Physico-chemical Quality of Soils under Cocoa Farm in Koffikro-Affema (Aboisso) in South-East of Côte d'Ivoire

The study was conducted in Koffikro-Affema village located in the South-East of Côte d'Ivoire to assess the morpho-physical and chemical quality of soils under cocoa farm, for the management of early degradation of orchards. Representative soil samples were taken by horizon under degraded cocoa farms after a morpho-pedological characterisation. These samples were then analysed in the laboratory for fertility parameters. The results indicate that the cocoa farms have a high rate of degradation and the study made it possible to identify the soil characteristics associated not only with the degradation of cocoa trees, but also with the drop in yield. These are the rate of coarse grains greater than 50%, the low organic matter content (less than 3.5%), a very slow rate of mineralisation (C/N > 12), poor internal drainage and the acidic pH of the soil (4.4-5.5). The soils surveyed are highly desaturated to moderately saturated and the main characteristics of the absorbing complex indicate that they are unfavourable for cocoa. Indeed, these soils are deficient in K⁺ (<0.2 cmol/kg), Ca²⁺ (between 5.1 and 11.41 cmol/Kg) and assimilable Nitrogen (˂0.2 cmol/Kg). Similarly, the Mg^2+/K⁺ ratio of less than 3 shows that they are magnesium deficient. The results also revealed an influence of the topographical position on the degradation of cocoa trees with, on the upper and middle slopes, strongly gravelly and poorly drained horizons, associated with the degradation of cocoa trees. On the other hand, on the lower slopes, these soils are deep, not gravelly, with good growth of cocoa trees and low yields.