Soil Conservation and Fertility Improvement Using Leguminous Shrubs in Central Highlands of Kenya: NARFP Case Study
Mugwe, J. N.
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Declining land productivity with reduced crop yields has been a major problem facing smallholder farmers in the central highlands of Kenya. The major factors contributing to the reduced land productivity is soil impoverishment caused by continuos cropping without addition of adequate fertilizer and manure, and soil erosion on steep slopes. The National Agroforestry Research Project (NAFRP) initiated research work in 1992 to try and address these problems. The research work investigated the potential of using two leguminous shrubs (Leucaena leucocephala and Calliandra calothyrsus) for improving soil fertility and soil conservation on steep slopes. The studies were carried out both at onstation and on-farm. Treatments where leafy prunings of calliandra and leucaena were incorporated yielded higher than the control treatments without prunings incorporation. Leucaena alley cropping system was beneficial and maintained crop yields at 4 t ha-1 in most seasons. Calliandra hedgerow intercropping system on the other hand depressed crop yields. However calliandra was effective in controlling soil erosion when planted as a contour-hedgerow system. The contour hedgerows in addition to conserving soil produced additional benefits in terms of high quality animal fodder. Ê This study concluded that in the central highlands of Kenya where land is slopy, and similar areas, it is advisable for the smallholder farmers to plant leguminous fodder trees on terraces as contour hedgerows for both soil conservation and biomass production. The resulting biomass could be incorporated into the soil to improve soil fertility for farmers without livestock, or fed to livestock for farmers who own livestock. If the biomass is fed to livestock, possibilities of recycling nutrient through animal manure should be explored to ensure soil nutrient replenishment.