KU Leuven, Division of Soil and Water Management, Kasteelpark Arenberg 20, 3001 BE, Heverlee, Belgium; Escuela Superior Politécnica Del Litoral, ESPOL, Facultad de Ciencias de La Vida, Campus Gustavo Galindo Km. 30.5 Vía Perimetral, P.O. Box 09-01-5863, Guayaquil, Ecuador.
Escuela Superior Politécnica Del Litoral, ESPOL, Facultad de Ciencias de La Vida, Campus Gustavo Galindo Km. 30.5 Vía Perimetral, P.O. Box 09-01-5863, Guayaquil, Ecuador.
Chemosphere. 2023 May;324:138318. doi: 10.1016/j.chemosphere.2023.138318. Epub 2023 Mar 10.
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 y, 2) gypsum at 2.0 and 4.0 Mg ha y and 3) compost at 12.5 and 25 Mg ha y, 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 M CaCl 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.
欧盟关于可可制品中镉（Cd）最大含量的新规定引发了减少可可豆中 Cd 浓度的对策研究。本研究旨在测试两种在厄瓜多尔建立的可可园（土壤 pH 值分别为 6.6 和 5.1）中的土壤改良剂的效果。土壤改良剂包括：1）农业石灰，用量为 2.0 和 4.0 Mg ha y；2）石膏，用量为 2.0 和 4.0 Mg ha y；3）堆肥，用量为 12.5 和 25 Mg ha y，所有改良剂均在随后的两年中施用于地表。石灰的施用将土壤 pH 值提高了一个单位，达到 20 cm 深度。在酸性土壤上，叶片 Cd 浓度因石灰的施用而降低，30 个月后，降低因子逐渐上升至 1.5。在 pH 值中性土壤上，石灰或石膏的施用对叶片 Cd 没有影响。在 pH 值中性土壤中施用堆肥，在 22 个月时可使叶片 Cd 浓度降低 1.2 倍，但在施用 30 个月后，这种效果消失。在施用后 22 个月（酸性土壤）或 30 个月（pH 值中性土壤），任何处理对豆 Cd 均无影响，表明任何处理对豆 Cd 的影响可能比叶片更滞后。实验室土壤柱实验表明，与单独施用石灰相比，石灰与堆肥混合可大大提高石灰的渗透深度。堆肥+石灰降低了 10 M CaCl 可提取土壤中的 Cd，而不会降低可提取的 Zn。我们的研究结果表明，在酸性土壤中，长期施用石灰有可能降低可可对 Cd 的吸收，应在田间尺度上测试堆肥+石灰处理，以加速缓解效果。
