Shading material changes the proportion of diffuse radiation in transmitted radiation

Abstract

Summary. A wide range of shading materials are used by horticulturists (to protect plants from direct light, wind and hail) and researchers (often to simulate shading by plant canopies). All materials reduce the incidence of direct shortwave radiation and, to varying degrees, alter the relative proportions of direct and diffuse radiation compared with the incident radiation outside the material. Plant responses under the shading material would be influenced by the changes in incident radiation. This study measures the proportion of shortwave radiation transmitted and the proportion of diffuse radiation under 12 commercially available shading materials. Colour of the material (white, green or black) greatly influenced the proportion of shortwave radiation transmitted by commercial shadecloths, with transmission highest under white shadecloth and lowest under black shadecloth. In addition, the mean proportion of diffuse radiation increased under white shademesh, clear solarweave, glasshouse film and dense lattice compared with incident radiation.