ABSTRACT

Erodibility potentials of soils of different parent materials under different land uses in Abia State, South Eastern Nigeria were studied. Soil samples were collected from four different land uses which are oil palm plantation, forest, arable crop land and fallow land, located at Umudike, Bende, Ameke and Owerrinta respectively. The experiment was a  4 x 4 x 3 factorial experiment in a Randomized Complete Block Design with five replications.  The factors include the four locations (Umudike, Bende, Owerrinta and Ameke), the four land uses (oil palm plantation, forest, arable crop land and fallow) and three depths (0-15, 15-30 and 30-45cm). The soil samples were analysed for their physical, chemical and mineralogical properties. The data obtained were subjected to Analysis of Variance, regression and correlation  analysis. The erodibility factors (k) of the soils were 0.186, 0.157, 0.124 and 0.114 for sandstone, shale, alluvium and coastal plain sands, respectively. The erodibility factors of the land uses were 0.272, 0.155, 0.099 and 0.044 for arable farm, fallow, oil palm and forest respectively. The arable farm had the highest k value while the lowest was observed in the forest land. Regarding Gerald’s erodibility indices, the soils of shale, alluvium, and coastal plain sands were in group II which were well drained soils in sandy grade free material. The soil of sandstone (0.186) was in group III which was graded loams and silt loam.  The erodibility of forest land (0.044) and oil palm (0.099) were in group I which indicated moderate erodibility. The erodibility of the soils under fallow (0.155) fell in group II and the soils of the arable crop (0.272) were in group III. There were significant differences (p≤ 0.05) in estimated soil loss among the soils. The estimated soil losses of the soils were 382.01, 340.32, 337.89 and 267.97 tons/ha/yr for shale, sandstone, alluvium and coastal plain sands respectively. The estimated annual soil losses were 562.95, 340.33, 250.42 and 147.57 tons/ha/yr for arable farm, fallow, oil palm and forest, respectively. The minerals identified include quartz, hematite, magnetite, kaolinite, microcline, albite, iroxide, and montmorrilonite. Most of the minerals were primary minerals especially fieldspars. The soils also contained some oxides of iron. The soils were dominated by quartz and kaolinite. The soils from alluvium parent material had montemorrillonite in reasonable quanitity. The presence of quartz and kaolinites showed that the soils were highly weathered and leached. The high erodibility observed from the study may be due to unsustainable land use which destroyed vegetative cover, reduced soil structural stability and organic matter content thereby making the soil very susceptible to erosive forces.