南亚热带三种典型植被土壤动物对模拟N沉降增加的早期响应

A field-scale experiment arranged in a complete randomized block design with three N addition treatments including a control （no addition of N）, a low N （5 g m^-2 year^-1）, and a medium N （10 g m^-2 year^-1） was performed in each of the three typical forests, a pine （Pinus massoniana Lamb.） forest （PF）, a pine-broadleaf mixed forest （MF） and a mature monsoon evergreen broadleaf forest （MEBF）, of the Dinghushan Biosphere Reserve in subtropical China to study the response of soil fauna community to additions of N. Higher NH4^＋ and NO3^- concentrations and a lower soil pH occurred in the medium N treatment of MEBF, whereas the NO3^- concentration was the lowest in PF after the additions of N. The response of the density, group abundance and diversity index of soil fauna to addition of N varied with the forest type, and all these variables decreased with increasing N under MEBF but the trend was opposite under PF. The N treatments had no significant effects on these variables under MF. Compared with the control plots, the medium N treatment had significant negative effect on soil fauna under MEBF. The group abundance of soil fauna increased significantly with additions of higher N rates under PF. These results suggested that the response of soil fauna to N deposition varied with the forest type and N deposition rate, and soil N status is one of the important factors affecting the response of soil fauna to N deposition.     

Short-term CO2 emissions from planted soil subject to elevated CO2 and simulated precipitation

Carbon dioxide emissions from soils beneath canopies of two Mediterranean plants, Artemisia absinthium L. and Festuca pratensis Huds. cv. Demeter, were monitored over a 7-day period that included an artificial precipitation event of 4 cm. The experiments were conducted using 0.2 m³ soil microcosms inside greenhouses with CO₂ concentrations of either 360 or 500 μmol mol⁻¹. Carbon dioxide flux from the soil surface, as calculated using a diffusive transport model agreed well with CO₂ flux measurements made using a dynamic flow system. Soil CO₂ emissions did not differ significantly between the 360 and 500 μmol mol⁻¹ CO₂ treatments when soils were dry (volumetric soil moisture content ≤9%). A simulated precipitation event caused an immediate exhalation of CO₂ from soil, after which CO₂ emissions declined slightly and remained constant for approximately 36 h. CO₂ emissions from soil microcosms with F. pratensis plants growing in 500 μmol mol⁻¹ CO₂ then rose to levels that were significantly greater than CO₂ emissions from soils in the microcosms exposed to 360 μmol mol⁻¹ CO₂. For A. absinthium growing in 500 μmol mol⁻¹ CO₂, the rise in soil CO₂ emissions following the wetting event was not significantly greater than emissions from soils with A. absinthium growing under 360 μmol mol⁻¹ CO₂. A. absinthium above ground biomass increased by 46.1 ± 17.9% (mean ± S.E., n = 4, P ≤ 0.05). Above ground biomass did not significantly increase for F. pratensis (14.4 ± 6.5%, P ≥ 0.10). Root biomass, on the other hand, increased for both species; by 50.6 ± 17.9% (P ≤ 0.05) for A. absinthium and by 55.9 ± 12.7% (P ≤ 0.05) for F. pratensis. Our results demonstrate two events following precipitation onto dry soils, an immediate release of CO₂ followed by a gradual increase from enhanced biological activity The gradual increase was greater for the herbaceous ruderal perennial F. pratensis under elevated CO₂.     

Responses of CO2 and N2O emissions from soil-plant systems to simulated warming and acid rain in cropland

Journal of Soils and Sediments - Climate warming is anticipated to change the terrestrial carbon/nitrogen cycle through its impact on the fluxes of greenhouse gases such as CO2 and N2O. This study...     

