liuchunlei 2025-12-15

Microbial involvement has long been regarded as the indispensable step for nitrate reduction to ammonium in nature. We found that specifically adsorbed Fe(II) ions (Fe(II)-spec) ubiquitously present on iron plaque can mediate an abiotic nitrate reduction to ammonium process in paddy fields. Experiments using sterile rice roots from the tillering stage in the field revealed that the nitrate reduction to ammonium mediated by the Fe(II)-spec accounts for over 70% of the total nitrate reduction. Theoretical calculations elucidated the Fe(II)-spec induces local electron depolarization and enhances interfacial charge transfer which drives NO3--N reduction to NH4+-N with the conversion of *NO to *NOH/*NHO identified as the rate-limiting step. Based on these findings, we proposed a regulatory strategy to establish a stable Fe(II)-spec/Fe(III)-spec cycle, enabling sustainable ammonium supply for rice uptakes.