Investigation on Erodibility and Water Stable Aggregates of Certain Soils of Eastern Nepal

The values of certain indices of erodibility such as erosion ratio, dispersion ratio, clay ratio, etc. of the forest soils of Kosi catchment in eastern Nepal are lower than those of arable soils even though they are under unprotected forests. The forest soils contain higher percentage of water stable aggregates, organic carbon, calcium, phosphorus and higher exchange capacity than the arable soils. The values of E. R. tend to increase in arable soils and decrease in forest soils with increase in altitude. Besides E. R. value, other factors such as W. S. aggregate, D. R., organic carbon etc. should be considered in erodibility studies of soils as they are closely correlated with E. R. The W. S. aggregate has been significantly correlated with water holding capacity, organic, carbon, phosphorus, Ex. Ca, C. E. C, D.R. and suspension percentage but not with clay and free iron oxide.