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Purpose <p>This study aimed to clarify how straw incorporation timing reshapes nitrogen (N)- cycling functional processes and regulates N retention and loss in paddy fields under different N fertilization regimes. It also evaluated the effects of these processes on rice yield and N uptake and utilization efficiency in cold-region rice systems, thereby addressing the shortage of field-based evidence from seasonally cold rice-growing regions.</p> Methods <p>A two-year field experiment was conducted with three straw treatments, including no straw incorporation (CK), spring straw incorporation (ST), and autumn wet-harrow straw incorporation (SW). These treatments were combined with conventional N fertilization (N2) and a 20% reduction in N input (N1), resulting in six treatments. Soil environmental variables and metagenomic functional information were integrated to clarify how soil conditions and N-cycling functional genes would drive rice yield and NUE.</p> Results <p>Autumn straw incorporation by wet harrowing under a 20% reduction in N input (SWN1), maintained rice yield, and improved N recovery efficiency (NRE). The SWN1 significantly increased dissolved organic carbon (DOC) and soil organic carbon (SOC). The sustained DOC supply likely increased microbial oxygen consumption, thereby shifting inorganic N toward the ammonium (NH<sub>4</sub><sup>+</sup>-N) form. The overall downregulation of the nitrification gene <i>amoB/pmoB</i> and the denitrification gene <i>norB</i> weakened the conversion of NH<sub>4</sub><sup>+</sup>-N to nitrate (NO<sub>3</sub><sup>−</sup>-N). Meanwhile, the upregulation of the N fixation gene <i>nifK</i> and the assimilatory nitrate reduction to ammonium (ANRA) related gene <i>nirD</i> may reduce redox-mediated N loss and improve N retention and recycling. These functional shifts helped maintain rice yield and improve NRE under lower N application rates.</p> Conclusions <p>The SWN1 maintained rice yield and improved NRE by increasing DOC and SOC, favoring NH<sub>4</sub><sup>+</sup>-N accumulation, and reshaping the N cycling functional gene network. These findings provide a mechanistic basis for efficient N fertilization and straw management in cold-region rice systems.</p>

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Mechanisms by which nitrogen-cycling functional genes enable reduced nitrogen input without yield loss under optimized straw incorporation

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年5月12日

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  • Xue Wan,
  • Yingying Feng,
  • Yuzhuo Liu,
  • Xinyue Ju,
  • Hongfang Jiang,
  • Zhongcheng Zhang,
  • Liqiang Chen,
  • Yanze Zhao,
  • Jiping Gao,
  • Mingda Liu,
  • Wenzhong Zhang,
  • Lina Zhang

摘要

Purpose

This study aimed to clarify how straw incorporation timing reshapes nitrogen (N)- cycling functional processes and regulates N retention and loss in paddy fields under different N fertilization regimes. It also evaluated the effects of these processes on rice yield and N uptake and utilization efficiency in cold-region rice systems, thereby addressing the shortage of field-based evidence from seasonally cold rice-growing regions.

Methods

A two-year field experiment was conducted with three straw treatments, including no straw incorporation (CK), spring straw incorporation (ST), and autumn wet-harrow straw incorporation (SW). These treatments were combined with conventional N fertilization (N2) and a 20% reduction in N input (N1), resulting in six treatments. Soil environmental variables and metagenomic functional information were integrated to clarify how soil conditions and N-cycling functional genes would drive rice yield and NUE.

Results

Autumn straw incorporation by wet harrowing under a 20% reduction in N input (SWN1), maintained rice yield, and improved N recovery efficiency (NRE). The SWN1 significantly increased dissolved organic carbon (DOC) and soil organic carbon (SOC). The sustained DOC supply likely increased microbial oxygen consumption, thereby shifting inorganic N toward the ammonium (NH4+-N) form. The overall downregulation of the nitrification gene amoB/pmoB and the denitrification gene norB weakened the conversion of NH4+-N to nitrate (NO3−-N). Meanwhile, the upregulation of the N fixation gene nifK and the assimilatory nitrate reduction to ammonium (ANRA) related gene nirD may reduce redox-mediated N loss and improve N retention and recycling. These functional shifts helped maintain rice yield and improve NRE under lower N application rates.

Conclusions

The SWN1 maintained rice yield and improved NRE by increasing DOC and SOC, favoring NH4+-N accumulation, and reshaping the N cycling functional gene network. These findings provide a mechanistic basis for efficient N fertilization and straw management in cold-region rice systems.