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Enhancing movement options for confined dairy cows, like in tie-stall housing, may boost natural behaviour and welfare. Yet, limited data exists on the environmental impact of both indoor and outdoor exercise areas. This study investigates the impact of exercise pen type on effluent properties and gas emissions during winter and/or summer conditions in a northern country such as Canada. Forty-five Holstein dairy cows were randomly assigned to three treatments: (1) no exercise [cows kept indoors with tie-stalls (TSs)]; (2) indoor exercise [access to a 28 m2 cow−1 indoor pen (IP) for 1.5 h d−1] and (3) outdoor exercise [access to a 28 m2 cow−1 outside nonaerated (OnAP) or aerated stand-off pad (OAP) for 1.5 h d−1]. The effluent composition of OnAP and OAP varied notably between seasons. In winter, OAP leachates showed higher biological oxygen demand (+89 %), pH (+1.2 units), ammonium (+96 %) and total solids (+50 %), lower faecal but higher total coliforms (−120 % and +20 %, respectively) than OnAP during summer. In addition, OAP presented higher biological and chemical oxygen demand (+80 %) than OnAP in both seasons. Both OAP and OnAP showed higher carbon dioxide emissions (+150 %) and lower methane emissions during summer (−200 %) than IP and TS. Nitrous oxide emissions were higher for OnAP (+600 %) than in OAP, IP and TS, with no changes in ammonia emissions across treatments. Outdoor exercise for dairy cows using a filtering pen didn't meet environmental limits for removing leached contaminants. Exercise pens raised carbon dioxide and nitrous oxide emissions but decreased methane emissions. • Non-aerated, aerated pads served as seasonal exercise areas for tie-stall cows. • Efficient woodchip matrix filters pad leachates by removing contaminants. • Aeration failed to enhance leachate contaminant removal in the stand-off pad. • Outside exercise pens reduce greenhouse gas emissions from dairy housing surfaces. [ABSTRACT FROM AUTHOR]

The mechanisms by which large-scale microbial community function emerges from complex ecological interactions between individual taxa and functional groups remain obscure. We leveraged network analyses of 16S rRNA amplicon sequences obtained over a seven-month timeseries in seasonally anoxic Saanich Inlet (Vancouver Island, Canada) to investigate relationships between microbial community structure and water column N2O cycling. Taxa separately broadly into three discrete subnetworks with contrasting environmental distributions. Oxycline subnetworks were structured around keystone aerobic heterotrophs that correlated with nitrification rates and N2O supersaturations, linking N2O production and accumulation to taxa involved in organic matter remineralization. Keystone taxa implicated in anaerobic carbon, nitrogen, and sulfur cycling in anoxic environments clustered together in a low-oxygen subnetwork that correlated positively with nitrification N2O yields and N2O production from denitrification. Close coupling between N2O producers and consumers in the anoxic basin is indicated by strong correlations between the low-oxygen subnetwork, PICRUSt2-predicted nitrous oxide reductase (nosZ) gene abundances, and N2O undersaturation. This study implicates keystone taxa affiliated with common ODZ groups as a potential control on water column N2O cycling and provides a theoretical basis for further investigations into marine microbial interaction networks. Network analysis of 16S rRNA-sequencing data collected over six months in the Sannich Inlet on Vancouver Island, Canada, suggests keystone microbial taxa that might contribute to water column N2O production and accumulation. [ABSTRACT FROM AUTHOR]

