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Aims <p>Subsoil (&gt; 20&#xa0;cm) stores a substantial proportion of terrestrial soil organic carbon (SOC) but receives limited fresh carbon (C) inputs. In nutrient-poor subsoil, crop straw with high C/N ratios may intensify nutrient limitation, yet their interactive effects with nitrogen (N) enrichment on SOC dynamics remain insufficiently understood.</p> Methods <p>Using <sup>13</sup>C-labelled straw incubation, we tested how N addition modulates native SOC stability and straw-derived C partitioning in two agriculturally relevant subsoils (clay vs. sandy loam).</p> Results <p>Nitrogen enrichment likely mitigated microbial N limitation from high C/N straw, elevating microbial carbon use efficiency (CUE) by 12.2–17.5% in subsoil. This stimulated microbial anabolism was beneficial to the retention of straw-derived C in subsoil. Nitrogen addition increased straw-derived SOC in subsoil by 28.6% in clay loam and 36.4% in sandy loam texture, and microbial necromass (amino sugars) by 79.7% and 70.9%, respectively, relative to no addition. Critically, N addition reduced priming effects on native SOC by 29.7–31.5%, evidenced by a negative correlation between priming C loss and native SOC content.</p> Conclusions <p>We demonstrate that N enrichment facilitates short-term C accrual in subsoil by dual mechanisms: suppressing SOC mineralization via attenuated priming and channeling straw C toward microbial biomass and stabilized fractions. These findings underscore the importance of co-optimized C and N inputs in developing subsoil C sequestration potential in croplands with similar soil conditions.</p>

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Nitrogen enrichment boosts subsoil carbon sequestration by enhancing microbial straw utilization

  • 期刊论文

  • 发表日期：

    2026年4月7日

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  • Zheng-Rong Kan,
  • Muhan Li,
  • Xinyue Wang,
  • Yixuan Luo,
  • Ahmad Latif Virk,
  • Gong Wu,
  • Haishui Yang,
  • Feng-Min Li

摘要

Aims

Subsoil (> 20 cm) stores a substantial proportion of terrestrial soil organic carbon (SOC) but receives limited fresh carbon (C) inputs. In nutrient-poor subsoil, crop straw with high C/N ratios may intensify nutrient limitation, yet their interactive effects with nitrogen (N) enrichment on SOC dynamics remain insufficiently understood.

Methods

Using 13C-labelled straw incubation, we tested how N addition modulates native SOC stability and straw-derived C partitioning in two agriculturally relevant subsoils (clay vs. sandy loam).

Results

Nitrogen enrichment likely mitigated microbial N limitation from high C/N straw, elevating microbial carbon use efficiency (CUE) by 12.2–17.5% in subsoil. This stimulated microbial anabolism was beneficial to the retention of straw-derived C in subsoil. Nitrogen addition increased straw-derived SOC in subsoil by 28.6% in clay loam and 36.4% in sandy loam texture, and microbial necromass (amino sugars) by 79.7% and 70.9%, respectively, relative to no addition. Critically, N addition reduced priming effects on native SOC by 29.7–31.5%, evidenced by a negative correlation between priming C loss and native SOC content.

Conclusions

We demonstrate that N enrichment facilitates short-term C accrual in subsoil by dual mechanisms: suppressing SOC mineralization via attenuated priming and channeling straw C toward microbial biomass and stabilized fractions. These findings underscore the importance of co-optimized C and N inputs in developing subsoil C sequestration potential in croplands with similar soil conditions.