Evaluation of Some Sandstone Derived Soils of Southern Nigeria for Rubber (hevea Brasiliensis )cultivation

Some soils derived from crustaceous sandstones at Iyanomo, Edo State, Southern Nigeria were mapped, characterised and evaluated for rubber cultivation, using local, USDA Soil Taxonomy and FAO systems. Conventional parametric and non-parametric land suitability evaluation systems as well as weighted parametric approach in Geographic Information System (GIS) methods were used to generate suitability ratings for rubber cultivation. Dry rubber yield from existing plantations on the site obtained in the 2005/2006 and 2006/2007 cropping seasons were used to validate the suitability ratings. A total land area of 2070 ha was surveyed and the soils studied were classified as Alagba, Orlu, Kulfo and Ahiara series. The soils were in the Ultisol and Inceptisol soil orders of the Soil Taxonomy which covered 73.1 % and 26.9 % of the study area respectively. Parametric and non-parametric land suitability evaluation rated 73.1 % and 26.9 % of studied area as moderately suitable (S2) and marginally suitable (S3) respectively. The GIS method however rated 88.0 % of the site as highly suitable (S1) and 12.0 % as S2. Dry rubber yield obtained over a two year period correlated significantly (r = .929**) with the GIS suitability rating. Suitability evaluation using weighted parametric method in GIS was found to be better than conventional methods in rating the soils for rubber productivity and predicting yield of rubber.