Use of erodibility indices in assessing soil erosion in central and northern Cross River State, Nigeria

Soil erodibility indices were used to assess erosion prone areas in central and northern Cross River State, Nigeria. Fourteen (14) composite soil samples were collected at a depth of 0-30 cm and analyzed using standard laboratory procedures. Results showed that the soils are coarse textured with high sand content dominated by textural class of loamy sand in both the central and northern. The vulnerability class used for rating of soil erodibility indices in the study showed that % water stable aggregate (WSA) was severe and moderate (mean values of 55.3 and 37.24%); indicating high and moderately vulnerable. The CV of the %WSA was high and moderate (38 and 34%) in the central and northern. Dispersion ratio (DR) was generally extreme (mean values of 0.36 and 0.32); indicating very high vulnerability. The CV of the DR was high and moderate (56 and 34%) in the central and northern. Clay ratio (CR) was generally moderate (mean values of 3.5 and 3.4); indicating moderately vulnerable. The CV of the CR was high (43 and 54%) in the central and northern. While that of clay flocculation index (CFI) was generally low (mean values of 0.87 and 0.85); indicating its inability to resist dispersion in water. The CV of the CFI was low (6%) in both the central and northern. The t-test analysis conducted on the DR, CR and CFI showed they were no significantly differences (p>0.05). While significantly differences (p<0.05) were observed in %WSA with sand, silt and clay of the water dispersed samples in the central and northern. Soil conservation measures such as contour farming, terracing, vegetative barriers and engineering measures such contour bunds and water ways should be adopted in the erosion prone areas to control the erosion.