冻融交替对土壤CO2及N2O释放效应的研究进展

在秋冬交替和冬春交替时期高纬度地区和高海拔生态系统表层土壤常有冻融交替频繁发生。由于冻融交替作用通过改变土壤水热性质而对土壤物理、化学、生物学特性产生效应。冻结通常导致土壤团聚体破裂、微生物细胞及细根死亡,释放出活性较高的有机物,增强随后融解的土壤的反硝化和呼吸活性,从而影响土壤生物、生物化学过程以及生物地化循环。已有对苔原、泰加林等北极和亚北极生态系统的研究表明,土壤冻融交替次数、冻融极端温度、土壤水分、土壤团聚体结构变化等对CO2和N2O的释放通量影响较为显著,一般在冻融的最初几个循环温室气体排放会增加,随后会降至一个较为稳定的水平。目前,冻融循环变化背景下的温室气体排放研究主要是针对北方高纬度地区,而且对冻融交替影响土壤温室气体排放的机理研究也不够。我国面积广大的青藏高原高海拔地带在全球增温背景下,轻微增温会导致季节性冻土表层冻融交替次数增加,甚至冻土季节消失,加强全球增温背景下我国高山亚高山季节性冻土生态系统效应和过程研究,特别是土壤暖化导致的温室气体排放变化通量和变化机理的研究,对揭示全球变化的区域效应以及高海拔生态系统的管理都具有重要作用。     

Linkages between soil micro-site properties and CO2 and N2O emissions during a simulated thaw for a northern prairie Mollisol

Biologically derived emissions of carbon dioxide (CO₂) and nitrous oxide (N₂O) at 0 °C vary with soil depth during soil thawing. Micro-site soil properties, especially those which influence porosity and substrate availability, also vary with depth and may help explain gas emissions. Intact soil cores collected to a depth of 80 cm from an undisturbed prairie Mollisol in central North Dakota were uniformly subjected to distinct temperature steps during a simulated soil thaw (−15 to 5 °C) and sampled for CO₂ and N₂O emissions throughout the soil profile. Emission data were fit to a first order exponential equation (E = αe^βT). Cores were then analyzed in 10 cm depth increments for micro-site properties including root length and mass, aggregation, and organic substrate availability (available, aggregate-protected and mineral-bound pools). Both CO₂ and N₂O emissions at 0 °C declined exponentially with depth. Emissions of CO₂ and N₂O at 0 °C were strongly related to root length (R² = 0.80 and 0.76, respectively), root mass (R² = 0.56 and 0.74), large macroaggregate mass (R² = 0.63 and 0.54), and aggregate-protected organic matter (R² > 0.57), while available organic matter was related to CO₂ (R² > 0.60) and not N₂O. When CO₂ and N₂O emissions were normalized by available and aggregate-protected carbon pools, respectively, nutrient use efficiency increased significantly with depth. Results suggest CO₂ and N₂O emissions are (1) positively influenced by the rhizosphere and (2) differentially affected by substrate pool or location. CO₂ emissions were more positively affected by available substrate, while N₂O emissions were more positively affected by less labile, aggregate-protected substrate.     

Multistate assessment of wetland restoration on CO2 and N2O emissions and soil bacterial communities

Over the last 200 years, wetlands have been converted to other land uses leading to the loss of approximately 53% of wetlands in the continental United States. In the late 1980's, policies were instated to mitigate further wetland loss through wetland creation and restoration. Restored wetlands provide important ecosystem services, such as filtration of nutrients and wildlife habitat. However, these benefits could be offset by increased greenhouse gas production. We assessed the impact of wetland conversion to agriculture and restoration on CO₂ and N₂O emissions and microbial communities in three land use types: wetlands with native vegetation (natural); wetlands converted to agricultural management (converted); and restored wetlands (restored). Soil properties varied among land use types. Most notably, soils from restored and converted sites had the lowest C and N, and higher pH. Multivariate analysis of soil properties showed the pocosin wetlands in North Carolina separating from all other locations, regardless of land use. Soil bacterial communities showed a similar trend with communities from North Carolina soils separating from the others with no significant effect of land use or season. Furthermore, land use did not have a significant effect on CO₂ or N₂O emissions, although there was significant temporal variation in CO₂ emissions. These findings indicate that while wetland conversion and restoration may alter some soil properties, these alterations do not appear to be great enough to override the underlying geographic and edaphic influences on soil bacterial communities. Furthermore, wetland restoration did not lead to increased N₂O emission at the dates sampled.     

CO2 and N2O emissions in response to dolomite application are moisture dependent in an acidic paddy soil

Journal of Soils and Sediments - Liming is the most widely used agricultural practice for acidic paddy soils amelioration, which is usually applied before rice transplanting. Both liming and soil...     

