Influence of AMF on decomposition of faba bean straw, and uptake of nutrients, cadmium and lead by maize in a cadmium-lead polluted soil

Objectives  Arbuscular mycorrhizal fungi (AMF) stimulates the uptake of mineral nutrients by crops. In cadmium (Cd) and lead (Pb) contaminated soil, crops often accumulate Cd and Pb in straws, and release them back to soil with the incorporation of straws. We explored the effects of fore crop(faba bean )straw returning and AMF single or combined application on soil fertility, mineral nutrients, Cd and Pb absorption of succeeding maize, so as to provide new understanding for the ecological function of AMF in regulating mineral nutrients, cadmium and lead accumulation in polluted farmland rotation system. w were 1.9 mg/kg and 10.9 mg/kg. For the determination of straw degradation, faba straws were ground to 0.5–2.0 mm length, placed into nylon bags, and buried into the soil with or without AMF inoculation. A maize pot experiment was carried out with treatments of the contaminated soil. The treatments in the study were: contaminated soil as control (CK), addition of faba straw (SI), addition of AMF (AMF), and addition of both straw and AMF (AMF+SI). The contents of NPK, Cd and Pb in soil and maize plants were measured.

Results  AMF inoculation significantly promoted the degradation of faba bean straw and the release of Cd and Pb. SI treatment increased contents of soil available nutrients and K content of maize, decreased Cd content in the roots of maize, but had no significant effect on maize height and biomass. AMF and AMF+SI significantly enhanced the available NPK contents in soil, increased the content and uptake of NPK, plant height and biomass of maize, decreased available Cd and Pb contents in soil as well as total Cd and Pb contents in maize plants, but did not affect Cd and Pb uptakes of plant. AMF+SI increased soil available nutrients, promoted nutrient absorptions, and decreased plant Cd and Pb contents than AMF did.

Conclusions  AMF promoted degradation of faba bean straw and release of nutrients and heavy metals. However, combined incorporation of AMF and straw in soil improved maize growth, but not the absorption of Cd and Pb. Thus, incorporation of AMF and straw could decrease the Cd and Pb content in crops and alleviate their hazards in Cd and Pb contaminated soil.