher nitrogen doses the variables decreased. The response surfaces showed stronger response to nitrogen dose for the water depths around 100% ETc and for the lower nitrogen doses, and greater water use efficiency for the production of oil for the water depths around 100% ETc, independently of nitrogen dose.