Vegetative development and content of calcium, potassium, and sodium in watermelon under salinity stress on organic substrates

Abstract: The objective of this work was to evaluate the vegetative development and determine the concentration of sodium, potassium, and calcium in watermelon (Citrullus lanatus) grown on two organic substrates and under increasing saline concentrations. The substrates were soil + earthworm humus (S1) and soil + bovine manure (S2), and the saline treatments consisted of irrigation water with different electrical conductivities: 1.36 (control), 3.56, 5.76, and 7.96 dS m-1. The experimental design used was a randomized complete block in a 2×4 (substrate × conductivity) factorial arrangement with five replicates. Main branch length, root length, stem diameter, leaf number, leaf area, and fresh matter mass of shoots and roots, as well as the sodium, potassium, and calcium contents in the plants, were determined. All phenological parameters showed interaction with the substrates, and S1 improved plant performance. Substrates interacted significantly with: leaf area; leaf number; stem diameter; main branch length; root length; fresh matter mass of shoots and roots; and the contents of sodium, potassium, and calcium, in both shoots and roots of watermelon irrigated with saline water for up to 27 days after emergence. There are also interactions between substrates and salinity for stem diameter, main branch length, fresh matter mass of roots, and calcium contents in both shoots and roots, and potassium and sodium contents in the roots.摘要：本研究旨在评估两种有机基质栽培、并在递增盐浓度胁迫下生长的西瓜（Citrullus lanatus）的营养生长状况，并测定其钠、钾、钙元素浓度。供试基质为土壤+蚯蚓粪（S1）与土壤+牛粪（S2），盐胁迫处理采用不同电导率的灌溉水：1.36（对照）、3.56、5.76及7.96 dS·m⁻¹。本试验采用完全随机区组设计，设置2×4（基质×电导率）因子组合，共5次重复。测定指标包括主枝长度、根长、茎粗、叶片数、叶面积、地上部与地下部鲜重，以及西瓜植株地上部与地下部的钠、钾、钙元素含量。所有物候参数均表现出与基质的交互效应，且S1基质可提升植株生长表现。在出苗后27天内采用咸水灌溉的西瓜中，基质与以下指标存在显著交互效应：叶面积、叶片数、茎粗、主枝长度、根长、地上部与地下部鲜重，以及植株地上部与地下部的钠、钾、钙元素含量。此外，基质与盐度对茎粗、主枝长度、地下部鲜重，以及植株地上部与地下部的钙元素含量、地下部的钾与钠元素含量存在交互效应。