Abstract
The use of anti-hail nets on orchards changes the microclimate underneath the net. This might be of great importance in apple growing regions characterized by high radiation levels and hot and dry climates during the summer season. But, depending on the net colour and on the local climatic conditions, the shade promoted triggers different responses by the trees. Grey and black anti-hail nets were applied in an apple orchard (cv. ‘Golden Delicious’) located in Northeast Portugal. Under the nets a lower concentration of glomalin related-soil proteins was observed, along with an improvement on trees water status, stomatal conductance, net photosynthetic rate, total chlorophylls, N, Mg, Fe and Cu concentrations, as well as an increase in mean fruit weight. The major difference between nets was on the photosynthetic efficiency, being higher on black net in sunny days, while grey net performed better under cloudy conditions. The use of netting systems proved to be effective in improving “Golden Delicious” apple trees performance under a Mediterranean climate, mainly when the radiation reaching the plants surpass the tree saturation point for photosynthesis. Therefore, these findings anticipate solutions for current and forecasted negative effects of climate change.
Highlights
The domestic apple tree (Malus × domestica Borkh.) is one of the most cultivated fruit crops worldwide, after Citrus and grapevine [1]
The values of total and extractable glomalin-related soil proteins (GRSP) were significantly higher in the plot kept uncovered in comparison with those that received the anti-hail nets, whereas no significant differences were found in GRSP between the plots covered with the grey net and black net (Table 1)
Under the conditions of the study, the microclimatic changes created by the grey and black nets contributed to reduce the orchard vulnerability to the highly irradiances far above the apple tree light saturation point and the hot and dry summer season
Summary
The domestic apple tree (Malus × domestica Borkh.) is one of the most cultivated fruit crops worldwide, after Citrus and grapevine [1]. It is cultivated in temperate regions or at high altitudes but, the climatic conditions of such regions may result in higher fruit production, these areas are frequently affected by hailstorms [2]. Netting is the most effective method to protect from hailstorms and to reduce the intensity of the transmitted light and wind speed [2,3,6,10,11,12], which may cause changes on orchard’s microclimate, including the reduction in air, leaf, fruit and soil temperature. Nets might be of great importance in the context of climate change, in conditions of extreme events, as the case of hailstorms and heat waves [15]
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