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Abstract: The objective of this work was to evaluate if nitrogen use efficiency (NUE) indexes can elucidate functional differences in nutrient uptake between the root system and tank of epiphytic bromeliads. The bromeliads Guzmania lingulata and Vriesea 'Harmony' received fertilizers in their tanks or through their roots using modified Hoagland & Arnon solution, with 0.00, 2.62, or 5.34 mmol L-1 nitrogen, as urea. After 90 days, nitrogen contents in leaves and plant biomass were evaluated, and NUE indexes were calculated. Guzmania lingulata and V. 'Harmony' fertilized in their tanks with 5.34 mmol L-1 had the highest averages of nitrogen uptake efficiency and recovery efficiency; those fertilized with 2.62 mmol L-1 through their roots showed the highest averages of NUE, nitrogen utilization efficiency, nitrogen physiological efficiency, and biomass conversion efficiency. The NUE indexes, besides being an effective tool to assess the nutritional status of ornamental bromeliads, reveal that the root system of epiphytic bromeliads is functional for nitrogen uptake and use.

O objetivo deste trabalho foi avaliar substratos alternativos para o cultivo da bromélia Aechmea fasciata (Lindley) Baker, para substituir com eficiência as misturas formuladas com o xaxim Dicksonia sellowiana (Presl.) Hook. Foram testados os substratos: casca de Pinus, casca de Eucalyptus, coxim, fibra de coco e xaxim, misturados com turfa e perlita, nas proporções 2:7:1, 5:4:1 e 8:1:1. O experimento foi realizado em condições de estufa com cobertura de polietileno, sombreada com tela a 70%. As bromélias foram cultivadas durante 435 dias, até o início do florescimento - estádio de comercialização. As variáveis analisadas foram as massas de matéria seca de: folhas, raiz, inflorescência, escapo floral e caule; além da massa de matéria seca total e a qualidade comercial. Os substratos formulados com xaxim ou casca de Pinus, nas proporções 2:7:1, 5:4:1 e 8:1:1, e com casca de Eucalyptus, fibra de coco ou coxim, na proporção 2:7:1, foram as misturas que apresentaram os melhores resultados. Os substratos formulados com casca de Eucalyptus, fibra de coco ou coxim, com 10% de turfa e 10% de perlita, na proporção 8:1:1, apresentaram os piores resultados.The objective of this study was to evaluate alternative substrates for the cultivation of the bromeliad Aechmea fasciata (Lindley) Baker, to substitute the formulated mixtures with fern tree fiber from Dicksonia sellowiana (Presl.) Hook. Tested substrates were: Pinus bark, Eucalyptus bark, coxim (made of coconut fiber), coir or fern tree fiber, mixed with peat and perlite, in the proportions 2:7:1, 5:4:1 and 8:1:1. The experiment was conducted in a greenhouse covered with polyethylene and shaded with shade cloth 70%. The bromeliads were cultivated during 435 days, until the beginning of the flowering, when they were suitable for commercialization. The evaluated parameters were dry masses of leaf, root, inflorescence, floral scape, and stem, besides total dry mass and the commercial quality. The substrates formulated with fern tree fiber or Pinus bark, in the proportions 2:7:1, 5:4:1 and 8:1:1, and with Eucalyptus bark, coir or coxim, in the proportion 2:7:1, showed the best results. The substrates formulated with Eucalyptus bark, coir or coxim in the proportion 8:1:1 presented the poorest results.