Landuse Changes and Variability in Properties and Erodibility Indices of Soil of Imo State Polytechnic, Owerri, Nigeria

摘要

Erodibility study is important in determining the susceptibility of soil to erosion. In this study, soils under different landuse types in Imo State Polytechnic, Owerri, were studied to determine how the various landuse types have'resulted in variability in selected properties of the soil, and the corresponding erodibility indices. The landuse types investigated are continuous cultivation, fallow land, grass land and forest land. The soils were analyzed for pH, organic carbon, organic matter, cationexchange capacity, and hydraulic conductivity using standard methods; while particle size distribution was performed using the sedimentation method. Results show that dispersion ratio (DR) increases in the order of continuous cultivation, > fallow land,> grass land, > forest land. Though all the soils under study were considered susceptible to erosion, the soil under continuous cultivation was the most susceptible (DR = 107), and the soil under forest land was the least susceptible to erosion (DR = 32). However, there was a high negative correlation (R = -0.85) between the organic matter content of the soils and their dispersion ratios. The soils in the study area are classified as loamy sand with organic carbon (OC) ranging from 1.01 % for the continuous cultivation land to 1.35 % for fallow land. The soils were observed to be slightly acidic with pH ranging from 5.0 for continuous cultivation to 6.2 for fallow land while cation exchange capacity (CEC) ranges from 4.11 cm/kg to 6.07 cm/kg. Dry unitweight of the soils ranges from 1.61 mg/km for continuous cultivation to 1.84 mg/km for forest land. It is thus recommended that adequate conservation measures be adopted to save the soils from possible erosion.