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

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.摘要：百香果植株对微量营养元素的均衡吸收，对提升产量与改善果实品质至关重要。然而，针对不同生产性能的品种采用统一的肥料管理模式，且施加高水平氮、钾肥，可能会引发植株营养失调问题。本研究旨在评估两种不同采样方法、不同氮钾施肥比例以及不同品种对百香果叶片微量营养元素浓度与含量的影响。本试验采用随机区组设计，设置3次重复，采用4×6因子组合设计方案，供试的黄色百香果品种共4个，分别为BRS Gigante Amarelo、IAC 275、BRS Ouro Vermelho以及BRS Sol do Cerrado；氮-氧化钾（N-K₂O）肥料施用量共6个梯度，分别为0-0、50-125、100-250、150-375、200-500以及250-625 kg·ha⁻¹·a⁻¹。本研究采用两种叶片采样方法开展营养评估：其一为采集果实邻近位置的叶片，其二为采集结果枝顶端的标准叶片。在试验田定植百香果幼苗240天后，每个小区采集20片叶片样本。果实邻近叶片的微量营养元素累积含量更高，这可能是因为相较于标准叶片，该类叶片重量更大，发育更为充分。品种IAC 275的果实邻近叶片中，铜（Cu）、铁（Fe）与锰（Mn）的浓度与含量均较低，表明供试品种间的微量营养元素水平存在差异，且各供试品种的微量营养元素需求各不相同。氮钾施肥对叶片微量营养元素浓度与含量的影响整体较小，但BRS Gigante Amarelo品种的标准叶片中，锌（Zn）的浓度与含量有所降低；而BRS Ouro Vermelho品种的标准叶片中，铜（Cu）的浓度与含量出现下降。