Reduction in N₂O and NH₃ emissions with combined use of dual inhibitors and biochar in a tea field soil in subtropical central China

Abstract

Excessive nitrogen (N) fertilization in tea plantations often leads to substantial nitrous oxide (N₂O) emissions, which exacerbate global warming, and to pronounced ammonia (NH₃) volatilization, which is closely associated with air pollution and aquatic eutrophication. Although N transformation inhibitors and biochar have shown promise in mitigating these gaseous losses, their combined effects and the underlying mechanisms in tea fields remain poorly understood. A 2-year field experiment was conducted in a subtropical hilly tea plantation to evaluate the individual and combined effects of dual inhibitors (the urease inhibitor N-(n-butyl) thiophosphoric triamide, NBPT, and the nitrification inhibitor 3,4-dimethylpyrazole phosphate, DMPP) and biochar (28 t ha⁻¹) on N₂O and NH₃ emissions. Four treatments were established: conventional N fertilization (CON), N fertilizer amended with dual inhibitors (NI), N fertilizer combined with both biochar and dual inhibitors (BNI), and a zero-N control (CK). The results showed that the CON treatment produced high cumulative gaseous emissions (N₂O: 25.8 kg ha⁻¹; NH₃: 75.8 kg ha⁻¹). The NI treatment reduced the N₂O and NH₃ emission factors by 54.5% and 20.0%, respectively, while the BNI treatment achieved comparable mitigation efficiencies (49.8% for N₂O and 20.2% for NH₃). Both treatments significantly suppressed the abundance of key N-cycling functional genes, including ammonia-oxidizing bacteria (AOB) and the nitrite reductase gene (nirS), with NI exerting a stronger inhibitory effect on AOB. Gaseous emissions originated predominantly from the tea rows rather than from the inter-row ridges. Structural equation modeling (SEM) and random forest (RF) analyses revealed that the mitigation effect was driven by shifts in soil N transformation dynamics and substrate availability. Specifically, NBPT significantly reduced short-term soil NH₄⁺–N concentrations following fertilization, thereby decreasing substrate availability for NH₃ volatilization, whereas DMPP significantly suppressed the abundance of key N-cycling functional genes, particularly AOB and nirS, thereby inhibiting nitrification-driven N₂O production. Additionally, the BNI treatment increased the tea yield by 6.7% and plant N uptake by 14.4%. In conclusion, applying dual inhibitors, either alone or in combination with biochar, effectively mitigates N₂O and NH₃ emissions while maintaining tea productivity offering a practical strategy for environmentally sustainable tea cultivation.

Highlights

•	Conventional fertilization caused high N2O and NH3 emissions from tea plantations.
•	Applying dual inhibitors alone or with biochar reduced N2O and NH3 emission factors by up to 50% and 20%.
•	Combining inhibitors with biochar increased tea yield by 6.7% and N uptake by 14.4%.
•	N emissions were cut by suppressing soil NO3−–N, altering NH4+–N transformation dynamics, and key microbial genes.

Graphical Abstract

Keywords

N cycling / Biochar / Urease and nitrification inhibitors / Flux monitoring / Functional gene

References

[1] Abdo AI, Xu Y, Shi D, Li J, Li H, El-Sappah AH, Elrys AS, Alharbi SA, Zhou C, Wang L, Kuzyakov Y. Nitrogen transformation genes and ammonia emission from soil under biochar and urease inhibitor application. Soil till Res, 2022, 223. ArticleID: 105491

[2] Bachtsevani E, Papazlatani C, Rousidou K, Lampronikou E, Menkissoglu-Spiroudi U, Nicol G, Karpouzas D, Papadopoulou E. Effects of the nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) on the activity and diversity of the soil microbial community under contrasting soil pH. Biol Fertil Soils, 2021, 57: 1-19.

[3] Bao SD. Soil and agro-chemistry analysis, 2000, 3rd ed, Beijing, China Agric. Press

[4] Borchard N, Schirrmann M, Cayuela ML, Kammann C, Wrage-Mönnig N, Estavillo JM, Fuertes-Mendizabal T, Sigua G, Spokas K, Ippolito JA, Novak J. Biochar, soil and land-use interactions that reduce nitrate leaching and N₂O emissions: a meta-analysis. Sci Total Environ, 2019, 651(2): 2354-2364.

