Influence of Tree Species and Specific Distances on Earthworm Population and Soil Properties in Cocoa (Theobroma cacao L.) Agroforestry

Tree species are important in cocoa agroforestry because they provide shade to cocoa plants and improve soil nutrients. However, the ideal planting distance between cocoa and shade trees for enhanced nutrient access and biological activity remains unclear. A factorial experiment, arranged in a randomised complete block design with four replications, was conducted to evaluate interactions between 11 trees and three distances from tree trunks on earthworm populations and soil properties in cocoa farms at Akim-Tafo. In 2021, Terminalia ivorensis increased available phosphorus and electrical conductivity at 6 m and 12 m. Soil pH varied with distance. Triplochiton scleroxylon resulted in the lowest pH at all distances. Terminalia superba, Terminalia ivorensis and Gliricidia sepium increased soil organic carbon at all distances, while Cedrela odorata and Albizia ferruginea had the lowest. Albizia ferruginea and Terminalia ivorensis increased total nitrogen at 6 and 12 m. In 2022, earthworm populations varied with distance. Milicia excelsa, Albizia ferruginea and Triplochiton scleroxylon increased electrical conductivity. Terminalia superba increased total nitrogen at 6 and 18 m. Antiaris toxicaria, Terminalia ivorensis and Spathodea campanulata recorded the highest pH. The findings highlight that ecological benefits vary by species and distance, requiring precise selection and spacing to optimise soil health and earthworm activity in agroforestry.