Effect of land shaping on soil properties and crop yield in tsunami inundated coastal soils of Southern Andaman Island

Abstract

The 2004 Indian Ocean tsunami severely damaged the coastal ecosystems of the Indian islands of Andaman and Nicobar. Restoring coastal ecosystems and degraded soils of these islands is essential to provisioning of numerous ecosystem services for the native islanders and ecological functions and services of these hotspots of biodiversity. Thus, the present study was conducted to assess the impact of bunding and broad bed and furrow (BBF) systems in restoring the productivity of tsunami inundated coastal areas of southern Andaman. Bunding of agricultural land leached out the salts by impounding of rainwater with significant reduction in electrical conductivity (ECe), sodium absorption ratio (SAR), and exchangeable ions (e.g., Na+, Ca2+ + Mg2+, Cl and SO4 2 ). The BBF system installed in the low lying waterlogged areas improved the drainage of the beds, harvested rain water (4476 m3 ha 1), prevented entry of tidal and runoff water into the furrow, and reduced the overall salinity. In addition, microbial biomass carbon was significantly improved (193–210 mg kg 1soil). Whereas the low lying areas were inundated during the 20 to 45th standard meteorological week by 25 to 85 cm of water, soils under BBF systems were adequately drained and had moisture content between field capacity and the saturation level. The depth of submergence (R2 = 0.798) and soil salinity (R2 = 0.787) were correlated with the rainfall amount. Consequently, the BBF systems enabled a higher cropping intensity (218%), increased fish production (2.32 Mg ha 1) and water productivity (47.36 Rs m 3) and enhanced employment generation (213 man days). These land forming interventions must be up scaled to tsunami-affected, low lying areas of Andaman and elsewhere in southeastern Asia.