2019 Volume 11 Issue 2 Pages 10-19
Raising rice seedlings in Japan typically starts early in the spring when ambient temperatures are low. To promote growth, temperature and insolation conditions around the seedlings are usually optimized by using greenhouses and/or by covering the seedlings with sheetings. However, on hot days with fine weather, using greenhouses and sheetings increases the risk of high-temperature damage to rice seedlings. In particular, organically grown seedlings are at higher risk because organic farming does not use agrochemicals to supplement growth. In this study, a new sheeting for covering growing seedlings was developed. The sheeting has a high-thermal-insulation capacity which prevents the damage. An optimal method for raising seedlings using the sheeting was also examined.
Air and bed-soil temperature under the new sheeting (Tokan-Honami/Tokankosan Co., Ltd. Japan) was 5°C cooler than when conventional sheeting was used (Silver-Love #80/Tokankosan Co., Ltd.) on hot days with fine weather. The new sheeting prevented damage to rice seedlings. Conversely, the growth of rice seedlings under the new sheeting was delayed at low air temperatures associated with cloudy and rainy weather. This delay in growth could be overcome by overlaying the new sheeting with the conventional sheeting (Silver-Polyto #80/Tokankosan Co., Ltd.) at only the chilly days.
Compared to conventional methods, the new sheeting provided a more secure environment for raising seedlings. Moreover, the new sheeting was particularly well suited to raising seedlings for organic farming in shallow outdoor plastic pools.
