Influences of king grass (Pennisetum sinese Roxb)-enhanced approaches for phytoextraction and microbial communities in multi-metal contaminated soil

•Ammonium fertilization enhanced soil bacteria, actinomycete and P. sinese total biomass.•Most of Cd and Zn was stored in the shoots, whereas the roots retained most of the Pb.•Ammonium chloride resulted in the higher Cd and Zn extracted by P. sinese than for Pb.

Additions of fertilizers or chelators to soils has been suggested as a potentially effective means of improving phytoextraction of heavy metals from polluted soils by large-biomass plants. The study investigated the effects of applications of three ammonium fertilizers (NH4NO3, [NH4]2SO4, and NH4Cl) and two chelators (ethylene-diamine-tetraacetic acid, EDTA, and nitrilotriacetic acid, NTA) on soil microbial community structure, and the biomass and metal distribution in tissues of king grass (Pennisetum sinese Roxb), in soils contaminated with Cd, Pb, and Zn. Analysis of phospholipid fatty acids (PLFAs) revealed that the ammonium fertilizers (especially NH4Cl) increased soil bacteria and actinomycete activity but did not affect fungi, whereas EDTA was found to be more toxic to bacteria and the actinomycetes than NTA. Ammonium fertilization enhanced P. sinese total biomass to a significantly greater degree than EDTA or NTA (P < 0.05), with shoots representing 91.8-94.8% of total biomass. Metal concentrations in the roots were 6.0-15.9 (Cd), 26.5-99.9 (Pb), and 3.4-8.4 (Zn) times higher than in the shoots. The highest shoot Cd and Zn concentrations occurred in plants treated with NH4Cl, whereas the highest shoot Pb concentrations occurred in plants treated with EDTA. The total accumulations of the metals in P. sinese were 0.71-1.60 mg plant− 1 for Cd, 0.97-1.83 mg plant− 1 for Pb, and 13.12-36.57 mg plant− 1 for Zn. The highest amounts of Cd and Zn were extracted in the shoots, whereas the 67.7-91.8% of total Pb extraction amounts were allocated to the roots. Treatment with ammonium chloride resulted in the highest total accumulation of both Cd and Zn, whereas EDTA was more efficient than the NTA and ammonium fertilizers in stimulating total Pb accumulation. The results indicated that P. sinese is incapable of removing multi-metals simultaneously, and that although NH4Cl fertilization enhances the removal of Cd and Zn from the soil, it has less of an effect on Pb-removal efficiency.