Abstract:
The sustainable use of the soil resource requires extensive knowledge about its morphology and other properties. Consequently, soil data are basis for improved land use management and soil conservation. Land evaluation provides information on the potential (capability or suitability) of the soil resources for use. The present study carried out at the Institute for Agricultural Research farm, Ahmadu Bello University, Zaria, situated in the Northern Guinea Savanna zone of Nigeria; include morphological, physical and chemical properties, and suitability evaluation of the soils. The soils were evaluated for their suitability for the production of cotton (Gossipium hirsutum), cowpea (Vigna unguiculata, L), maize (Zea mays, L) and sorghum (Sorghum bicolar, L) on a sustainable basis, using the additive and limiting methods of Sys et al. Parent materials (Granites and Schist), topography and drainage had a pronounced effect on the soil properties. The main pedogenetic processes occurring in the soils were argillation, organic matter mineralization, eluviations, illuviation, textural and structural differentiation, and horizonation. From the results obtained, the soil showed more variation in morphological and physical properties than in chemical properties. Three distinct soil units were scattered in the various landscape positions. Soil unit A occupied the upper slope position, soil unit B occupies the middle slope position and soil unit C occupies the lower slope. The soils were shallow to very deep (4 to 166cm depth), depth increased down slope. Soil Unit B was higher in clay than the other soil units. Silt dominated the particle size fraction of the fine earth (< 2mm) portion of the soils. The bulk density was higher in surface soils. The chemical properties indicate strongly acid to neutral pH (4.7 to 7.2), medium to high exchangeable bases and high base saturation. The CEC (NH4OAc, ECEC) and CEC (Clay) did not differ significantly among the soil units. The organic carbon of the surface soils was generally rated low. The soils are viii classified as Typic Haplustalfs for soils of units A and B, except pedon A2 that was classified as Lithic Ustipsamment and soil unit C1 and C2 as Typic Endoaqualfs and Typic Endoaquepts respectively, according to the USDA Soil Taxonomy, or as Lixisols and Gleysols for soil units A and B, and soil unit C respectively, except pedon A2 classified as Leptosols, according to the classification system of the World Reference Base for Soil Resources. The principle of matching fertility and climatic requirements of crop to the characteristics of the land was used as a basis for developing a land suitability classification for the selected crops. Land characteristics needed to assess the land suitability were obtained from the soil survey, while crop requirements were obtained from literatures. The soils of the three soil units identified were grouped into three land units namely land unit one (LU1), land unit two (LU2) and land unit three (LU3) for soil unit A, soil unit B and soil unit C respectively. Land units LU1 and LU2 were moderately suitable (S2) for cotton and maize, and highly suitable (S1) for cowpea and sorghum. LU3 was moderately suitable (S2) for cowpea and sorghum and not suitable (N) for cotton and maize.
LAND SUITABILITY EVALUATION FOR SOME SELECTED LAND USE TYPES IN THE INSTITUTE FOR AGRICULTURAL RESEARCH FARM, ZARIA, NIGERIA.
