One disadvantage of using nets is that they also cause loss of light. In the experiments reported here, the subjects were nine-year-old trees of 'Gala Mondial' apples planted in north-south oriented rows in Germany and spaced 3.5x1.5m apart.
A hail net was placed over the trees in May and five reflective ground covers spread in the aisles between the tree rows on 13 August. The covers included a white, woven plastic material, a similar but less reflective plastic material, a white, biodegradable paper, an aluminium-coated plastic and a plastic with aluminium strips.
All the materials reflected incident light so did better than grass. Most of the ground covers improved fruit colour on the shaded sides of fruit, especially on the lower side, and the fruit also ripened slightly earlier.
Economic assessment based on a nine per cent increase in the proportion of well-coloured fruit and a 10-year lifespan for the woven plastic materials concluded that only the white, woven plastic (Extenday(R)) generated a profit.
Reflective Materials Under Hailnet Improve Orchard Light Utilisation, Fruit Quality and Particularly Fruit Colouration by Meinhold, Damerow and Blanke (2011). Scientia Horticulturae 127 (3): 447-451. The contents of issues of Scientia Horticulturae and abstracts of papers are provided at www.elsevier.com/locate/scihorti