Light interception by tomato plants (Solanum lycopersicum) grown on a sloped field

To promote tomato (Solanum lycopersicum) production on sloping land that has the advantage of cool temperature in summer due to high altitude, light interception by plants was investigated. Tomato plants were grown in a sloped greenhouse on an east–south-east facing 20° ground slope and in a conventional greenhouse on a 0° ground terrace and transplanted in south–south-west to north–north-east lines in both greenhouses. Light interception by individual leaves was measured using simple recording films for measuring cumulative solar radiation. Light interception by middle and lower leaves on the sloped field were higher than that on the flat field. Light interception was also investigated using a ray-tracing simulation. A plant in the simulation was simplified as follows: stems and leaves were represented by vertical lines and plane circles, respectively; all plants had the same shape and size. The simulation showed that light attenuation in the plant canopy on the slope was significant less than that on the flat land. Based on the simulation, the difference was caused by higher light interception by middle and lower leaves for certain hours during the day.