Improving fruit coloration of horticultural crops

The aim of this research was to improve inner and external fruit quality and fruit coloration using four-year-old apple cultivar 'Braeburn Hillwell' trees on M9 (3×1 m spacing) by employing reflective ground covers at Klein-Altendorf near Bonn, Germany (50°N). Reflective ground covers were spread out on both sides of tree rows seven weeks before anticipated harvest. Adjacent trees of the same row without reflective ground cover served as control. For the first time, we compared two reflective mulches(woven textiles). Apple trees with Extenday® and Lumilys® also produced 69 and to 44% well-colored fruit (with 75-100% fruit coloration) compared with 16-26% in the control. There was no acceleration of ripening in plots with reflective ground covers compared with the control. There were no differences in sugar contents (°Brix) and fruit firmness (kg cm‑2), but starch breakdown in fruit with reflective mulch was significantly delayed compared with the control resulting in retarded maturation. An economic analysis based on material costs and lifespan - excluding the labor costs for spreading and removing the ground covers - showed an economic advantage, if these mulches are used more than once a year.