Biochar-Bacteria Partnership Alleviates Toxic Effects of Soil Antimony Contamination on Rice Growth, In-Vitro Bio-accessibility, Soil Properties and Microbial Community Diversity

Bio-remediation with biochar (BC) is a strategy of growing interest to mitigate antimony (Sb) soil contamination. A rice pot experiment was set up involving six treatments: unstressed soil (Ctrl); 1,200 mg Sb kg-1, (Sb stress); Sb stress + 1% BC (1% BC); Sb stress + 2.5% BC (2.5% BC); Sb stress + 1% BC + Bacillus subtilis bio-inoculum (1% BC+BI); Sb stress + 2.5% BC + Bacillus subtilis bio-inoculum (2.5% BC+BI). The serious impairment in rice growth, physiology and final yield determined by Sb stress was reduced by BC and associated BI: the maximum stress relief treatment (2.5% BC+BI) closed an average three-quarters of the gap between Sb stress and Ctrl in most plant traits. BC+BI curbed Sb concentration in plant organs, whereas Sb content in the whole plant was reduced to a lesser extent as result of a growth driven Sb uptake effect. Upon 2.5% BC+BI, soil total Sb concentration and in vitro bio-accessibility were similarly reduced (average, -35%). Adding BC and BC+BI influenced the relative abundance of dominant soil bacteria and facilitated soil microbiome resistance to Sb stress. Overall, our findings highlight BC+BI potential to improve rice production, reduce Sb plant accumulation, soil in-vitro bio-accessibility, and ameliorate soil bacterial community diversity.