Abstract
In the semiarid Sahel, farmers commonly lay stone lines in fields to disperse runoff. This study was conducted in northern Burkina Faso to assess the chemical fertility of soil under a permanent, non-fertilised sorghum crop, which is the main production system in this area, 5 years after laying stone lines. The experimental design consisted of four plots in which stone lines had been laid. The spacing between the lines was 100 m in the first plot, 50 m in the second, 33 m in the third, and 25 m in the fourth. To determine soil chemical characteristics in relation to the stone line spacing patterns studied, soil samples were taken from subplots at regular and fixed distances from the lines at the start of the trial and then 5 years later. Under the continuous non-fertilised sorghum cropping system, the beneficial effect of stone lines on soil fertility was limited. Five years after installing stone lines, soil organic C, total N, available P and Na concentrations and soil pH had decreased. Within the plots, these same variables were higher upslope than downslope of stone lines, probably because of water storage and sediment accumulation in front of the stone lines. In plots where stone lines were relatively close together (<33 m) the decrease in soil fertility was less. It is concluded that in Sahelian zones, stone lines alone are not sufficient to insure the conservation of soil fertility. Combining soil and water conservation techniques with soil fertility management practices are needed to sustain soil productivity.
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