Fertilisation based on a chemical, mineral, and microbiological approach to mitigate Cd content in cacao crops in Arauca, Colombia

Cadmium contamination in cacao crops from Arauca, Colombia, is a major concern for exports. One of the causes is the contaminated fertilisers or the lack of a fertilisation scheme. This study assesses a pilot-field application of a chemical fertiliser (Agrocacao), zeolite, and a cadmium-tolerant bacterial (CdtB) formulation developed by AGROSAVIA. The treatments comprised combinations and varying proportions of the three amendments, a full-dose treatment, and an untreated control. The treatments were administered over 2 years, with a dosage applied twice a year. The Cd content was tested in soil and cacao leaves. The best treatments were identified for each location; however, no single treatment proved to be the best across all locations. Nonetheless, treatments T5 and T8 showed a significant positive trend for soil Cd (p = 0.124) and leaf Cd (p = 0.056) at two of the four locations tested in soil and leaves, respectively. These treatments included Agrocacao and Cd-tolerant bacteria (CdtB). The soil Cd concentrations ranged from 0.1 to 5.6 mg kg−1, whereas the leaf Cd concentrations varied from 0.2 to 38 mg kg−1. Cd immobilisation in soils reached up to 80%, whereas leaf Cd decreased by approximately 20%, exhibiting a trend in high-Cd-content locations. The trending positive treatments combined two amendments and varied by location. The assessed fertilisation strategies exhibited a promising trend for mitigating Cd accumulation in cacao production in Arauca.