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Machine learning (ML) is an advanced computer algorithm that simulates the human learning process to solve problems. With an explosion of monitoring data and the increasing demand for fast and accurate prediction, ML models have been rapidly developed and applied in air pollution research. In order to explore the status of ML applications in air pollution research, a bibliometric analysis was made based on 2962 articles published from 1990 to 2021. The number of publications increased sharply after 2017, comprising approximately 75% of the total. Institutions in China and United States contributed half of all publications with most research being conducted by individual groups rather than global collaborations. Cluster analysis revealed four main research topics for the application of ML: chemical characterization of pollutants, short-term forecasting, detection improvement and optimizing emission control. The rapid development of ML algorithms has increased the capability to explore the chemical characteristics of multiple pollutants, analyze chemical reactions and their driving factors, and simulate scenarios. Combined with multi-field data, ML models are a powerful tool for analyzing atmospheric chemical processes and evaluating the management of air quality and deserve greater attention in future.
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Poluentes Atmosféricos , Poluição do Ar , Poluentes Ambientais , Humanos , Estados Unidos , Poluição do Ar/análise , Poluentes Atmosféricos/análise , Aprendizado de Máquina , Poluentes Ambientais/análise , BibliometriaRESUMO
Ammonia (NH3) is an important alkaline reactive nitrogen (Nr) species which is involved in global nitrogen (N) biogeochemical cycling, but which has negative impacts on the environment and human health. In order to better understand and control the NH3 loss potential in soil-upland crop systems in China, an integrated data analysis including 1302 observations from 236 published articles between 1980 and 2021 was conducted. The typical NH3 volatilization rate (AVR) and the main factors influencing AVR in the major Chinese upland crops (maize, wheat, openfield vegetables and greenhouse vegetables and others) were estimated and analyzed. The mean AVR for maize, wheat, openfield vegetables and greenhouse vegetables were 7.8%, 5.3%, 8.4% and 1.8%. The most important influencing factors were fertilizer placement, meteorological conditions (especially temperature and rainfall) and soil properties (especially SOM). Subsurface N application produced a significantly lower AVR compared to surface application. High N recovery efficiency and N agronomic efficiency were generally associated with low AVRs. In conclusion, high N application rates, inefficient application methods and the use of loss-prone N fertilizer types are the main factors responsible for high AVRs in major Chinese croplands.
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Amônia , Fertilizantes , Humanos , Amônia/análise , Volatilização , Fertilizantes/análise , Solo/química , Agricultura/métodos , Nitrogênio/análise , Verduras , China , Zea mays , TriticumRESUMO
Excessive application of chemical nitrogen (N) fertilizer and inefficient N management are still common in the North China Plain, leading to large reactive N (Nr) losses and pollution, threatening environmental security and public health. Three improved N management practices (33% reduction in N applied (OU), OU combined with partial organic fertilizer substitution (UOM) and the urea in UOM amended with a urease inhibitor (ULOM)) together with no N application (CK) and farmers' conventional practice (CU) were tested on a maize-wheat rotation at Quzhou, Hebei, North China Plain (NCP). Nr emissions were related to WFPS (Water Filled Pore Space), soil mineral N (NH4+-N and NO3--N) and soil temperature. Nr emissions and yield-scaled Nr emissions were significantly reduced by partial substitution of organic fertilizer for chemical fertilizer: NH3 emissions were reduced by 55.8-62.4%. Using a urease inhibitor (Limus®), further reduced NH3 emissions by 40.2-64.5%. Yield-scaled NH3 emissions were, on average, reduced by 60.0% and 55.2% in the maize and wheat growing season, respectively, relative to the UOM treatment. Long-term application of organic fertilizer had a significant positive effect on N use efficiency (NUE). Overall, the study shows that appropriated N management such as reducing the N application rate, partial substitution of chemical N by organic N and using a urease inhibitor can reduce Nr emissions and promote NUE in the North China Plain. The methods corresponding to the ULOM and UOM treatments were the most and second most effective, respectively, with high net economic benefits.
