POSSIBILITIES OF INCREASING PRODUCTION AND QUALITY OF STRAWBERRY FRUITS AND SEVERAL FLOWERS BY NEW BLUE FLUORESCENT GREENHOUSE FILMS

Within the framework of the project SPECTRAFOIL funded by the EU and Grafe Color Batch (Germany), together with the industrial partners Palrig (Israel), Sunsaver (Spain) and several growers and research partners in Israel, Cyprus, Spain and The Netherlands, new fluorescent greenhouse films for several climates and several horticultural production systems were developed. One of the results of SPECTRAFOIL was the development of new blue fluorescent greenhouse films. Technical aspects were investigated, such as spectral light transmission, fluorescent effect, stability of pigments and films. The effect of different fluorescent films on the production and quality of strawberry fruits was investigated at A&F, Wageningen. In these experiments, strawberry plants were grown in small tunnels covered with films containing blue fluorescent pigments in different concentrations, which increased total light transmission and influenced light quality (more blue light) during the years 2002 and 2003. Both fruit production (number of fruits, fruit weight) and fruit quality (color, size, shape, dry matter, freedom from physiological disorders and diseases, balance between sugars and acids) were determined. Blue fluorescent films caused strawberry plants to produce a higher yield, a higher number of fruits and a slightly higher mean fruit size. Differences in fruit quality were small. Moreover, the effects of blue fluorescent films on different shrubs, perennials and annuals were tested at two growers in The Netherlands. Blue fluorescent films gave a 4 days earlier yield to Alchemilla and a 2 days earlier yield to Virburnum. Flower quality of Alchemilla was improved. This was probably due to higher day temperatures and lower humidity caused by a higher light transmission of the film. The same film caused a 5 days earlier yield to Celosia, at the same time improving flower quality. Blue fluorescent films have potentials to increase the yield of strawberry and force the flowering of perennials.