Canada has targeted a 30% reduction in N 2 O emissions from fertilizer by 2030 in its commitments to reduce greenhouse gas emissions. To help achieve these commitments, a 'Pipes & Valves' conceptual visualization of the DNDC model was combined with the DeNitrification-DeComposition (DNDC) model to evaluate a suite of nutrient management and conservation practices. The objectives were to meet the 30% reduction targets in N 2 O emissions as well as other reactive-N species (N 2 O, NH 3 and NO 3 - leaching) to provide a systems approach while increasing corn yields. This was accomplished by: 1) developing a 'Pipes & Valves' conceptual visualization model; 2) evaluating a full system DNDC model with 3-years of NH 3 volatilization, N 2 O emission, inorganic N, crop yield and N uptake data; 3) applying the 'Pipes & Valves' DNDC system to identify N-management strategies that mitigate N-loss and improve yields. The DNDC model compared simulated and measured N-loss and crop performance over 3 years for N- management practices including pre-plant versus side-dress UAN injection with either no inhibitors, a urease inhibitor or a dual urease and nitrification inhibitor. A Pipe and Valves conceptual visualization model was developed and used with the DNDC model to simulate 14 management scenarios based on moldboard plow tillage versus conservation tillage, and fertilizer management including fertilizer type (urea vs. urea ammonium nitrate, UAN), inhibitor (none, nitrification inhibitor, urease inhibitor or both), placement (broadcast vs. injection), timing (at planting vs. split application), and N rate (recommended vs. 15% reduction). The DNDC model was evaluated using field data and had excellent performance for yields, cumulative N 2 O emissions and soil temperature while soil water predictions were fair using standard performance metrics. Multiple nutrient management and/or conservation tillage practices decreased NH 3 losses by 36–96% compared to broadcast urea. A pre-plant broadcast urea and nitrification inhibitor treatment and a conservation tillage treatment with side-dressed injected UAN with a dual urease and nitrification inhibitor reduced N 2 O losses by 37-40%. Although several management practices reduced one N-loss pathway by ≥ 30%, only side-dress injected UAN with urease plus nitrification inhibitors under conservation tillage achieved multiple reductions of 40%, 93% and 62% in N 2 O, NH 3 and reactive-N, respectively while increasing corn grain yields by 7%. Combining the 'Pipes & Valves' conceptual visualization model with DNDC modelling was effective for determining how 4R nutrient management and conservation tillage can be stacked and used worldwide to meet N-loss reduction targets without compromising yields. • The DeNitrification DeCompositon (DNDC) model successfully predicted corn yield & nitrogen losses. • The Pipes & Valves conceptual visualization model will help mitigate N losses to air and water. • DNDC identified management practices that can reduce N 2 O, NH 3 and reactive-N by ≥30%. • Crop yields can increase by ≥ 10% using nutrient management & conservation practices. • The Pipes & Valves and DNDC model are tools to help reduce world-wide fertilizer N-loss. [ABSTRACT FROM AUTHOR]

Aims: UK-DNDC model was modified to (1) enhance the estimates of soil temperature and N2O emissions in Denitrification Decomposition (DNDC) model by considering snow melt and frozen and unfrozen conditions along with the impacts of water flux density, thermal diffusivity, crop-canopy, snowmelt routine and snow-depth on N2O emission and (2) validate the modified DNDC model against measured data from five experimental cropping sites located in the west Canada. Methods: Heat transfer processes and snowmelt routine of the DNDC have been modified to account for soil heat and water fluxes driven by snowmelt routine and their effects on denitrification and N2O emissions. The modified DNDC model was tested against the data from five sites, Canada. Then, the model was used to predict the spatial and temporal change of snowpack depth, soil temperature and N2O emissions. Results: The validation results show that the modified model predicted daily soil mean temperature and daily N2O fluxes accurately in all seasons with very high average Pearson's correlation coefficients at the three sites (Ravg = 0.91 and 0.85 for soil temperature and N2O emissions, respectively). Conclusions: The modelled N2O emissions were sensitive to snowmelt and freeze-thaw cycle in the cold climate region while the modelled soil temperature was sensitive to water flux. This provides a tool for N2O estimate in Canada and should also be appropriate for utilize in the similar cold climate regions. [ABSTRACT FROM AUTHOR]

