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Reflective materials under hailnet improve orchard light utilisation, fruit quality and particularly fruit colouration
- Meinhold, Tobias, Damerow, Lutz, Blanke, Michael
- Scientia horticulturae 2011 v.127 no.3 pp. 447-451
- adverse effects, aluminum, apples, autumn, climate change, color, energy use and consumption, fruit quality, fruits, grasses, greenhouses, hail, labor, light intensity, mechanization, orchards, paper, photoperiod, plastics, prices, ripening, screening, sugars, taste, Europe
- The increase in hailstorms, possibly due to climate change, has led to installation of hailnets in fruit orchards worldwide. This is associated with poorer fruit quality, particularly fruit colouration, which is determined by the light conditions viz diminishing light intensities and shorter day length in the autumn. To overcome these adverse effects of hailnets, five materials were examined as possible ground covers as to their light reflection and the subsequent effect on fruit quality including fruit colouration, using a 9-year-old apple orchard cv. âGala Mondialâ on M9 under black hailnet near Bonn. The ground covers included the woven white plastic Extendayá´¿/Daybrightâ¢, the kaolin-coated, bio-degradable paper UniSet Oâ¢ and the aluminium-coated plastic Mylarâ¢ and Svensson ILS Aluâ¢; the latter is a white plastic interwoven with aluminium strips used as energy saving screen in greenhouses. The ground covers were spread in the alleyways 4â5 weeks before anticipated harvest; adjacent uncovered grass strips under the hailnet served as control. Light reflection, measured perpendicular at 1m height in the alleyways at the time of fruit colouration, was 79â80% by Extendayá´¿/Daybrightâ¢, 75% by UniSet Oâ¢, 68% by Mylarâ¢ and 58% by Svensson Alu ILSâ¢. Apple fruit with any of the reflective ground covers ripened 2â3 days earlier without affecting internal fruit quality and sugar as indicative of taste. The reflective ground covers under black hailnet improved the proportion of well-coloured class I fruit relative to the control (uncovered grass) by an averaged 9%. Economic analysis showed that Extendayá´¿, with an expected lifetime of ten years (based on 4â6 weeks spread time per year) under hail nets in North-Western Europe, scored best based on 45thaâ»Â¹ yield in cv. âGala Mondialâ and 0.40â¬kgâ»Â¹ farm-gate price, resulting in 200â¬haâ»Â¹ net return. Manual labour for spreading and retrieving the ground covers had the major share of the overall gross cost and offers scope for improvement by mechanisation.