Cadmium (Cd) distribution and soil-plant relationship in cacao farms in Costa Rica

Abstract

Abstract The current cadmium (Cd) regulations in chocolate threatens cacao supply chain in different Latin American countries. The factors involve in cadmium accumulation in cacao beans have been poorly studied in Central America. The objective of this research was to identify the geographical location of Cd hotspots as well as soil and management factors contributing to Cd concentration in cacao beans. A survey was carried out and soil, leaves and beans samples were taken in 150 producing farms in the three major cacao regions in Costa Rica. Total soil Cd concentration was found in a range of < 0.1 to 1.05 mg kg− 1 (mean 0.22 mg kg− 1), these concentrations are within the range of uncontaminated soils. Bean Cd concentration was found in a range of 0.12 to 3.23 average (0.56 mg kg− 1) and 22% of the samples exceeded a selected threshold of 0.8 mg kg− 1. These elevated Cd concentrations were distributed mostly in the Huetar Caribe and Huetar Norte regions. Variability in bean Cd concentration were better explained with total soil Cd and % of soil organic carbon (SOC) (R2 = 0.62, p < 0.05). In addition, bean Cd concentration was affected by leaf nutrient content and management practices. Leaf Zn and P were positively correlated to bean Cd while K and Mn were negatively correlated (p < 0,05). Likewise, altitude and orchard age were also negatively correlated. Overall, this study highlights that Cd contamination does not occur in the extend of other Latin American countries such as Ecuador, Colombia or Honduras. Nevertheless, research is needed in hotspot areas to assess the feasibility of mitigation strategies, particularly the use of mineral or organic amendments, which will allow better planning for existing development or expansion of new cacao-growing areas in the country.