To study effect of C2H2 and change of headspace gas on N2O emission, denitrification, as well as CO2emission, slumes of an agricultural soil were anaerobically incubated for 7 da3’s at 25 ℃. Both N2O reduction and C...To study effect of C2H2 and change of headspace gas on N2O emission, denitrification, as well as CO2emission, slumes of an agricultural soil were anaerobically incubated for 7 da3’s at 25 ℃. Both N2O reduction and CO2 emissions were inhibited by the addition of 100 mL L-1 of C2H2. However, the inhibition to CO2 emission was alleviated by the replacement of headspace gas, and the N2O emission was enhanced by the replacement. Acetylene disappeared evidently from the soil slumes during the incubation. Consequently results obtained from the traditional C2H2 blocking technique for determination of denitrification rate, especially in a long-time incubation, should be explained with care because of its side effect existing in the incubation environments without change of headspace gas. To reduce the possible side effect on the processes other than denitrification, it is suggested that headspace gas should be replaced several times during a long-time incubation.展开更多
In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were...In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） method, inductively coupled plasma atomic emission spectrometer （ICP-AES）, temperature programmed reduction （H2-TPR）, CO chemisorption, energy dispersive X-ray （EDX） and scanning electron microscopy （SEM） techniques. Kinetic properties of all catalysts were investigated in a batch re- actor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/AlzO3 catalyst enhances its activity as compared to Fe/AlaO3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/AlzO3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fez（MoO4）3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fez（MoO4）3 phase has low reducibility, therefore the Fe2（MoO4）3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.展开更多
The preparation of the iron-based catalysts promoted by cobalt with a small amount of copper and aluminum for the high temperature shift reaction （HTS） with different sequences of adding catalyst raw materials durin...The preparation of the iron-based catalysts promoted by cobalt with a small amount of copper and aluminum for the high temperature shift reaction （HTS） with different sequences of adding catalyst raw materials during neutralization and precipitation was investigated. XRD, BET and particle size distribution （PSD） were used to characterize the prepared catalysts. It was found that the catalyst crystals were all γ-Fe2O3, and the intermediate of the catalyst after aging was Fe3O4. The crystallographic form of the catalyst and its intermediate was not affected by the addition sequence in the neutralization and precipitation process. The results showed that the specific surface area and the particle size of the catalysts depended on the addition sequence to the mother liquor. Cobalt with a small amount of copper and aluminum could increase the specific surface area and decrease the particle size of catalysts.展开更多
Managed peatlands are a significant source of nitrous oxide(N_(2)O),a powerful greenhouse gas and stratospheric ozone depleter.Due to the complexity and diversity of microbial N_(2)O processes,different methods such a...Managed peatlands are a significant source of nitrous oxide(N_(2)O),a powerful greenhouse gas and stratospheric ozone depleter.Due to the complexity and diversity of microbial N_(2)O processes,different methods such as tracer,isotopomer,and microbiological technologies are required to understand these processes.The combined application of different methods helps to precisely estimate these processes,which is crucial for the future management of drained peatlands,and to mitigate soil degradation and negative atmospheric impact.In this study,we investigated N_(2)O sources by combining tracer,isotopomer,and microbial analysis in a drained peatland forest under flooded and drained treatments.On average,the nitrification genes showed higher abundances in the drained treatment,and the denitrification genes showed higher abundances in the flooded treatment.This is consistent with the underlying chemistry,as nitrification requires oxygen while denitrification is anaerobic.We observed significant differences in labelled N_(2)O fluxes between the drained and flooded treatments.The emissions of N_(2)O from the flooded treatment were nearly negligible,whereas the N_(2)O evolved from the nitrogen-15(^(15)N)-labelled ammonium(^(15)NH4+)in the drained treatment peaked at 147μg ^(15)N m^(-2) h^(-1).This initially suggested nitrification as the driving mechanism behind N_(2)O fluxes in drained peatlands,but based on the genetic data,isotopic analysis,and N_(2)O mass enrichment,we conclude that hybrid N_(2)O formation involving ammonia oxidation was the main source of N_(2)O emissions in the drained treatment.Based on the ^(15)N-labelled nitrate(^(15)NO3-)tracer addition and gene copy numbers,the low N_(2)O emissions in the flooded treatment came possibly from complete denitrification producing inert dinitrogen.At atomic level,we observed selective enrichment of mass 45 of N_(2)O molecule under ^(15)NH4+amendment in the drained treatment and enrichment of both masses 45 and 46 under ^(15)NO3-amendment in the flooded treatment.The selective enrichment of mass 45 in the drained treatment indicated the presence of hybrid N_(2)O formation,which was also supported by the high abundances of archaeal genes.展开更多
Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2...Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2)photosynthesis via 2e–oxygen reduction reactions(ORR)remain to be explored for understanding the forming mechanism of active sites.Herein,we report a facile doping method to introduce boron-nitrogen(B–N)bonds into the structure of graphitic carbon nitride(g-C_(3)N_(4))nanosheets(denoted as BCNNS)to provide significant photocatalytic activity,selectivity and stability.The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer.The units are also proved to be superior active sites for selective O_(2)adsorption and activation,reducing the energy barrier for*OOH formation,and thereby enabling an efficient 2e–ORR pathway to H_(2)O_(2).Consequently,with only bare loss of activity during repeated cycles,the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L^(–1)·h^(–1)under 365 nm-monochrome light emitting diode(LED365nm)irradiation,increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts.This work gives the first example of applying B–N bonds to enhance the photocatalytic H_(2)O_(2)production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.展开更多
Nitric oxide reductases(NORs)have a central role in denitrification,detoxification of nitric oxide(NO)in host-pathogen interactions,and NO-mediated cell-cell signaling.In this study,we focus on the phylogeny and detec...Nitric oxide reductases(NORs)have a central role in denitrification,detoxification of nitric oxide(NO)in host-pathogen interactions,and NO-mediated cell-cell signaling.In this study,we focus on the phylogeny and detection of qNOR and cNOR genes because of their nucleotide sequence similarity and evolutionary relatedness to cytochrome oxidases,their key role in denitrification,and their abundance in natural,agricultural,and wastewater ecosystems.We also include nitric oxide dismutase(NOD)due to its similarity to qNOR.Using 548 nor sequences from publicly accessible databases and sequenced isolates from N2O-producng bioreactors,we constructed phylogenetic trees for 289 qnor/nod genes and 259 cnorB genes.These trees contain evidence of horizontal gene transfer and gene duplication,with 13.4%of the sequenced strains containing two or more nor genes.By aligning amino acid sequences for qnor+cnor,qnor,and cnor,we identified four highly conserved regions for NOR and NOD,including two highly conserved histidine residues at the active site for qNOR and cNOR.Extending this approach,we identified conserved sequences for:1)all nor(nor-universal);2)all qnor(qnor-universal)and all cnor(cnor-universal);3)qnor of Comamonadaceae;4)Clade-specific sequences;and 5)nod of Candidates Methylomirabilis oxyfera.Examples of primer performance were confirmed experimentally.展开更多
A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron micro...A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.展开更多
Nitrification inhibitors are widely used in agriculture to mitigate nitrous oxide(N_(2)O)emission and increase crop yield.However,no concrete information on their mitigation of N_(2)O emission is available under soil ...Nitrification inhibitors are widely used in agriculture to mitigate nitrous oxide(N_(2)O)emission and increase crop yield.However,no concrete information on their mitigation of N_(2)O emission is available under soil and environmental conditions as in Pakistan.A field experiment was established using a silt clay loam soil from Peshawar,Pakistan,to study the effect of urea applied in combination with a nitrification inhibitor,nitrapyrin(2-chloro-6-tri-chloromethyl pyridine),and/or a plant growth regulator,gibberellic acid(GA_3),on N_(2)O emission and the nitrogen(N)uptake efficiency of maize.The experimental design was a randomized complete block with five treatments in four replicates:control with no N(CK),urea(200 kg N ha^(-1))alone,urea in combination with nitrapyrin(700 g ha^(-1)),urea in combination with GA_3(60 g ha^(-1)),and urea in combination with nitrapyrin and GA_3.The N_(2)O emission,yield,N response efficiency,and total N uptake were measured during the experimental period.The treatment with urea and nitrapyrin reduced total N_(2)O emission by 39%–43%and decreased yield-scaled N_(2)O emission by 47%–52%,relative to the treatment with urea alone.The maize plant biomass,grain yield,and total N uptake increased significantly by 23%,17%,and 15%,respectively,in the treatment with urea and nitrapyrin,relative to the treatment with urea alone,which was possibly due to N saving,lower N loss,and increased N uptake in the form of ammonium;they were further enhanced in the treatment with urea,nitrapyrin,and GA_3 by 27%,36%,and 25%,respectively,probably because of the stimulating effect of GA_3 on plant growth and development and the reduction in biotic and abiotic stresses.These results suggest that applying urea in combination with nitrapyrin and GA_3 has the potential to mitigate N_(2)O emission,improve N response efficiency,and increase maize yield.展开更多
文摘To study effect of C2H2 and change of headspace gas on N2O emission, denitrification, as well as CO2emission, slumes of an agricultural soil were anaerobically incubated for 7 da3’s at 25 ℃. Both N2O reduction and CO2 emissions were inhibited by the addition of 100 mL L-1 of C2H2. However, the inhibition to CO2 emission was alleviated by the replacement of headspace gas, and the N2O emission was enhanced by the replacement. Acetylene disappeared evidently from the soil slumes during the incubation. Consequently results obtained from the traditional C2H2 blocking technique for determination of denitrification rate, especially in a long-time incubation, should be explained with care because of its side effect existing in the incubation environments without change of headspace gas. To reduce the possible side effect on the processes other than denitrification, it is suggested that headspace gas should be replaced several times during a long-time incubation.
