Nigeria: Soil and Water Resources Survey of the Sokoto Valley, final report. Vol 5, soil survey and land classification. Part 1, text. App. 1, description of the soil classification units

arcilla argile chemicophysical properties classification des sols clay drainage drenaje elemento primario del suelo estructura del suelo fertilidad del suelo geologia geologie geology land use perfil del suelo permeabilidad permeability profil du sol sloping land soil classification soil fertility soil morphological features soil parent materials soil profiles soil structure structure du sol terre en pente terreno en declive trait morphologique du sol utilisation des terres valles valleys vegetation