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Aims <p>Straw decomposition may contribute to the accumulation of relatively stable soil organic carbon pools including microbial necromass carbon (MNC) and mineral-associated organic carbon (MAOC). However, little is known how inorganic nitrogen forms i.e. nitrate and ammonium impact the mechanisms regarding straw decomposition, MNC accumulation as well as MAOC stability in terms of its molecular composition and diversity.</p> Methods <p>Wheat straw was co-added with 50&#xa0;mg N kg<sup>−1</sup> (low) or 150&#xa0;mg N kg<sup>−1</sup> (high) of either nitrate or ammonium in a 90-day indoor experiment. The dynamic changes in soil respiration, particular organic carbon (POC), MNC and MAOC were monitored, and the molecular composition of MAOC were characterized using pyrolysis gas chromatography-mass spectrometry (Py-GCMS).</p> Results <p>Nitrate could promote straw decomposition and MNC accumulation more significantly than ammonium due to the higher microbial utilization i.e. less N<sub>2</sub>O emission. Compared with CK, high concentration of nitrate with straw resulted in the greatest increase in soil CO<sub>2</sub>-C emission by 12.7 times and total MNC by 64.8%. Compared with straw addition alone, nitrate with straw significantly promoted the decomposition of relatively unstable POC by 41.8% without affecting MAOC accumulation. MAOC molecular composition and diversity were altered more by nitrate than by ammonium. Nitrate decreased the relative abundance of plant-derived phenolic compounds, but increased that of aromatic compounds more prominently than ammonium, facilitating microbial oxidation and the persistence of MAOC.</p> Conclusions <p>This study highlights the advantages of nitrate co-added with straw in enhancing MNC accumulation as well as MAOC stability from its molecular composition aspect.</p>

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Nitrate promotes straw decomposition, microbial necromass accumulation and stability of mineral-associated organic carbon at molecular compositional level more significantly than ammonium

  • 期刊论文

  • 发表日期：

    2026年2月21日

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  • Weijie Dai,
  • Rongbo Xiao,
  • Fen Yang,
  • Chaoyang Wei

摘要

Aims

Straw decomposition may contribute to the accumulation of relatively stable soil organic carbon pools including microbial necromass carbon (MNC) and mineral-associated organic carbon (MAOC). However, little is known how inorganic nitrogen forms i.e. nitrate and ammonium impact the mechanisms regarding straw decomposition, MNC accumulation as well as MAOC stability in terms of its molecular composition and diversity.

Methods

Wheat straw was co-added with 50 mg N kg−1 (low) or 150 mg N kg−1 (high) of either nitrate or ammonium in a 90-day indoor experiment. The dynamic changes in soil respiration, particular organic carbon (POC), MNC and MAOC were monitored, and the molecular composition of MAOC were characterized using pyrolysis gas chromatography-mass spectrometry (Py-GCMS).

Results

Nitrate could promote straw decomposition and MNC accumulation more significantly than ammonium due to the higher microbial utilization i.e. less N2O emission. Compared with CK, high concentration of nitrate with straw resulted in the greatest increase in soil CO2-C emission by 12.7 times and total MNC by 64.8%. Compared with straw addition alone, nitrate with straw significantly promoted the decomposition of relatively unstable POC by 41.8% without affecting MAOC accumulation. MAOC molecular composition and diversity were altered more by nitrate than by ammonium. Nitrate decreased the relative abundance of plant-derived phenolic compounds, but increased that of aromatic compounds more prominently than ammonium, facilitating microbial oxidation and the persistence of MAOC.

Conclusions

This study highlights the advantages of nitrate co-added with straw in enhancing MNC accumulation as well as MAOC stability from its molecular composition aspect.