Abstract
Field and laboratory studies were conducted to evaluate the fertility status of the soils of three major cocoa-producing States in Nigeria. A Survey of the selected Local Government Areas was carried out and soil samples were collected at 0-30 and 31-60 cm depths. The Physico-chemical properties of the soils were assessed in relation to cocoa nutritional requirements using standard methods while descriptive statistics were used to interpret the results. The physical properties of the soils indicated that the mean sand, silt and clay content of the soils were 64.84%, 9.09% and 26.09% respectively. The average texture of the soils (sandy clay loam) was assessed to be adequate for cocoa production. However, the soil pH in water (pHw) which ranged from 4.25-6.90 was considered sub-optimal especially in Cross River State where the mean pHw was <5.0. The exchangeable Mg, Ca and K which averaged 0.62, 4.21 and 0.17 cmol kg-1 respectively were also considered inadequate for cocoa production. Furthermore, the soil total nitrogen (TN) and available P (Bray-1 P) contents which averaged 0.11% and 2.77 mg kg-1 were also not adequate for cocoa production. While the level of the copper (Cu), Zinc (Zn) and Boron (B) which had mean values of 9.0, 0.49 and 1.34 mg kg-1 were considered adequate, the soil average content of iron (243.60 mg kg-1) and manganese (363.00 mg kg-1) was considered toxic. It was therefore concluded that due to the low effective cation exchange capacities (ECEC <10 cmol kg-1) of these soils, sustainable cocoa production on these soils will require the split application of appropriate inorganic fertilizers.
Keywords:
soilfertility
micronutrients
particlesizedistribution
cocoaproducingareas
nigeria
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