Evaluation of Deterioration Index in Soil Nutrients due to Cultivation of Different Cocoa Species in Southwest Nigeria

The study uses the index of soil deterioration to evaluate the soil nutrient status as a result of cultivating different species of cocoa in Idanre, Odigbo and Owo areas of Southwest Nigeria. Soil samples were randomly taken and analyzed using standard methods. The results indicated variation in soil properties under both species due to the difference in nutrient uptake. Results also show that soil properties deteriorate more under hybrid than on indigenous cocoa plantations. Amongst the nutrients, phosphorus had the highest rate of increase for indigenous than hybrid cocoa plantations. Average weight of cocoa pod ranges from 0.50 to 0.60kg in indigenous and 0.56 to 0.85kg in hybrid species. Removal of the nutrients is directly linked to the rapid development of the hybrid species, their weight and size as opposed to the indigenous species. The study recommends seasonal relocation of podhusk deposit sites and spread of accumulated podhusk across the farm, application of chemical and podhusk fertilizer, and development of cocoa variety with low soil fertility tolerance.