Effects of biological techniques in soil conservation and subsoil inorganic-N accumulation in the central highlands of Kenya
Mutegi, J. K.
Mugwe, J. N.
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Soil erosion and nutrient leaching are some of the factors hindering realization of full crop production potential in the central highlands of Kenya. A participatory trial involving use of calliandra, leucaena, napier, leucaena + napier and calliandra + napier contour hedges was started in farmers' fields . of central highlands of Kenya in September 2001 to evaluate the effectiveness of hedges in soil conservation and nutrient cycling. At the start of the trial there was a substantial accumulation of inorganic N with depth. Twenty months later, leucaena,' calliandra, and leucaena + napier substantially depleted the subsoil inorganic N by more than 50%. On the other hand napier decreased mineral-N leaching slightly and showed a small bulge beyond 30-90 cm depth. Treatments on 10-20 % slope category registered a higher average soil loss compared to others on 5-10, 10-20, 20-30 and30 % slope categories. There was soil loss of up to 140 t ha-' on the control at 10¬20% slope category over the study period and a reduction of up 78% of this by sole napier (Pennisetum purporeum) hedge. The overall efficiency of the hedges in soil erosion control followed the order: napier calliandra + napier leucaena + napier calliandra leucaena control.