Evaluation of the light profile and carbon assimilation of tomato plants in greenhouses with respect to film diffuseness and regional solar radiation using ray-tracing simulation

Abstract

Diffuse fraction, which can be increased by using diffuse films, has been considered to influence light interception and photosynthesis of crops in greenhouses. However, quantifying the influence of diffuse films is challenging owing to the complicated optical interactions between climatic factors inside and outside greenhouses. Thus, versatile methods for evaluating the effect of diffuse films are required. The objective of this study was to evaluate the effect of diffuse films on the improvement of the light profile and photosynthesis of tomatoes in greenhouses according to film diffuseness and regional solar radiation using ray-tracing simulation. The structural and optical properties of the greenhouse components were applied in a 3D-framework combined with a ray-tracing module. The light transmission patterns of diffuse films and solar radiation properties were incorporated. The reliability of the simulation was confirmed by comparing measured and estimated irradiances inside greenhouses covered with films having different haze factors. For scenarios, the diffuse film efficiency was assessed under typically different solar radiations, a low irradiance, high diffuse radiation fraction (LIHD) and a high irradiance, low diffuse radiation fraction (HILD). The light interception was estimated through the simulation and used to calculate the photosynthesis using the Farquhar-von Caemmerer-Berry model. The simulation was found to be reliable with R2 of 0.95 and 0.94 for the two greenhouses covered with different diffuse films. The light distribution on the tomato plants were less affected by film diffuseness under LIHD than HILD. With increasing film diffuseness, carbon uptake and light use efficiency increased by 5.30% and 4.58% under HILD, but did not change under LIHD. The light distribution and photosynthesis in diffuse film-covered greenhouses under different light environments could be reasonably estimated by the simulation. Thus, this method can be used to evaluate the applicability of diffuse films to various regions with diverse meteorological characteristics.