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Rice rhizosphere soil is a hotspot of microbial activity and a complex interplay between soil abiotic properties, microbial community and organic carbon (C). The iron (Fe) plaque formation in the rice rhizosphere promotes Fe-bound organic C formation and increases microbial activity. Yet, the overall impact of Fe on C storage via physicochemical stabilization and microbial mineralization of rhizodeposits (rhizo-C) and soil organic C (SOC) in the rice rhizosphere remain unclear. We conducted a microcosm experiment using 13C-CO2 pulse labeling to grow rice (Oryza sativa L.) with four levels of α-FeOOH addition (Control, Fe-10 %, Fe-20 %, Fe-40 % w/w of α-FeOOH per total Fe in soil). This study aimed to evaluate the impact of Fe oxides on rhizo-C mineralization, the rhizosphere priming effect, and Fe-OM formation. Microbial community composition and localization of enzyme activities were also quantified through 16S rRNA sequencing and zymography. The hotspot area, as being indicated by zymography, increased by 20-50% in the presence of Fe compared to the soil without Fe addition. Despite being a hotspot, strong coprecipitation of Fe-OM in the rhizosphere promoted C immobilisation. Fe-20 % and Fe-40 % resulted in a 41 % and 33 % decrease of rhizodeposits derived 13C-CO2 emission and increased 13C stabilization mainly in 0.25–2 mm soil aggregates due to coprecipitation and aggregate formation with α-FeOOH. Moreover, Fe addition led to a dominance of Fe-oxidizing bacteria genera such as Pseudomonas, which fostered coprecipitation of Fe-OM formation. We highlight larger physicochemical stabilization of organic C by α-FeOOH addition despite raised hotspot area of microbial activity in the rice rhizosphere.
Original languageEnglish
Article number178019
JournalScience of the Total Environment
Volume958
Early online date13 Dec 2024
DOIs
Publication statusPublished - 1 Jan 2025
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