Biogenic emissions of CO2 and N2O at multiple depths increase exponentially during a simulated soil thaw for a northern prairie Mollisol

The fate of carbon (C) and nitrogen (N) belowground is important to current and future climate models as soils warm in northern latitudes. Currently, little is known about the sensitivity of microbial respiration to temperature changes at depths below 15 cm. We used whole-core (7.6 cm dia. × 90 cm) laboratory incubations to determine if temperature response quotients (Q₁₀) for CO₂ and N₂O varied with depth for undisturbed prairie while plants were senescent and clipped at the surface. We collected intact soil cores from an undisturbed prairie in central North Dakota and uniformly subjected them to freezing (5 to ?15 °C) and thawing (?15 to 5 °C). We measured rates of CO₂ and N₂O emissions at 5 °C temperature increments at 0, 15, 30, 45, 60, and 75 cm depths. During freezing, active and sterilized core emissions occurred only between 0 and ?10 °C. During thawing, a simple first-order exponential model, E = αe^βT, fit observed CO₂ and N₂O emissions (R² = 0.91 and 0.99, respectively). Parameter estimates for β were not significantly different across depths for CO₂ and for N₂O (Q₁₀ = 4.8 and 13.7, respectively). Parameter estimates for α (emissions when temperature is 0 °C) exponentially declined with depth for both gases for similar depth-response curves. Stepwise regressions of soil properties on α parameter estimates indicated emissions of CO₂ and N₂O at 0 °C during thawing were positively correlated (R² > 0.6) with soil porosity. Results indicate pedogenic properties associated with depth may not necessarily influence temperature response curves during thawing but will affect emissions at 0 °C for both CO₂ and N₂O.     

Soil engineering ants increase CO2 and N2O emissions by affecting mound soil physicochemical characteristics from a marsh soil: A laboratory study

As ecosystem engineers, ants can mediate soil processes and functions by producing biogenic structures. In their mounds, ants not only directly produce CO₂ by respiration, but may also indirectly impact soil greenhouse gas emissions by affecting substrate availability and soil physicochemical characteristics. Recent studies focused on overall gas production from ant mounds. However, little is known about mound material respiration and N₂O emissions in ant mounds in wetlands. We measured CO₂ and N₂O emissions from mound soils of three different ant species (Lasius niger Linnaeus, Lasius flavus Fabricius, and Formica candida Smith) and natural marsh soils in a laboratory incubation experiment. On the whole, average soil CO₂ and N₂O emission rates from ant mounds were significantly higher than from the natural marsh soils. Over the 64 days incubation, the cumulative soil CO₂ and N₂O production from ant mounds was, respectively, 1.5–3.0 and 1.9–50.2 times higher than from the natural soils. Soil gas emissions from ant mounds were significantly influenced by the specific ant species, with soil CO₂ and N₂O emissions from L. niger mounds being higher than those from F. candida or L. flavus mound soils. Cumulative CO₂ and N₂O emissions from ant mound soils were positively correlated with soil clay, total carbon, dissolved organic carbon, total nitrogen and NH₄⁺ content. Our laboratory results indicated that mound soil is an important source of CO₂ and N₂O emission from ant mounds in marshes, making mounds potential “hot spots” for CO₂ and N₂O emissions. Ants may increase the spatial heterogeneity of soil gas emissions by changing mound soil physicochemical properties, especially carbon and nutrition content, and soil texture. Contributions from ant mound materials should be considered when describing soil C and N cycles and their driving factors in wetland ecosystems.     

不同种植模式对黄壤烟田 N2O排放的影响

为探明烤烟-玉米轮作和烤烟连作在黄壤烟田N_2O排放变化特征,并探明不同环境因子对其排放通量的影响。2016年于贵州省烟草科学研究院龙岗长期养分定位试验站,采用静态箱—气相色谱法测定了N_2O含量,试验共设3个处理,不施任何肥料+轮作(CK);常规施肥+轮作(CR);常规施肥+连作(CC)。试验结果表明,烤烟生长季,各施肥处理的黄壤烟田N_2O排放均有2次高峰,峰值主要出现在烤烟施基肥后3～5 d和追肥后1～7 d,其中施基肥后N_2O排放累积量占整个生长季N_2O排放累积量的比例较高,范围为16.26%～18.30%。各个处理N_2O平均排放通量的顺序是CCCRCK,其平均排放通量分别为0.044、0.022和0.013 mg·m~(-2)·h~(-1);相同施肥量条件下,烤烟连作较轮作N_2O排放总量提高了2倍,烤烟生物量降低了30.01%。相关分析表明,施肥+轮作的烟田N_2O排放通量与土壤硝态氮含量有关(P0.05)。黄壤烟田轮作后显著降低了土壤N_2O排放量,合理轮作是降低黄壤烟田温室气体N_2O排放的重要途径。     

Simulated warming and low O2 promote N2O and N2 emissions in subtropical montane forest soil

Journal of Soils and Sediments - The montane subtropical forest soils contain huge nitrogen stocks, and climate warming might drive its volatilization due to the promotion of gaseous losses of...     

