The use of parent material/slope positions as soil mapping units in irrigation soil surveys of Northern Nigeria

Abstract

The problems of different mapping units which hitherto formed the basis for irrigation soil surveys of the savanna landscapes in Nigeria are discussed. Using data from a semi-detailed soil survey, the possibility of establishing the major variations in soil properties which are relevant to irrigation by using a combination of parent material and slope position as mapping units are examined. In the mapping units considered, thirteen topsoil and eleven subsoil properties are significantly different between mapping units and have smaller variances within than between the mapping units. The variations of these topsoil and subsoil properties are also adequately accounted for by using parent material/slope position as a basis for mapping, suggesting that units based on parent material/slope position are of high utility for establishing the irrigation potentials of areas at the feasibility level of survey.