2020 Volume 11 Issue 2 Pages 38-45
Salt-affected soil is a serious problem in Thailand, and most of this soil is found in the northeastern part of Thailand. The total area of saline land in Northeast Thailand is 2.85 million ha, which accounts for about 17% of this area (Land Development Department,2011). The objective of this study is to evaluate the effect of desalinization by digging drainage channels in salt-affected fields during rainfall. The study was conducted on a high salinity field in Khon Kaen, Thailand. In April 2019, the main drainage channel of a depth of 1 m, was excavated across the center of the field in the south-to-north direction. Additionally, side ditches were installed along the circumference of the west part of the field. We constructed drainage channels to promote field drainage and effectively induce salt leaching with rainfall. Field observations were conducted eight times, especially in the rainy season, from August 2018 to September 2019. Soil apparent electricity conductivity (ECa) was measured using an electromagnetic induction meter in three distinct depth ranges, i.e., 0.375 m, 0.75 m, and 1.5 m, from the soil surface. Soil salinity was represented as contour maps based on spatially interpolated data and spatial distribution and temporal changes were analyzed. The soil ECa in the field gradually increased from upstream to downstream. Moreover, it was higher near the surface and lower deep underground. By comparing the soil salinity observed in the later part of the rainy season in both the years, ECa was observed to have decreased by 20% from August 2018 to September 2019. The ECa values at depths of 0.375 m and 0.75 m in the west part of the field, which had side ditches, were significantly lower than those in the east part of the field two months after the drainage channels were constructed. However, a contrary result was obtained after a heavy flood. These results indicate that drainage channels contribute to salt leaching with rainfall. Our results suggested that excavating drainage channels could effectively reduce soil salinity during the rainy season under good drainage conditions.
