Suitability assessment of soils of Okemesi Association for Maize, Rice and Cassava Production using parametric and GIS-based methods
The study characterized, assessed the suitability for the production of maize, rice and cassava using parametric and geographic information system approaches, compared the current land use with potential land use of soils of Okemesi Association and developed a management strategy. This was with a view to providing information on the suitability of the soils of Okemesi Association for crop production in the area. The study was carried out at the immediate surroundings of Okemesi and Efon Alaaye settlements’ area, in Ekiti State. Two toposequences, one at Efon Alaaye (ET) and the other at Okemesi (OT), were established and each was delineated into its physiographic units. A total of ten soil profile pits were established, described and sampled. The soil samples were analyzed for the particle-size distribution, pH, electrical conductivity, available phosphorus, organic matter, total nitrogen, exchangeable acidity, exchangeable bases and extractable micronutrients. The effective cation exchange capacity (ECEC) and base saturation were also computed. The site and soil properties were used to formulate the land characteristics and qualities used for parametric scores and GIS analysis. The results showed that the colour, depth and texture of the soils varied in response to changes in slope position and drainage condition. Surface soil colour ranged from very dark gray (5YR 3/1) to dark yellowish brown (10YR 3/4) in soils on ET and dark reddish brown (5YR 3/3) to dark yellowish brown (10YR 3/4) on OT. The texture of the soils varied from slightly gravelly sand to very gravelly sandy clay, and slightly gravelly loamy sand to very gravelly sandy clay on ET and OT, respectively. The soils were slightly to strongly acid in reaction on ET and OT. Total exchangeable bases (TEB), total exchangeable acidity (TEA), the organic matter, total nitrogen and available phosphorus were generally low in soils on ET and OT. The extractable micronutrients’ (Cu, Fe, Mn and Zn) concentrations varied from low to medium in soils of the two toposequences. Parametric suitability evaluation showed that soils on the two toposequences were not suitable (NS) for the cultivation of maize, rice and cassava in their current condition, and the potential suitability of the soils for maize, rice and cassava were marginally suitable (S3) irrespective of the physiographic position. The GIS-based suitability ratings mapped the soils as S3 and NS for the cultivation of the three crops. This showed that parametric and GIS suitability rating approaches seemed not to give exactly the same results with respect to the marginal soils of Okemesi Association. It was concluded that the soils of Okemesi Association are better reserved for nature conservation in order to prevent their rapid degradation as a way of managing the land resources.