Paddy soils experience long-term redox alternations affecting the interactions between the biogeochemical cycling of iron (Fe) and carbon (C). Differences in particle aggregation and soil organic matter (SOM) turnover are likely to both affect and be affected by the trajectory of Fe mineral evolution/crystallinity with redox fluctuations. We hypothesized that the legacy effects of redox cycling under paddy management affects particle aggregation, the distribution and mineralogy of Fe (hydr)oxides between particle-size fractions, and the interaction with SOM stabilization. Moreover, we expected underlying processes to be different in paddy eluvial and illuvial horizons, particularly due to the different inputs and redox conditions these horizons experience. To test these hypotheses, we evaluated the distribution of Fe species and organic C between different aggregate and particle-size fractions in topsoil (eluvial) and subsoil (illuvial) horizons of soils under long-term paddy and non-paddy management in NW Italy, as well as mineralogical changes in Fe phases by Fe K-edge Extended X-ray Adsorption Fine Structure (EXAFS) and X-ray Absorption Near Edge Structure (XANES) spectroscopy. Our findings indicate that although paddy topsoils are depleted in hydrous Fe oxides with respect to non-paddy soils, they can stabilize important amounts of C through mineral associations, particularly with finer particle-size fractions rich in less crystalline Fe phases. We also show that redox cycling can influence microaggregate stability and consequently the distribution of Fe phases and OC between intra and inter-microaggregate fractions. On the other hand, illuvial horizons under paddy management were enriched in short-range ordered hydrous Fe oxides and this contributed to enhanced microaggregate formation and C stabilization with respect to non-paddy subsoils.

稻田经历了长期的氧化还原交替，影响了铁 (Fe) 和碳 (C) 的生物地球化学循环之间的相互作用。颗粒聚集和土壤有机质 (SOM) 周转的差异可能会影响铁矿物演化/结晶度与氧化还原波动的轨迹，并受其影响。我们假设稻谷管理下氧化还原循环的遗留效应会影响颗粒聚集、颗粒大小部分之间 Fe（氢）氧化物的分布和矿物学，以及与 SOM 稳定的相互作用。此外，我们预计水稻残积层和洪积层的潜在过程不同，特别是由于这些层经历的不同输入和氧化还原条件。为了检验这些假设，我们评估了意大利西北部长期稻田和非稻田管理下土壤表层（残积）和底土（残积）层中不同团聚体和粒度级分之间 Fe 种类和有机碳的分布，以及矿物学变化通过 Fe K-edge Extended X-ray Adsorption Fine Structure (EXAFS) 和 X-ray Absorption Near Edge Structure (XANES) 光谱分析 Fe 相。我们的研究结果表明，尽管与非稻田土壤相比，稻田表层土壤中的水合铁氧化物耗尽，但它们可以通过矿物缔合稳定重要数量的 C，特别是与富含较少结晶 Fe 相的更细粒度部分。我们还表明，氧化还原循环会影响微团聚体的稳定性，从而影响 Fe 相和 OC 在微团聚体内和微团聚体间的分布。