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Background and aims <p>Nitrogen (N) addition can substantially affect soil carbon cycling in agroecosystems. Microbial necromass carbon (MNC) is widely recognized as a key contributor to soil organic C (SOC) fractions. However, the mechanisms underlying the responses of MNC and SOC fractions to N fertilization in paddy soils remain unclear.</p> Methods <p>A field experiment with four N rates, namely, 0, 300, 450, and 600&#xa0;kg N ha<sup>–1</sup>&#xa0;yr<sup>–1</sup> was conducted to determine the effects of N addition on SOC fractions, soil microbial necromass carbon (MNC), enzyme activity, and microbial biomass in paddy soils with rice–wheat rotation.</p> Results <p>N addition increased SOC and POC concentrations by 2.88–8.41% and 14.6–41.2%, respectively, but did not affect MAOC. The ratio of MAOC to POC was reduced by N addition, indicating that N addition decreased SOC stability. N addition increased MNC concentration by 7.32–22.5% and its contribution to SOC by 4.14–13.7%. The activity of β-1,4-<i>N</i>-acetyl-glucosaminidase was decreased, while the activities of leucine amino peptidase and acid phosphatase were increased under N addition. Structural equation modeling and random forest revealed that N-induced decrease in soil pH promoted the accrual of MNC by increasing root and microbial biomass, consequently improving POC.</p> Conclusions <p>POC is likely more vulnerable to N addition than MAOC. N-induced acidification is the primary driver for promoting SOC accrual by increasing POC in paddy soils.</p>

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Nitrogen-induced acidification increases soil organic carbon accrual by promoting particulate organic carbon and microbial necromass under long-term experiments in the paddy soils of East China

  • 期刊论文

  • 发表日期：

    2025年6月8日

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  • Zhaoming Chen,
  • Qiang Wang,
  • Jinchuan Ma,
  • Feng Wang,
  • Junwei Ma,
  • Jing Ye,
  • Ping Zou,
  • Wanchun Sun,
  • Qiaogang Yu

摘要

Background and aims

Nitrogen (N) addition can substantially affect soil carbon cycling in agroecosystems. Microbial necromass carbon (MNC) is widely recognized as a key contributor to soil organic C (SOC) fractions. However, the mechanisms underlying the responses of MNC and SOC fractions to N fertilization in paddy soils remain unclear.

Methods

A field experiment with four N rates, namely, 0, 300, 450, and 600 kg N ha–1 yr–1 was conducted to determine the effects of N addition on SOC fractions, soil microbial necromass carbon (MNC), enzyme activity, and microbial biomass in paddy soils with rice–wheat rotation.

Results

N addition increased SOC and POC concentrations by 2.88–8.41% and 14.6–41.2%, respectively, but did not affect MAOC. The ratio of MAOC to POC was reduced by N addition, indicating that N addition decreased SOC stability. N addition increased MNC concentration by 7.32–22.5% and its contribution to SOC by 4.14–13.7%. The activity of β-1,4-N-acetyl-glucosaminidase was decreased, while the activities of leucine amino peptidase and acid phosphatase were increased under N addition. Structural equation modeling and random forest revealed that N-induced decrease in soil pH promoted the accrual of MNC by increasing root and microbial biomass, consequently improving POC.

Conclusions

POC is likely more vulnerable to N addition than MAOC. N-induced acidification is the primary driver for promoting SOC accrual by increasing POC in paddy soils.