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

Abstract

ABSTRACT Balanced uptake of micronutrients by the passion fruit plant is essential for increased production and fruit quality. However, similar fertilizer management in varieties with different productive capacities and high levels of nitrogen and potassium can cause nutritional disorders in plants. The objective of this study was to evaluate leaf micronutrient concentrations and contents in passion fruit as affected by two different sampling methods, different N-K fertilization proportions, and different cultivars. The study was conducted in a randomized block design, with three replications, following a 4 × 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 ofN-K2O fertilizer (0-0, 50-125, 100-250, 150-375, 200-500, and 250-625 kg ha-1 year-1). Two leaf sampling methods (leaf located at a position adjacent to the fruit, and leaf located at the end of the fruit-bearing branch) were adopted for nutritional assessment. At 240 days after planting passion fruit seedlings in the experimental area, 20 leaves per plot were sampled. Higher accumulated micronutrient contents were obtained in the adjacent leaves, possibly because of greater leaf weight (more fully developed leaf) compared to the standard leaf. The cultivar IAC 275 had lower concentration and content of Cu, Fe, e Mn in the adjacent leaf, indicating variations in the levels of micronutrients among the cultivars and different micronutrient demands by the cultivars studied. N and K fertilization had less effect on leaf micronutrient concentration and content, but the Zn concentration and content decreased in the standard leaf of the BRS Gigante Amarelo cultivar, and Cu decreased in the standard leaf of the BRS Ouro Vermelho cultivar.