Formas de aplicação de nitrogênio em três cultivares de girassol na savana de 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 20% at sowing, 30% at 20 DAS,. 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.

Irrigation With Saline Water and Nitrogen in Production Components and Yield of Sunflower

“…Although lower than 19.9 and 22.4 cm, obtained by Lobo and Grassi Filho (2007) in the soil without and with 50 kg ha -1 of N, these values surpass the value of 11.9 cm in the capitulum diameter of the sunflower cultivar H358 at the dose of 44.9 kg ha -1 of N reported by Biscaro et al (2008). In this context, Ivanoff et al (2010) claim that adequate N fertilisation management promotes increments of approximately 16% in the mean diameter of sunflower capitulum; this was also observed by Siddiqui et al (2009) …”

“…Adequate nutritional supply stands out as a criterion for yield and profitability increase in plantations, and N is the macronutrient required in the largest amounts by most crops (LAVRES JUNIOR et al, 2005), mainly because N participates in the formation of proteins, amino acids and other compounds that are vital for plant metabolism. In addition, N plays an important role in the metabolism and nutrition of crops and is the most required nutrient by sunflowers (SACHS et al, 2006).…”

Características agronômicas e o estado nutricional de cultivares de girassol irrigado

“…O maior número de folhas durante o enchimento de aquênios tem relação direta com o estado nutricional da planta e este, por sua vez, com a produtividade do girassol (Palmer et al, 1996;Biscaro et al, 2008;Ivanoff et al, 2010;Aguiar Neto et al, 2010;Zobiole et al, 2010b). Conforme Zobiole et al (2010b), quando o híbrido BRS 191 foi cultivado em densidade de 42.858 plantas ha -1 , com espaçamento de 70 cm e sem déficit hídrico e nutricional, uma quantidade de 35 folhas, 0,8 m 2 de área foliar e 2 m de altura, foi imprescindível para obter altas produtividades de aquênios.…”

“…A sensibilidade à baixa concentração do nitrogênio e do fósforo também promove o decréscimo da altura e do diâmetro do caule (Prado & Leal, 2006;Ivanoff et al, 2010). Desta forma, avaliações dos caracteres agronômicos durante a fase vegetativa e reprodutiva associadas ao estado nutricional podem explicar melhor o desempenho da produtividade das cultivares em competição.…”

Nitrogen and phosphorus fertilization of sunflower crop in alkaline Cambisol

“…If the doses varied from 0 to 120 kg ha -1 , the magnitudes of the responses would probably be higher, especially for the interval from 0 to 30 kg ha -1 of N and P 2 O 5 , due to the very low contents of available P and organic matter in the soil of the experimental area. In the study of Eltz et al (2010), P 2 O 5 doses between 40 and 80 kg ha -1 were sufficient to reach sunflower grain yield of 2,000 kg ha -1 , whereas Ivanoff et al (2010) observed yield of 1,639 kg ha -1 with N fertilization of 60 kg ha -1 , split into 30% at planting and 70% as top-dressing.…”