Effect of anti-hail nets with different colors on ‘Eva’ apple trees agronomical responses

Abstract The aim of the current research was to evaluate the impact of ‘Eva’ apple tress cultivation under nets with different colors as opposed to cultivation deprived of net treatment on the attributes related to the vigor of the plant, production and fruit quality. The evaluations were carried out during the 2017/18 and 2018/19 crop growing seasons at commercial production fields located in the municipality of Porto Amazonas, PR. The treatments in study consisted of a control (plants grown with no protecting net), along with plants protected by anti-hail nets of distinct colors such as white, crystal (transparent) and black. The following response variables were assessed herein: length and diameter of the branch, plant height and branch diameter as plant vigor measurements, crop production (kg plant-1) and yield (kg ha-1), and number of fruits per plant as to productive yield of the cropping system, as well as shape (height and diameter) of the fruits, mass, Hue angle, firmness, soluble solids and titratable acidity to test grade or fruit quality. There was no significant effect of protecting nets on both vigor and development of the plants. However, production and yield were consistently more expressive under crystal and white protecting nets throughout the second crop growing season. This demonstrated that ‘Eva’ apple trees were conducive to render as well as or even better than those plants bereft of protecting nets in view of the fact that the former treatments caused the plants to suffer less harmful impacts promoted by hail events, excess of wind, and sun burning disorders. The black anti-hail net resulted in negative outcomes as to coloration of the fruits in conjunction with titratable acidity, making them reddish and acidic and, therefore, less attractive for in natura commercial consumption.摘要 本研究旨在评估不同颜色防雹网（anti-hail net）覆盖下‘Eva’苹果的栽培模式，与无网覆盖栽培相比，对植株长势、产量及果实品质相关性状的影响。试验于2017/2018和2018/2019两个生长季，在巴西巴拉那州（PR）波托阿马佐纳斯（Porto Amazonas）市的商业种植园区内开展。本试验设置的处理包括：对照组（无防护网覆盖的植株），以及分别使用白色、无色（透明）、黑色防雹网覆盖的植株。本研究测定的响应变量包括：作为植株长势指标的枝条长度、枝条直径、株高；单株产量（kg·株⁻¹）与单位面积产量（kg·公顷⁻¹）、单株结果数（反映种植体系的生产能力）；以及用于评价果实品质的果实形状（果高与果径）、单果质量、色相角、果实硬度、可溶性固形物含量与可滴定酸度。研究结果显示，防雹网覆盖对植株长势与发育无显著影响。但在第二个生长季中，无色与白色防雹网覆盖下的作物产量与单位面积产量始终更高。这表明，相较于无防护网覆盖的植株，使用防雹网覆盖的‘Eva’苹果植株表现相当甚至更优，原因在于防雹网可减轻植株遭受冰雹、强风与日灼伤害的程度。黑色防雹网则对果实着色与可滴定酸度产生负面影响，使果实色泽偏红、酸度偏高，因此鲜食商业价值有所降低。