ABSTRACT
Among the cultures used for the production of biofuels, the sunflower is one of the most important. Although some information exists, the water and nutritional needs of sunflower in the north east of Brazil are not well known. To fill knowledge gaps, an experiment was carried out to evaluate the effect of nitrogen (N), phosphorus (P), potassium (K) fertilization and available soil water (ASW) on sunflower yields. The sunflower cultivar Embrapa 122-V2000 was subjected to 44 treatments on a completely randomized design generated by the Baconian Matrix with four rates of N (0, 60, 80 and 100 kg·ha-1), four rates of P2O5 (0, 80, 100 and 120 kg·ha-1), four rates of K2O (0, 80, 100 and 120 kg·ha-1), and four available soil water (ASW) levels (55%, 70%, 85% and 100%) replicated three times. Urea was used as a source of N, triple super phosphate as P and potassium chloride as K. In all the experimental units was applied 2 kg·B·ha-1 as boric acid. The components of production evaluated were dry matter of the head, total number of achenes, total achenes’ weight and 1000 achenes’ weight. The results of this research showed that nitrogen had a significant effect on the dry matter of the head, total number of achenes and total achenes’ weight. Phosphorus affected all production components and potassium affected the total number and the weight of achenes. With the exception of the 1000 achenes’ weight, all the production components of the sunflower increased with the increased ASW level influenced significantly at 0.01 level of probably the total number of achenes. The highest rates of N, P and K (100, 120 and 120 kg·ha-1, respectively) and 100% of available soil water produced the highest production.