Carbon variability in different soil organic fractions according to land use patterns in West Africa

Abstract

The nature of organic matter in different particle size fractions is a better indicator of the level of soil degradation. The objective of the present study is to evaluate the influences of different land use patterns on the distribution of organic carbon in the different soil fractions in the upper basin of Magou. Three sites were selected on a reasoned basis. One hundred and eight soil samples were collected from the three sites according to land use, depth, and toposequence. Soil organic carbon content was determined by the Walkley and Black method. Soil samples were fractionated according to Feller's principle and then the data for C/N ratio and soil organic fractions were subjected to multiple regression analysis by land use. The results revealed that in the organic-mineral fraction, the soil organic carbon content decreases from 0-10 cm (0.13%) to 20-30 cm (0.09%). This decrease is also observed from downslope (1.01%) to topslope (0.97%), in particular in the fine sand fraction. Moreover, on the agricultural lands, the organic matter is more stable in the organo-mineral fraction than in the natural formations where it is the sandy fractions that increase the organic matter over the first 30 cm.  It is therefore necessary to develop sustainable agricultural practices likely to stimulate the accumulation of carbon at all levels of the topo-sequence and then in the three fractions in order to increase the fertility and productivity of the land.

Key words: land degradation, agricultural practices, organic carbon, soil fertility, upper basin of Magou