Effect of Agricultural Inputs on the Water-soil Couple in Cocoa-growing Area in the Department of Soubré, Southwestern of Côte d’Ivoire

Background: The cocoa crisis in the 1970s decade in Côte d’Ivoire was manifested by the proliferation of crops pests, reduced production and decreased rainfall. To cope with all these constraints, the producers adopted various strategies, including the use of agricultural inputs to improve the production. Thus, this study aimed to characterize the effects of these inputs on water-soil couple. Methods: First, 12 soil and surface water samples were taken for analysis. Second, determination of trace metal content was done using an atomic absorption spectrophotometer (AAS). Also chemical elements were analyzed using a HACH DR 6000 spectrophotometer. Results: Soil concentrations of exchangeable base Ca2+, K+ and Mg2+ are low with average values of 5.71 cmol/kg, 0.35 and 1.66 cmol/kg, respectively. The soils of cocoa orchards are quite rich in assimilable phosphorus (P). The average phosphorus content is 24.31 cmol/kg with a minimum of 3.92 cmol/kg and a maximum of 78.4 cmol/kg. The study of surface water quality showed that the average values of biochemical oxygen demand for 5 days (BOD5) (18.64 mg/L) and chemical oxygen demand (COD) (15.49 mg/L) are lower than the respective standards of 25 and 125 mg/L of the world health organization (WHO) standard. These surface waters have average concentrations of 0.015 mg/L for cadmium (Cd), 0.042 mg/L for zinc (Zn) and 0.062 mg/L for manganese (Mn), below the respective standards of 0.003, 3 and 0.4 mg/L. Conclusion: This study shows that surface waters are not yet very polluted by these inputs.