1. Soil amendments to reduce cadmium in cacao (Theobroma cacao L.): A comprehensive field study in Ecuador.
- Author
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Argüello, D., Chavez, E., Gutierrez, E., Pittomvils, M., Dekeyrel, J., Blommaert, H., and Smolders, E.
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CACAO , *ACID soils , *LIMING of soils , *SOIL amendments , *FAVA bean , *SOIL acidity , *CACAO beans , *SOIL profiles - Abstract
The new EU regulations on maximum levels of cadmium (Cd) in cacao products sparked research on countermeasures to reduce Cd concentrations in cacao beans. This study was set up to test the effects of soil amendments in two established cacao orchards (soil pH 6.6 and 5.1) in Ecuador. Soil amendments included: 1) agricultural limestone at 2.0 and 4.0 Mg ha−1 y−1, 2) gypsum at 2.0 and 4.0 Mg ha−1 y−1 and 3) compost at 12.5 and 25 Mg ha−1 y−1, all amendments were applied at the surface during two subsequent years. Lime application increased the soil pH by one unit down to 20 cm depth. On the acid soil, leaf Cd concentrations decreased by lime application and the reduction factor gradually rose to 1.5 after 30 months. No effects of liming or gypsum on leaf Cd was found in the pH neutral soil. Compost application in the pH neutral soil reduced leaf Cd concentration with factor 1.2 at 22 months but that effect was absent at 30 months after application. Bean Cd concentrations were unaffected by any of the treatments at 22 months after application (acid soil) or 30 months (pH neutral soil) suggesting that any treatment effects on bean Cd might be even more delayed than in leaves. Soil columns experiments in the laboratory showed that mixing lime with compost largely enhanced the depth of lime penetration compared to lime only. Compost + lime reduced 10−3 M CaCl 2 extractable Cd in soil without lowering extractable Zn. Our results suggest that soil liming has the potential to lower Cd uptake in cacao in the long term in acid soils and that the compost + lime treatment should be tested at field scale to accelerate the effects of the mitigation. [Display omitted] • Soil amendments significantly reduced Cd in leaves but not cacao beans in long-term field experiments. • Surface lime application increased soil pH only at the first 15 cm soil layer. • The lowest leaf Cd concentrations occurred during the flowering/filling stage of cacao. • Compost and gypsum effects on elemental leaf composition were inconsistent over time. • Lime + compost applications are advocated for future research as compost increases lime penetration into the soil profile. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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