Sunflower Development with Saline Water Irrigation and Nitrogen Fertilization

There is evidence that nitrogen fertilization, in addition to promoting the growth of plants grown under saline conditions, also mitigates the deleterious effects of water stress, thus increasing the plants' tolerance. The objective was to evaluate the development of sunflower (Helianthus annuus L.) under different salinity levels of irrigation water and nitrogen fertilizer levels. The experiment was conducted in a greenhouse in the state of Paraiba, Brazil, using plastic pots with 20 L of soil - Regosols. A completely randomized 5x5 factorial design was used, with five water salinity levels (0.5, 1.5, 2.5, 3.5, and 4.5 dS m(-1)) and five nitrogen levels (60%, 80%, 100%, 120%, and 140% of the recommended nitrogen dose) with three repetitions, totaling 75 experimental units. At 15, 30, 45, 60, 75 and 95 days after sowing, the height, stalk diameter, number of leaves, leaf area and water consumption by the plant were evaluated; the dry biomass of the shoots was evaluated 100 days after sowing. The results were statistically analyzed using variance and regression testing at 5% significance. All the variables were affected by salinity 30 days after sowing, demonstrating sunflower salt tolerance at the early stage of growth. The salinity sunflower crop limit was 1.5 dS m(-1), with reduced growth above this electric conductivity. The amount of nitrogen that attenuated the effect of salinity on water consumption by the plant was 100% of the recommended dose.