The upper troposphere and lower stratosphere (UTLS) region is a highly variable region of the atmosphere and critical for understanding climate. Yet, it remains undersampled in the observational satellite record. Due to recent advances in interferometer and infrared detection technologies, imaging Fourier transform spectrometer (FTS) technology has been identified as a feasible remote sensing approach to obtain the required precision and spatial resolution of atmospheric trace gas composition in the UTLS. Building on the success of instruments such as the Michelson Interferometer for Passive Atmospheric Sounding and gimbaled limb observer for radiance imaging of the atmosphere, the limb imaging Fourier transform spectrometer experiment (LIFE) instrument, of which this paper details the design and performance, is a balloon-borne infrared imaging FTS developed as an early prototype of a low earth orbit satellite instrument. LIFE is constructed primarily with commercially available off-the-shelf components, with a design emphasis on greatly reducing the complexity of the instrument, particularly the cooling requirements, with a minimal reduction in information gain on the target atmospheric greenhouse gases of water vapor, methane, ozone, and nitrous oxide. The developed instrument was characterized through a series of thermal and vacuum tests and validated through a successful demonstration balloon flight during the 2019 Strato-Science campaign in Canada. In the calibration of the data from the balloon flight, an issue was identified regarding a lack of knowledge in the emissivity of the on-board blackbody calibration sources. These systematic effects were minimized through the application of an emissivity ratio determined from the characterization tests where a wider range of known blackbody temperatures were available. Despite this identified calibration issue, the results demonstrate that the instrument is capable of meeting primary performance requirements for trace gas retrievals of the target atmospheric species. [ABSTRACT FROM AUTHOR]

Canadian nitrous oxide (N 2 O) emissions over 2011–2015 are estimated using the CarbonTracker-Lagrange (CT-L) regional inversion. The uncertainty in the whole-country total is high, on the order of 100% or more, with a net flux not significantly different from zero. Emissions are better resolved in Canadian cropland, primarily in Alberta, Saskatchewan, and Manitoba, where the total flux is estimated at 0.08 ± 0.08 Tg N/yr. The uncertainty is improved by the addition of 4 new Canadian sites to the inversion, but remains large, mainly due to the low signal to background ratio at all Canadian N 2 O measurement sites. The seasonal patterns in Canadian cropland emissions suggest a dual maximum, with a late winter freeze-thaw pulse and a growing season flux of similar magnitude. Overall, Canadian cropland accounts for ∼1% of the global anthropogenic N 2 O source according to the inversion, although some process-based models suggest a source more on the order of 2%. • Canadian cropland emits 0.08 ± 0.08 Tg N 2 O–N/yr according to a regional inversion. • This represents ∼1% of the global anthropogenic N 2 O source. • Including 4 new Canadian monitoring sites modestly improves inversion uncertainty. • Canadian cropland N 2 O fluxes have comparable freeze-thaw and growing season peaks. [ABSTRACT FROM AUTHOR]

Spatially explicit, accurate inventories of greenhouse gas (GHG) emissions are of primary importance when calculating the carbon footprint, identifying sources and sinks, pricing carbon pollution, and creating policy that is effective in reducing emissions. However, there are few reports available on methane and nitrous oxide emissions from each type of livestock and crop in all counties of the province due to a lack of statistical data of sub-categories, such as the different fertilizer quantities used in each crop in the county. Because fertilizer input is the most significant factor for N 2 O emissions from agricultural soils, how to best distribute the total fertilizer mass to a crop-specific fertilizer rate for each county is a major challenge in agricultural management. In this study, authors developed a crop-specific method correlating the recommended fertilizer rate and planted area of each crop for a reasonable distribution of total fertilizer mass to fertilizer rate. This is based on a balance between the sum of fertilizer used in all crops and the total fertilizer mass used by each municipality. Using this method, our calculations in 69 municipalities in the province of Alberta, Canada showed that the fertilizer rate for each crop was reasonably distributed from the total fertilizer mass of a municipality: less than 170 kg-N ha−1. The obtained fertilizer rates for each crop in 69 municipalities were used in GHG inventories using IPCC 2006 tier 1 and 2 methods. The total CH 4 and N 2 O emissions from agriculture in all of Alberta in 2011 were 328 Gg CH 4 yr−1 and 23.5 Gg N 2 O yr−1, respectively. The southeastern municipalities generally emitted more CH 4 and N 2 O than northwestern municipalities. The southern municipality of Lethbridge emitted the largest amount of CH 4 and N 2 O of all municipalities (25.3 Gg CH 4 yr−1 (7.70% of total CH 4 of entire Alberta) and 1.26 Gg N 2 O yr−1 (5.40% of total N 2 O of entire Alberta), respectively). This was due to its largest cattle population (414,627 head) and larger synthetic fertilizer input (32,111 ton-N) and planted area (206,077 ha). The second largest CH 4 and N 2 O emission source was also located at the south. The Taber municipality emitted 15.8 Gg CH 4 yr−1 (4.80% of total CH 4 of entire Alberta) and 1.14 Gg N 2 O yr−1 (4.80% of total N 2 O of entire Alberta), respectively. • A method to calculate crop specific fertilizer rates from total fertilizer mass. • Increase of emissions from Northwestern to Southeastern municipalities in Alberta. • CO 2 eq. from CH 4Tot (54% of total CO 2 eq.) higher that from N 2 O Tot. • Direct N 2 O emission larger than indirect emissions. • The maximum N 2 O contribution from synthetic fertilizers in direct emissions. [ABSTRACT FROM AUTHOR]

