The ratio of nitrogen (N) to potassium (K) is important in the production of specialty coffees because the relative amounts of N and K can either suppress the formation or increase the concentration of compounds that are essential to the flavor and aroma of specialty coffees. The purpose of this study was to evaluate the effect of different N:K ratios (w/w) and K doses on the cup quality of coffee. The concentrations of chemical compounds essentials to achieve good flavor and aroma, the N and K contents, and the caffeine contents of coffee leaves and beans were evaluated in this study. The N:K ratio and the K dose were found to be important factors in cup quality, the best quality corresponding to an N:K ratio of 1:1.56. The best cup quality was obtained from beans with greater PPO activity, caffeine, color index, and sugars and lower total tritatable acidity, pH, electrical conductivity and leached potassium.

Recebido para publicação em 15/05/2014 e aprovado em 11/10/2014. 1 Engenheira-Agrônoma, Doutora. Departamento de Fitotecnia, Universidade Federal de Viçosa, Campus Viçosa, Avenida Peter Henry Rolfs, s/n, 36570-000, Viçosa, Minas Gerais, Brasil. herminia@ufv.br (autora para correspondência Nutrição mineral do cafeeiro e qualidade da bebidaOs nutrientes minerais interferem na qualidade final do café por duas vias, uma direta, por seu papel no metabolismo da planta e acúmulo de compostos químicos desejáveis, do ponto de vista do aroma e sabor do café, e, outra, indireta, por seu papel na produção de compostos que desfavorecem o desenvolvimento microbiano nos grãos. Neste trabalho, procurou-se destacar as características químicas dos grãos associadas à qualidade da bebida e suas possíveis interações com os macro e micronutrientes, bem como relatar os resultados de pesquisa que relacionam nutrição mineral, qualidade da bebida e produção de compostos a ela associados. Palavras-chave: Coffee mineral nutrition and beverage qualityMineral nutrients influence the final quality of coffee in two ways: first directly, for their functions in plant metabolism and accumulation of desirable chemical compounds from the standpoint of flavor and taste of coffee; and indirectly, for its role in producing compounds that are harmful to microbial growth in beans. In this study, we focused on the chemical compounds of green coffee related to good beverage quality and its possible interactions with macro and micronutrients. We also report research findings that relate mineral nutrition, beverage quality and production of compounds in coffee beans.

RESUMOCrescimento, produção e tamanho de grãos de café decorrentes de doses de N e K em solução nutritiva O suprimento adequado de nutrientes ao cafeeiro é essencial para obtenção de alta produtividade. O objetivo deste trabalho foi avaliar o efeito do nitrogênio, do potássio e da relação N:K no crescimento vegetativo e reprodutivo do cafeeiro. Para isto, plantas de café receberam solução nutritiva, contendo K nas concentrações de 1,08; 2,15; 3,23 e 5,38 mmol L -1 , combinadas com a dose de 6 mmol L -1 de N, obtendo-se as relações N:K (p/p):1,0:0,5; 1,0:1,0; 1,0:1,5; 1,0:2,5. O tratamento controle continha as doses de 3 e 1,61 mmol L -1 de N e K, respectivamente, resultando na relação N:K (p/ p) de 1,0:1,5. Avaliaram-se a altura, o diâmetro do caule, número de nós do oitavo ramo plagiotrópico (ramo índice), o número de pares de ramos plagiotrópicos e o número de nós do ramo ortotrópico a cada três semanas após o início do experimento. Realizaram-se também análises da composição química dos grãos beneficiados e folhas, no período entre a floração e expansão rápida dos frutos, produção de café cereja por planta e classificação dos grãos quanto ao tamanho. O N influenciou principalmente as características de crescimento vegetativo e o K influenciou principalmente as características de crescimento reprodutivo, avaliadas pela produção. A menor produção resultou em percentagens mais elevadas de grãos retidos nas peneiras com crivos maiores que 16/64 polegadas, enquanto a maior produção promoveu aumento na percentagem de grãos retidos nas peneiras com crivos menores que 16/64 polegadas.Palavras-chave: crescimento, produção, Coffea. Received: 29/12/2011; Accepted: 08/02/2013 Effect of N and K doses in nutritive solution on growth, production and coffee bean sizeAn adequate supply of nutrients is essential for obtaining high yields of coffee. The objective of this study was to evaluate the effect of N, K and the N:K ratio on vegetative and reproductive growth of coffee. For this purpose, coffee plants were grown in nutrient solution containing K in the concentrations of 1.08; 2.15; 3.23 and 5.38 mmol L -1 combined with a dose of 6 mmol L -1 N, resulting in the N:K ratios (w/w): 1:0.5; 1:1; 1:1.5 and 1:2.5. The control treatment consisted of the doses 3 and 1.61 mmol L -1 of N and K respectively, resulting in the N:K ratio (w/w) 1.0:1.5. The following variables were evaluated: height, stem diameter, number of nodes of the eighth plagiotrofic branch (index branch), pairs of plagiotrofic branches and number of nodes in the orthotropic branch every three weeks from the beginning of the experiment. Additionally, it was evaluated the chemical composition of processed beans and leaves between the flowering and the rapid expansion stage of the cherry beans, production of cherry beans per plant and classification of beans according to the size. N influenced mainly the characteristics of vegetative growth and K influenced mainly the reproductive growth evaluated by the production. The lowest production resulted in the hig...