[5] Cai S, Zhao X, Pittelkow CM, Fan M, Zhang X, Yan X. Optimal nitrogen rate strategy for sustainable rice production in China. Nature, 2023, 615: 73-79.

[6] Chen D, Li Y, Wang C, Liu X, Wang Y, Shen J, Qin J, Wu J. Dynamics and underlying mechanisms of N₂O and NO emissions in response to a transient land-use conversion of Masson pine forest to tea field. Sci Total Environ, 2019, 693. ArticleID: 133549

[7] Chen H, Yin C, Fan X, Ye M, Peng H, Li T, Zhao Y, Wakelin SA, Chu G, Liang Y. Reduction of N₂O emission by biochar and/or 3,4-dimethylpyrazole phosphate (DMPP) is closely linked to soil ammonia oxidizing bacteria and nosZI-N₂O reducer populations. Sci Total Environ, 2019, 694. ArticleID: 133658

[8] Cheng Y, Elrys AS, Wang J, Xu C, Ni K, Zhang J, Wang S, Cai Z, Pacholski A. Application of enhanced-efficiency nitrogen fertilizers reduces mineral nitrogen usage and emissions of both N₂O and NH₃ while sustaining yields in a wheat-rice rotation system. Agric Ecosyst Environ, 2022, 324. ArticleID: 107720

[9] Cui X, Chen S, Yang J, Zhao L, Hu T, Lu J, Li A, Zhang J, Chang Z, Liu J, Wang X. Ammonia volatilization and nitrous oxide emission and their responses to environmental indicators under different irrigation levels and nitrogen fertilizer synergists. J Environ Manag, 2025, 377. ArticleID: 124580

[10] Deng B, Wang S, Xu X, Wang H, Hu D, Guo X, Shi Q, Siemann E, Zhang L. Effects of biochar and dicyandiamide combination on nitrous oxide emissions from Camellia oleifera field soil. Environ Sci Pollut Res, 2019, 26: 4070-4077.

[11] Ding W, Chen Z, Yu H, Luo J, Yoo G, Xiang J, Zhang H, Yuan J. Nitrous oxide emission and nitrogen use efficiency in response to nitrophosphate, N-(n-butyl) thiophosphoric triamide and dicyandiamide of a wheat cultivated soil under sub-humid monsoon conditions. Biogeosciences, 2015, 12(3): 803-815.

[12] Elrys AS, Uwiragiye Y, Zhang Y, Abdel-Fattah MK, Chen Z, Zhang H, Meng L, Wang J, Zhu T, Cheng Y, Zhang J, Cai Z, Chang SX, Müller C. Expanding agroforestry can increase nitrate retention and mitigate the global impact of a leaky nitrogen cycle in croplands. Nat Food, 2023, 4: 109-121.

[13] Food and Agriculture Organization of the United Nations Website. 2018. https://www.fao.org/faostat/en/

[14] Fungo B, Lehmann J, Kalbitz K, Thiongo M, Tenywa M, Okeyo I, Neufeldt H. Ammonia and nitrous oxide emissions from a field ultisol amended with tithonia green manure, urea, and biochar. Biol Fertil Soils, 2019, 55: 135-148.

[15] Gao X, Yang J, Liu W, Li X, Zhang W, Wang A. Effects of alkaline biochar on nitrogen transformation with fertilizer in agricultural soil. Environ Res, 2023, 233. ArticleID: 116084

[16] Han B, Yao Y, Liu B, Wang Y, Su X, Ma L, Liu D, Niu S, Chen X, Li Z. Relative importance between nitrification and denitrification to N₂O from a global perspective. Glob Change Biol, 2023, 30(1. ArticleID: e17082

[17] Han X, Yu HY, Zheng NG, Ge CQ, Yao HY. Nitrous oxide emissions from tea plantations: a review. Chin J Appl Ecol, 2023, 34: 805-814

