Biochar amendment is an effective strategy for mitigating methane (CH4) emissions in paddy fields. However, the long-term efficacy of different biochar amendment strategies for mitigating CH4 emissions remains unclear, particularly under different water management regimes. To address this knowledge gap, a 5-year (2018–2022) field experiment was conducted to determine CH4 production potential, CH4 oxidation potential, and CH4 emissions in paddy fields under six treatments: flooded irrigation (F) without biochar amendment (FB0), F with once biochar amendment (12.5 t ha−1, FB1), F with continuous biochar amendment (2.5 t ha−1 year−1, FB5), controlled irrigation (C) without biochar amendment (CB0), C with once biochar amendment (12.5 t ha−1, CB1), and C with continuous biochar amendment (2.5 t ha−1 year−1, CB5). Additionally, random forest analysis and structural equation modeling (SEM) were used to elucidate interaction pathways among biochar amendment, water management, CH4 production and oxidation potentials, and key soil properties affecting CH4 emissions. In the first year, once biochar amendment demonstrated optimal CH4 mitigation efficacy under different water management regimes, reducing cumulative CH4 emissions by 18.87–36.32% compared to other treatments. However, this mitigation effect diminished progressively over 5 years under different water management regimes, with the most rapid decline occurring under C. Consequently, there was no significant difference in the 5-year cumulative CH4 emissions between FB1 and FB5, while CB5 achieved a significant 29.32% reduction in 5-year cumulative CH4 emissions compared to CB1. Random forest analysis and SEM identified soil redox potential (Eh), dissolved organic carbon (DOC), and ammonium nitrogen (<InlineEquation ID="IEq100"> <EquationSource Format="TEX">$\text{NH}^{+}_{4}\text{-N}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mtext>NH</mtext> <mn>4</mn> <mo>+</mo> </msubsup> <mtext>-N</mtext> </mrow> </math></EquationSource> </InlineEquation>) as key soil properties driving CH4 emissions. CB5 maintained higher soil Eh and <InlineEquation ID="IEq101"> <EquationSource Format="TEX">$\text{NH}^{+}_{4}\text{-N}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mtext>NH</mtext> <mn>4</mn> <mo>+</mo> </msubsup> <mtext>-N</mtext> </mrow> </math></EquationSource> </InlineEquation> levels with lower DOC, leading to the lowest CH4 production potential and highest CH4 oxidation potential over 5 years, ultimately achieving the greatest CH4 mitigation. Furthermore, CB5 achieved the lowest CH4-attributed greenhouse gas intensity and net greenhouse gas emissions over 5 years. These findings highlight the necessity of long-term monitoring to accurately assess the effects of biochar amendments on CH4 mitigation and offer technical guidance for implementation of biochar strategies in paddy fields under different water management regimes.Highlights<UnorderedList Mark="Bullet"> <ItemContent> Water-saving irrigation rapidly diminished the CH4 mitigation effect of the once biochar amendment. </ItemContent> <ItemContent> Continuous biochar amendment combined with water-saving irrigation was the most effective strategy for CH4 mitigation over 5 years. </ItemContent> <ItemContent> Soil Eh, DOC, and <InlineEquation ID="IEq105"> <EquationSource Format="TEX">$\text{NH}^{+}_{4}\text{-N}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mtext>NH</mtext> <mn>4</mn> <mo>+</mo> </msubsup> <mtext>-N</mtext> </mrow> </math></EquationSource> </InlineEquation> were key drivers of CH4 emissions over 5 years. </ItemContent> </UnorderedList> Graphical Abstract

Continuous biochar amendment to achieve long-term CH₄ mitigation in paddy fields under water-saving irrigation: a 5-year experiment

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2026年3月6日

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Yu Han,
Peng Chen,
Zhongxue Zhang,
Xiaoyuan Yan,
Guangbin Zhang,
Zuohe Zhang,
Tiecheng Li,
Tangzhe Nie,
Sicheng Du

摘要

Biochar amendment is an effective strategy for mitigating methane (CH₄) emissions in paddy fields. However, the long-term efficacy of different biochar amendment strategies for mitigating CH₄ emissions remains unclear, particularly under different water management regimes. To address this knowledge gap, a 5-year (2018–2022) field experiment was conducted to determine CH₄ production potential, CH₄ oxidation potential, and CH₄ emissions in paddy fields under six treatments: flooded irrigation (F) without biochar amendment (FB0), F with once biochar amendment (12.5 t ha⁻¹, FB1), F with continuous biochar amendment (2.5 t ha⁻¹ year⁻¹, FB5), controlled irrigation (C) without biochar amendment (CB0), C with once biochar amendment (12.5 t ha⁻¹, CB1), and C with continuous biochar amendment (2.5 t ha⁻¹ year⁻¹, CB5). Additionally, random forest analysis and structural equation modeling (SEM) were used to elucidate interaction pathways among biochar amendment, water management, CH₄ production and oxidation potentials, and key soil properties affecting CH₄ emissions. In the first year, once biochar amendment demonstrated optimal CH₄ mitigation efficacy under different water management regimes, reducing cumulative CH₄ emissions by 18.87–36.32% compared to other treatments. However, this mitigation effect diminished progressively over 5 years under different water management regimes, with the most rapid decline occurring under C. Consequently, there was no significant difference in the 5-year cumulative CH₄ emissions between FB1 and FB5, while CB5 achieved a significant 29.32% reduction in 5-year cumulative CH₄ emissions compared to CB1. Random forest analysis and SEM identified soil redox potential (Eh), dissolved organic carbon (DOC), and ammonium nitrogen ( $\text{NH}^{+}_{4}\text{-N}$ ${NH}_{4}^{+} -N$ ) as key soil properties driving CH₄ emissions. CB5 maintained higher soil Eh and $\text{NH}^{+}_{4}\text{-N}$ ${NH}_{4}^{+} -N$ levels with lower DOC, leading to the lowest CH₄ production potential and highest CH₄ oxidation potential over 5 years, ultimately achieving the greatest CH₄ mitigation. Furthermore, CB5 achieved the lowest CH₄-attributed greenhouse gas intensity and net greenhouse gas emissions over 5 years. These findings highlight the necessity of long-term monitoring to accurately assess the effects of biochar amendments on CH₄ mitigation and offer technical guidance for implementation of biochar strategies in paddy fields under different water management regimes.

Highlights

Water-saving irrigation rapidly diminished the CH₄ mitigation effect of the once biochar amendment.

Continuous biochar amendment combined with water-saving irrigation was the most effective strategy for CH₄ mitigation over 5 years.

Soil Eh, DOC, and $\text{NH}^{+}_{4}\text{-N}$ ${NH}_{4}^{+} -N$ were key drivers of CH₄ emissions over 5 years.

Graphical Abstract

Continuous biochar amendment to achieve long-term CH4 mitigation in paddy fields under water-saving irrigation: a 5-year experiment

摘要

Continuous biochar amendment to achieve long-term CH₄ mitigation in paddy fields under water-saving irrigation: a 5-year experiment