Biomass and Iron Nanoparticles Synergistically Reduce Cadmium and Boost Rice Yield: A Field Remediation While Production Demonstration

ABSTRACT Although a wide range of materials have been employed for remediating heavy metal‐contaminated soils, research on the combined use of low‐cost and eco‐friendly amendments that enable “remediation while production” remains limited. In this study, a field experiment was conducted to evaluate the effects of 15 different materials (biomass‐derived materials: oyster shell, biochar, tea extract; and phytogenic iron nanoparticles: iron oxide, iron sulfide) on cadmium (Cd) accumulation and grain yield in two rice cultivars: a low‐Cd‐accumulating variety (Anliangyou 02) and a conventional one (Junliangyou 318). The combined application of biomass and iron nanoparticles increased grain yield by 21.01%–37.53% for Anliangyou 02 and 14.32%–51.08% for Junliangyou 318. Moreover, the co‐application showed a pronounced effect on Anliangyou 02, with most treatments significantly reducing grain Cd content to 0.006–0.045 mg kg −1 . These materials may function synergistically through four primary mechanisms: firstly, oyster shell effectively raised the rhizosphere soil pH, promoting the conversion of exchangeable Cd into less bioavailable forms; secondly, biochar reduced Cd bioavailability and potentially influenced its uptake; thirdly, iron nanoparticles facilitated Cd immobilization via specific adsorption and precipitation; finally, the combined use of biomass and iron nanoparticles modulated the rhizosphere microbial community, enriching bacterial genera reported to be associated with Cd resistance or immobilization. This study proposes a practical strategy that integrates biomass and phytogenic iron nanoparticle amendments with low‐Cd‐accumulating rice cultivars to achieve simultaneous production and remediation in Cd‐contaminated paddy fields.