Earthworm-mycorrhiza interaction on Cd uptake and growth of ryegrass

The effects of inoculation of earthworms and arbuscular mycorrhiza separately, and in combination, on Cd uptake and growth of ryegrass were studied in soils contaminated with 0, 5, 10, 20 mg of Cd kg(-1) soil. Both earthworms and mycorrhiza were able to Survive in all the treatments with added Cd. Earthworm activity significantly increased mycorrhizal infection rate of root and ryegrass shoot biomass. Earthworm activity decreased soil pH by about 0.2 units, and enhanced root Cd concentration and ryegrass Cd uptake. Mycorrhiza inoculation increased shoot and root Cd concentration substantially, and at the highest dosage of 20 mg Cd kg(-1) decreased biomass of ryegrass. Inoculation of both earthworms and mycorrhiza increased ryegrass shoot Cd uptake at low Cd concentrations (5 and 10 mg Cd kg(-1) soil), when compared with inoculation of earthworms or mycorrhiza alone. In conclusion, earthworm, mycorrhiza and their interaction may have a potential role in elevating phytoextraction efficiency in low to medium level metal contaminated soil. (C) 2004 Elsevier Ltd. All rights reserved.