Uso de fontes de nitrogênio visando retardar a senescência em girassol ornamental

Abstract

Ornamental sunflowers present senescence of the basal leaves, which is a negative factor from the viewpoint of commercialization. Even though being the fourth in production of grains in the world, the sunflower has some genotypes that are used with ornamental purpose for pot and cut flower. The study aimed to evaluate the effect of different nitrogen sources on some parameters of growth and development, and on the retardation of the senescence of the basal leaves in pot sunflower. The experiment was carried out with the variety cv. Sunflower F1 Sumbrite Supreme, planted in pots with a volume of 1,3 L, under controlled cultivation, at the Department of Vegetal Production of the State University of the North of Parana, Luiz Meneghel Campus, in Bandeirantes (Parana, Brazil). The experimental design was entirely in randomized blocks, with seven treatments and five repetitions. The pots had been filled with 50% of the commercial substratum Plantmax® and 50% of earthworm castings. The following treatments were done: control, fertilizer Super N ®, sulfamide®, urea, ammonium nitrate, ammonium sulphate and calcium nitrate at 100 mg L-1 of N, in two weekly applications, with 100 mL each pot. Two evaluations were performed, one at 30 days after planting (DAP), when the number of leaves and plant height (cm) were examined, and another at harvest, when the number of leaves, plant height, diameter of inflorescences and number of days between harvest and senescence of inflorescences where examined. There were no significant differences between the nitrogen sources used in the experiment, which allows the conclusion that all sources of nitrogen fertilizers examined in the experiment can be used to improve the quality of sunflower plants.