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Fertilizantes , Óxido Nitroso , Agricultura/métodos , China , Produtos Agrícolas , Fertilizantes/análise , Nitrogênio/análise , Solo , Triticum , Urease , Zea maysRESUMO
China is experiencing intense air pollution caused in large part by anthropogenic emissions of reactive nitrogen. These emissions result in the deposition of atmospheric nitrogen (N) in terrestrial and aquatic ecosystems, with implications for human and ecosystem health, greenhouse gas balances and biological diversity. However, information on the magnitude and environmental impact of N deposition in China is limited. Here we use nationwide data sets on bulk N deposition, plant foliar N and crop N uptake (from long-term unfertilized soils) to evaluate N deposition dynamics and their effect on ecosystems across China between 1980 and 2010. We find that the average annual bulk deposition of N increased by approximately 8 kilograms of nitrogen per hectare (P < 0.001) between the 1980s (13.2 kilograms of nitrogen per hectare) and the 2000s (21.1 kilograms of nitrogen per hectare). Nitrogen deposition rates in the industrialized and agriculturally intensified regions of China are as high as the peak levels of deposition in northwestern Europe in the 1980s, before the introduction of mitigation measures. Nitrogen from ammonium (NH4(+)) is the dominant form of N in bulk deposition, but the rate of increase is largest for deposition of N from nitrate (NO3(-)), in agreement with decreased ratios of NH3 to NOx emissions since 1980. We also find that the impact of N deposition on Chinese ecosystems includes significantly increased plant foliar N concentrations in natural and semi-natural (that is, non-agricultural) ecosystems and increased crop N uptake from long-term-unfertilized croplands. China and other economies are facing a continuing challenge to reduce emissions of reactive nitrogen, N deposition and their negative effects on human health and the environment.
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Poluentes Atmosféricos/análise , Poluição do Ar/análise , Ecossistema , Monitoramento Ambiental/estatística & dados numéricos , Nitrogênio/análise , Poluentes Atmosféricos/metabolismo , Poluentes Atmosféricos/provisão & distribuição , Poluição do Ar/estatística & dados numéricos , Animais , China , Efeito Estufa , Atividades Humanas , Humanos , Nitratos/análise , Nitratos/metabolismo , Nitrogênio/metabolismo , Plantas/química , Plantas/metabolismo , Compostos de Amônio Quaternário/análise , Compostos de Amônio Quaternário/metabolismoRESUMO
Atmospheric nitrogen (N) deposition has been shown to decrease biodiversity and change nutrient cycles in terrestrial ecosystems. However, our understanding of ecological responses to chronic N addition and ecological recovery of grassland from N enrichment is limited. Here we present evidence from an 11-year grassland experiment with a range of N addition rates (0, 30, 60, 120, 240, and 480 kg N·ha-1 ·yr-1 ) in Inner Mongolia, China. Chronic N addition led to a reduction in species richness, Shannon diversity index, and soil pH and an increase in aboveground biomass, foliar N, and soil mineral N. High N addition rates (240 and 480 kg N·ha-1 ·yr-1 ) showed significant effects in the first and second years, which stabilized over time. Nitrogen addition at low rates (30 and 60 kg N·ha-1 ·yr-1 ) took longer (e.g., three years or more) to achieve significant effects. The negative impacts of high N addition (480 kg N·ha-1 ·yr-1 ) were reduced and species richness, Shannon diversity index, and soil pH showed a limited but rapid recovery with the cessation of N addition. Our findings suggest serious and cumulative impacts of N addition on plant and soil communities but the potential for partial system recovery over time if N inputs decline or cease.
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Biodiversidade , Fertilizantes , Pradaria , Ciclo do Nitrogênio , Mongólia , Plantas/química , Solo/químicaRESUMO
China accounts for a third of global nitrogen fertilizer consumption. Under an International Panel on Climate Change (IPCC) Tier 2 assessment, emission factors (EFs) are developed for the major crop types using country-specific data. IPCC advises a separate calculation for the direct nitrous oxide (N2O) emissions of rice cultivation from that of cropland and the consideration of the water regime used for irrigation. In this paper we combine these requirements in two independent analyses, using different data quality acceptance thresholds, to determine the influential parameters on emissions with which to disaggregate and create N2O EFs. Across China, the N2O EF for lowland horticulture was slightly higher (between 0.74% and 1.26% of fertilizer applied) than that for upland crops (values ranging between 0.40% and 1.54%), and significantly higher than for rice (values ranging between 0.29% and 0.66% on temporarily drained soils, and between 0.15% and 0.37% on un-drained soils). Higher EFs for rice were associated with longer periods of drained soil and the use of compound fertilizer; lower emissions were associated with the use of urea or acid soils. Higher EFs for upland crops were associated with clay soil, compound fertilizer or maize crops; lower EFs were associated with sandy soil and the use of urea. Variation in emissions for lowland vegetable crops was closely associated with crop type. The two independent analyses in this study produced consistent disaggregated N2O EFs for rice and mixed crops, showing that the use of influential cropping parameters can produce robust EFs for China.
