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<p>Mineral amendments offer a promising strategy for soil carbon sequestration, but the main factors governing their effectiveness across soil depths remain poorly understood. Using a <sup>14</sup>C-radiolabelling approach, we quantified the effects of three mineral amendments (iron, calcium, and basaltic rock dust (BRD)) on microbial carbon use efficiency (CUE) and <sup>14</sup>C-glucose mineralization across soil depth (0–10, 10–25, 25–50&#xa0;cm). Our results revealed a pronounced divergence in amendment effects across mineral types and soil depths. Calcium addition significantly increased microbial CUE (from 0.70 to 0.76), while concurrently reducing <sup>14</sup>C-glucose mineralization. Conversely, iron addition, especially at 10 to 100 mmol kg<sup>-1</sup>, decreased microbial CUE (from 0.73 to 0.62) and increased mineralization, whereas BRD had limited effects on both CUE and mineralization. These responses were modulated by depth. Calcium increased microbial CUE only in the topsoil (0–10&#xa0;cm) with no detectable effect at 10–50&#xa0;cm, while microbial CUE response to iron or BRD were largely depth-invariant. In addition, iron induced strong positive priming of native <sup>14</sup>C-SOM in the topsoil (119 ± 3%), while calcium and BRD caused a negative priming effect (ca. -11 to -13%). Variable-importance analysis identified soil pH as the dominant driver of microbial CUE, with path analysis identifying how the pathways through which soil pH regulates microbial CUE differ among calcium, iron and BRD treatments. Our findings suggest that increasing calcium inputs to agricultural soils may serve as a practical, pH-mediated strategy to promote C sequestration in topsoil, while high iron inputs may destabilize soil C stocks via reduced CUE and enhanced priming, although these implications require further field validation.</p>

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Biogeochemical trade-offs in mineral-amended agricultural soils: insights from a 14C-glucose tracing microcosm experiment

  • 期刊论文

  • 发表日期：

    2026年7月1日

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  • Mengmeng Xie,
  • Emily C. Cooledge,
  • Deqiang Zhao,
  • Jinhua Yin,
  • David R. Chadwick,
  • Xuhui Zhou,
  • Davey L. Jones

摘要

Mineral amendments offer a promising strategy for soil carbon sequestration, but the main factors governing their effectiveness across soil depths remain poorly understood. Using a 14C-radiolabelling approach, we quantified the effects of three mineral amendments (iron, calcium, and basaltic rock dust (BRD)) on microbial carbon use efficiency (CUE) and 14C-glucose mineralization across soil depth (0–10, 10–25, 25–50 cm). Our results revealed a pronounced divergence in amendment effects across mineral types and soil depths. Calcium addition significantly increased microbial CUE (from 0.70 to 0.76), while concurrently reducing 14C-glucose mineralization. Conversely, iron addition, especially at 10 to 100 mmol kg-1, decreased microbial CUE (from 0.73 to 0.62) and increased mineralization, whereas BRD had limited effects on both CUE and mineralization. These responses were modulated by depth. Calcium increased microbial CUE only in the topsoil (0–10 cm) with no detectable effect at 10–50 cm, while microbial CUE response to iron or BRD were largely depth-invariant. In addition, iron induced strong positive priming of native 14C-SOM in the topsoil (119 ± 3%), while calcium and BRD caused a negative priming effect (ca. -11 to -13%). Variable-importance analysis identified soil pH as the dominant driver of microbial CUE, with path analysis identifying how the pathways through which soil pH regulates microbial CUE differ among calcium, iron and BRD treatments. Our findings suggest that increasing calcium inputs to agricultural soils may serve as a practical, pH-mediated strategy to promote C sequestration in topsoil, while high iron inputs may destabilize soil C stocks via reduced CUE and enhanced priming, although these implications require further field validation.