Different ways of nitrogen placements in three cultivars of sunflower in the savannah of Roraima

Abstract

Nitrogen is the nutrient that limits most the production in the culture of sunflower (Helianthus annuus L). The nutritional requirements among cultivars of the same species is distinct, under the same conditions of culture and for the same agricultural year. With the objective of evaluating four different ways of nitrogen application in the production components of different genotypes of sunflower, an experiment was carried out in a randomized block design in a 3 x 4 factorial scheme (genotypes x ways of nitrogen applying) with four replicates . The treatments consisted on the combination of three varieties: Agrobel 960, Agrobel 962 and V - 2000 and four different ways of nitrogen application: 100% at 20 days after sowing (DAS) - (0-100-0-0); 30% at sowing and 70% at 20 DAS - (30-70-0-0); 30% at sowing, 30% at 20 DAS e 40% at 40 DAS (30-30-40-0); 20% at sowing, 30% at 20 DAS, 30% at 40 DAS e 20% at 60 DAS (20-30-30-20). Measured variables were: height of the plant, height of the capitulum, diameter of the stem, diameter of the capitulum and achene yield. The ways of nitrogen application affected all components of yield. The N formulation (30-70-0-0) has determined the best results for the variables studied, but the form (30-30-40-0) provided results comparable to treatment (30-70-0-0); treatments where N was applied as (20-30-30-20) caused decrease in the performance of sunflower for all variables. The varietal effect was observed only for plant height and height of the capitulum. The highest yield of achene achieved was 1.639 kg ha-1, with no superiority for the hybrids Agrobel 960 and 962 in relation to the variety 122/V2000 Embrapa.