Greenhouse gas (GHG) emissions from arable soils are released to the atmosphere in the form of nitrous oxide (N 2 O), carbon dioxide (CO 2) and methane (CH 4). These soil emissions were measured from three horticultural production systems in Quebec and Ontario, Canada, for the following crops: (1) cranberry production in an artificial bog on sandy soil; (2) tomato production on a conventionally farmed loamy sand soil; and, (3) onion production on an organic soil. In-situ soil N 2 O, CO 2 and CH 4 fluxes were measured at each site using the non-steady-state static chamber method. Tomato production on the loamy sand and onion production on the organic soils were the greatest producers of soil GHG emissions, with highest global warming potentials of 11,000 kg CO 2 -eq ha−1 and 7800 kg CO 2 -eq ha−1, respectively. The cranberry crop had the lowest global warming potential (2700 kg CO 2 -eq ha−1). Water management (water table depth, subsurface and surface drip irrigation) had a negligible impact on soil GHG emissions. The main factors influencing the production of N 2 O were spring thaw, rate and timing of inorganic fertilizers, and precipitation. Soil CO 2 fluxes were primarily governed by soil temperature. Soil CH 4 fluxes were low, as the soils from all crops were both oxidizing and producing CH 4 simultaneously. Production of CH 4 increased when the cranberry fields were flooded. Organic and mineral soils produced comparable amounts of soil greenhouse gas emissions. • Soil N 2 O flux was influenced by spring thaw, fertilization and rainfall. • Soil CO 2 flux was primarily influenced by soil temperature. • Soil CH 4 emissions were mostly negative indicating that soils were CH 4 sinks. • N 2 O exhibited the greatest site-to-site and temporal variations of the three GHGs. [ABSTRACT FROM AUTHOR]

In eastern Canada, climate change-related warming and increased precipitation may alter winter snow cover, with potential consequences for soil conditions, nitrogen (N) cycling, and microbes. We conducted a 2-year field study aimed at determining the influence of snow removal, snow accumulation, and ambient snow in a potato-barley crop system on the abundance and expression of denitrifier (nirS , nirK , nosZ) and nitrifier (ammonium oxidizing archaeal (AOA) and bacterial (AOB) amoA) genes. Denitrifier and nitrifier abundance and expression results were compared to N2O production, soil atmosphere accumulation, and surface fluxes. In the first winter, nirK abundance was lowest while AOB abundance was greatest in snow accumulation treatments. In the second winter, greatest abundances were observed in the ambient snow treatment, which had greatest N2O accumulation and spring thaw fluxes, suggesting a link between microbial populations and biogeochemical functioning. Treatment effects on gene expression were limited, but greatest AOA, AOB, and nosZ expression was measured near 0°C and above 15°C, indicating that activity was promoted by freeze-thaw conditions and at summer temperatures. Overall, effects of changing snow depth on denitrifier and nitrifier abundance were not solely due to change in soil temperature, but also to soil moisture and/or interactions between these parameters. [ABSTRACT FROM AUTHOR]

