A two-year tea field experiment in subtropical China shows that combining nitrogen transformation inhibitors with biochar can reduce harmful nitrogen gas emissions while supporting tea productivity.
Tea is one of the world's most widely consumed beverages, but intensive tea cultivation often depends on heavy nitrogen fertilizer use. In many tea-growing regions, this practice can release large amounts of nitrous oxide, a potent greenhouse gas, and ammonia, an air pollutant linked to fine particulate matter formation and nutrient pollution in ecosystems.
A new study published in Biochar reports that dual nitrogen inhibitors, used either alone or together with biochar, substantially reduced nitrous oxide and ammonia losses from tea field soil. The findings offer a practical route toward cleaner and more efficient tea production in subtropical agricultural regions.
"Tea plantations are important agricultural systems, but excessive nitrogen fertilization can create serious environmental costs," said corresponding author Jianlin Shen. "Our study shows that better nitrogen management can reduce gaseous nitrogen losses while maintaining, and in some cases improving, tea productivity."
The research team conducted a two-year field experiment in a subtropical hilly tea plantation in Hunan Province, China. They compared four treatments: no nitrogen fertilizer, conventional nitrogen fertilization, reduced nitrogen fertilizer with two inhibitors, and reduced nitrogen fertilizer with both inhibitors and biochar. The inhibitors included NBPT, which slows the conversion of urea into ammonium and helps reduce ammonia volatilization, and DMPP, which slows nitrification and limits nitrous oxide formation.
Under conventional nitrogen fertilization, the tea field produced high cumulative gaseous nitrogen losses, with average emissions of 25.8 kg ha⁻¹ nitrous oxide and 75.8 kg ha⁻¹ ammonia. Adding the two inhibitors reduced nitrous oxide and ammonia emission factors by 54.5% and 20.0%, respectively. When biochar was added together with the inhibitors, emission factors were reduced by 49.8% for nitrous oxide and 20.2% for ammonia.
The study also found that gaseous nitrogen losses came mainly from the fertilized tea rows rather than the inter-row ridges. This suggests that targeted management of fertilized zones could be especially important for reducing emissions from tea plantations.
To understand why the treatments worked, the researchers measured soil nitrogen forms and key microbial genes involved in nitrogen cycling. Their analyses showed that the inhibitors changed soil nitrogen transformation dynamics and reduced the abundance of microbial genes associated with nitrification and denitrification, including ammonia-oxidizing bacteria and the nitrite reductase gene nirS. These shifts helped limit the availability of substrates that drive nitrous oxide and ammonia production.
Importantly, the environmental benefits did not come at the expense of crop performance. The treatment combining biochar and dual inhibitors increased tea yield by 6.7% and plant nitrogen uptake by 14.4%, indicating that emission reduction and productivity can be achieved together.
Biochar is a carbon-rich material produced from biomass under limited oxygen. Because of its porous structure and soil-improving properties, it has attracted growing attention as a tool for sustainable agriculture. In this study, biochar did not further enhance nitrous oxide mitigation compared with inhibitors alone, but it improved tea yield and nitrogen uptake, supporting its potential role in integrated nutrient management.
"These results provide field-based evidence that dual inhibitors and biochar can be used as practical tools for sustainable tea cultivation," Shen said. "The approach may help reduce greenhouse gas emissions and reactive nitrogen pollution while supporting farmers' production goals."
The authors note that the effectiveness of biochar and inhibitors may vary with soil type, climate, fertilizer rate, and field management. Further long-term studies across different tea-growing regions will help refine recommendations for broader application.
The study highlights a promising strategy for reducing the environmental footprint of tea production while maintaining high-yield agriculture.
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Journal Reference: Li, Y., Li, Y., Zhang, H. et al. Reduction in N2O and NH3 emissions with combined use of dual inhibitors and biochar in a tea field soil in subtropical central China. Biochar 8, 114 (2026).
https://doi.org/10.1007/s42773-026-00635-7
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
