THE CHARACTERIZATION, CLASSIFICATION, AND EVALUATION OF ACID SOILS ON UPPER COASTAL PLAINS OF LAGOS STATE, NIGERIA.

Abstract

The global drive for the identification of criteria for sustainable land management evaluation has stemmed from the desire to manage appropriately and conserve the soil resources especially those of marginal lands. The objectives of the study were to characterize and classify the soils and to identify relevant land characteristics for sustainable land management evaluation for upland rice cultivation. The soils were classified at the series level using the existing local system of soil classification and these series includes Oteyyi, Alagba, Ibeshe, Asaba, Ugbolu, Owode, Agege, Iju, Ipaja, Atan, and Mesan. Physiography position and elevation have strong relationship to the soil types of the tertiary sediments. Crestal positions are almost level and possibly indicative of past erosional surfaces and/or static groundwater positions. Soils are mostly sandy clay/sandy loamy, very strongly acid (pH 5-5.0) with low cation exchange capacity. Exchangeable AI constitute >50% of the exchangeable cations in the most subsoil horizons. Surface soils on upper slope positions are considered droughty (sandy) but the subsoils are medium/fine textured. Typic Kandiustults and Typic Kanhaplustults dominant the upper slope and middle slope position of the landscape. Those of the lower slope positions mostly belong to the Tropic Fluvaquents and Humaqueptic Psammaquents. Selected criteria for land evaluation for sustainable upland rice management include soil texture, soil solum (as determined either by depth to compacted  subsoil horizons (including concretionary/petroplinthites) or gravelly soil material), slope and its length. Land suitability classesidentified range from S1 (one series) through S2 (five series) to S3 (four series), and one in N1 class.