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<p>Clarifying phosphorus (P) availability in particulate organic matter (POM) and mineral- associated organic matter (MAOM) is essential for improving plant utilization of soil P pools and guiding rational P management in the Mollisols of Northeast China. However, where and why POM and MAOM differ in soil P availability, and the precise manner by which organic carbon (OC) and mineral characteristics regulate P availability, remain poorly understood. Here, uncultivated Mollisols at 0–10 cm, 10–20 cm, and 20–40 cm depths were analyzed to examine the vertical distribution of P fractions and to identify key drivers in POM and MAOM. Sequential fractionation revealed that, Res-P was the highest fraction in both pools followed by NaOH-Po. Non-labile P (NLP) constituted the majority of total P (62.42–76.57% in POM; 69.93–74.55% in MAOM), whereas labile P (LP) was the smallest contributor. With depth, LP and moderately labile P (MLP) decreased in both pools, while NLP increased. POM consistently contained higher contents of LP, MLP, and NLP than MAOM. LP and MLP contributed significantly to available phosphorus in POM, but only LP was a significant contributor in MAOM (p &lt; 0.05). PLS-PM revealed that OC was the dominant regulator of P in POM, whereas OC, iron oxides, and their interaction governed P fractions in MAOM. Our results underscored that POM and MAOM contained variable amounts of P species and followed distinct pathways regulating P availability. Given their differentiated roles in P “supply” and “storage”, accounting for these divergent behaviors is essential for developing strategies to enhance P availability in Mollisols.</p>

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Organic Carbon and Iron Oxides Differentially Drive Soil Phosphorus Bioavailability in Particulate- and Mineral-Associated Organic Matter Pools of Uncultivated Mollisols

  • 期刊论文

  • 发表日期：

    2026年8月5日

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  • Yanxia Peng,
  • Kaixin Yang,
  • Xiangwei Chen,
  • Erhui Guo,
  • Xiaoyan Yang

摘要

Clarifying phosphorus (P) availability in particulate organic matter (POM) and mineral- associated organic matter (MAOM) is essential for improving plant utilization of soil P pools and guiding rational P management in the Mollisols of Northeast China. However, where and why POM and MAOM differ in soil P availability, and the precise manner by which organic carbon (OC) and mineral characteristics regulate P availability, remain poorly understood. Here, uncultivated Mollisols at 0–10 cm, 10–20 cm, and 20–40 cm depths were analyzed to examine the vertical distribution of P fractions and to identify key drivers in POM and MAOM. Sequential fractionation revealed that, Res-P was the highest fraction in both pools followed by NaOH-Po. Non-labile P (NLP) constituted the majority of total P (62.42–76.57% in POM; 69.93–74.55% in MAOM), whereas labile P (LP) was the smallest contributor. With depth, LP and moderately labile P (MLP) decreased in both pools, while NLP increased. POM consistently contained higher contents of LP, MLP, and NLP than MAOM. LP and MLP contributed significantly to available phosphorus in POM, but only LP was a significant contributor in MAOM (p < 0.05). PLS-PM revealed that OC was the dominant regulator of P in POM, whereas OC, iron oxides, and their interaction governed P fractions in MAOM. Our results underscored that POM and MAOM contained variable amounts of P species and followed distinct pathways regulating P availability. Given their differentiated roles in P “supply” and “storage”, accounting for these divergent behaviors is essential for developing strategies to enhance P availability in Mollisols.