The Combined Effect of Arbuscular Mycorrhizal Fungi and Compost Improves Growth and Soil Parameters and Decreases Cadmium Absorption in Cacao (Theobroma cacao L.) Plants

This study aims to investigate the synergistic effect of arbuscular mycorrhizal fungi (AMF) inoculation and organic amendment on Theobroma cacao plants growing in Cd-contaminated soils. A pot experiment was carried out to investigate the influence of AMF inoculation, compost (CP) application, and cadmium (Cd) addition on the development of cocoa plants and associated soil. At 90 days of growth, the cocoa plants treated with a combination of AMF + CP showed the greatest plant growth. AMF + CP treatment also reduced the Cd content in the cocoa plant stems. The combined treatment, AMF + CP (with or without Cd addition), was the most effective in increasing the pH, organic matter, and available phosphorus content in soil. Compost addition with AMF (AMF + CP) decreased AMF root colonization and extraradical mycelium to the same extent as treatments with Cd addition (AMF + Cd and AMF + Cd + CP). These results indicate that AMF inoculation in combination with compost has significant synergistic benefits, not only for plant growth and improvement of soil chemical properties, but also for decreasing Cd uptake by cocoa grown in Cd-contaminated soil.