Abstract
Plastic shading nets are being used extensively in hot and sunny regions to protect plants from intense solar radiation. However, the choice of net to fulfill specific shading requirements often depends on empirical or economic criteria, not on scientific considerations because parameters used to characterize the different types of nets is not available. Solar radiation transmission is the most important parameter characterizing nets. A simple measuring method is presented and used to quantify global, diffuse and direct beam solar radiation transmission trough seven plastic shading nets. Nets with colors and nominal shading factors that are most commonly used in the Arabian Peninsula were selected for the study. The results showed that the behaviors of the plastic nets and their radiative properties under solar radiation conditions were similar to translucent materials. Accordingly, investigating equivalent optical constants (i.e., refractive indexes and extinction coefficients) for plastic nets similar to translucent materials is possible. Determining these constants can help to predict the radiative properties of the net without the need of measurements. Solidity and color of the net had significant effects on the radiative properties. The shading factor of a plastic net depends on the time of the day and on the design and meteorological parameters. Daily integral of the shading factor, solidity and the total radiative properties are appropriate parameters describing a net whereas, nominal shading factors provided by the producers cannot be used.