The objective of this work was to evaluate macronutrient uptake and export by transgenic corn hybrids under medium and high fertilization levels. For each fertilization level, a randomized complete block design was carried out in the summer crop season, under no-tillage and supplementary irrigation, with four cultivars and four replicates. Plants were sampled throughout the entire cycle and separated into leaves, stalk, husk, cob, and grains for the determination of dry matter mass and accumulation of macronutrients in the different growth stages. Under the high fertilization level, a greater dry matter mass and nutrient uptake were observed, but grain yield was similar to that under the medium fertilization level. The uptake of N, P, Ca, Mg, and S occurs until later in the cycle of the transgenic cultivars, which also showed lower concentrations of P, K, and S in grains, when compared to older hybrids. The differential behavior of the evaluated cultivars under different fertilization levels indicates the need of updating and improving nutritional management and fertilizer recommendations for the corn crop.

RESUMO: Vários estudos têm demonstrado resposta acentuada das forrageiras tropicais a doses de adubação nitrogenada. Dessa maneira objetivou-se avaliar o perfilhamento, a relação lâmina:colmo, o índice de área foliar e o acúmulo de forragem da Brachiaria decumbens Stapf cv. Basilisk em função de doses de nitrogênio (0, 100, 200 e 400 kg/ha) utilizando uréia parcelada em três aplicações. O delineamento experimental utilizado foi o inteiramente casualizado com três repetições. A adubação nitrogenada aumentou o número de perfilhos vivos e mortos, o índice de área foliar e a taxa de acúmulo de forragem do capim-braquiária, devendo assim ser utilizada como opção de manejo.Palavras-chave: índice de área foliar, perfilhamento, relação lâmina:colmo, taxa de acúmulo de forragem. STRUCTURAL CHARACTERISTICS OF A Brachiaria decumbens STAPF CV. BASILISK PASTURE UNDER NITROGEN DOSESABSTRACT: Several studies have shown marked response of nitrogen increasing fertilization doses of tropical pastures. Tillering, leaf:stem ratio, leaf area index and accumulated forage of Brachiaria decumbens Stapf cv. Basilisk, under nitrogen increasing doses condition (0, 100, 200 and 400 kg/ha) using urea in three applications, were evaluated. The experiment design was a completely randomized with three replications. Nitrogen fertilization increased the number of tillers, leaf area index and herbage accumulation rate of signal grass and should therefore be used as a management option.

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