[18] Hao X, Sun L, Zhou B, Ma X, Wang S, Liu S, Ji J, Kuang E, Qiu S. Change in maize yield, N use efficiencies and climatic warming potential after urea combined with Nitrapyrin and NBPT during the growing season in a black soil. Soil till Res, 2023, 231. ArticleID: 105721

[19] He T, Liu D, Yuan J, Ni K, Zaman K, Luo J, Lindsey S, Ding W. A 2-year study on the combined effects of biochar and inhibitors on ammonia volatilization in an intensively managed rice field. Agric Ecosyst Environ, 2018, 264: 44-53.

[20] He T, Yuan J, Xiang J, Lin Y, Luo J, Lindsey S, Liao X, Liu D, Ding W. Combined biochar and double inhibitor application offsets NH₃ and N₂O emissions and mitigates N leaching in paddy fields. Environ Pollut, 2022, 292. ArticleID: 118344

[21] He D, Dong Z, Zhu B. An optimal global biochar application strategy based on matching biochar and soil properties to reduce global cropland greenhouse gas emissions: findings from a global meta-analysis and density functional theory calculation. Biochar, 2024, 6: 92.

[22] Hu W, Zhang Y, Rong X, Zhou X, Fei J, Peng J, Luo G. Biochar and organic fertilizer applications enhance soil functional microbial abundance and agroecosystem multifunctionality. Biochar, 2024, 6. ArticleID: 3

[23] Jin F, Piao J, Miao S, Che W, Li X, Li X, Shiraiwa T, Tanaka T, Taniyoshi K, Hua S, Lan Y. Long-term effects of biochar one-off application on soil physicochemical properties, salt concentration, nutrient availability, enzyme activity, and rice yield of highly saline-alkali paddy soils: based on a 6-year field experiment. Biochar, 2024, 6: 40.

[24] Ju X, Xing G, Chen X, Zhang S, Zhang L, Liu X, Cui Z, Yin B, Christie P, Zhu Z, Zhang F. Reducing environmental risk by improving N management in intensive Chinese agricultural systems. Proc Natl Acad Sci U S A, 2009, 106(9): 3041-3046.

[25] Kravchenko AN, Snapp SS, Robertson GP. Field-scale experiments reveal persistent yield gaps in low-input and organic cropping systems. Proc Natl Acad Sci U S A, 2017, 114(5): 926-931.

[26] Li HR, Song XT, Bakken LR, Ju XT. Reduction of N₂O emissions by DMPP depends on the interactions of nitrogen sources (digestate vs. urea) with soil properties. J Integr Agric, 2023, 22(1): 251-264.

[27] Li Z, Wang B, Liu Z, Zhang P, Yang B, Jia Z. Ridge–furrow planting with film mulching and biochar addition can enhance the spring maize yield and water and nitrogen use efficiency by promoting root growth. Field Crops Res, 2023, 303. ArticleID: 109139

[28] Liu Q, Zhang Y, Liu B, Amonette JE, Lin Z, Liu G, Ambus P, Xie ZB. How does biochar influence soil N cycle? A meta-analysis. Plant Soil, 2018, 426: 211-225.

[29] Ngaba MJY, Mgelwa AS, Ibrahim MM, Rennenberg H, Hu B. Biochar amendments mitigate soil greenhouse gas emissions by shifted soil properties, enzyme activities, and nitrogen cycling processes. Carbon Res, 2026, 5: 14.

[30] Park MH, Jeong S, Kim JY. Adsorption of NH₃–N onto rice straw-derived biochar. J Environ Chem Eng, 2019, 7(2. ArticleID: 103039

[31] Pokharel P, Chang SX. Biochar decreases the efficacy of the nitrification inhibitor nitrapyrin in mitigating nitrous oxide emissions at different soil moisture levels. J Environ Manage, 2021, 295. ArticleID: 113080

[32] Qi Z, Wang M, Dong Y, He M, Dai X. Effect of coated urease/nitrification inhibitor synergistic urea on maize growth and nitrogen use efficiency. J Soil Sci Plant Nutr, 2022, 22: 5207-5216.

