In the semiarid region of Northeastern Brazil, reduced water availability and the occurrence of soils of low fertility, mainly in potassium, are among the factors that have limited agricultural production. In this context, the objective of this study was to evaluate the biomass and yield of sunflower cv. ‘Hélio 251’ as a function of irrigation with different levels of water replenishment and potassium fertilization under protected ambient at the Center of Technology and Natural Resources UFCG, Campina Grande, PB. A randomized block design was used, studying five levels of water replacement (40, 60, 80 100 (control) and 120% of the real evapotranspiration-ETr) associated with potassium fertilizer levels (50, 75, 100 , 125 and 150% K2O of the recommendation for assays in pots). Increasing water levels associated with potassium doses caused increase in dry weight of stem, aerial parts and dry matter of chapter. The maximum external and internal diameters of sunflower chapter occurred with water depths ranging between 99-120% of ETr. Levels of water replenishments up to 120% of ETr linearly increased the total mass of the seeds and mass of hundred seeds of sunflower. The interaction between levels of water replacement and potassium doses significantly affected the dry matter of stem, shoot and the chapter.
Helianthus annuus L.; irrigation; potassium
