Purpose Acid-modified biochar can effectively inhibit the transportation of nitrate (NO3−) in water via adsorption. Clarifying the impact of biochar acidification characteristics on soil nitrification and acidification is vital for understanding the mechanisms through which acid-modified biochar regulates nitrate transportation and leaching in soils in subtropical regions of China. Methods In this study, upland soil (SU) and brushwood soil (SB) from Jiangxi Province were sampled, treated with 0%, 2%, and 4% (w/w) acid-modified biochar, and fertilized with 0 or 200 mg N kg− 1 nitrogen (N)-fertilizer (ammonium bicarbonate) respectively. After a 21-day incubation at 60% WHC (water holding capacity) and 25 °C, changes in the soil nitrification rate, pH, metal oxides (Fe, Al, Mn), soil electrochemical parameters (surface charge density, electric field strength), and abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) were analyzed for different treatments. Results The results revealed that acid-modified biochar significantly inhibited nitrification in both upland (SU) and brushwood (SB) soils during incubation (P < 0.05), with a mean NO3− reduction ratio of 11% (SU) and 37% (SB) in the biochar-only treatment and 9% (SU) and 31% (SB) in the coapplication treatment (biochar and fertilizer). The NO3− content decreased with increasing addition ratio (P < 0.05). The inhibition of nitrification by acid-modified biochar might be related to its effects on reducing soil pH, decreasing free and amorphous iron/aluminum content, lowering surface charge density and electric field strength, and subsequently inhibiting microbial activity and colonization capacity, consequently reducing the abundance of ammonia-oxidizing archaea (AOA) and related nitrification ability. However, this inhibitory effect was mitigated by the application of nitrogen fertilizer, which increased the soil pH and AOB abundance. Conclusion The inhibitory effect of acid-modified biochar acidity on soil nitrification and acidification might be offset by the application of N fertilizer, which could promote soil nitrification and subsequently increase acidification. Hence, when acid-modified biochar is used to control NO3− transport in soils, it is crucial to note that the combined effects of fertilizer type, soil type, and biotic and abiotic properties on NO3−-N formation and soil acidification.

Effects of modified biochar and fertilizer application on soil nitrification and acidification in subtropical regions of China

期刊论文
发表日期：

2026年1月30日

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Wei Zhao,
Ai Chen,
Wenjia Han,
Zheng Tang,
Zhihong Xu,
Kai Zhang,
Jingjing Ma,
Xiuying Lv,
Xiali Zhang

摘要

Purpose

Acid-modified biochar can effectively inhibit the transportation of nitrate (NO₃⁻) in water via adsorption. Clarifying the impact of biochar acidification characteristics on soil nitrification and acidification is vital for understanding the mechanisms through which acid-modified biochar regulates nitrate transportation and leaching in soils in subtropical regions of China.

Methods

In this study, upland soil (SU) and brushwood soil (SB) from Jiangxi Province were sampled, treated with 0%, 2%, and 4% (w/w) acid-modified biochar, and fertilized with 0 or 200 mg N kg^− 1 nitrogen (N)-fertilizer (ammonium bicarbonate) respectively. After a 21-day incubation at 60% WHC (water holding capacity) and 25 °C, changes in the soil nitrification rate, pH, metal oxides (Fe, Al, Mn), soil electrochemical parameters (surface charge density, electric field strength), and abundance of ammonia-oxidizing bacteria (AOB) and archaea (AOA) were analyzed for different treatments.

Results

The results revealed that acid-modified biochar significantly inhibited nitrification in both upland (SU) and brushwood (SB) soils during incubation (P < 0.05), with a mean NO₃⁻ reduction ratio of 11% (SU) and 37% (SB) in the biochar-only treatment and 9% (SU) and 31% (SB) in the coapplication treatment (biochar and fertilizer). The NO₃⁻ content decreased with increasing addition ratio (P < 0.05). The inhibition of nitrification by acid-modified biochar might be related to its effects on reducing soil pH, decreasing free and amorphous iron/aluminum content, lowering surface charge density and electric field strength, and subsequently inhibiting microbial activity and colonization capacity, consequently reducing the abundance of ammonia-oxidizing archaea (AOA) and related nitrification ability. However, this inhibitory effect was mitigated by the application of nitrogen fertilizer, which increased the soil pH and AOB abundance.

Conclusion

The inhibitory effect of acid-modified biochar acidity on soil nitrification and acidification might be offset by the application of N fertilizer, which could promote soil nitrification and subsequently increase acidification. Hence, when acid-modified biochar is used to control NO₃⁻ transport in soils, it is crucial to note that the combined effects of fertilizer type, soil type, and biotic and abiotic properties on NO₃⁻-N formation and soil acidification.