Foram conduzidos dois experimentos sobre nutrição do guaranazeiro (Paullinia cupana, var. sorbilis no Estado do Amazonas: um com mudas, visando estabelecer os efeitos de tipos de substrato e formas de fornecimento de nutrientes no crescimento e composição em macronutrientes das mudas; o outro em condições de campo, com plantas adultas, visando determinar os efeitos dos macronutrientes na produção de frutos de guaraná. No primeiro experimento, as mudas de guaranazeiro foram cultivadas nos seguintes substratos: (a) areia + barro + esterco de galinha; (b) areia + barro + esterco de gado; (c) areia + barro. A unidade experimental constou de 10 mudas, plantadas individualmente em sacos plásticos. Cada 3 unidades foram preparadas com o mesmo substrato, e as mudas dos mesmos foram pulverizadas com água e com solução nutritiva em intervalos de 15 e 30 dias respectivamente. Numa unidade extra, constando de areia + barro, foi adicionada solução nutritiva diretamente no substrato, completando-se 10 tratamentos. As mudas cultivadas no substrato com esterco de gado, mostraram maior crescimento e melhor balanceamento de macronutrientes. Os substratos sem matéria orgânica apresentaram mudas de menor crescimento e baixos teores de macronutrientes nas folhas. A aplicação de solução nutritiva, por qualquer via, não apresentou efeitos no crescimento ou no teor de macronutrientes nas mudas. Ocorreram condições de deficiência de N em todo os tratamentos. Os teores de elementos nas folhas variaram desde o nível de deficiência ao de “consumo de luxo”. Para o segundo experimento, selecionou-se 160 plantas de aproximadamente 25 anos, sendo 80 (40 e 40) em dois locais não adubados e 80 (40 e 40) em dois locais adubados. Foram coletadas e analisadas quimicamente amostras de solos, folhas e frutos e a produção foi acompanhada. Verificou-se que a adubação efetuada não apresentou efeitos relativos na produção de frutos ou concentração de macronutrientes nas folhas. As correlações entre teores de macronutrientes e produções individuais apontaram limitações devido ao N, P e Ca mm local e Mg em outro local. Os teores de Ca e Mg nas folhas das plantas adultas apresentaram-se muito baixos, quando comparados aos teores nas mudas. O N mostrou ser o elemento mais exigido, extraído e exportado pela planta, seguido do K.

Two experiments on the nutrition of guaraná (Paullinia cupana, var. sorbilis) were conducted in the State of Amazonas with the purpose of studying the effects of substrate and supply of nutrients in the growth, nutrient content of seedlings and fruit production. The first two objectives were attained by means of a pot experiment in which “guaranᔠseedlings were grown in three different, specially mixed substrates, namely: (a) sand + loam + chicken manure; (b) sand + loam + cattle manure, and (c) sand + loam. The experimental unit consisted of ten seedlings individually planted in plastic containers. Three of these units were prepared for each substrate and the seedlings growing in each received a foliar application of water as needed and nutrient solution at 15 and 30 days intervals, respectively. An extra unit was added using sand + loam + nutrient solution as substrate, thus comprising ten treatments. Substrate and leaf chemical analysis were conducted to evaluate treatment effects. The third objective was accomplished using commercial plantations located at four different sites, two of which were fertilized. Forty mature plants (25 years old, approximately) were considered in each site for experimental purposes. Soil, leaf and fruit samples were collected in each site and chemically analysed as to their nutrient content. Data on fruit production was also collected. It was verified in the pot experiment that the seed lings grown in the cattle manure substrate showed better growth and balance of macronutrients when compared with the substrates which had no organic matter. The application of nutrient solution (foliar or mixed-in) had no effect on the growth and macronutrient content of the seedlings leaves. Symptoms of nitrogen deficiency were observed in all treatments. Nutrient content of the leaves varied from the deficiency level to that of “luxury consumption”. No effect was observed in the fertilized sites as to fruit production and leaf macronutrient concentration. Correlations between leaf macronutrient concentration and fruit production indicated a limiting effect due to N, P, Ca and Mg. Calcium and magnesium leaf contents were considerably lower in the nature plant as compared to that of the seedlings. The results from both experiments indicated that nitrogen was the element most required, extracted and exported by the “guarana” plants, followed by potassium.