Rehabilitation of Old and Moribund Cacao Soil Using Organic Amendments in Ibadan and Owena of South West Nigeria

Aims: To evaluate the effects of organic amendment in the rehabilitation of two moribund cacao plantations at Ibadan (Oyo State) and Owena (Ondo State) using organic materials that included Cocoa Pod Husk (CPH) and Neem Leaf powder (NL). Study Design: The experiment was laid out in a Randomized Complete Block Design in four replicates with four treatments which were CPH, CPH+NL (90:10), CPH+NL (80:20) and untreated. Place and Duration of Study: Cocoa plantations at Ibadan and Owena, Nigeria between May, 2014 and Dec 2017. Methodology: Initial soil sampling was done. Organic materials were applied to eight cacao trees in a ring at the base of trees in treated plots at the beginning of the rains in April/May and August/September. The treatments are: CPH Only @ 0.5 kg/tree, CPH Fortified with Neem Leaf (90:10) @ 0.45 kg + 0.05 kg/tree, respectively, CPH fortified with Neem Leaf (80:20) @ 0.40 kg + 0.10 kg/tree respectively. No application (control treatment). Results: Eleven fungi species assigned to seven genera were recovered across the treatments. Organic amendments significantly (p<0.05) increased soil mineralization, microbial populations and pod production. After the second year of applications, CPH had the highest percentage of pod production over the control (64%) in Ibadan, while in Owena, CPH, CPH+NL (80:20) and CPH+NL (90:10) had percentage pod increase of 68, 64 and 63%, respectively, over the control. Organic materials had significant (p≤0.05) effect in raising the soil pH in the two locations from 6.41 to 6.82 in Owena and from 6.50 to 6.89 in Ibadan, compared to untreated soil. Conclusion: The use of organic amendments in the rehabilitation of old and moribund cocoa (near death), improved soil nutrients as well as increased pod production and the microbial populations from the two plantations.