Pig slurry treatment modifies slurry composition,N2O,and CO2 emissions after soil incorporation

The treatment of manures may improve their agricultural value and environmental quality, for instance with regards to greenhouse gases mitigation and enhancement of carbon (C) sequestration. The present study verified whether different pig slurry treatments (i.e. solid/liquid separation and anaerobic digestion) changed slurry composition. The effect of the slurry composition on N₂O and CO₂ emissions, denitrification and soil mineral nitrogen (N), after soil incorporation, was also examined during a 58-day mesocosm study. The treatments included a non-treated pig slurry (NT), the solid fraction (SF), and the liquid fraction (LF) of a pig slurry and the anaerobically digested liquid fraction (DG). Finally, a non-fertilized (N0) and a treatment with urea (UR) were also present.The N₂O emissions measured represented 4.8%, 2.6%, 1.8%, 1.0% and 0.9% of N supplied with slurry/fertilizer for NT, LF, DG, SF and UR, respectively. Cumulative CO₂ emissions ranged from 0.40 g CO₂-C kg^?1 soil (0.38 Mg CO₂-C ha^?1) to 0.80 g CO₂-C kg^?1 soil (0.75 Mg CO₂-C ha^?1). They were highest for SF (56% of C applied), followed by NT (189% of C applied), LF (337% of C applied) and DG (321% of C applied). Ammonium was detected in the soil for all treatments only at day one, while nitrate concentration increased linearly from day 15 to day 58, at a rate independent of the type of slurry/fertilizer applied. The nitrate recovery at day 58 was 39% of the N applied for NT, 19% for SF, 52% for LF, 67% for DG, and 41% for UR. The solid fraction generally produced higher potential denitrification fluxes (75.3 for SF, 56.7 for NT, 53.6 for LF, 47.7 for DG and 39.7 mg N₂O + N₂-N kg^?1 soil for UR). The high variability of actual denitrification results obfuscated any treatment effect.We conclude that treatment strongly affects slurry composition (mainly its C, fibre and NH₄⁺ content), and hence N₂O and CO₂ emission patterns as well as denitrification processes and nitrate availability. In particular, the solid fraction obtained after mechanical separation produced the most pronounced difference, while the liquid fraction and the anaerobically digested liquid fraction did not show significant difference with respect to the original slurry for any of the measured parameters. Combining data from the different fractions we showed that separation of slurry leads to reduced N₂O emissions, irrespective of whether the liquid fraction is digested or not. Furthermore, our results suggested that the default emission factor for N₂O emissions inventory is too low for both the non-treated pig slurry and its liquid fraction (digested or not), and too high for the separated solid fraction and urea.     

Earthworm-induced N2O emissions in a sandy soil with surface-applied crop residues

Earlier research with endogeic and epigeic earthworm species in loamy arable soil has shown that both earthworm groups can increase nitrous oxide (N₂O) emissions, provided that crop residue placement matches the feeding strategy of the earthworm ecological group(s). However, it is not yet clear whether these effects also occur in sandy soils which typically contain less soil organic matter and have low soil aggregation levels. Here, we aimed to quantify N₂O emissions as affected by endogeic and/or epigeic earthworm species, and to relate changes in N₂O emissions to earthworm-induced changes in soil properties in a sandy soil. A 90 day mesocosm study was conducted with sandy soil and ¹⁵N-labeled radish (Raphanus sativus cv. Adagio L.) residue applied on top. Treatments included: (i) no earthworm addition, (ii) addition of the endogeic species Aporrectodea caliginosa (Savigny), (iii) addition of the epigeic species Lumbricus rubellus (Hoffmeister), and (iv) both species combined. An additional treatment was included without earthworms and with residue manually incorporated into the soil. L. rubellus significantly increased cumulative N₂O emissions from 228 to 859 μg N₂O–N kg^?1 (F_1,12 = 83.12, P < 0.001), whereas A. caliginosa did not affect N₂O emissions. In contrast to earlier studies in loamy soil, no positive interaction between both species with regard to N₂O emissions was found. This was probably related to high competition for organic resources in the relatively poor soil and a low potential for stable soil aggregate formation (and associated anaerobic microsites) by endogeic worms in sandy soil. ¹⁵N isotope analysis revealed that the activity of L. rubellus significantly increased (F_1,12 = 6.20, P = 0.028) the recovery of ¹⁵N in the 250–8000 μm size fraction, indicating incorporation of crop residues into the mineral soil. When residues were manually incorporated, N₂O emissions were significantly (P < 0.008) lower (509 μg N₂O–N kg^?1) than when incorporated by L. rubellus. The high N₂O emissions in the presence of L. rubellus, when compared to manual mixing, suggest a stimulation of microbial activity and/or changes in the microbial community composition. Insights on the earthworm effects on N₂O emission from such soils are discussed.     

