Effect of Increasing Elevation of Lowland Coastal Saline Soils of Sundarbans (India) on Soil Salinity and Its Seasonal Variation

The delta region of the river Ganges spreads over India (West Bengal) and Bangladesh is popularly known as Sundarbans. Crop productivity of the region is very poor. Agricultural lands of the region are mostly saline and low-lying with drainage congestion due to presence of brackish groundwater table at shallow depth and flat topography. In recent years, improvement in productivity of these lands was witnessed by farmers when the elevation of lowlands was increased through land shaping. In the present study changes in the salinity status of soil were due to raise of land elevation through land shaping was investigated for two years and 3 seasons (winter, summer and late summer). It was found that there was a considerable decrease in soil salinity due to increase in elevation of lowlands through land shaping. The salinity of original lowlands was about 200% higher than the raised lands or uplands made through land shaping. Salinity of rhizosphere soil decreased with depth and there was a strong seasonal variation of soil salinity. At all soil depths soil salinity increased as the dry season progressed from winter to late summer through summer and soil salinity was highest in the surface (0-10 cm). The depth to groundwater table and the groundwater salinity also showed strong seasonal variation and were maximum in late summer season. The drainage condition of soil improved with increasing in land elevation.