Suprimento de fósforo e boro no desenvolvimento e rendimento de óleo na cultura de girassol em Latossolo

Abstract

This study aimed to analyse the growth and nutritional condition of the hybrid sunflower “Helio 358” (Helianthus annuus L.) in different development stages, the production and the oil production according to the soil phosphorus and boron supply, cultivated in conventional system in the city of Cruz das Almas, Bahia State. The experiment was carried in the Bahia Reconcavo Region University, in cohesive Yellow Latosol, during the period from July to November in 2008. Took up the 5x2 factorial trial involving five levels of phosphorus (0; 40; 80; 120 e 200 kg ha-1 de P) and two of boron (0 e 2 kg ha-1 de B), with the treatments distributed in randomized blocks with three replicates and the sampling plot. In each harvest it was evaluated the aerial full dry mass yield, separated in stems, leaves, petiole and chapter, so as the leave area, the plant height, stems diameter and nutrients content. In the end of cicle was evaluated the oil production and yield. The phosphorus application accelerated the sunflower development and its blossom, anticipating the harvest and the achievement of an excellent leave area index. The nutrients accumulation occurred in the following decreasing order: in the leaves the Ca>N>K>S>P>B; in the stems K>Ca>N>S>P>B; in the petioles the Ca>K>N>S>P>B; and in the chapters the K>N>Ca>P>S>B. The sunflower extracted a great amount of K, but approximately a half of what was accumulated was exported by the chapters. A little Phosphorus was extracted, but almost all of it was exported by the chapters. The phosphorus application provided an increase in the achene production and influenced negatively the proteins rate. The PxB interaction influenced positively the oil rate in the achenes, and consequently their yield per area.