基金Supported by the Iranian Nano Technology Initiative Council and Petroleum University of Technology
文摘In reverse water gas shift （RWGS） reaction COa is converted to CO which in turn can be used to pro- duce beneficial chemicals such as methanol. In the present study, Mo/AlaO3, Fe/AlaO3 and Fe-Mo/Al2O3 catalysts were synthesised using impregnation method. The structures of catalysts were studied using X-ray diffraction （XRD）, Brunauer-Emmett-Teller （BET） method, inductively coupled plasma atomic emission spectrometer （ICP-AES）, temperature programmed reduction （H2-TPR）, CO chemisorption, energy dispersive X-ray （EDX） and scanning electron microscopy （SEM） techniques. Kinetic properties of all catalysts were investigated in a batch re- actor for RWGS reaction. The results indicated that Mo existence in structure of Fe-Mo/AlzO3 catalyst enhances its activity as compared to Fe/AlaO3. This enhancement is probably due to better Fe dispersion and smaller particle size of Fe species. Stability test of Fe-Mo/AlzO3 catalyst was carried out in a fixed bed reactor and a high CO yield for 60 h of time on stream was demonstrated. Fez（MoO4）3 phase was found in the structures of fresh and used catalysts. TPR results also indicate that Fez（MoO4）3 phase has low reducibility, therefore the Fe2（MoO4）3 phase significantly inhibits the reduction of the remaining Fe oxides in the catalyst, resulted in high stability of Fe-Mo/Al2O3 catalyst. Overall, this study introduces Fe-Mo/Al2O3 as a novel catalyst with high CO yield, almost no by-products and fairly stable for RWGS reaction.
文摘The preparation of the iron-based catalysts promoted by cobalt with a small amount of copper and aluminum for the high temperature shift reaction （HTS） with different sequences of adding catalyst raw materials during neutralization and precipitation was investigated. XRD, BET and particle size distribution （PSD） were used to characterize the prepared catalysts. It was found that the catalyst crystals were all γ-Fe2O3, and the intermediate of the catalyst after aging was Fe3O4. The crystallographic form of the catalyst and its intermediate was not affected by the addition sequence in the neutralization and precipitation process. The results showed that the specific surface area and the particle size of the catalysts depended on the addition sequence to the mother liquor. Cobalt with a small amount of copper and aluminum could increase the specific surface area and decrease the particle size of catalysts.
基金supported by the Ministry of Education and Science of Estonia(No.SF0180127s08)the Estonian Research Council(Nos.IUT2-16,PRG-352,and MOBERC20)+1 种基金the European Union through the European Regional Development Fund(Estonian EcolChange Centre of Excellence,Estonia,and MOBTP101 returning researcher grant by the Mobilitas Pluss programme)the European Social Fund(Doctoral School of Earth Sciences and Ecology).
