Estimation of soil loss by gully erosion in Mubi, Adamawa state, Nigeria

Abstract

Six locations in Mubi, Adamawa State (Digil, Muvur, Vimtim Gella, Lamorde and Madanya) affected by gully erosion were surveyed between April, 2003 and November, 2004. Parameters related to soil erosion losses such as slope, topography, vegetation and land use were noted or measured. Photographs of the affected areas were also taken. Soils were sampled and analysed for some physicochemical properties in the laboratory. Estimates of soil loss by gully erosion were evaluated by measuring the weights and volumes of soil loss. Survey of the gully sites revealed a gentle to steep slopes with undulating topography. Land-use types were of arable farming and livestock production. Gully shapes in the areas studied were either of U or V shaped channels with low to moderate depths at considerable lengths. The soils are loamy in texture with moderate organic matter. The soil erodibility index values averaged between 0.16 and 0.23, while the seasonality of rainfall shows that most of the areas are under markedly seasonal regime (SI = 0.08 – 0.99) with an average rainfall erosivity index of 683. 60 ± 0.05 in year 2003 and 655.25 ± 0.05 in year 2004. The magnitude of soil loss ranged from 159,574.14kg to 725,345.01kg per hectare furrow slice in 2003, and from 101,556kg to 984,400.56 kg per hectare furrow slice in 2004. The Magnitude of soil loss through gully erosion was greater in Digil followed by Muvur then Madanya and Lamorde. While volume of soil lost to erosion was least in Vimtim and Gella. It is therefore recommended that simple agriculturally based gully control measures should be employed to control the menace.