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Biodiesel Co-Product (BCP) is a complex organic material formed during the transesterification of lipids. We investigated the effect of BCP on the extracellular microbial matrix or 'extracellular polymeric substance' (EPS) in soil which is suspected to be a highly influential fraction of soil organic matter (SOM). It was hypothesised that more N would be transferred to EPS in soil given BCP compared to soil given glycerol. An arable soil was amended with BCP produced from either 1) waste vegetable oils or 2) pure oilseed rape oil, and compared with soil amended with 99% pure glycerol; all were provided with 15N labelled KNO3. We compared transfer of microbially assimilated 15N into the extracellular amino acid pool, and measured concomitant production of exopolysaccharide. Following incubation, the 15N enrichment of total hydrolysable amino acids (THAAs) indicated that intracellular anabolic products had incorporated the labelled N primarily as glutamine and glutamate. A greater proportion of the amino acids in EPS were found to contain 15N than those in the THAA pool, indicating that the increase in EPS was comprised of bioproducts synthesised de novo. Moreover, BCP had increased the EPS production efficiency of the soil microbial community (µg EPS per unit ATP) up to approximately double that of glycerol, and caused transfer of 21% more 15N from soil solution into EPS-amino acids. Given the suspected value of EPS in agricultural soils, the use of BCP to stimulate exudation is an interesting tool to consider in the theme of delivering sustainable intensification.
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Atmosfera , Nitrogênio , Poluentes Atmosféricos , China , Ecossistema , Monitoramento Ambiental , Humanos , Estados UnidosRESUMO
Metal pollutants in fine particulate matter (PM2.5) are physiologically toxic, threatening ecosystems through atmospheric deposition. Biotoxicity and bioavailability are mainly determined by the active speciation of metal pollutants in PM2.5. As a megacity in China, Beijing has suffered severe particulate pollution over the past two decades, and the health effects of metal pollutants in PM2.5 have received significant attention. However, there is a limited understanding of the active forms of metals in PM2.5 and their ecological risks to plants, soil or water in Beijing. It is essential that the ecological risks of metal pollutants in PM2.5 are accurately evaluated based on their bioavailability, identifying the key pollutants and revealing historic trends to future risks control. A two-year project measured the chemical speciation of pollution elements (As, Cd, Cu, Cr, Ni, Mn, Pb, Sb, Sr, Ti, and Zn) in PM2.5 in Beijing, in particular their bioavailability, assessing ecological risks and identifying key pollutants. The mass concentrations of total and active species of pollution elements were 199.12 ng/m3 and 114.97 ng/m3, respectively. Active fractions accounted for 57.7 % of the total. Cd had the highest active proportion. Based on the risk assessment code (RAC), most pollution elements except Ti had moderate or high ecological risk, with RAC exceeding 30 %. Cd, with an RAC of 70 %, presented the strongest ecological risk. Comparing our data with previous research shows that concentrations of pollution elements in PM2.5 in Beijing have decreased over the past decade. However, although the total concentrations of Cd in PM2.5 have decreased by >50 % over the past decade, based on machine model simulation, its ecological risk has reduced by only 10 %. Our research shows that the ecological risks of pollution elements remain high despite their decreasing concentrations. Controlling the active species of metal pollutants in PM2.5 in Beijing in the future is vital.
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Poluentes Atmosféricos , Monitoramento Ambiental , Metais , Material Particulado , Material Particulado/análise , Medição de Risco , Pequim , Poluentes Atmosféricos/análise , Metais/análise , Disponibilidade BiológicaRESUMO
The effectiveness of national policies for air pollution control has been demonstrated, but the relative effectiveness of short-term emission reduction measures in comparison with national policies has not. Here we show that short-term abatement measures during important international events substantially reduced PM2.5 concentrations, but air quality rebounded to pre-event levels after the measures ceased. Long-term adherence to strict emission reduction policies led to successful decreases of 54% in PM2.5 concentrations in Beijing, and 23% in atmospheric nitrogen deposition in China from 2012 to 2020. Incentivized by "blue skies" type campaigns, economic development and reactive nitrogen pollution are quickly decoupled, showing that a combination of inspiring but aggressive short-term measures and effective but durable long-term policies delivers sustainable air quality improvement. However, increased ammonia concentrations, transboundary pollutant flows, and the complexity to achieving reduction targets under climate change scenarios, underscore the need for the synergistic control of multiple pollutants and inter-regional action.