The pressure to change agricultural practices in order to mitigate emissions is high, with persisting environmental, social, and economic dimensions. In December 2020, the Government of Canada released A Healthy Environment and a Healthy Economy , a climate plan that proposed Canada's first national emission reduction target for the agricultural sector. This target aimed to reduce fertilizer-based emissions by 30 percent of 2020 levels by 2030. This target relies on the adoption of Best Management Practices for fertilizer use at the on-farm level. Choice to adopt the emission reduction strategies and practices is ultimately decided by the landowner, operator, and/or producer. The proposed target was met with significant resistance opposition from producers and producer groups across Canada's agricultural sector, particularly in western Canada, with claims that the target was the equivalent to a ban on fertilizer. This research aims to better understand the attitudes and perceptions towards the emission reduction target and more generally around emissions mitigation strategies within the crop sectors. This report takes a qualitative approach by conducting 26 h-long interviews with stakeholders along the production chain. Interviews with producers, geneticists, actors in crop inputs and manufacturing, and stakeholders in agricultural production policy and advocacy were conducted over July and August 2022. Participants were asked questions about climate change, the role of different levels of government in the development of emission regulations, potential strategies on a short- and long-term horizon basis, and incentives. Interviews were transcribed and categorically defined, highlighting reoccurring themes. These themes provide insight into awareness of different strategies considered by different actors within the agricultural supply chain, and potentially anticipate avenues which the Government of Alberta should prioritize in developing policies. Ensuring future protocols account for benchmarks of current agricultural operations and management is critical for accessible and producer-inclusive policy, that optimizes transition risks and secures the pathway forward, balancing the precarious equilibrium of burden on agricultural producers, food security, and sustainable, resilient agriculture. • Significant disconnect between government objectives and on-farm operations. • Require re-investment in agricultural extension programs and services. • A need to demonstrate the benefits of adopting certain on-farm strategies. • Need to re-establish trust in the relationship between government and producers. [ABSTRACT FROM AUTHOR]

Forest fires are one of the most important natural disturbances in boreal forests, and their occurrence and severity are expected to increase as a result of climate warming. A combination of factors induced by fire leads to a thawing of the near-surface permafrost layer in subarctic boreal forest. Earlier studies reported that an increase in the active layer thickness results in higher carbon dioxide (CO 2 ) and methane (CH 4 ) emissions. We studied changes in CO 2 , CH 4 and nitrous oxide (N 2 O) fluxes in this study, and the significance of several environmental factors that influence the greenhouse gas (GHG) fluxes at three forest sites that last had fires in 2012, 1990 and 1969, and we compared these to a control area that had no fire for at least 100 years. The soils in our study acted as sources of CO 2 and N 2 O and sinks for CH 4 . The elapsed time since the last forest fire was the only factor that significantly influenced all studied GHG fluxes. Soil temperature affected the uptake of CH 4 , and the N 2 O fluxes were significantly influenced by nitrogen and carbon content of the soil, and by the active layer depth. Results of our study confirm that the impacts of a forest fire on GHGs last for a rather long period of time in boreal forests, and are influenced by the fire induced changes in the ecosystem. [ABSTRACT FROM AUTHOR]

