Soil Fertility Evaluation of Some Kola Plantations in Kwara and Kogi States, Nigeria for Enhanced Productivity

This study was carried out to assess the soil fertility condition of some selected kola plantations in Kwara and Kogi States. Ten core soil samples at 0-20cm and 20-40cm depth were randomly collected in each plantation using soil auger and bulked into composite samples to obtain representative soil samples. The soil samples were air dried, sieved through 2mm sieve and some physical and chemical properties were determined following standard laboratory procedures. Thesoil texture of the plantations studied in Kwara and Kogi States were either loamy sand or sandy soils. Soil organic carbon contents of both states were lower than the critical value of 30.00g/kg soil considered to be optimum and ideal for tree crop plantation. This indicates that there has been a great loss of organic matter from the soil reflecting the sandy texture of the plantations. The low organic matter content and slightly acidic soil could affect major nutrients availability and may result in nutrient imbalance. Nitrogen content of some of the location studied were low, this could be because sandy soil under high rainfall are prone to N deficiency which may have affected N leaf content as well, this makes N fertilizer application necessary because N is needed for vegetative growth and profitable yields. Available P and exchangeable cation (Mg and Ca) were found adequate for most of the plantations. The kola leaf N contents were below critical levels of 1.09% recommended for kola.Variation in soil nutrient content of top soil and sub soil of some of the plantation shows that an adequate fertilizer management system specifically directed to address the need of the soil is required.