THE EFFECT OF COVERING MATERIALS FOR GREENHOUSES ON GROWING CONDITIONS AND YIELDS OF ROSES

Experiments were carried out with Baccara Roses in four greenhouses of the same shape, structure and size (208 m²); one was covered with glass, one with fibreglass and two with polyethylene. The greenhouses were equiped with a specially designed air conditioning system that made it possible to maintain identical air flow and temperatures in all the buildings.

Measurements of light intensity, air, temperature, air humidity and leaf temperature were carried out. There were slight differences in light intensity under all coverings because of dust that settled on them. Temperatures were equal in the four greenhouses: about 18° C at night and 25° C by day during the export season (autumn, winter and spring),and did not exceed 32° C during summer. The humidity was almost equal, but during the export season somewhat lower in the glass-covered house during the hot test hours of the days in summer. Leaf temperature was highest under glass and lowest under polyethylene. The yield and quality of Baccara rosses varied between greenhouses during the export season, but the total number of flowers harvested in that season was not affected.