Summary Of Project Proposals For Pre-Centre Research Advisory Committee Meeting

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Date
2010
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Kenya Agricultural Research Institute
Abstract
Sasumua catchment is characterized by high population density and has several sources of land degradation. These include; deforestation, encroachment of forest, soil nutrient depletion due to continuous cultivation with limited soil fertility management, overgrazing and cultivation on steep slopes without adequate soil and water conservation measures (Kimigo et ai., 2008). Land use changes, especially cultivation of deforested land may rapidly diminish soil quality leading to severe land degradation (Kang and Juo, 1986; Nardi et at., 1996; Islam et at., 1999). ). Land use changes in Sasumua catchment have been associated with loss in total carbon, exchangeable calcium and magnesium, increase in cation exchange capacity and soil pH and silt-clay ratio (Kimigo et at., 2008). Land degradation also leads to off-site effects such as sedimentation of surface water bodies, runoff and flooding (FAO, 2007; Pagiola, 1999; Scherr and Yadav, 1996: Schrodeder, 1993; Unruh et ai., 1993).Measurements of cost of land degradation may involve the cost of silt removal from Sasumua dam, the inputs required to offset nutrient depletion and the cost of soil and water conservation measures. Silt removal and water treatment cost can be obtained from the water treatment plant at the dam while the net nutrient loss can be quantified using the difference between (soil nutrient levels + the nutrient input) - (crop uptake +loss due to surface runoff and leaching). Annual Crop yield data can give an estimated of nutrient harvest from the catchment while prices of fertilizer and manure input can give the net costs of nutrient input.
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