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Background <p>Maintaining the quality of the soil organic carbon (SOC) pool is crucial for mitigating fertility degradation in rubber plantations. However, the long-term efficacy of fertilization strategies, particularly organic substitution, in enhancing SOC pool stability remains inadequately assessed.</p> Methods <p>Using a 12-year field trial in a mature rubber plantation on Hainan Island, China, we evaluated the effects of four fertilization regimes: no fertilization (CK), conventional chemical fertilizer (CF), and two organic substitution fertilization treatments (NM: 50% chemical N + 50% non-composted manure, NC: 50% chemical N + 50% composted manure) on soil nutrient availability, SOC pool composition, the carbon pool management index (CPMI), and extracellular enzyme activities to assess microbial nutrient limitations.</p> Results <p>Compared with CF, organic substitution fertilization (NM, NC) significantly enhanced soil pH, SOC content, and CPMI by 0.97–10.14%, 14.85–52.35%, and 35.06–105.86%, respectively, within the 0–20&#xa0;cm depth. These improvements were mechanistically linked to alleviated microbial carbon and nitrogen limitations, as evidenced by shifts in enzyme stoichiometry (increased vector angle, decreased vector length), indicating enhanced microbial metabolic efficiency. Random forest regression showed that soil properties collectively explained 91.05% of the variation in CPMI. Structural equation modeling further revealed that the fertilization regime exerted the primary indirect effect on CPMI, with enzyme stoichiometry and key physical properties being the most significant direct drivers.</p> Conclusion <p>Long-term organic substitution fertilization sustains rubber plantation soil fertility by alleviating microbial nutrient limitations and enhancing the SOC pool stability. The composted manure substitution (NC) was identified as the optimal strategy, confirming our hypothesis. This study provides critical mechanistic evidence supporting the adoption of organic substitution practices in tropical plantation ecosystems for climate-smart agriculture.</p>

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Twelve-year organic substitution fertilization mitigates microbial nutrient limitation and enhances soil carbon pool stability in a rubber plantation

  • 期刊论文

  • 发表日期：

    2026年3月11日

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  • Wenxian Xu,
  • Yingying Zhang,
  • Wenjie Liu,
  • Congju Zhao,
  • Ashar Tahir,
  • Chuan Yang,
  • Xinwei Guo,
  • Rui Sun,
  • Xiangshuai Yan,
  • Huifang Yuan,
  • Qiu Yang,
  • Zhixiang Wu

摘要

Background

Maintaining the quality of the soil organic carbon (SOC) pool is crucial for mitigating fertility degradation in rubber plantations. However, the long-term efficacy of fertilization strategies, particularly organic substitution, in enhancing SOC pool stability remains inadequately assessed.

Methods

Using a 12-year field trial in a mature rubber plantation on Hainan Island, China, we evaluated the effects of four fertilization regimes: no fertilization (CK), conventional chemical fertilizer (CF), and two organic substitution fertilization treatments (NM: 50% chemical N + 50% non-composted manure, NC: 50% chemical N + 50% composted manure) on soil nutrient availability, SOC pool composition, the carbon pool management index (CPMI), and extracellular enzyme activities to assess microbial nutrient limitations.

Results

Compared with CF, organic substitution fertilization (NM, NC) significantly enhanced soil pH, SOC content, and CPMI by 0.97–10.14%, 14.85–52.35%, and 35.06–105.86%, respectively, within the 0–20 cm depth. These improvements were mechanistically linked to alleviated microbial carbon and nitrogen limitations, as evidenced by shifts in enzyme stoichiometry (increased vector angle, decreased vector length), indicating enhanced microbial metabolic efficiency. Random forest regression showed that soil properties collectively explained 91.05% of the variation in CPMI. Structural equation modeling further revealed that the fertilization regime exerted the primary indirect effect on CPMI, with enzyme stoichiometry and key physical properties being the most significant direct drivers.

Conclusion

Long-term organic substitution fertilization sustains rubber plantation soil fertility by alleviating microbial nutrient limitations and enhancing the SOC pool stability. The composted manure substitution (NC) was identified as the optimal strategy, confirming our hypothesis. This study provides critical mechanistic evidence supporting the adoption of organic substitution practices in tropical plantation ecosystems for climate-smart agriculture.