Effects of greenhouse covers on seedless cucumber growth, productivity, and energy use

Abstract

Effects of single-glass (glass), double inflated polyethylene film (D-poly), and rigid twin acrylic (acrylic) panels, as greenhouse covers, on seedless cucumber growth, productivity and energy use were investigated over three spring seasons (1988, 1990 and 1992). The early and final marketable yields of plants grown in D-poly houses were similar to or higher than those grown in glass houses. Also, plants grown in D-poly houses produced a similar or higher percentage of large and a lower percentage of small fruits than the plants grown in glass houses. The early and final marketable yield and percentages of fruit grades were similar in D-poly and acrylic houses; an exception was the early marketable yield in 1992 which was higher in the acrylic houses. Light transmission was the highest in glass houses, intermediate in acrylic houses and the lowest in D-poly houses. Relative humidity was highest in D-poly, intermediate in acrylic, and the lowest in glass houses. The plants in D-poly houses grew and developed faster (more leaves and flowers) than those in glass houses. The leaf size of plants in D-poly houses and glass houses was similar, but the dry matter content and specific leaf weight of plants grown in D-poly houses were significantly lower (40% less) than those in glass houses. Plants in D-poly houses might have acclimated to the low light conditions by reducing specific leaf weight and increasing their light interception efficiency. Plant growth and development in acrylic and D-poly houses was similar. For cucumber production in climatic conditions similar to South Western Ontario, the D-poly greenhouse is strongly recommended, because there is no loss of productivity in comparison with a glass house, while great savings on initial investment and energy use are achieved.