Abstract
To identify ways to improve the winter production of ‘Kyo-temari’ parthenocarpic tomatoes without the use of heating, we compared the effect (October 2011 to March 2012) of covering a poly tunnel with a newly developed polyvinyl alcohol and polyethylene (PVA) film instead of with a conventional film, i.e., polyvinyl chloride (PVC). Light transmittance at wavelengths of 2,500–25,000 nm was lower in the PVA than in the PVC film, so it retained a higher level of heat. The daily minimum temperatures in both tunnels were 0.5–2.8°C higher than in a non-covered tunnel during the same period, and the time during which the temperature remained below 5°C was shorter in the PVA-covered tunnel. The relative humidity and daily maximum temperature in this tunnel were lower than in the PVC-covered tunnel. The number of fruits was higher in the PVA-covered tunnel. Furthermore, the proportion of small ones was larger, and their Brix was significantly higher. Thus, covering tunnels with this newly developed film can increase the number and quality of ‘Kyo-temari’ tomato fruits grown in winter using a non-heated production system.
