Pedological Investigation of Edaphic Factors Limiting the Yield of Cocoa in Atakumosa West Local Government Area of Osun State

Abstract

The need to double cocoa production as a step towards the diversification of Nigeria's economy require an assessment of the edaphic factors limiting cocoa yield in the major cocoa-producing areas of the country. Field and laboratory studies were conducted to investigate the edaphic factors limiting the yield of cocoa in Atakumosa West Local Government Area (LGA) of Osun State. Soil samples were collected from the pedogenic horizons of eight profile pits dug in selected villages after a free survey covering about fourteen villages within the LGA. The physico-chemical properties of the soils were determined using standard laboratory procedures and the results were used to assess the suitability of the soils for cocoa production. The three major soil series from which samples were collected were Itagunmodi, Owena and Araromi. Overall actual suitability evaluation of the soil series showed that the soils of Itagunmodi series and Owena series were marginally (S3) suitable while those of Araromi series were currently not (N) suitable for cocoa production. Apart from the apparent effective cation exchange capacity (ECEC) which was lower than 16 cmol kg-1 and the acid reaction of the soils, the major limitations of the soils were suboptimal rainfall and the dry seasons which are longer than the stipulated period. Also the slope gradient of the soils of Araromi series was a major limitation. Split application of Nitrogen/Phosphorus/Potassium (NPK) fertiliser at recommended rate for low fertility soils using non-acidifying fertiliser sources containing adequate quantities of Magnesium Oxide (MgO) or Calcium oxide (CaO) will upgrade the suitability status of the soils of Itagunmodi and Owena series to moderately suitable (S2) for cocoa production.