Abstract:
Contour hedgerow systems consisting of various combinations of tree and grass species can be used on sloping lands to
minimize erosion, restore fertility, and improve crop productivity, but there is need to evaluate the effectiveness of each system
for its suitability at any locality as effective erosion control. The objectives of this study were to determine the amount of soil
conserved by contour calliandra (Calliandra calothyrsus)–Napier grass (Pennisetum purpureum) hedgerows, and then develop
a support practice P-subfactor for conservation planning in central Kenya. As a benefit beyond soil conservation, biomass
yield and N and P retention by the hedgerows were determined. Cumulative data for five cropping seasons from 1997 to 1999
indicated that the contour hedges on 20% slope conserved more soil (168 Mg ha-1) than on the 40% slope (146 Mg ha-1)
compared to the control plots. For both slopes, this was equivalent to a 0.7 P-subfactor for use by the Revised Universal Soil
Loss Equation (RUSLE) model in predicting soil erosion.