文摘Managed peatlands are a significant source of nitrous oxide(N_(2)O),a powerful greenhouse gas and stratospheric ozone depleter.Due to the complexity and diversity of microbial N_(2)O processes,different methods such as tracer,isotopomer,and microbiological technologies are required to understand these processes.The combined application of different methods helps to precisely estimate these processes,which is crucial for the future management of drained peatlands,and to mitigate soil degradation and negative atmospheric impact.In this study,we investigated N_(2)O sources by combining tracer,isotopomer,and microbial analysis in a drained peatland forest under flooded and drained treatments.On average,the nitrification genes showed higher abundances in the drained treatment,and the denitrification genes showed higher abundances in the flooded treatment.This is consistent with the underlying chemistry,as nitrification requires oxygen while denitrification is anaerobic.We observed significant differences in labelled N_(2)O fluxes between the drained and flooded treatments.The emissions of N_(2)O from the flooded treatment were nearly negligible,whereas the N_(2)O evolved from the nitrogen-15(^(15)N)-labelled ammonium(^(15)NH4+)in the drained treatment peaked at 147μg ^(15)N m^(-2) h^(-1).This initially suggested nitrification as the driving mechanism behind N_(2)O fluxes in drained peatlands,but based on the genetic data,isotopic analysis,and N_(2)O mass enrichment,we conclude that hybrid N_(2)O formation involving ammonia oxidation was the main source of N_(2)O emissions in the drained treatment.Based on the ^(15)N-labelled nitrate(^(15)NO3-)tracer addition and gene copy numbers,the low N_(2)O emissions in the flooded treatment came possibly from complete denitrification producing inert dinitrogen.At atomic level,we observed selective enrichment of mass 45 of N_(2)O molecule under ^(15)NH4+amendment in the drained treatment and enrichment of both masses 45 and 46 under ^(15)NO3-amendment in the flooded treatment.The selective enrichment of mass 45 in the drained treatment indicated the presence of hybrid N_(2)O formation,which was also supported by the high abundances of archaeal genes.
基金supported by the Jiangsu Provincial Double-Innovation Doctor Program(JSSCBS20210996).
文摘Metal-free catalyst for photocatalytic production of H_(2)O_(2)is highly desirable with the long-term vision of artificial photosynthesis of solar fuel.In particular,the specific chemical bonds for selective H_(2)O_(2)photosynthesis via 2e–oxygen reduction reactions(ORR)remain to be explored for understanding the forming mechanism of active sites.Herein,we report a facile doping method to introduce boron-nitrogen(B–N)bonds into the structure of graphitic carbon nitride(g-C_(3)N_(4))nanosheets(denoted as BCNNS)to provide significant photocatalytic activity,selectivity and stability.The theoretical calculation and experimental results reveal that the electron-deficient B–N units serving as electron acceptors improve photogenerated charge separation and transfer.The units are also proved to be superior active sites for selective O_(2)adsorption and activation,reducing the energy barrier for*OOH formation,and thereby enabling an efficient 2e–ORR pathway to H_(2)O_(2).Consequently,with only bare loss of activity during repeated cycles,the optimal H2O2 production rate by BCNNS photocatalysts reaches 1.16 mmol·L^(–1)·h^(–1)under 365 nm-monochrome light emitting diode(LED365nm)irradiation,increasing nearly 2–5 times as against the state-of-art metal-free photocatalysts.This work gives the first example of applying B–N bonds to enhance the photocatalytic H_(2)O_(2)production as well as unveiling the underlying reaction pathway for efficient solar-energy transformations.
基金supported in part by a grant from the US National Science Foundation Engineering Research Center Reinventing the Nation's Urban Water Infrastructure(ReNUWIt)(Award No.EEC-1028968)in part by a grant from the NASA Center(USA)for the Utilization of Biological Engineering in Space(CUBES)(Award No.NNX17AJ31G).
文摘Nitric oxide reductases(NORs)have a central role in denitrification,detoxification of nitric oxide(NO)in host-pathogen interactions,and NO-mediated cell-cell signaling.In this study,we focus on the phylogeny and detection of qNOR and cNOR genes because of their nucleotide sequence similarity and evolutionary relatedness to cytochrome oxidases,their key role in denitrification,and their abundance in natural,agricultural,and wastewater ecosystems.We also include nitric oxide dismutase(NOD)due to its similarity to qNOR.Using 548 nor sequences from publicly accessible databases and sequenced isolates from N2O-producng bioreactors,we constructed phylogenetic trees for 289 qnor/nod genes and 259 cnorB genes.These trees contain evidence of horizontal gene transfer and gene duplication,with 13.4%of the sequenced strains containing two or more nor genes.By aligning amino acid sequences for qnor+cnor,qnor,and cnor,we identified four highly conserved regions for NOR and NOD,including two highly conserved histidine residues at the active site for qNOR and cNOR.Extending this approach,we identified conserved sequences for:1)all nor(nor-universal);2)all qnor(qnor-universal)and all cnor(cnor-universal);3)qnor of Comamonadaceae;4)Clade-specific sequences;and 5)nod of Candidates Methylomirabilis oxyfera.Examples of primer performance were confirmed experimentally.