Mitigating the greenhouse gas emissions that arise during the use of livestock manure is a crucial environmental challenge. We evaluated the management effects of liquid manure timing (fall vs. spring) and nitrification inhibitors (NIs) [2-chloro-6-(trichloromethyl) pyridine (nitrapyrin) vs. 3, 4-dimethylpyrazole phosphate (DMPP)] on N2O emissions, soil mineral N transformations, barley (Hordeum vulgare L.) productivity, and N uptake. Eight treatments were established in an incomplete split-plot design in Lacombe and Edmonton, AB, Canada. Repeated measurements included N2O fluxes by manual static chambers, and soil ammonium (NH4-N) and nitrate (NO3-N) concentrations. Relative to the manured soils without NIs, the use of NIs with fall injection significantly reduced annual N2O emissions by 81 % with DMPP and 58% with nitrapyrin in our Lacombe site; however, this difference was not found in the comparable spring treatments applied during the dry growing season. These beneficial effects were discernable in Lacombe, which was relatively wetter than Edmonton, indicating the overriding role of varying moisture on N dynamics and fluxes. Following a 5-mo freezing winter, the spring thaw caused at least 64% of annual N2O emissions from the fall-manured soils, and these intense episodic fluxes also revealed that the efficacy of fall-added NIs still continued during the early spring. On average, fall injections amplified the N2O direct emission factors by about threefold compared with the corresponding spring treatments. Thus implementing liquid manure injections with NIs at the right timing has the potential opportunity to increase N uptake by crops and simultaneously diminish global warming effects. [ABSTRACT FROM AUTHOR]

Urease and/or nitrification inhibitors applied to urine patches or pastures may increase N retention in the soil-plant system, but how N2O emissions respond to these N stabilizers in semiarid regions is poorly understood. The objectives of this research were (i) to quantify N2O emissions and the associated emission factors, based on the percentage of applied urine-N emitted as N2O-N, from beef cattle urine patches (urine) and (ii) to test the N2O reduction potential of three N stabilizers [2-chloro-6(trichloromethyl) pyridine (nitrapyrin), N-(n-butyl)-thiophosphoric triamide (NBPT), and NBPT plus dicyandiamide (DCD)] on a semiarid tame pasture over two grazing seasons in western Canada. A deionized water control was also included. Nitrapyrin reduced cumulative N2O emissions by 39% and the N2O emission factor by 50% compared with untreated urine in a dry grazing season and reduced cumulative N2O emissions by 58% and the N2O emission factor by 68% compared with untreated urine in a grazing season with normal precipitation. The NBPT and NBPT + DCD had similar cumulative N2O emissions compared with untreated urine patches. The N2O emission factors ranged from 0.03 to 0.08% over 103 d in 2015 and from 0.06 to 0.21% over 119 d in 2016, all lower than the 2% Intergovernmental Panel on Climate Change default 365-d value. Extrapolating over 1 -yr periods, N2O emission factors ranged from 0.11 to 0.64%. Based on the N stabilizers tested, nitrapyrin most effectively reduced N2O emissions from beef cattle urine patches on a tame pasture in a nonirrigated semiarid region of Canada. [ABSTRACT FROM AUTHOR]

TheGlenlea long-term study in Manitoba, Canada compares annual grain and forage-grain rotations under organic and conventional management. Organic systems are split into compost manure amended and no compost treatments. The objective of this study was to evaluate selected soil biological parameters over one entire growing season (2011). Microbial biomass carbon (MBC), microbial metabolic quotient (qCO 2 ), and microbial biomass phosphorus (MBP) were measured five times in spring wheat ( Triticum aestivum L.) and compared with a restored prairie grassland system. Significant interactions between management system and sample occasion were attributed to stronger recovery for MBC and MBP after soil rewetting in the organic vs the conventional system. The qCO 2 was lowest (0.37 mg C g MBC h −1 ) under dry mid-summer conditions and highest in late spring and after soil rewetting in fall (1.19 mg C g MBC h −1 ). When qCO 2 levels increased, the increase was greater in the forage-grain than the annual grain rotation. Organic management increased MBC compared with conventional management in the forage-grain rotation (1718 vs 1476 μg g −1 ) but decreased MBC in the annual grain rotation (1080 vs 1115 μg g −1 ). Among the six arable treatments, only the organic treatments in the forage-grain rotation behaved similarly (P > 0.05) to the grassland in terms of MBC, soil respiration and qCO 2 . N 2 O emissions per unit of MBC were 60–80% lower in organic compared with conventional systems. In conclusion, seasonal changes in soil biological C and P parameters were observed. Under conditions conducive to increased soil biological activity, organic systems outperformed conventional systems, especially in the forage-based rotation. [ABSTRACT FROM AUTHOR]