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Atmospheric reactive nitrogen (Nr) deposition has been modified significantly by human activities such as agriculture and fossil fuel combustion. Understanding the changes in Nr deposition is essential for maintaining the functionality and sustainability of ecosystems. Taking Beijing as a case study, we report long-term measurements of wet Nr deposition from 1999 to 2022 and dry Nr deposition from 2010 to 2022 and their relationship with China's air pollution control. Total Nr deposition to Beijing decreased by 34 % during 2010-2022, mainly caused by a decrease in dry N deposition by 54.27 %, from 47.86 kg N ha-1 yr-1 in 2010-2014 to 21.89 kg N ha-1 yr-1 in 2018-2022; reduced and oxidized N in dry deposition decreased by 29.93 % and 72.05 %, respectively. This was a result of the "Action Plan for Prevention and Control of Air Pollution (APCP)" and the implementation of the "Zero Growth in Fertilizer Use by 2020" in 2015. Our ground-based measurements provide evidence to support recent achievements in air pollution control and a reference and guidance for other regions of China and other countries for abating Nr pollution.
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Reducing cropland ammonia (NH3) emissions while improving air quality and food supply is a challenge, particularly in China where there are millions of smallholder farmers. We tested the effectiveness of a tailored nitrogen (N) management strategy applied to wheat-maize cropping systems in 'demonstration squares' across Quzhou County in the North China Plain. The N-management techniques included optimal N rates, deep fertilizer placement and application of urease inhibitors, implemented through cooperation between government, researchers, businesses and smallholders. Compared with conventional local smallholder practice, our NH3 mitigation campaign reduced NH3 volatilization from wheat and maize by 49% and 39%, and increased N-use efficiency by 28% and 40% and farmers' profitability by 25% and 19%, respectively, with no detriment to crop yields. County-wide atmospheric NH3 and fine particulate matter (with aerodynamic diameter <2.5 µm) concentrations decreased by 40% and 8%, respectively. County-wide net benefits were estimated at US$7.0 million. Our demonstration-square approach shows that cropland NH3 mitigation and improved air quality and farm profitability can be achieved simultaneously by coordinated actions at the county level.
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Amônia , Fazendeiros , Humanos , Grão Comestível , Fazendas , China , Triticum , Zea maysRESUMO
Air pollution has become one of the main environmental concerns in China since the 1980s due to China's rapid economic growth and resultant pollution. However, it is difficult to directly evaluate the anthropogenic contribution to air pollution in China. The 2008 Olympic Games in Beijing provided a unique opportunity for testing the contribution of anthropogenic pollution because of the clean-up controls on air quality in Beijing enforced over the period of the Games. In this case study, we monitored the concentrations of major air pollutants before, during, and after the Olympics at a suburban site in Beijing. Atmospheric concentrations of PM10, PM2.5, NH3, NO2, SO2, and the particulate ions NH4+, NO3-, SO4(2-) Ca2+, Mg2+, and K+ all decreased during the Olympic period because of strict emission controls, compared with the same period from 2005 to 2007. For example, the average PM10 concentration (61 microg m(-3)) during the Olympics was only 37% of that (166 microg m(-3)) in the same month (August) from 2005 to 2007. However, just 1 mo and 1 yr after the Games had ended, mean concentrations of these pollutants had increased significantly again. This rapid "recovery' of air pollutant concentrations after the Olympics suggests that China needs to implement long-lasting decreases in its air pollution in Beijing and other major cities.
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Poluentes Atmosféricos/química , Poluição do Ar/prevenção & controle , Monitoramento Ambiental/métodos , Esportes , Amônia/química , Atmosfera/análise , China , Dióxido de Nitrogênio/química , Material Particulado , Dióxido de Enxofre/química , Fatores de TempoRESUMO
The Clean Air Action implemented by the Chinese government in 2013 has greatly improved air quality in the North China Plain (NCP). In this work, we report changes in the chemical components of atmospheric fine particulate matter (PM2.5) at four NCP sampling sites from 2012/2013 to 2017 to investigate the impacts and drivers of the Clean Air Action on aerosol chemistry, especially for secondary inorganic aerosols (SIA). During the observation period, the concentrations of PM2.5 and its chemical components (especially SIA, organic carbon (OC), and elemental carbon (EC)) and the frequency of polluted days (daily PM2.5 concentration ≥ 75 µg m-3) in the NCP, declined significantly at all four sites. Asynchronized reduction in SIA components (large decreases in SO42- with stable or even increased NO3- and NH4+) was observed in urban Beijing, revealing a shift of the primary form of SIA, which suggested the fractions of NO3- increased more rapidly than SO42- during PM2.5 pollution episodes, especially in 2016 and 2017. In addition, unexpected increases in the sulfur oxidation ratio (SOR) and the nitrogen oxidation ratio (NOR) were observed among sites and across years in the substantially decreased PM2.5 levels. They were largely determined by secondary aerosol precursors (i.e. decreased SO2 and NO2), photochemical oxidants (e.g. increased O3), temperature, and relative humidity via gas-phase and heterogeneous reactions. Our results not only highlight the effectiveness of the Action Plan for improving air quality in the NCP, but also suggest an increasing importance of SIA in determining PM2.5 concentration and composition.
