สภาพฟ้าอากาศที่เปลี่ยนแปลง: ผลกระทบของอากาศหนาวเย็นต่อผลผลิตของข้าวในเขตภาคเหนือตอนล่าง

Abstract

Rice growing areas in the Lower North of Thailand has been severely affected by extreme climate change seen as cold injury in 2007 dry season. The total affected area was 621,176 rai (99,388 ha) resulted in a drastic loss of 2,749 million Baht ($US 89 million). Since it has been reported that the most sensitive stage to cool temperature is the young microspore stage, approximately 8.5-10 days before flowering, and the critical range of temperature for cold injury resulted in panicle sterility is 15-20 oC. This preliminary investigation firstly aimed to observe visible changes after exposing to cool temperatures. Secondly, to observe the relationship between low temperature and sterility. Thirdly, to measure a subsequent reduction in grain yield of rice cv. Suphanburi 3 sown during 2007 dry season on 26th October 2006 and harvested on 26th February 2007. The temperature recorded on a 3-h basis showed that the daily minimum temperature throughout the growth period was between 1-7 a.m. starting from 25 oC at sowing and continued to reduce further to mostly lower than 20 oC from mid December to the first week of February. This cool period was assumed to be the panicle initiation to grain filling stage. Thus, the most sensitive young microspore stage was estimated to be from 4-6 January 2007 with the minimum daily temperature being 16.3-21.3 oC. Results revealed that low daily minimum temperatures from 25 oC and below throughout the growing period of Suphanburi 3 caused leaf discoloration at tillering, 67% spikelet sterility on average, some panicle tip degeneration, extension of maturity by 13 days and a drastic yield loss being 54%.