Title : Change of optimal transplanting date caused by heat wave in 2018 in Korea
Abstract:
The temperature over the globe has been rising due to global warming. Much like Europe, Korean peninsula is suffering from severe heat wave recently. In South Korea, average summer temperature for recent 5-year (Jul-Aug, 2014-2018) was 25.1o C,which is 0.9o C higher compared to the 30-year average (Jul-Aug, 1988-2013). In 2018, average temperature reached 26.5o C during summer as a result of heat wave. Heat waves are expected to become more frequent due to climate change, and it can affect the productivity and quality of crops. This study was conducted to investigate the change of rice yield by transplanting dates (10-day intervals from 10-May to 20-June) over different maturity types (early maturing, mid-maturing and mid-late maturing) in several agricultural zones (plain, inland, sub-alpine, coastal). In plain regions, the highest head rice yield was obtained from 15-Jun and 30-May transplanting date (4.6 and 5.4 t ha-1 respectively) for mid-maturing and mid-late maturing cultivars, respectively. This result shows the optimum transplanting dates in plain area were delayed 20 and 12 days compared to the transplanting date recommended for midmaturing and mid-late maturing cultivars in normal years, respectively. Meanwhile, the yield of early maturing cultivars increased with delaying transplanting time. In sub-alpine regions, the highest head rice yield was obtained from 21-Jun transplanting date (4.8 t ha-1) for early maturing cultivars, which indicate 30-day delay of recommended transplanting date. The yield of mid-maturing cultivars increased with delaying transplanting time. Although mid-late maturing cultivars are not adaptable to sub-alpine regions in normal years, the highest grain yield in mid-late maturing cultivars in 2018 (5.2 t ha-1) was greater than that in early or mid-maturing cultivars. The effect of transplanting date on head rice yield was not clear in inland and coastal regions. In conclusion, heat wave condition caused 12 to 30-day delay of optimum transplanting date for maximum head rice yield compared to current recommendation dates, as well as the increase of cultivation areas for mid-late maturing cultivars
