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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Organic amendments may improve the quality of acidic tropical agricultural soils with low organic carbon contents under conventional management (mineral fertilization and irrigation) in Southeast Asia. We investigated the effect of biochar, compost and their combination on maize growth and yield, soil physical, biological and chemical properties at harvesting time at four sites in three countries: Thailand, Vietnam and Laos. Treatments consisted of 10 t·ha−1 cow manure compost and 7 t·ha−1 of Bamboo biochar and their combination. Maize biomass production and cop yields were recorded for two seasons. Elemental content, pH and nutrient availability of soils were analyzed after the first growing season. We also characterized macrofauna abundance and water infiltration. Few changes were noted for maize biomass production and maize cop yield. Soil chemical parameters showed contrasting, site-specific results. Compost and biochar amendments increased soil organic carbon, pH, total K and N, P and K availability especially for sandy soils in Thailand. The combination of both amendments could reduce nutrient availability as compared to compost only treatments. Physical and biological parameters showed no treatment response. We conclude that the addition of compost, biochar and their mixture to tropical soils have site-specific short-term effects on chemical soil parameters. Their short-term effect on plants is thus mainly related to nutrient input. The site-dependent results despite similar crops, fertilization and irrigation practices suggest that inherent soil parameters and optimization of organic amendment application to specific pedoclimatic conditions need future attention.

In northeast Thailand, the irrigated agricultural land was only 7.6% (in 2012) of total and others were classified as rain-fed so that climate change makes agricultural production unstable and also makes negative impact to the societies and economics in rural area. To mitigate these issues, it is desirable to develop enhanced adaptation measures. In this study, we focused on weather induced economic damages and effectiveness of index-based insurance system in Northeast Thailand. Firstly, we evaluated how affect the seasonal rainfall amount and patterns on rice yield and production through regression analysis by using the meteorological and agricultural statistic data. 8 province had positive correlation R>0.3 with Jul-Sep accumulated rainfall. And then, probability analysis was applied to monthly rainfall which was employed for insurance index value. As a result, setting amount and periods of insurance index was suitable. Secondly, household survey was conducted to investigate farmers' conditions of water use, cultivation, income balance.In recent year, agricultural damage on farmers' income was not so large (less than 3%), because 65% of farmers' income relied on non-agricultural sector. That might be the one reason of constraints of insurance sales.

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