FITOMASSA DE GIRASSOL CULTIVADO SOB ADUBAÇÃO NITROGENADA E NÍVEIS DE ÁGUA DISPONÍVEL NO SOLO

Nitrogen is the most required nutrient by plants to assume exerting important functions in the vegetable metabolism. In sunflower crop, its deficiency causes nutritional disorder, being the nutrient that most limits the yield. Besides, the lack of water limits the growth and yield of plants. Therefore, the study was conducted at the experimental area of Department of Agricultural Engineering, University of Campina Grande, in the period March to June 2010, aiming to evaluate the dry matter of sunflower cv EMBRAPA 122/V-2000 subjected to nitrogen levels (0; 60; 80 e 100 kg ha -1 ) and levels of available soil water (55; 70; 85; e 100%). The experimental design was completely randomized in factorial analysis (4 x 4) with three replications totaling 48 experimental units. The sunflower plants were grown in pots with 35 L capacity containing Luvisol (Alfisol) and kept under daily irrigation. At harvest the following variables were evaluated: Fresh and dry biomass of shoot, stem and leaves, and from these, the water content in the shoot. Nitrogen fertilization did not influence the production of fresh and dry biomass of sunflower cv EMBRAPA 122/V-2000, except the dry stem. All variables increased linearly as a function of available soil water. The interaction between dose 80 kg N ha -1 and the level of 100% of available soil water was adequate for the best results in the production of biomass.