Evaluation of the effect of doses and sources of nitrogen on morphological variables, radiation interception and yield of sunflower

ABSTRACT

The objective of this study was to evaluate the effect of doses and sources of nitrogen on themorphological variables related to yield of two sunflower cultivars. The design was randomized blocks in a factorial design 5 x 2 x 2, with five doses of nitrogen (0, 40, 80, 120 and 160 kg ha^-1), two sources of nitrogen (N), fertilizer conventional (urea), with 44% N, and the fertilizer nitrogenated of slow-release, with 26% N, and two sunflower cultivars (Olisun 3 and Aguará 6) with three replications. Was evaluated theplant height, leaf area index, global radiation interception, thousand achenes weight, diameter of achenes, yield and estimate the chlorophyll content. Increasing doses of N promotes an increase in the leaf area index and interception of global radiation at flowering full and the sunflower yield, in a differentiated way between cultivars. The use of fertilizer nitrogenated of slow-release provides higher leaf area index in the beginning of achenes filling, compared the use of urea, from the dose of 120 Kg ha^-1 N. The cultivar Olisun 3 shows greater leaf area index at flowering full and yield, from the doses of 80 and 120 kg ha^-1 N, respectively.

Key words: leaf area; photosynthetic rate; Helianthus annuus L