. The four diagnostic methods generated similar reference values of nutrients, but different from those found in the literature. Leaf diagnosis through nutrient content in the shoot at harvest time indicated Mn as the most limiting nutrient for growing carrot, followed by Mg, K, and Ca.

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Micronutrients perform speci c and essential functions in plant metabolism, and their de ciency may lead to metabolic disturbances that a ect co ee production and quality beverage. In Brazil, the B, Cu, and Zn are the main micronutrients, and these are provided by soil or foliar fertilization, frequently with low recovery e ciency. is work objected verifying the feasibility of supplying of B, Cu, and Zn via insertion of tablets in the orthotropic branch of Co ea arabica, as well as to evaluate the co ee plant response in terms of productivity and quality of the beverage. Adult plants received B, Cu, and Zn, each micronutrient alone or combined with the other two, by foliar fertilization or by tablets inserted in the trunk base. e productivity, cupping quality, and some chemical indicators of beans quality were evaluated in two crop seasons. Boron, copper, and zinc supplied by foliar spray or solid injections in the trunk in uenced the chemical composition and quality of the co ee beans, characterized by the cupping test and the levels of ca eine, trigonelline, sucrose, glucose, arabinose, mannose, 3-ca eoylquinic acid, 5-ca eoylquinic acid, polyphenol oxidase activity, and total phenolic compounds. Copper and zinc were equivalent in either form of supply regarding the production and quality of co ee.

Zinc is essential for the synthesis of amino acids, carbohydrates, and proteins, which are directly related to the chemical composition of raw coffee (Coffea arabica L.) beans, and it may influence the quality of the beverage. This study aimed at evaluating the influence of Zn doses on the chemical composition of coffee beans and beverage quality. Increased Zn availability in the growth medium maximized attributes related to beverage quality, such as polyphenol oxidase activity, color index, and contents of sucrose, caffeine, and trigonelline, reaching maximum values in plants with Zn leaf contents within the sufficiency range of 8.0 to 12.7 mg kg−1. Zinc doses lower or higher than the one that provided maximum quality (∼2 μmol L−1 in nutrient solution) increased the attributes related to loss of beverage quality, such as content of total phenols, 5‐caffeoylquinic acid, leached K, and electrical conductivity. Zinc supply influences the quality of coffee beans, having a positive effect on polyphenol oxidase activity, color index, and contents of sucrose, caffeine, and trigonelline. Adequate Zn doses reduce total phenol content, 5‐caffeoylquinic acid, leached K, and electrical conductivity. The leaf contents, which related to the minimum or maximum points of the quality attributes studied, varied between 8.0 and 12.7 mg Zn kg−1.

Univariate methods for diagnosing nutritional status such as the sufficiency range and the critical level for garlic crops are very susceptible to the effects of dilution and accumulation of nutrients. Therefore, this study aimed to establish bivariate and multivariate norms for this crop using the Diagnosis and Recommendation Integrated System (DRIS) and Nutritional Composition Diagnosis (CND), respectively. The criteria used were nutritional status and the sufficiency range, and then the diagnoses were compared. The study was performed in the region of Alto Paranaíba, MG, Brazil, during the crop seasons 2012 and 2013. Samples comprised 99 commercial fields of garlic, cultivated with the cultivar "Ito" and mostly established in Latossolo Vermelho-Amarelo Distrófico (Oxisol). Copper and K were the nutrients with the highest number of fields diagnosed as limiting by lack (LF) and limiting by excess (LE), respectively. The DRIS method presented greater tendency to diagnose LF, while the CND tended towards LE. The sufficiency range of both methods presented narrow ranges in relation to those suggested by the literature. Moreover, all ranges produced by the CND method provided narrower ranges than the DRIS method. The CND method showed better performance than DRIS in distinguishing crop yield covered by different diagnoses. Turning to the criterion of evaluation, the study found that nutritional status gave a better performance than sufficiency range in terms of distinguishing diagnoses regarding yield.