EFFECT OF SHADING USING WATER CURTAIN WITH LIGHT IMPERMEABLE GRANULE ON MICROCLIMATE, AND PHOTOSYNTHETIC RATE, GROWTH, AND YIELD OF SWEET PEPPER GROWN UNDER RAINSHELTER IN SUMMER SEASON

A new shading technology (CWC shading) has been developed that is based on the recirculating cool water curtain with light impermeable granule. The shading rate of CWC is changed automatically by control of supply amount of granule as solar radiation intensity, and that is capable to control inside light intensity in greenhouse not to exceed level of light saturation point of crop.
This study was established to investigate the effects of CWC shading on micro¬climate, and photosynthetic rate, growth and yield of sweet pepper under rainshelter in summer season. Our study showed that the new shading technology improved rain shelter climate. During some sunny day, there were differences about 4°C in inside air temperature and about 3°C at leaf temperature between the unshaded and shaded rainshelter. Compared to control (no shading), the CWC shading increased relative humidity about up to 16% during daytime, and decreased solar radiation up to maximum 48.5% during cultivation period. Photosynthetic rate of sweet pepper plant leaf increased about 24% from 25.2 μmol CO₂∙m^-2∙s^-1 under unshaded rainshelter to 31.1 μmol CO₂∙m^-2∙s^-1 under the shaded rainshelter, and also yield of sweet pepper increased about 25% from yield of 24,500 kg∙ha^-1 under unshaded rainshelter to that of 30,570 kg∙ha^-1 under the shaded rainshelter.