Effect of Ca–modified biochar coupling with low–Cd accumulation maize cultivars on remediation of Cd contaminated soils and microbial community composition

To investigate the remediation efficiency of Ca–modified biochar (CBC) coupling with low cadmium (Cd)–accumulation cultivars on weakly alkaline Cd–contaminated farmland, a field experiment was conducted to explore the distribution of Cd in soil aggregates, Cd uptake in maize (Zea mays L.) grain, and soil microbial communities. Our results showed that treatments of CBC were observed to reduce available Cd in the bulk soil and soil aggregates by 12.09–16.20 % and 3.67–24.72 %. The grain size fraction metals loading (GSFloading) and distribution factors (DFx) analysis showed that Cd was preferentially enriched on fine particle fractions in soil, and CBC promoted the redistribution of Cd from micro–aggregates to macro–aggregates. Compared with the control group, Cd content in grains of low–Cd varieties of Liyu16 and Sanbei218 after the addition of CBC was significantly reduced by 37.55–50.80 % and 23.60–51.20 %, respectively. High–throughput sequencing results indicated that the microbial community structure and composition changed significantly after the addition of CBC, which were characterized by a significant increase in the number of operational taxonomic units (OTUs), the alpha diversity indices (including Shannon, Chao1 and ACE indies) and the abundance of the dominant phylum. The above results showed that the management of combining CBC and low Cd accumulation maize should be an efficient way to remediate weakly alkaline Cd contaminated soils, associated with ensuring of grain production safety and improvement of soil eco–environment function.