Abstract
ABSTRACTRainfall variability in Northeast Thailand during 2000–2015 was examined with objectives to determine any changes in rainfall pattern with time, and to determine its effects on duration of rice growing period and grain yield using a simulation model. Variation in mean annual rainfall over 16 years in 93 locations in the region ranged from over 1,600 to less than 1,200 mm, and the locations were grouped into 4 based on the annual rainfall. The change in annual rainfall, and early, mid and late season rainfall was analysed for the rainfall groups. There was a significant reduction in the amount of early season rainfall during the 16-year period in all groups. However, there was no significant change for annual, and mid and late season rainfall. Simulation study showed that the start of rice growing period (SGP) was delayed with reduced early rainfall during the 16 year period and the end of rice growing period (EGP) was also delayed while there was no significant change for the length of rice growing period (LGP). Simulation results showed that grain yield of KDML105, leading variety in Thailand, tended to increase during the 16 year period, as delayed planting time was optimum for achieving maximum yield in all rainfall groups. With general delay in rainfall season, occurrence of late season drought was predicted to be reduced and this helped to increase simulated grain yield. However, adaptation to changing rainfall pattern needs to be planned in advance to maximize its effect.
Highlights
Rainfed lowland is a major rice production system in Northeast (NE) Thailand with areas of 5.4 million ha or 60% of country’s total rice areas of 9 million ha (OAE, 2016)
Jongdee, Inthavong, Budhaboon and Jongrungklang (2017) showed yield loss due to late season drought during 2010–2014, and this was estimated by a simulation model to be about 12–39%, the estimated loss depending on the growth duration of rice varieties
Rainfall data obtained from Thai Meteorological Department (TMD) across NE Thailand from 2000 to 2015 were used to determine whether rainfall pattern changed with time during the period, and using the model of Inthavong et al (2011) we evaluated whether this rainfall pattern change had any effect on the duration of rice growing period and grain yield
Summary
Rainfed lowland is a major rice production system in Northeast (NE) Thailand with areas of 5.4 million ha or 60% of country’s total rice areas of 9 million ha (OAE, 2016). Climate change is taking place in the lower part of NE Thailand, and the maximum temperature has increased by 0.3–0.8°C per decade in October-November (Prabnakorn, Maskey, Suryadi & Fraiture, 2018) These authors showed negative correlation between temperature and rice grain yield in the 30 years between 1984 and 2013. The extreme climate events that threaten rainfed lowland rice cultivation in some provinces in NE Thailand include prolonged dry-spells during vegetative stage (Chinvanno et al, 2006) This early season drought in turn could increase the cost of production with replanting or supplying irrigation water to maintain rice growth. Rice yield in the region is considered to decrease in the future according to Babel, Agarwal, Swain and Herath (2011), and this may be due to the damaging effect of higher rainfall on the crop during harvesting time (Felkner, Tazhibayeva & Townsend, 2009)
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