Saturday, 15 July 2006

Ethno-Management of Plinthic and Ironpan Soils in the Savanna Regions of West Africa.

Rexford D. Asiamah and Owusu Dwomo. Soil Research Institute, Academy Post Office, Kwadaso, Kumasi, Ghana

The savanna regions of West Africa consist of countries whose economy and development depend principally on agriculture and agro-based industries. Agriculture contributes over 40% of the GDP, accounts for nearly 60% of foreign exchange earnings, employs over 70% of the rural labour force and provides over 90% of the food needs of the people in most countries of the subregion. The region consisting of Guinea, Sudan and Sahel savannas which together form the bulk of lands for the production of cereals, grains, vegetables, legumes, root and tubers, tree crops as well as livestock production. As a result of persistent land degradation resulting from both natural and anthropogenic causes, such as annual bush burning, deforestation, overgrazing, soil erosion incidence of pests and crop diseases, etc. food insecurity and rural poverty are prevalent. The most serious threat to land use for agricultural production is the insidious formation of plinthite and ironpan (Petroplinthite) in the agricultural soils of the regions. Plinthite is an iron-rich, humus-poor clayey material which hardens irreversibly into ironpan upon repeated wetting and drying conditions over the seasons. The presence of these materials within the agricultural soils adversely affect the performance and yield of crops. Farmers of these areas have developed and adopted management practices to mitigate the problems associated with the presence of these materials. The authors of this paper had travelled extensively within the savanna regions of West Africa during which they observed sites where the materials have been formed and their effects on agricultural performance. Discussions were also held with farmers, scientists, extension officers and NGO and literature on the materials consulted. It was found that the materials occur extensively in the soils of the uplands which are mostly used for cultivations. Indigenous farmers management practices that circumvent the problems posed by the materials and boost yields within the region include, stone bunds, vertiver grass bunds, other anti-erosion measures, fertilization, mulching, cover cropping, agroforestry practices and incorporation of legumes in their farming system. In a very serious situations where the ironpan is close to the surface or even exposed the zaļ methodology of chiselling into the pan and growing crops in the pits is practiced. Key words: Land degradation, plinthite, petroplinthite, enrichment, zaļ.

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