Crescimento e floração do girassol sob estresse salino e adubação nitrogenada

Abstract

Considering the importance of the sunflower (Helianthus annuus L.) as a potential source of renewable energy and the lack of information regarding its cultivation. In this study the growth variables and flowering of sunflower cv. Embrapa 122/V-2000 were evaluated under different levels of salinity of irrigation water (ECw) and doses of nitrogen. The experiment was conducted in protected environment at UFCG, between July and October 2009. Randomized block design was used to test 5 levels of salinity of irrigation water - ECw (0.5 - control, 1.6; 2.7; 3.8 and 4.9 dS m-1) and 4 doses of nitrogen (50; 75; 100 and 125% of nitrogen recommended for pot experiment) in 5 x 4 factorial scheme, with 3 replications. The increase of ECw from 0.5 dS m-1 promoted reduction in plant height, stem diameter, dry biomass of aerial parts, external and internal diameter of head, in addition to delay in flowering of plants. The internal diameter of head was most affected by salinity with a linear reduction of 7.6% for unit increase of ECw (dS m-1) and is the variable which best expresses the effects of water salinity on the sunflower. Nitrogen doses ranging from 0.46 to 0.64 g kg-1 of soil did not affect significantly the studied variables' of growth and flowering of sunflower cv. Embrapa 122/V-2000.