Agroforestry Practices Impacts on Soil Properties in the Drylands of Eastern Kenya

Agroforestry is one of the land use practices that is perceived to be sustainable and that has beneficial impacts on soil properties. However, as a universal statement, this may not be true as best documented successful agroforestry practices are located largely on good soils. Its impacts on dryland soils have rarely been quantified and studied in detail. This study determined the impacts of selected agroforestry practices on soil properties in Makueni, Eastern Kenya. A total of 252 soil samples were collected along transects located within mixed tree woodlots established in 2007, 2010 and 2013 and adjacent parklands and grazing lands at depths of 0-15cm, 15-30cm, 30-45cm and 45-60cm. Tree density per agroforestry practice was also determined using the quadrat technique. The soil samples were analyzed using laboratory soil physico-chemical properties techniques. The results showed that Soil Organic Carbon (SOC) and Total Nitrogen (TN) were significantly higher in the woodlots than in the parkland and grazing lands (p≤0.05). SOC was significantly higher in woodlots established in 2007 than those established in 2013 and strongly correlated with the tree density. Phosphorus was significantly higher in parkland as compared to woodlots and grazing lands. Phosphorus and Potassium were significantly higher at 0-15 cm depth compared to other soil depths. bulky density was significantly higher with a corresponding lower total porosity in grazing lands than in the woodlots and parklands. Mixed woodlots positively influenced soil property and could be considered as a strategy to restore degraded dryland soils as well act as important carbon dioxide and nitrogen sinks.