Changes in Soil Properties Following Conversion of Humid Tropical Rainforest of Nigeria Into Cocoa Agroforests

This study examined and compared some physical, chemical and microbiological properties of soil under a natural rainforest ecosystem and in young (10-12 yrs) and old (>50yrs) cocoa agroforests. Soil samples were collected to a depth of 30 cm from plots demarcated within each type of ecosystem and soil properties were determined using standard laboratory procedures. No significant differences were noted in the soil textural properties but soil chemical properties such as organic C, total N extractable P and exchangeable Ca and Mg showed significant decline as a result of the conversion to cocoa agroforests. Surface soil organic C was reduced by 12% and 31% under old and young cocoa agroforests respectively in Idanre, while a reduction of 24% and 36% were observed in Omo. Lower microbial population was also observed in the cocoa plots compared to the natural forest.