Interactions between earthworms and mesofauna has no significant effect on emissions of CO2 and N2O from soil

Soil fauna can significantly affect soil CO₂ and N₂O emissions, but little is known about interactions between faunal groups and their relative contribution to such emissions. Over a 64-day microcosm incubation, we studied the effects of an epigeic earthworm (Eisenia fetida), mesofauna (Collembola plus oribatid mites) and their combinations on soil CO₂ and N₂O emissions under two faunal densities. Earthworms significantly enhanced soil CO₂ and N₂O emissions, while mesofauna only increased N₂O emissions. Soil CO₂ and N₂O emissions were significantly affected by earthworm density, but not by mesofauna density. No significant interactive effects between earthworms and mesofauna were found on soil CO₂ and N₂O emissions. Our results indicate that earthworms probably play the dominant roles in determining soil CO₂ and N₂O emissions where they coexist with soil mesofauna.     

Quantifying soil N pools and N2O emissions after application of chemical fertilizer and straw to a typical chernozem soil

Biology and Fertility of Soils - An incubation experiment with equivalent N rates was conducted for 56&nbsp;days using a typical black soil amended with chemical fertilizer with or without...     

Elevated CO2 and O3 modify N turnover rates,but not N2O emissions in a soybean agroecosystem

In order to predict and mitigate future climate change, it is essential to understand plant-mediated effects of elevated CO₂ (eCO₂) and O₃ (eO₃) on N-cycling, including N₂O emissions. This is of particular interest for agroecosystems, since N-cycling and N₂O emissions are responsive to adaptive management. We investigated the interaction of soil moisture content with eCO₂ and eO₃ on potential N₂O emissions from SoyFACE during a 28-day laboratory incubation experiment. We also assessed field N₂O fluxes during 2 soybean-growing seasons. In addition, we sought to link previously observed changes in soybean growth and production to belowground processes over a longer time scale by analyzing changes in natural abundance stable isotope ratios of soil N (δ¹⁵N). This method relies on the concept that soil δ¹⁵N can only change when inputs or outputs with an isotope signature different from that of soil N are altered. We found no major effects of eCO₂ and eO₃ on laboratory and field measured N₂O emissions. Natural abundance isotope analyses suggested, however, a decrease in belowground allocation of biologically fixed N in combination with decreased total gaseous N loss by eCO₂, resulting in a tighter N cycle in the longer-term. In contrast, the isotope data suggested an increase in belowground allocation of biologically fixed N under eO₃, leading to increased gaseous N loss, most likely in the form of N₂. Given that effects of eCO₂ and eO₃ on N pools and instantaneous transformation rates in surface soil layers of this agroecosystem have been minimal, our results illustrate the importance of evaluating longer-term changes in N turnover rates. We conclude that eCO₂ decelerates whereas eO₃ accelerates N-cycling in the longer-term, but feedback through changed N₂O emissions is not occurring in this soybean system.     

