Assessment of the state of soils, shallow sediments and groundwater salinity in Abi, Cross River State, Nigeria

Abi area in Nigeria borders the salinity enriched Lower Benue Trough (LBT) and plans are currently underway to extend large-scale irrigation facilities under construction in the LBT to Abi area. In order to generate baseline soil and water salinity information about Abi area under non-irrigation condition, integrated information from constrained analyses of vertical electrical sounding data, two-dimensional electrical resistivity tomographies and laboratory analyses of soil and water samples were used to assess and map the spatial salinity distribution. Existence of widespread heterogeneities in the distribution of soil and water salinity between the shaly and sandy materials that dominate the shallow geology of the area was observed. Minimum values of water electrical conductivity (WEC) and total dissolved solids (TDS) were observed to be 19.2 μS/cm and 13 mg/L, respectively, in the sandstone-dominated areas. Maximum values of WEC and TDS were observed to be 931.0 μS/cm and 624 mg/L, respectively, within the shale-dominated areas. Soil electrical conductivity was observed to vary from 5.0 μS/cm in the sandstone areas to 14.0 μS/cm in the shale-dominated areas. Minimum and maximum soil pH observations were 4.53 in the shale-dominated area and 6.55 in the sandstone-dominated area, respectively. These results show that the water and soil resources in the area vary from fresh to slightly saline and non-saline to high salinity levels, respectively. Consequently, both resources are still good for agricultural purposes.