Regional distribution and soil extractability of cadmium in cacao systems across the Cordillera subregion of Nariño in Colombia

Abstract The primary objective of this observational study was to characterize the regional distribution of cadmium (Cd) in cacao-growing soils and beans and to identify soil properties associated with extractable Cd and plant accumulation. A secondary exploratory objective was to describe clone-related patterns at intentionally selected high-risk farms. Sampling was conducted in two phases during 2020–2021. Phase 1 included 143 farms across eight Soil Cartographic Units (SCUs), where pseudo-total and DTPA-extractable soil Cd, soil chemical properties, and bean Cd were evaluated at the farm-plot scale. Phase 2 included seven farms intentionally selected because bean Cd exceeded 1.0 mg kg −1 . The Phase 2 analytical dataset comprised 23 tree-level observations (13 CCN-51 and 10 ICS-95); both clones co-occurred in four farms, which provided the independent pairs for exploratory clone comparisons. Pseudo-total soil Cd differed among SCUs, whereas DTPA-extractable Cd did not show significant SCU-level differences. Soil pH, Ca, Mg, P, and Zn were associated with soil Cd fractions and bean accumulation. Median bean Cd was 0.404 mg kg −1 , and 20.0% of samples were above the 0.6 mg kg −1 screening benchmark derived from the EU maximum level for certain cocoa products; this comparison does not establish compliance of processed products. Leiva showed the highest regional values. Farm-level paired analyses in Phase 2 did not support a statistically robust clone effect on litter, leaf, or bean Cd. These findings provide a regional Cd baseline and a scale-explicit framework for integrating soil mapping, soil chemistry, plant tissues, and exploratory within-farm clone comparisons in heterogeneous cacao landscapes.