Soil organic carbon (SOC) is a key component of maintaining favorable soil physical, biological and chemical health and ensures the sustainability of agricultural practices. Fe- and Mn-(oxy)hydroxide minerals play an important role in SOC stabilization and sequestration, as well as nutrient adsorption. To better understand the mineral phases responsible for the stabilization and sequestration of SOC, as well as PO₄⁻³ and NO₃⁻; a four-step chemical sequential extraction (SE) was applied to soils from eight agricultural fields. Our SE scheme targeted operationally defined mineral phases namely, water extractable (Step 1), reductive dissolution of Mn-(oxy)hydroxide (Step 2), reductive dissolution of amorphous Fe-(oxy)hydroxide (Step 3), reductive dissolution of crystalline Fe-(oxy)hydroxide (Step 4) and residual minerals. Results showed that SOC was stabilized in the following order: crystalline Fe-(oxy)hydroxide > amorphous Fe-(oxy)hydroxide > Mn-(oxy)hydroxide. Fe- and Mn-(oxy)hydroxide minerals can promote the stabilization and long-term sequestration of SOC via the formation of inner sphere complexes (e.g., ligand-exchange) within the mineral surfaces contact zone. Fe- and Mn-(oxy)hydroxide minerals adsorbed PO₄⁻³ species to a large extent; however, NO₃⁻ was adsorbed marginally. Results indicated that PO₄⁻³ adsorption is largely mediated by Fe- and Mn-(oxy)hydroxide minerals, and NO₃⁻ by bulk soil organic matter. The coupling interaction between SOC, nutrients, and mineral phases in agricultural soils can better inform the application of conservation management practices to fully understand their effect on soil chemistry and health.

土壤有机碳（SOC）是维持良好的土壤物理，生物和化学健康的关键组成部分，并确保农业实践的可持续性。Fe和Mn-（羟基）氢氧化物矿物在SOC稳定和螯合以及养分吸收中起重要作用。为了更好地理解负责SOC的稳定化和多价螯合的矿物相，以及PO ₄ ^-3和NO ₃ ^-; 对八个农业领域的土壤进行了四步化学序贯提取（SE）。我们的SE方案针对可操作定义的矿物相，即水可萃取（步骤1），Mn-（羟基）氢氧化物的还原溶解（步骤2），非晶态Fe-（羟基）氢氧化物的还原溶解（步骤3），晶体的还原溶解氢氧化铁（氧）（步骤4）和残留矿物质。结果表明，SOC按以下顺序稳定：结晶的Fe-（羟基）氢氧化物>无定形的Fe-（羟基）氢氧化物> Mn-（羟基）氢氧化物。Fe-和Mn-（羟基）氢氧化物矿物可通过在矿物表面接触区内形成内球络合物（例如配体交换）来促进SOC的稳定和长期隔离。Fe-和Mn-（羟基）氢氧化物矿物吸附PO ₄ ^-3种类很大；然而，NO ₃ ^-被轻微吸附。结果表明，PO ₄ ^-3吸附在很大程度上是由铁-和MN-（氧）氢氧化物矿物质，和NO介导的₃ ^-通过本体土壤有机质。农业土壤中SOC，养分和矿物质相之间的耦合相互作用可以更好地指导保护管理措施的应用，以充分了解其对土壤化学和健康的影响。