Sheep excreta cause no positive priming of peat-derived CO2 and N2O emissions

Large areas of peatlands in Germany and the Netherlands are affected by drainage and high nitrogen deposition. Sheep grazing is a common extensive management activity on drained peatlands, in particular on nature protection areas. However, input of easily mineralisable material such as sheep excrements could enhance degradation of soil organic carbon (C_org), thereby increasing the effect of these ecosystems on national GHG budgets. Thus, a microcosm experiment on the influence of sheep excreta on GHG emissions from a histic Gleysol with strongly degraded peat was set up. The ¹⁵N and ¹³C stable isotope tracer technique was used to partition sources of CO₂ and N₂O. Labeled sheep faeces and urine were obtained by feeding enriched material. Undisturbed soil columns were treated with surface application of urine, faeces or mixtures of both in different label combinations to distinguish between direct effects and possible priming effects. Incubation was done under stable temperature and precipitation conditions. Fluxes as well as ¹⁵N and ¹³C enrichment of N₂O and CO₂, respectively, were measured for three weeks. Addition of sheep excreta increased emission of total CO₂ in proportion to the added carbon amounts. There was no CO₂ priming in the peat. No effect on CH₄ and N₂O was observed under the aerobic experimental conditions. The N₂O–N source shifted from peat to excreta, which indicates negative priming, but priming was not significant. The results indicate that sheep excreta do not significantly increase GHG emissions from degraded peat soils. Considering the degraded peatland preserving benefits, sheep grazing on peatlands affected by drainage and high nitrogen deposition should be further promoted.     

Nitrogen mineralization and CO2 and N2O emissions in a sandy soil amended with original or acidified pig slurries or with the relative fractions

The following six pig slurries obtained after acidification and/or solid/liquid separation were used in the research: original (S) and acidified (AS) pig slurry, nonacidified (LF) and acidified (ALF) pig slurry liquid fraction, and nonacidified (SF) and acidified (ASF) pig slurry solid fraction. Laboratory incubations were performed to assess the effect of the application of these slurries on N mineralization and CO₂ and N₂O emissions from a sandy soil. Acidification maintained higher NH₄ ⁺-N contents in soil particularly in the ALF-treated soil where NH₄ ⁺-N contents were two times higher than in LF-treated soil during the 55–171-day interval. At the end of the incubation (171 days), 32.9 and 24.2 mg N kg⁻¹ dry soil were mineralized in the ASF- and SF-treated soils, respectively, but no mineralization occurred in LF- and S-treated soils, although acidification decreased N immobilization in ALF- (−25.3 mg N kg⁻¹ soil) and AS- (−12.7 mg N kg⁻¹ soil) compared to LF- (−34.4 mg N kg⁻¹ soil) and S-treated (−18.6 mg N kg⁻¹ soil) soils, respectively. Most of the dissolved CO₂ was lost during the acidification process. More than 90% of the applied C in the LF-treated soil was lost during the incubation, indicating a high availability of the added organic compounds. Nitrous oxide emissions occurred only after day 12 and at a lower rate in soils treated with acidified than nonacidified slurries. However, during the first 61 days of incubation, 1,157 μg N kg⁻¹ soil was lost as N₂O in the AS-treated soil and only 937 in the S-treated soil.     

Biochar suppresses N2O emissions while maintaining N availability in a sandy loam soil

Nitrous oxide (N₂O) from agricultural soil is a significant source of greenhouse gas emissions. Biochar amendment can contribute to climate change mitigation by suppressing emissions of N₂O from soil, although the mechanisms underlying this effect are poorly understood. We investigated the effect of biochar on soil N₂O emissions and N cycling processes by quantifying soil N immobilisation, denitrification, nitrification and mineralisation rates using ¹⁵N pool dilution techniques and the FLUAZ numerical calculation model. We then examined whether biochar amendment affected N₂O emissions and the availability and transformations of N in soils.Our results show that biochar suppressed cumulative soil N₂O production by 91% in near-saturated, fertilised soils. Cumulative denitrification was reduced by 37%, which accounted for 85–95 % of soil N₂O emissions. We also found that physical/chemical and biological ammonium (NH₄⁺) immobilisation increased with biochar amendment but that nitrate (NO₃⁻) immobilisation decreased. We concluded that this immobilisation was insignificant compared to total soil inorganic N content. In contrast, soil N mineralisation significantly increased by 269% and nitrification by 34% in biochar-amended soil.These findings demonstrate that biochar amendment did not limit inorganic N availability to nitrifiers and denitrifiers, therefore limitations in soil NH₄⁺ and NO₃⁻ supply cannot explain the suppression of N₂O emissions. These results support the concept that biochar application to soil could significantly mitigate agricultural N₂O emissions through altering N transformations, and underpin efforts to develop climate-friendly agricultural management techniques.