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Poluentes Atmosféricos , Poluição do Ar , Aerossóis/análise , Poluentes Atmosféricos/análise , Poluição do Ar/análise , Pequim , China , Monitoramento Ambiental , Material Particulado/análise , Estações do AnoRESUMO
China has experienced a dramatic change in atmospheric reactive nitrogen (Nr) emissions over the past four decades. However, it remains unclear how nitrogen (N) deposition has responded to increases and/or decreases in Nr emissions. This study quantitatively assesses temporal and spatial variations in measurements of bulk and calculated dry N deposition in China from 1980 to 2018. A long-term database (1980-2018) shows that bulk N deposition peaked in around 2000, and had declined by 45% by 2016-2018. Recent bulk and dry N deposition (based on monitoring from 2011 to 2018) decreased from 2011 to 2018, with current average values of 19.4 ± 0.8 and 20.6 ± 0.4 kg N ha-1 yr-1, respectively. Oxidized N deposition, especially dry deposition, decreased after 2010 due to NOx emission controls. In contrast, reduced N deposition was approximately constant, with reductions in bulk NH4+-N deposition offset by a continuous increase in dry NH3 deposition. Elevated NH3 concentrations were found at nationwide monitoring sites even at urban sites, suggesting a strong influence of both agricultural and non-agricultural sources. Current emission controls are reducing Nr emissions and deposition but further mitigation measures are needed, especially of NH3, built on broader regional emission control strategies.
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Poluentes Atmosféricos , Nitrogênio , Agricultura , Poluentes Atmosféricos/análise , China , Monitoramento Ambiental , Nitrogênio/análiseRESUMO
Nitrogen (N) fertilizer application and atmospheric N deposition will profoundly affect greenhouse gas (GHGs) emissions, especially nitrous oxide (N2O) and methane (CH4) fluxes and ecosystem respiration (Re, i.e. CO2 emissions). However, the impacts of long-term N inputs and the often associated N-induced soil acidification on GHG fluxes in arid and semi-arid ecosystems, especially temperate grasslands, are still uncertain. An in situ experiment was conducted to investigate the effect of long-term (13-years) N addition on N2O and CH4 fluxes and Re from a temperate grassland in Inner Mongolia, northeast China, from April 2017 to October 2018. Soil pH values in the 0-5â¯cm layer receiving 120 (N120) and 240 (N240) kg N ha-1 decreased from 7.12 to 4.37 and 4.18, respectively, after 13 years of N inputs. Soil CH4 uptake was significantly reduced, but N2O emission was enhanced significantly by N addition. However, N addition had no impact on Re. Structural Equation Modeling indicated that soil NH4+-N content was the dominant control of N2O emissions, but with less effect of the decreasing pH. In contrast, CH4 uptake was generally controlled by soil pH and NO3--N content, and Re by forb biomass. The measured changes in N2O and CH4 fluxes and Re from temperate grassland will have a profoundly impact on climate change.
