Koshi Yoshida, Supranee Sritumboon, Mallika Srisutham, Koki Homma, Masayasu Maki, Kazuo Oki
Received 2021/08/17, Accepted 2021/09/13, Published 2021/11/26

Koshi Yoshida¹⁾, Supranee Sritumboon²⁾, Mallika Srisutham³⁾, Koki Homma⁴⁾, Masayasu Maki⁵⁾, Kazuo Oki⁶⁾⁷⁾

1) Graduate School of Frontier Sciences, The University of Tokyo, Japan
2) Regional Office 5, Land Development Department, Thailand
3) Faculty of Agriculture, Khon Kaen University, Thailand
4) Graduate School of Agricultural Science, Tohoku University, Japan
5) Faculty of Food and Agricultural Sciences, Fukushima University, Japan
6) Faculty of Engineering, Kyoto University of Advanced Sciences, Japan
7) Institute of Industrial Science, The University of Tokyo, Japan

In northeast Thailand, 17% of the total agricultural land is classified as salt-affected. In the future, climate change may exacerbate salt-affected soil problems. Therefore, in this study, we conducted a field survey to evaluate seasonal changes in soil electrical conductivity (ECe) in salt-affected paddy areas of Ban Phai District, Khon Kaen Province, northeast Thailand. Fifteen soil samples were collected every 2 weeks from October 2016 to December 2018, and the ECe, soil water content, and soil textures were analyzed. Then, the HYDRUS-1D model was applied to estimate seasonal changes in the salinity level, and the simulated results corresponded well with observed data. Using HYDRUS-1D and the global circulation model (MIROC5) outputs under the Representative Concentration Pathways 8.5 scenario, future ECe was predicted. Under a temperature increase of 2.8°C from 2016 to 2100, annual potential evapotranspiration increased from 1,430 mm (2016–2025) to 1,584 mm (2081–2100). The average ECe in cultivation season increased from 2.63 dS/m (2016–2025) to 3.31 dS/m (2081–2100). As a countermeasure to mitigate soil salt accumulation, a 5 cm reduction in groundwater level offsets the negative impact of climate change, and a 10 cm reduction significantly improves the soil ECe relative to the current soil salinity level.

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