Increased biomass and reduced heavy metal accumulation of edible tissues of vegetable crops in the presence of plant growth-promoting Neorhizobium huautlense T1-17 and biochar

•Strain T1-17 and biochar increased the edible tissue biomass of the two vegetables.•T1-17 and biochar reduced the edible tissue Cd and Pb uptake of the vegetables.•T1-17 and biochar decreased the available Cd and Pb contents of the rhizosphere soil.•T1-17 increased the ratio of IAA-producing bacteria and small aggregates in the soil.•Biochar+T1-17 was best to increase the biomass and decrease tissue Cd or Pb uptake. The effects of a plant growth-promoting Neorhizobium huautlense T1-17, biochar, and their combination on the biomass and Cd and Pb accumulation of Chinese cabbages and radishes and the mechanisms involved were characterized. T1-17 increased the biomass and reduced the above-ground tissue (Chinese cabbages) or root (radishes) Cd and Pb contents of the seedlings compared to the control. T1-17 and biochar+T1-17 significantly increased the edible tissue biomass (ranging from 56% to 112%) of the two vegetables compared to the control. T1-17, biochar, and their combination significantly reduced the edible tissue Cd and Pb contents (ranging from 46% to 86%) and total Cd and Pb uptake (ranging from 16% to 78%) of the two vegetables compared to the controls. Biochar+T1-17 had higher ability to increase the biomass and decrease the edible tissue Cd (Chinese cabbages) and Pb (radishes) contents than T1-17 or biochar. Furthermore, T1-17, biochar, and their combination significantly decreased the water-soluble (ranging from 32% to 88%) and DTPA-extractable (ranging from 14% to 51%) Cd and Pb contents in the rhizosphere soils compared to the controls. Notably, biochar+T1-17 had higher ability to decrease the water-soluble Cd and Pb contents of the rhizosphere soils than T1-17 or biochar. T1-17 and biochar+T1-17 significantly increased the ratios of small soil aggregate particles (