Evaluation on near infrared-reflective diffuse coating for muskmelon production in simple plastic greenhouse during summer season

Muskmelon is a potential high-valued crop, and its production is affected by light and temperature significantly. Cooling and improving light use efficiency (LUE) are key environmental controls in summer under protected facilities. This study investigated the effects of the application of near infrared (NIR)-reflective diffusion coating on muskmelon cultivated under a simple plastic greenhouse during summer. Microclimate, plant physiological response, and fruit traits were monitored. Results indicate that NIR-reflective diffusion coating reduced the mean air temperature inside the greenhouse by 1.8, 1.9, 0.7 degrees C as well as maximum temperature by 6.0, 7.1, 3.7 degrees C in June, August and September, respectively. Although the accumulated solar radiation in the coated greenhouse exhibited a 5.2% reduction compared with non-coated greenhouse, a more uniform spatial and deeper light distribution was noted. Photosynthetic photon flux density (PPFD) improved 1.6 and 1.5 times in the 100 cm and 50 cm-canopy, and a 10-20% increase in photosynthetic and electron transport rate was observed. Plants could maintain a higher transpiration rate in top canopy. Except for elongation of plant height and internode length after topping on 48 DAP, plant height, internal node number, shoot tip diameter, and shoot fresh weight were not significantly affected. Fruit traits such as weight, width/length ratio, pulp thickness, soluble sugar, starch, and crude fiber were also unchanged. However, total soluble solids content had 0.8 degrees Brix decrease while K, Ca, and Mg content were elevated. NIR-reflective diffusion coating can be used as an energy-saving method for cooling and improving LUE, therefore, its application method, crop, and related cultivated model are worthy for further examination.