Iron hydroxides serve as an efficient ‘rusty sink’ promoting the stabilization of rhizodeposits into soil organic carbon (SOC). Our work aimed to understand the physicochemical and microbial mechanisms promoting rhizodeposit (rhizo-C) stabilization as influenced by goethite (α-FeOOH) or nitrogen (N), using ¹³C natural abundance methodologies and DNA sequencing, in the rhizosphere of maize (Zea mays L.). The addition of N fertilizer to soil increased the mineralization of both rhizo-C and SOC, while amendment with α-FeOOH decreased rhizo-C derived CO₂ and lowered the rhizosphere priming effect by 0.57 and 0.74-fold, respectively, compared to the control soil. This decrease resulted from the co-precipitation of rhizo-C at the reactive α-FeOOH surfaces as Fe-organic matter complexes (FeOM), which was 10-times greater than the co-precipitation on short-range ordered minerals. The highest portion of rhizo-C (67% of the total accumulated in soil) was protected within macroaggregates (>2 mm). Carbon overlapped with α-FeOOH mainly in >2 mm aggregates, as shown by HRTEM-EDS imaging, suggesting that α-FeOOH associated rhizo-C stimulated aggregate formation. Random forest analysis confirmed that the stabilization of rhizo-C was controlled mainly by physiochemical binding within FeOM complexes and macroaggregates. Rhizo-C mineralization was regulated by the keystone microbiome: Paucimonas (β-Proteobacteria) being an r-strategist with rapid growth under soil without nutrient limitation (N treated) and Steroidobacter (Actinobacteria) with branched filaments that can access C and nutrients under oligotrophic conditions (goethite enriched soil). Two-way orthogonal partial least squares analysis revealed that the rhizosphere priming effect was facilitated mainly by the same genera, most likely due to co-metabolism. The genera belonging to Acidimicrobiaceae (Actinobacteria), Cryptococcus and Cystofilobasidium (Basidiomycota) were positively correlated with the accumulation of rhizo-C in the >2 mm aggregate size, which might due to their high affinity towards α-FeOOH and contribution to the development of aggregation via filamentary structures that interact with microaggregates. We suggest that rhizodeposit stabilization in soil was balanced by microbial mineralization and abiotic associations with the “rusty sink” and organisms with branched filaments contributing to the development of aggregation.

氢氧化铁可作为有效的“生锈的水槽”，促进根状茎沉积物稳定到土壤有机碳（SOC）中。我们的工作旨在利用¹³ C自然丰度方法和DNA测序方法，了解玉米（Zea）根际中受针铁矿（α-FeO​​OH）或氮（N）影响的促进根茎沉积（rhizo-C）稳定的理化和微生物机制。mays L.）。向土壤中添加氮肥可增加根际C和SOC的矿化度，而用α-FeO​​OH进行改性可降低根际C衍生的CO ₂与对照土壤相比，分别降低了根际启动作用0.57和0.74倍。这种减少是由于根际C在反应性α-FeO​​OH表面上以铁-有机物络合物（FeOM）的形式共沉淀所致，比在短程有序矿物上的共沉淀高10倍。根茎-C的最高部分（占土壤中累积总量的67％）在大骨料中（> 2 mm）受到保护。如HRTEM-EDS成像所示，碳主要在> 2 mm的聚集体中与α-FeO​​OH重叠，表明α-FeO​​OH相关的根际C促进了聚集体的形成。随机森林分析证实，根际C的稳定主要受FeOM复合物和大聚集体中的物理化学结合控制。Rhizo-C矿化作用受关键微生物组的调控：Paucimonas（β-Proteobacteria）是在没有营养限制的土壤下快速生长的R策略家（N处理）和带有分枝细丝的类固醇杆菌（Actinobacteria），在贫营养条件下（富含针铁矿的土壤）可以获取C和养分。双向正交偏最小二乘分析表明，根际启动作用主要由同一属促进，最可能是由于共代谢引起的。属于酸性微菌科（放线菌），隐球菌和丝状纤毛虫属（Basidiomycota）与> 2 mm聚集体大小的根际C的积累呈正相关，这可能是由于它们对α-FeO​​OH的高度亲和力以及通过与微聚集体相互作用的丝状结构对聚集发展的贡献。我们建议土壤中的根状茎稳定作用通过微生物矿化作用和与“生锈的水槽”以及具有分支细丝的生物的非生物联系而得以平衡，从而有助于聚集的发展。