基金financially supported by the National Natural Science Foundation of China (Nos. 51004060, 51104074, and 51174105)the Natural Science Foundation of Yunnan Province (No. 2010ZC018)
文摘A series of Fe2O3/Al2O3, Fe2O3/CeO2, Ce0.7Zr0.3O2, and Fe2O3/Ce1-xZrxO2（x = 0.1–0.4） oxides was prepared and their physicochemical features were investigated by X-ray diffraction（XRD）, transmission electron microscope（TEM）, and H2-temperature-programmed reduction（H2-TPR） techniques. The gas–solid reactions between these oxides and methane for syngas generation as well as the catalytic performance for selective oxidation of carbon deposition in O2-enriched atmosphere were investigated in detail. The results show that the samples with the presence of Fe2O3show much higher activity for methane oxidation compared with the Ce0.7Zr0.3O2solid solution,while the CeO2-contained samples represent higher CO selectively in methane oxidation than the Fe2O3/Al2O3sample. This suggests that the iron species should be the active sites for methane activation, and the cerium oxides provide the oxygen source for the selective oxidation of the activated methane to syngas during the reaction between methane and Fe2O3/Ce0.7Zr0.3O2. For the oxidation process of the carbon deposition, the CeO2-containing samples show much higher CO selectivity than the Fe2O3/Al2O3sample, which indicates that the cerium species should play a very important role in catalyzing the carbon selective oxidation to CO. The presence of the Ce–Zr–O solid solution could induce the growth direction of the carbonfilament, resulting in a loose contact between the carbon filament and the catalyst. This results in abundant exposed active sites for catalyzing carbon oxidation, strongly improving the oxidation rate of the carbon deposition over this sample. In addition, the Fe2O3/Ce0.7Zr0.3O2also represents much higher selectivity（ca. 97 %） for the conversion of carbon to CO than the Fe2O3/CeO2sample, which can be attributed to the higher concentration of reduced cerium sites on this sample. The increase of the Zr content in the Fe2O3/Ce1-xZrxO2samples could improve the reactivity of the materials for methane oxidation, but it also reduces the selectivity for CO formation.
基金funded by the International Atomic Energy Agency through a Coordinated Research Project(CRP D1.50.16)“Minimizing Farming Impacts on Climate Change by Enhancing Carbon and Nitrogen Capture and Storage in Agro-Ecosystems”(18595)of Soil and Water Management and Crop Nutrition Section,Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture,Department of Nuclear Sciences and Applications。
文摘Nitrification inhibitors are widely used in agriculture to mitigate nitrous oxide(N_(2)O)emission and increase crop yield.However,no concrete information on their mitigation of N_(2)O emission is available under soil and environmental conditions as in Pakistan.A field experiment was established using a silt clay loam soil from Peshawar,Pakistan,to study the effect of urea applied in combination with a nitrification inhibitor,nitrapyrin(2-chloro-6-tri-chloromethyl pyridine),and/or a plant growth regulator,gibberellic acid(GA_3),on N_(2)O emission and the nitrogen(N)uptake efficiency of maize.The experimental design was a randomized complete block with five treatments in four replicates:control with no N(CK),urea(200 kg N ha^(-1))alone,urea in combination with nitrapyrin(700 g ha^(-1)),urea in combination with GA_3(60 g ha^(-1)),and urea in combination with nitrapyrin and GA_3.The N_(2)O emission,yield,N response efficiency,and total N uptake were measured during the experimental period.The treatment with urea and nitrapyrin reduced total N_(2)O emission by 39%–43%and decreased yield-scaled N_(2)O emission by 47%–52%,relative to the treatment with urea alone.The maize plant biomass,grain yield,and total N uptake increased significantly by 23%,17%,and 15%,respectively,in the treatment with urea and nitrapyrin,relative to the treatment with urea alone,which was possibly due to N saving,lower N loss,and increased N uptake in the form of ammonium;they were further enhanced in the treatment with urea,nitrapyrin,and GA_3 by 27%,36%,and 25%,respectively,probably because of the stimulating effect of GA_3 on plant growth and development and the reduction in biotic and abiotic stresses.These results suggest that applying urea in combination with nitrapyrin and GA_3 has the potential to mitigate N_(2)O emission,improve N response efficiency,and increase maize yield.
