MACRONUTRIENT CONCENTRATION AND CONTENT IN PASSION FRUIT LEAVES UNDER SAMPLING METHODS AND N-K FERTILIZATION RATES

ABSTRACT Nitrogen and potassium fertilization and assessment of adequate nutritional status are essential for increasing fruit production of passion fruit. However, studies related to characterization of the leaf nutrient concentration and content in passion fruit with different production capacities are scarce in the literature in Brazil. The objective of this study was to evaluate macronutrient leaf concentration and content in different parts of the reproductive shoot of yellow passion fruit subjected to different ratios of N and K fertilization. The study was conducted in a randomized block design, with three replications, following a 4 x 6 factorial arrangement consisting of four cultivars of yellow passion fruit (BRS Gigante Amarelo, IAC 275, BRS Ouro Vermelho, and BRS Sol do Cerrado) and six application rates of N-K2O fertilizer (0-0, 50-125, 100-250, 150-375, 200-500, and 250-625 kg ha-1 year-1). Two leaf sampling methods were adopted (leaf located at a position adjacent to the fruit, and leaf located at the end of the reproductive branch) for nutritional assessment. The leaf located at the adjacent position had lower N, P, K, Mg, and S concentration and higher Ca concentration than the concentrations observed in the standard leaf. However, the higher leaf dry matter in adjacent leaves resulted in increased macronutrient concentration/content. The increase in N-K fertilizations inhibited Ca and Mg content in the leaves adjacent to the fruit of the Gigante Amarelo, IAC, and Ouro Vermelho passion fruit cultivars, but did not affect Ca and Mg content in the standard leaf. The passion fruit cultivars showed different leaf nutrient contents after N-K fertilization, indicating variable nutritional demands and the need for specific diagnostic methods for each cultivar. RESUMO A adubação nitrogenada e potássica e a avaliação adequada do estado nutricional são imprescindíveis para o aumento da produção de frutos de maracujá, no entanto, são consideradas escassas no Brasil informações literárias relacionadas à caracterização dos teores e acúmulos foliares de nutrientes em maracujazeiros com distintas capacidades produtivas. Objetivou-se avaliar os teores e acúmulos foliares de macronutrientes em partes distintas do ramo frutífero de cultivares de maracujazeiro azedo submetidos à adubação com N e K. O delineamento utilizado foi em blocos casualizados, com três repetições, no esquema fatorial 4 × 6, consistindo de quatro cultivares de maracujazeiro azedo (BRS