Produção de girassol sob estresse salino e adubação nitrogenada

The limited availability of low-salinity water in Brazilian semiarid region causes producers to use water of moderate to high salinity for irrigation. In view of the increasing importance of sunflower (Helianthus annuus L.) in this region as a potential source of renewable energy, this study was conducted to evaluate sunflower crops irrigated with different water salinity levels (ECw) and fertilized with nitrogen. The experiment was conducted in a greenhouse of the Federal University of Campina Grande (UFCG), from July to October 2009, in a randomized block design, to test five ECw levels (0.5 - control, 1.6, 2.7, 3.8, and 4.9 dS m-1) and four N rates (50, 75, 100 and 125 % of the rate recommended for pot experiments) in a 5 x 4 factorial scheme, with three replications. The salinity of irrigation water and nitrogen fertilization affected the sunflower plants in independent ways. Water salinity affected the leaf area, biomass of aerial parts and roots, weight and total production of achenes and harvest index linearly and negatively. Higher N rates on the other hand reduce the crop cycle and period from achene formation to physiologic maturity, and increased its mass.