Comparative Assessment of Copper Bioavailability, Pollution, and Ecological Risks in Soil-Cacao Systems under Organic versus Conventional Management: A Case Study from Suhum Municipality, Ghana

Comparative Assessment of Copper Bioavailability, Pollution, and Ecological Risks in Soil-Cacao Systems under Organic versus Conventional Management: A Case Study from Suhum Municipality, Ghana
The continuousÌýuse of fertilizers and fungicides has triggered copper (Cu) contamination in cacao soils in Ghana, which is a critical issue for the ecological risk and health safety of cacao products. In this study, we investigated Cu pollution, bioavailability, and ecological risk in soil and determined Cu levels in the cacao nib, shell, and pod husk. Soils were collected at two soil depths (0-15 cm and 15-30 cm) from 20 cacao farms, under conventional (CCM: relies on chemical-based fertilizers) and organic (OCM: relies on organic-based fertilizers) management practices together with pods. The total Cu concentration ranged fromÌý67.6-96.8 mg kg-1Ìýin OCM and 28.5-33.9 mg kg-1Ìýin CCMÌýand decreasedÌýwith soil depth. The enrichmentÌýfactor values revealedÌýminimal Cu enrichment, which was attributed toÌýanthropogenic activity (fungicide and fertilizer applications). The contamination factor and geoaccumulation index values wereÌýlow for the CCM soils, and moderate for the OCM soils. Both management systems pose a low potential ecological risk to soil biota activity. Bioavailable Cu extracted with CaCl2, NH4OAc, and DTPA was dominant in CCM but decreased with soil depth. The Cu concentration in the cacao decreasedÌýin theÌýorder of nib < pod husk < shell. Nib-Cu was below the threshold (50.0 mg kg-1) of contamination. The results from the pairwise correlation analysis showed that extracting soil-available Cu with CaCl2Ìýis a better approach for evaluating the Cu content of cacao plants (nib, shell, and pod husk). This study reveals theÌýpollution levels associated with cacao management practices and, thus providing valuable insights for developing appropriate mitigation strategies.