Reducing Cd Uptake by Wheat Through Rhizosphere Soil N-C Cycling and Bacterial Community Modulation by...

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• Heavy metal bioavailability in soil is influenced by interactions with soil components.
• The combined effects of urease-producing bacteria and organo-Fe hydroxide coprecipitates (OFCs) on cadmium (Cd) accumulation in wheat and their mechanisms are not well understood.

Purpose of the Study:

• To investigate the impact of urease-producing bacterial strain TJ6, ferrihydrite (Fh), and OFCs on Cd accumulation in wheat grains.
• To elucidate the underlying soil-microbial mechanisms responsible for these effects.

Main Methods:

• Pot experiments were conducted to assess the effects of the TJ6-Fh/OFC consortium.
• High-throughput sequencing was employed to analyze soil microbial communities.
• Measurements included bioavailable and residual Cd content, soil physicochemical properties (pH, iron oxide, electrical conductivity, dissolved organic carbon), and nutrient cycling.

Main Results:

• The TJ6-Fh/OFC consortium significantly reduced bioavailable Cd in rhizosphere soil by 50.1-66.7% and Cd accumulation in wheat grains by 77.4%.
• Amendments increased soil pH, iron oxide content, and electrical conductivity, while decreasing dissolved organic carbon, enhancing Cd immobilization.
• Ureolytic activity of TJ6 increased soil NH4+ content and NH4+/NO3- ratio, inhibiting Cd uptake. Beneficial bacterial taxa abundance increased, promoting Cd immobilization through EPS production, phosphate precipitation, and biosorption.

Conclusions:

• The combination of urease-producing bacteria and OFCs effectively reduces Cd accumulation in wheat by immobilizing Cd in soil through multiple mechanisms.
• This microbial-organic-mineral strategy offers a promising approach for the remediation of Cd-contaminated agricultural lands.
• The study provides foundational insights into collaborative strategies for managing heavy metal contamination in soils.