Bioavailability of cadmium and nickel to Daucus carota L. and Corchorus olitorius L. treated by compost and microorganisms

The research work investigates the impact of the interaction between several rates of compost and microorganisms (bacteria, fungi, mycorrhiza) and their residual effects on growth and metals (Cd and Ni) uptake in carrot (Daucus carota L.) and jew's mallow (Corchorus olitorius L.) grown thereafter. Soil samples were collected from agricultural areas near the superphosphate factory and used for the pot experiments. Microorganisms were isolated from the area under study of which four fungal isolates (Aspergillus niger, A. terreus, Penicillium funiculosum and Fusarium culmorum), one bacterial species (Bacillus sp.) and four species of arbuscular mycorrhizal fungi (AMF) (Acaulospora bireticulata, Gigaspora margarit, Glomus lamellosum and Glomus mosseae) were used for inoculations in the pot experiments. Also, four compost rates were applied equivalent to 0, 5, 10, 15 t ha-(1) dry compost. The application of amendments increased the biomass of carrot and jew's mallow plants. The highest reduction of Cd and Ni contents in both plants were observed by the simultaneous applications of compost with microbes or AMF to polluted soils. The DTPA extractable values of Cd and Ni in soils of jew's mallow plants were higher those of carrot plants. The transfer factor (TF) for Cd and Ni in both plants decreased significantly (p<0.05) as the result of interaction between compost and microorganism. This study concluded that the integration between compost and microorganisms have a positive effect on reducing the bioavailability of the metal polluted soil.