The influence of earthworm and arbuscular mycorrhizal fungi on Cadmium fractionation in sunflower (Helianthus annuus L.) cultivation

Cd in the soil is a serious threat to both the environmental quality and human health over the long-term. So following the availability and mobility of Cd in soil is very important. Soil microorganisms and fauna are factors which may have an influence on the mobility and bioavailability of Cd in soil-plant systems. Specifically, both earthworms and arbuscular mycorrhizal fungi (AMF) have been found to affect Cd chemistry with changes in its immobilization and mobilization in Cd-polluted soils. To examine the effects of these organisms on soil Cd fractionation, chemical forms of Cd were measured in a calcareous soil artificially spiked with Cd (0, 10 and 20 mg Cd kg-1), inoculated with earthworm (Lumbricus rubellus L.), and AMF (Glomus intraradices, and Glomus mosseae species) under sunflower (Helianthus annuus L.) crop for 90 days. Three Cd, two earthworm and three mycorrhizal treatments were applied in a 3×2×3 factorial experiment with three replicates for each treatment. Results showed that the percentage of the total Cd content in exchangeable늉湮 (0-5.7%) and organic (0-1.3%) forms were very low. But the percentage of carbonate fraction of the total Cd content was between 54-87%. Earthworm addition increased exchangeable늉湮 and organic Cd, while AMF had no influence on these Cd fractions. Both earthworm and AMF species decrease carbonate fraction of Cd but they had no influence on sulfide fraction of Cd.