Mitigating the effects of food safety regulation on cadmium in cacao – where do we stand?

Food safety regulation on cadmium (Cd) in cocoa has led to new challenges for cocoa producers and supply chain actors. This is especially the case in the Andean countries of South America, where naturally elevated levels of Cd in soils are common, although with strong variations across and within cocoa growing areas. The combination of natural soil conditions, and the affinity of cacao trees for Cd, are the main reasons explaining the relatively high Cd concentrations in cacao beans.

Our research on Cd in cacao production systems has mainly focused on the following aspects: 1) understanding the spatial variation in Cd in cocoa and soils in cocoa growing areas through digital soil mapping; and 2) identifying soil management practices that can effectively lower cadmium uptake by plants. This presentation will provide an overview of the different research approaches, and how these can be integrated to enhance our understanding of the Cd uptake and mitigation in cocoa production systems. Results have shown that the use of organic and inorganic soil amendments can help to reduce Cd uptake by cacao trees. However, the effects are relatively slow and strongly soil- and amendment- specific, making it challenging to provide clear management recommendations to farmers.

Here we show how the combination of laboratory and pot experiments, field trials and geochemical modelling has been used to advance our understanding of the soil-plant relations affecting Cd accumulation in cocoa. The use of geochemical multi-surface models (MSMs), in combination with lab experiments using different soil amendments, revealed increases in pH as the main mechanism for decreasing Cd availability. We also showed that clay may represent a prompt buffer of Cd taken up by plants, thus reducing the effectiveness of soil amendments. Based on our work so far, we explain the often ambiguous effects of Cd mitigation strategies found in field studies in cacao. Finally, will identify and discuss the most promising strategies for Cd mitigation in cocoa production systems, as well as remaining research gaps.