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Pradaria , Metano/análise , Óxido Nitroso/análise , Dióxido de Carbono/análise , China , Ecossistema , Monitoramento Ambiental , Fertilizantes , Gases de Efeito Estufa , Nitrogênio/farmacologia , Solo/químicaRESUMO
Nitrogen (N) partitioning between plant and soil pools is closely related to biomass accumulation and allocation, and is of great importance for quantifying the biomass dynamics and N fluxes of ecosystems, especially in low N-availability desert ecosystems. However, partitioning can differ among species even when growing in the same habitat. To better understand the variation of plant biomass allocation and N retention within ephemeral and annual species we studied the responses of Malcolmia Africana (an ephemeral) and Salsola affinis (an annual) to N addition, including plant growth, N retention by the plant and soil, and N lost to the environment using 15N (double-labeled 15NH4 15NO3 (5.16% abundance) added at 0, 0.8, 1.6, 3.2, and 6.4 g pot-1, equivalent to 0, 15, 30, 60, and 120 kg N ha-1) in a pot experiment. Higher N addition (N120) inhibited plant growth and biomass accumulation of the ephemeral but not the annual. In addition, the aboveground:belowground partitioning of N (the R:S ratio) of the ephemeral decreased with increasing N addition, but that of the annual increased. The N input corresponding to maximum biomass and 15N retention of the ephemeral was significantly less than that of the annual. The aboveground and belowground retention of N in the ephemeral were significantly less than those of the annual, except at low N rates. The average plant-soil system recovery of added 15N by the ephemeral was 70%, significantly higher than that of the annual with an average of 50%. Although the whole plant-soil 15N recovery of this desert ecosystem decreased with increasing N deposition, our results suggested that it may vary with species composition and community change under future climate and elevated N deposition.
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The electronic Rothamsted Archive, e-RA (www.era.rothamsted.ac.uk) provides a permanent managed database to both securely store and disseminate data from Rothamsted Research's long-term field experiments (since 1843) and meteorological stations (since 1853). Both historical and contemporary data are made available via this online database which provides the scientific community with access to a unique continuous record of agricultural experiments and weather measured since the mid-19th century. Qualitative information, such as treatment and management practices, plans and soil information, accompanies the data and are made available on the e-RA website. e-RA was released externally to the wider scientific community in 2013 and this paper describes its development, content, curation and the access process for data users. Case studies illustrate the diverse applications of the data, including its original intended purposes and recent unforeseen applications. Usage monitoring demonstrates the data are of increasing interest. Future developments, including adopting FAIR data principles, are proposed as the resource is increasingly recognised as a unique archive of data relevant to sustainable agriculture, agroecology and the environment.
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Desert ecosystems are likely to change in response to global climate change and nitrogen (N) deposition. The effects of increased precipitation and N deposition on plant growth and the N cycle largely depend on N allocation and N recovery efficiency in the plant-soil ecosystem, but there is limited research on this in desert ecosystems. Here we report results using double-labeled 15NH415NO3 (30 and 60kgNha-1yr-1) as a tracer under ambient (no additional water addition) and enhanced precipitation (60mm water addition) in a Haloxylon ammodendron dominated ecosystem in the Gurbantunggut Desert of Northwest China. Herbaceous plants were a significantly larger sink for added 15N than the H. ammodendron trees, and N retention varied with water and N addition, relative to growing season precipitation. The retention of added 15N varied within the components of H. ammodendron, with the stems retaining most, followed by the assimilation branches. Soil was the dominant sink for added 15N, in which the topsoil and subsoil respond differently to water and N addition over the two-year period. Nitrogen relative recovery percentage in the whole ecosystem ranged from 43% to 61%, lower than average recovery rate in temperate forests; N tracer recovery percentage significantly increased with water addition but decreased with enhanced N deposition. Future N cycling in central Asian deserts will depend on changes in precipitation.
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Chenopodiaceae/fisiologia , Ecossistema , Monitoramento Ambiental , Ciclo do Nitrogênio , Mudança Climática , Clima Desértico , Nitrogênio/análise , Água/análiseRESUMO
Overuse of urea, low nitrogen (N) utilization, and large N losses are common in maize production in North China Plain (NCP). To solve these problems, we conducted two field experiments at Shangzhuang and Quzhou in NCP to test the ability of a newly developed urease inhibitor product Limus® to decrease NH3 volatilization from urea applied to maize. Grain yield, apparent N recovery efficiency (REN) and N balance when using urea applied with or without Limus were also measured over two maize growing seasons. Cumulative NH3 loss in the two weeks following urea application without Limus ranged from 9-108 kg N ha-1, while Limus addition significantly decreased NH3 loss by a mean of 84%. Urea with Limus did not significantly increase maize yields (P < 0.05) compared with urea alone. However, a significant 11-17% improvement in REN with Limus was observed at QZ. The use of urea-N plus Limus would permit a reduction in N applications of 55-60% compared to farmers' practice and/or further 20% N saving compared with optimized urea-N rate (150 kg N ha-1, based on N requirement by target yield of 7.5 t ha-1), and would achieve the same maize yields but with significantly decreased NH3 loss and increased N utilization.