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<p>Biochar is a promising amendment for enhancing soil organic carbon (SOC) sequestration in paddy soils, yet its effects on rice rhizodeposited carbon (C) stabilization and the underlying mechanisms remain unclear. A pot experiment was conducted using two representative paddy soils from southern China: a red earth derived soil (RP) with high iron (Fe) content and a clay-rich soil (LP) derived from lacustrine sediments. Biochar was applied at 1% (<i>w</i>/<i>w</i>), and rice plants were pulse-labeled with <sup>13</sup>CO<sub>2</sub> at the jointing stage and heading stage. The labeled pots were either sampled immediately after labeling or at the maturity stage (MS). The allocation of rhizodeposited C at MS was quantified among soil aggregates, Fe-bound organic C (FeOC), and microbial biomass C (MBC). Results showed that biochar increased rice rhizodeposited C input by 28.3% to 39.4% and enhanced rhizodeposited C stabilization in soil by reducing its loss by 6.9% to 30.1%. Although biochar decreased the percentage of <sup>13</sup>C-SOC present as <sup>13</sup>C-MBC in both soils, the stabilization pathways differed between the two soils. In RP, biochar increased the percentage of <sup>13</sup>C-SOC present as <sup>13</sup>C-FeOC, whereas it promoted the redistribution of <sup>13</sup>C-SOC from the silt and clay fraction to macroaggregates in LP. Partial least square path models indicated that biochar stabilized rhizodeposited C mainly through Fe association in RP and aggregate occlusion in LP. These findings reveal distinct biochar-mediated stabilization pathways of rhizodeposited C in paddy soils and support the optimization of soil-specific biochar application strategies for C sequestration.</p>

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Biochar enhances rice rhizodeposited carbon stabilization through distinct pathways of iron association and aggregate occlusion in two contrasting paddy soils

  • 期刊论文

  • 发表日期：

    2026年5月19日

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  • Ruiling Ma,
  • Yujia Yu,
  • Ruiyu Wang,
  • Zheng Zhao,
  • Zuhang Shen,
  • Qi Yi,
  • Shaopan Xia,
  • Rongjun Bian,
  • Xuhui Zhang,
  • Zhiwei Liu,
  • Kun Cheng,
  • Jufeng Zheng

摘要

Biochar is a promising amendment for enhancing soil organic carbon (SOC) sequestration in paddy soils, yet its effects on rice rhizodeposited carbon (C) stabilization and the underlying mechanisms remain unclear. A pot experiment was conducted using two representative paddy soils from southern China: a red earth derived soil (RP) with high iron (Fe) content and a clay-rich soil (LP) derived from lacustrine sediments. Biochar was applied at 1% (w/w), and rice plants were pulse-labeled with 13CO2 at the jointing stage and heading stage. The labeled pots were either sampled immediately after labeling or at the maturity stage (MS). The allocation of rhizodeposited C at MS was quantified among soil aggregates, Fe-bound organic C (FeOC), and microbial biomass C (MBC). Results showed that biochar increased rice rhizodeposited C input by 28.3% to 39.4% and enhanced rhizodeposited C stabilization in soil by reducing its loss by 6.9% to 30.1%. Although biochar decreased the percentage of 13C-SOC present as 13C-MBC in both soils, the stabilization pathways differed between the two soils. In RP, biochar increased the percentage of 13C-SOC present as 13C-FeOC, whereas it promoted the redistribution of 13C-SOC from the silt and clay fraction to macroaggregates in LP. Partial least square path models indicated that biochar stabilized rhizodeposited C mainly through Fe association in RP and aggregate occlusion in LP. These findings reveal distinct biochar-mediated stabilization pathways of rhizodeposited C in paddy soils and support the optimization of soil-specific biochar application strategies for C sequestration.