BIOCHAR AND BACILLUS AMYLOLIQUEFACIENS NS16 CAN INCREASE BIOMASS AND REDUCE CADMIUM ACCUMULATION OF PAKCHOI EXPLAINED BY CHANGES OF CADMIUM AVAILABILITY,MICROBIAL BIOMASS AND COMMUNITY IN THE RHIZOSPHERE SOIL

摘要

Inoculation of Bacillus may mediate plantgrowth and decrease uptake of heavy metals,but thecombined effects and the mechanisms of Bacillus sp.and biochar on the cadmium availability and plantuptake are far less investigated.The effects of a plantgrowth-promoting B.amyloliquefaciens NS16,bio-char,and their combination on the plant biomass andCd accumulation in pakchoi and the mechanisms in-volved were characterized.Results showed that thebiochar addition and NS16 inoculation,in combina- tion or alone,significantly promoted plant biomassand decreased Cd uptakeby plants with increased or- ganic matter contents (by 13.2-44.5%) and increasedmicrobial biomass carbon and nitrogen (by 6.91-56.3%),and populations of bacteria and fungi (by11.2-103%),and the decreased available Cdconcen-trations measured by DGT (by 13.2-44.5%),in therhizosphere soils.Compared with the initial pH,theinoculation of NS16 did not affect the pH values sig-nificantly,while the treatments of biochar and bio-char +NS16 increased that of the rhizosphere soilsignificantly.Results suggested that the alkalinizedrhizosphere,promoted organic matter contents,en-hanced microbial biomass and community,and de-creased Cd availability may have contributed to thedecreased Cd accumulation in plants under effects ofbiochar addition and NS16 inoculation.