Effect of N and K doses in nutritive solution on growth, production and coffee bean size Crescimento, produ o e tamanho de gr os de café decorrentes de doses de N e K em solu o nutritiva

An 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 highest percentages of beans retained on sieves with holes larger than 16/64", while the highest production promoted an increase in the percentage of beans retained on sieves with holes smaller than 16/64". O suprimento adequado de nutrientes ao cafeeiro é essencial para obten o de alta produtividade. O objetivo deste trabalho foi avaliar o efeito do nitrogênio, do potássio e da rela o N:K no crescimento vegetativo e reprodutivo do cafeeiro. Para isto, plantas de café receberam solu o nutritiva, contendo K nas concentra es 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 rela es 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 rela o N:K (p/ p) de 1,0:1,5. Avaliaram-se a altura, o diametro 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 composi o química dos gr os beneficiados e folhas, no período entre a flora o e expans o rápida dos frutos, produ o de café cereja por planta e classifica o dos gr os quanto ao tamanho. O N influenciou principalmente as características de crescimen