Ethno-management of plinthic and ironpan soils in the savanna regions of West Africa

Abstract

The savanna regions of West Africa, consisting of Guinea, Sudan and Sahel savannas, form the bulk of lands for producing cereals, vegetables, legumes, root crops, tree crops, and livestock. As a result of land degradation from natural and anthropogenic factors (such as deforestation, overgrazing, annual bush burning and soil erosion), 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, humuspoor, clayey material which hardens irreversibly into ironpan on repeated wetting and drying over the seasons. They occur extensively in the savanna soils of West Africa, especially within the groundwater laterites. It was found that the materials also occur in the soils of the uplands, which are extensively used for cultivation. Their presence and effect on agricultural performance have been observed throughout the region. Farmers have developed and adopted management practices to mitigate the problems associated with these materials. Discussions have been held with farmers, scientists, extension officers, and NGOs on the importance of the material on agricultural productivity. Indigenous farmers’ management practices that circumvent the problems posed by the materials and boost yields within the region include stone bunds, vertiver bunds, other anti-erosion measures, fertilization, mulching, cover cropping, agroforestry practices and incorporation of legumes in their farming systems. For serious situations in which the ironpan is too close to the surface or even exposed over large tracts of land, the Zaï method of chiselling into the pan and growing crops in the pits is adopted These indigenous farmers’ practices need scientific improvement to make them more effective.