Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Vulnerability of soils to change in agricultural use around Lake Naivasha Kenya

Auteur : Kwacha, Jonathan C P H

Etablissement de soutenance : International Institute for Aerospace Survey, Netherlands

Grade : Master of Science (MSc) 1998

Résumé
This study is concerned with vulnerability of soils due to change in land use around the shore of Lake Naivasha (Kenya). The soils have been developed on the lacustrine sediments and volcanic deposits. An attempt has been made to investigate soil chemical properties in and between sample areas, and also in different land use, by comparing with existing data of the same area. Some samples were collected from a natural forest (control area), where there is no current observable human influences, for the purpose of comparing soil properties with the cultivated area. Three sample areas were selected which cover different land use.Most soils of the study area are moderately well drained to well drained, moderately deep to very deep, but also shallow soils are found mainly over the raised ridges in the volcanic plain. The top soil varies from a very dark brown to dark brown, silty clay loam to sandy clay, and the subsoil varies from a dark grayish brown to yellowish brown, which is silty clay to sandy loam, The topsoil pH varies from 4.7 to 8.3 while pH at depth of 50 cm varies from 6.6 to 9.4 and pH at the depth of 120cm varies from 7.3 to 10.6.In general soils has a high Phosphorus, Calcium and Magnesium content, Nitrogen and carbon levels are low while Potassium content is very high. Following the USDA Soil classification system the soils belong to three orders Alfisols, Inceptisols and Entisols. Crop production in the area are mainly flower and horticultural crops which depends abstraction of water from lake Naivasha. Soil cultivation and in combination with other soil management practices has modified some soil properties ; topsoil properties being more modified than the subsoil ones. The investigation of soil properties show that C, Ca, EC, Mn, Na and P are liable to change in the study area.

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