[33] Qiao C, Liu L, Hu S, Compton JE, Greaver TL, Li Q. How inhibiting nitrification affects nitrogen cycle and reduces environmental impacts of anthropogenic nitrogen input. Glob Change Biol, 2015, 21(3): 1249-1257.

[34] Ren B, Huang Z, Liu P, Zhao B, Zhang J. Urea ammonium nitrate solution combined with urease and nitrification inhibitors jointly mitigate NH₃ and N₂O emissions and improves nitrogen efficiency of summer maize under fertigation. Field Crops Res, 2023, 296. ArticleID: 108909

[35] Shen J, Tang H, Liu J, Wang C, Li Y, Ge T, Jones DL, Wu J. Contrasting effects of straw and straw-derived biochar amendments on greenhouse gas emissions within double rice cropping systems. Agric Ecosyst Environ, 2014, 188: 264-274.

[36] Shen J, Li Y, Wang Y, Li Y, Zhu X, Jiang W, Li Y, Wu J. Soil N cycling and environmental impacts in the subtropical hilly region of China: evidence from measurements and modeling. Front Agric Sci Eng, 2022, 9(3): 407-424

[37] Smerald A, Kraus D, Rahimi J, Fuchs K, Kiese R, Butterbach-Bahl K, Scheer C. A redistribution of nitrogen fertiliser across global croplands can help achieve food security within environmental boundaries. Commun Earth Environ, 2023, 4: 315.

[38] Song Y, Zhang X, Ma B, Chang SX, Gong J. Biochar addition affected the dynamics of ammonia oxidizers and nitrification in microcosms of a coastal alkaline soil. Biol Fertil Soils, 2014, 50: 321-332.

[39] Song L, Wang A, Li Z, Kang R, Walters WW, Pan Y, Quan Z, Huang S, Fang Y. Large seasonal variation in nitrogen isotopic abundances of ammonia volatilized from a cropland ecosystem and implications for regional NH₃ source partitioning. Environ Sci Technol, 2024, 58(2): 1177-1186.

[40] Troy SM, Lawlor PG, O’Flynn CJ, Healy MG. Impact of biochar addition to soil on greenhouse gas emissions following pig manure application. Soil Biol Biochem, 2013, 60: 173-181.

[41] Uwiragiye Y, Wang J, Huang Y, Wu L, Zhou J, Zhang Y, Chen M, Jing H, Qian Y, Elrys AS, Cheng Y, Cai Z, Xu M, Chang SX, Müller C. Global ecosystem nitrogen cycling reciprocates between land-use conversion and its reversal. Glob Change Biol, 2024, 30(10. ArticleID: e17537

[42] Wang C, Shen J, Liu J, Qin H, Yuan Q, Fan F, Hu Y, Wang J, Wei W, Li Y, Wu J. Microbial mechanisms in the reduction of CH₄ emission from double rice cropping system amended by biochar: a 4-year study. Soil Biol Biochem, 2019, 135: 251-263.

[43] Wang L, O’Connor D, Rinklebe J, Ok YS, Tsang DCW, Shen Z, Hou D. Biochar aging: mechanisms, physicochemical changes, assessment, and implications for field applications. Environ Sci Technol, 2020, 54(23): 14797-14814.

[44] Wang C, Li Z, Shen J, Li Y, Chen D, Bolan N, Li Y, Wu J. Biochar amendment increases the abundance and alters the community composition of diazotrophs in a double rice cropping system. Biol Fertil Soils, 2023, 59: 873-886.

