Erosion effect on soil properties in Karimama (Northern Benin)

Abstract

Water erosion, chemical degradation, wind erosion and physical degradation have been reported as main types of soil degradation in the world. In Karimama district water erosion is a major process for soil degradation. Nevertheless, water erosion can be a consequence of degradation of the soil structure, especially the functional attributes of soil pores to transmit and retain water, and to facilitate root growth. The current study aims to find out water erosion effects on soil physical and chemical characteristics. Pedological soil profiles have been done both in W National Park and its peripheral land use areas. Soil samples are collected for laboratory analyses (i) in three depth H 1 : 0 - 20 cm top soil, H 2 : 20 - 50 cm and H : > 50 cm (ii) in three types of gullies (dongas) from the less deep to the deeper one and on their plateau (nearby and far from donga). Soil acidity, texture, organic carbon, total nitrogen, available and total phosphorous sum of exchangeable bases and cation exchange capacity are the studied parameters. Soil texture is clay-sandy-loamy in the W National Park and its periphery. The soil of the two sites has a clay-sandy loam texture. Water erosion began with the selective removal of fine sand. It significantly affects bulk density and soil porosity. The erosion acidifies the soil because the soil is more acidic in dongas than on plateaus. The organic matter contents on the studied soils are extremely low in the soil and are not significantly influenced by the erosion intensity. However, erosion has significantly reduced the cation exchange capacity of the soil or a loss of soil metal cations (especially Ca2+).This decalcification of the soil explains soil acidification as a result of erosion. Nitrogen appears to be deficient element that must be given to the soil in order to increase crop yield in a sustainable way in this part of northern Benin.