Application of erodibility nomograph from universal soil loss equation in the assessment of soil erosion in two agroecological zones

Abstract This paper exhibits application of erodibility nomograph from Universal Soil Loss Equation (USLE ) in the assessment of soil erosion in two agroecological zones. Seventeen composite soil samples were collected from sites showing active erosion menace at the plough depth of 0–30 cm with the use of soil auger by random sampling method and analyzed using routine laboratory procedures. Results showed that the soil texture was dominated by sandy loam in the central and loamy sand textures in the northern agroecological zones. After all requisite parameters were obtained, the erodibility nomograph used for assessment of the soils’ erodibility, K, values showed low to medium (0.10–0.40 Mg ha −1  MJ mm −1 ) with mean of 0.21 Mg ha −1  MJ mm −1 in the central and medium (0.1–0.8 Mg ha −1  MJ mm −1 ) with mean of 0.22 Mg ha −1  MJ mm −1 in the northern agroecological zones. Statistically, the results indicated high coefficient of variability (CV); the CV ranged from 52 to 118% in both zones. The low to medium status of soils erodibility in the central and the medium status of soils erodibility in the northern suggests how vulnerable the soils are prone to erosion triggered by agents of erosion which cause easy detachment of the soil’s particles. The multiple correlation analysis performed on the soils data to uncover which soil properties are significantly correlated with the soil erodibility parameters in the zones showed same statistically significant parameters with those in the nomograph . It was therefore concluded that, the nomograph is still valid tool in assessment of soil erosion even in tropical areas such as central and northern Cross River State, Nigeria. Soil conservation measures such as contouring, mulching and cover cropping were recommended to be adopted by stakeholders to combat the accelerating soil erodibility in the area.