[45] Wang J, Sha Z, Zhang J, Qin W, Xu W, Goulding K, Liu X. Improving nitrogen fertilizer use efficiency and minimizing losses and global warming potential by optimizing applications and using nitrogen synergists in a maize-wheat rotation. Agric Ecosyst Environ, 2023, 353. ArticleID: 108538

[46] Wang J, Wang B, Bian R, He W, Liu Y, Shen G, Xie H, Feng Y. Bibliometric analysis of biochar-based organic fertilizers in the past 15 years: focus on ammonia volatilization and greenhouse gas emissions during composting. Environ Res, 2024, 243. ArticleID: 117853

[47] Wang M, He P, Fan D, Jiang R, Zou G, Song D, Zhang L, Zhang Y, He W. Trade-offs between agronomic and environmental benefits: a comparison of inhibitors with controlled release fertilizers in global maize systems. Field Crops Res, 2025, 323. ArticleID: 109768

[48] Wu Y, Li Y, Fu X, Liu X, Shen J, Wang Y, Wu J. Three-dimensional spatial variability in soil microorganisms of nitrification and denitrification at a row-transect scale in a tea field. Soil Biol Biochem, 2016, 103: 452-463.

[49] Wu Y, Li F, Zheng H, Hong M, Hu Y, Zhao B, De H. Effects of three types of soil amendments on yield and soil N balance of maize-wheat rotation system in the Hetao Irrigation Area, China. J Arid Land, 2019, 11: 904-915.

[50] Wu Y, Li Y, Wang H, Wang Z, Fu X, Shen J, Wang Y, Liu X, Meng L, Wu J. Response of N₂O emissions to biochar amendment on a tea field soil in subtropical central China: a 3-year field experiment. Agric Ecosyst Environ, 2021, 318. ArticleID: 107473

[51] Xia L, Lam SK, Chen D, Wang J, Tang Q, Yan X. Can knowledge-based N management produce more staple grain with lower greenhouse gas emission and reactive nitrogen pollution? a meta-analysis. Glob Change Biol, 2017, 23(5): 1917-1925.

[52] Xu Q, Yang Y, Hu K, Chen J, Djomo SN, Yang X, Knudsen MT. Economic, environmental, and emergy analysis of China’s green tea production. Sustain Prod Consum, 2021, 28: 269-280

[53] Yang Z, Liu W, Fan X, Gao H, Xu X, Liu C, Chai Y, Zhang M, Drosos M, Shan S. The molecular composition of soil organic matter is regulated by bacterial community under biochar application. Geoderma, 2025, 457. ArticleID: 117308

[54] Yi W, Liu G, Wang M, Wang J, Chen D, Shen J. Increased nitrogen deposition and airborne particulate matter pollution in the vicinity of intensive animal farms caused by ammonia emissions. Agric Ecosyst Environ, 2025, 387. ArticleID: 109634

[55] Zaman M, Saggar S, Blennerhassett JD, Singh J. Effect of urease and nitrification inhibitors on N transformation, gaseous emissions of ammonia and nitrous oxide, pasture yield and N uptake in grazed pasture system. Soil Biol Biochem, 2009, 41(6): 1270-1280.

[56] Zhang C, Song X, Zhang Y, Wang D, Rees RM, Ju X. Using nitrification inhibitors and deep placement to tackle the trade-offs between NH₃ and N₂O emissions in global croplands. Glob Change Biol, 2022, 28(14): 4409-4422.

[57] Zhong L, Wang P, Gu Z, Song Y, Cai X, Yu G, Xu X, Kuzyakov Y. Biochar reduces N₂O emission from fertilized cropland soils: a meta-analysis. Carbon Res, 2025, 4: 31.

[58] Zhou X (2017) Influence of biochemical inhibitor combination on nitrogen transformation in yellow clayey soil and its ecological environment effect. PhD dissertation, Zhejiang University

[59] Zhu X, Shen J, Li Y, Liu X, Wu W, Zhou F, Wang J, Reis S, Wu J. Nitrogen emission and deposition budget in an agricultural catchment in subtropical central China. Environ Pollut, 2021, 289. ArticleID: 117870

[60] Zou ZH, Shen C, Li X, Zhang LP, Zhang L, Han WY, Yan P. Status quo of nitrogen fertilizer application and loss in tea garden of China. Plant Nutr Fertil Sci, 2021, 27: 153-160

Funding

National Natural Science Foundation of China(42161144002)

National Key Research and Development Program of China(2017YFD1700801)

RIGHTS & PERMISSIONS

The Author(s)