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Aims <p>Soil aggregates are fundamental structural units of soil ecosystems and play critical roles in nutrient storage and cycling. However, the influence of fertilization regimes on the interactions between bulk soil and aggregate properties across soil layers remain insufficiently understood. This study aims to explore how long-term fertilization practices affect soil aggregate fractions, their carbon (C), nitrogen (N), and phosphorus (P) stocks, and overall soil quality across different soil layers (0–40&#xa0;cm).</p> Methods <p>The 22-year long-term field trial included four treatments: no fertilizer (CK), only chemical fertilizer (NPK), organic manure added at a rate of 15&#xa0;Mg&#xa0;ha<sup>−1</sup> y<sup>−1</sup>, in addition to chemical fertilizer (NPKO1), and organic manure added at a rate of 22.5&#xa0;Mg&#xa0;ha<sup>−1</sup> y<sup>−1</sup>, in addition to chemical fertilizer (NPKO2). Analyses were conducted on bulk soil and aggregate fractions, focusing on carbon (C), nitrogen (N), and phosphorus (P) stocks, as well as the soil quality index (SQI) of bulk soil. The experiment was conducted under a maize–soybean rotation system, with soybean as the standing crop at the time of soil sampling.</p> Results <p>The application of organic manure increased the proportion of large and medium aggregates and enhanced their nutrient contents in both topsoil (0–20&#xa0;cm) and subsoil (20–40&#xa0;cm). Organic manure application also raised the soil quality index (SQI) by 18.32%–33.08% in topsoil and 2.43%–16.99% in subsoil. Random forest analysis identified soil bulk density as the main factor influencing C, N, and P stocks in large aggregates across both soil layers, while N stocks were the primary determinant of SQI. Among aggregate fractions, large aggregates contributed most to total P, thereby exerting the greatest influence on C, N, and P stocks and SQI in topsoil. In contrast, the contribution of microaggregates to soil organic C in subsoil had the strongest effect on SQI. Partial least squares models further confirmed that C, N, and P stocks significantly affect soil quality, with medium aggregates serving as the main contributors to these nutrient stocks.</p> Conclusions <p>Long-term application of organic manure improves soil quality in maize–soybean rotation systems by increasing bulk soil C, N, and P stocks, primarily through the enhancement of large and medium aggregate fractions. Medium (2000–250&#xa0;μm) aggregates play a critical role in mediating nutrient contributions to soil quality.</p>

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Long-term manure application enhances soil quality via aggregate-scale nutrient stock regulation in maize-soybean rotation

  • 期刊论文

  • 发表日期：

    2025年10月13日

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  • Zhimin Wu,
  • Yves Uwiragiye,
  • Xiaozeng Han,
  • Haoliang Feng,
  • Min Zhang,
  • Yuxuan Ji,
  • Yuanchen Zhu,
  • Xu Chen,
  • Jun Yan,
  • Xinchun Lu,
  • Wenxiu Zou

摘要

Aims

Soil aggregates are fundamental structural units of soil ecosystems and play critical roles in nutrient storage and cycling. However, the influence of fertilization regimes on the interactions between bulk soil and aggregate properties across soil layers remain insufficiently understood. This study aims to explore how long-term fertilization practices affect soil aggregate fractions, their carbon (C), nitrogen (N), and phosphorus (P) stocks, and overall soil quality across different soil layers (0–40 cm).

Methods

The 22-year long-term field trial included four treatments: no fertilizer (CK), only chemical fertilizer (NPK), organic manure added at a rate of 15 Mg ha−1 y−1, in addition to chemical fertilizer (NPKO1), and organic manure added at a rate of 22.5 Mg ha−1 y−1, in addition to chemical fertilizer (NPKO2). Analyses were conducted on bulk soil and aggregate fractions, focusing on carbon (C), nitrogen (N), and phosphorus (P) stocks, as well as the soil quality index (SQI) of bulk soil. The experiment was conducted under a maize–soybean rotation system, with soybean as the standing crop at the time of soil sampling.

Results

The application of organic manure increased the proportion of large and medium aggregates and enhanced their nutrient contents in both topsoil (0–20 cm) and subsoil (20–40 cm). Organic manure application also raised the soil quality index (SQI) by 18.32%–33.08% in topsoil and 2.43%–16.99% in subsoil. Random forest analysis identified soil bulk density as the main factor influencing C, N, and P stocks in large aggregates across both soil layers, while N stocks were the primary determinant of SQI. Among aggregate fractions, large aggregates contributed most to total P, thereby exerting the greatest influence on C, N, and P stocks and SQI in topsoil. In contrast, the contribution of microaggregates to soil organic C in subsoil had the strongest effect on SQI. Partial least squares models further confirmed that C, N, and P stocks significantly affect soil quality, with medium aggregates serving as the main contributors to these nutrient stocks.

Conclusions

Long-term application of organic manure improves soil quality in maize–soybean rotation systems by increasing bulk soil C, N, and P stocks, primarily through the enhancement of large and medium aggregate fractions. Medium (2000–250 μm) aggregates play a critical role in mediating nutrient contributions to soil quality.