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