The Holos model is a Canadian whole-farm model that uses IPCC Tier II emission factors to calculate greenhouse gas (GHG) emissions from Canadian farming systems. These Tier II emission factors are Canada-specific with respect to land-based nitrous oxide emission, but are universal with respect to the livestock calculation. Here, however, Tier II is limited to ruminant animals, as so far only Tier I models are available for monogastrics. The model is designed to permit farmers to enter readily available farm management information themselves in order to calculate GHG sources and management driven mitigation practices. The presentation will provide an overview of the model and its design (interface and algorithms), and will showcase some of the scientific studies (cradleto-farmgate) that were accomplished using the Holos model for assessing the carbon footprint of Canadian beef and dairy production systems. [ABSTRACT FROM AUTHOR]

Background and aims: Approximately 50 % of belowground organic carbon is present in the northern permafrost region and due to changes in climate there are concerns that this carbon will be rapidly released to the atmosphere. The release of carbon in arctic soils is thought to be intimately linked to the N cycle through the N cycle's influence on microbial activity. The majority of new N input into arctic systems occurs through N-fixation; therefore, N-fixation may be the key driver of greenhouse gases from these ecosystems. Methods: At Alexandra Fjord lowland, Ellesmere Island, Canada concurrent measurements of N-fixation, N mineralization and nitrification rates, dissolved organic soil N (DON) and C, inorganic soil N and surface greenhouse gas fluxes (CO, NO and CH) were taken in two ecosystem types (Wet Sedge Meadow and Dryas Heath) over the 2009 growing season (June-August). Using Structural Equation Modelling we evaluated the hypothesis that CO, CH and NO flux are linked to N-fixation via the N cycle. Results: The soil N cycle was linked to CO flux in the Dryas Heath ecosystem via DON concentrations, but there was no link between the soil N cycle and CO flux in the Wet Sedge Meadow. Methane flux was also not linked to the soil N cycle, nor surface soil temperature or moisture in either ecosystem. The soil N cycle was closely linked to NO emissions but via nitrification in the Wet Sedge Meadow and inorganic N in the Dryas Heath, indicating the important role of nitrification in net NO flux from arctic ecosystems. Conclusions: Our results should be interpreted with caution given the high variability in both the rates of the N cycling processes and greenhouse gas flux found in both ecosystems over the growing season. However, while N-fixation and other N cycling processes may play a more limited role in instantaneous CO emissions, these processes clearly play an important role in controlling NO emissions. [ABSTRACT FROM AUTHOR]

Abstract: Agricultural soils are a significant anthropogenic source of nitrous oxide (N2O) to the atmosphere. Despite likely having large emissions of N2O, there are no continuous multi-year studies of emissions from poorly drained floodplain soil. In the present study, the micrometeorological flux of N2O (F N ) was measured over three years (2006–2008) in a maize (Zea mays L.)/faba (Vicia faba minor L.)/spring-wheat (Triticum aestivum L.) rotation in the Red River Valley, Manitoba, Canada on a gleyed humic verticol soil. Comparison of newly established reduced and intensive tillage treatments showed no difference in F N within the constraints of the high variability between duplicate plots. The annual gap-filled ΣF N across tillage treatments was 5.5, 1.4, and 4.3kgNha−1 in the maize, faba, and spring-wheat crop years, respectively. Emissions from fertilizer N addition and soil thaw the following spring was responsible for the greater ΣF N in the maize and spring-wheat years. Using four approaches to approximate background ΣF N resulted in estimates of 3.5–3.8% and 1.4–1.8% of applied fertilizer N emitted as N2O for the maize and spring-wheat crops, respectively. The CO2 global warming potential equivalent of ΣF N over the three study years was an emission of 5.4MgCO2-equiv.ha−1 which adds to the previously determined C balance emission of 11.6MgCO2-equiv.ha−1. [Copyright &y& Elsevier]

Drainage and cultivation of organic soils often result in large nitrous oxide (N2O) emissions. The objective of this study was to assess the impacts of nitrogen (N) fertilizer on N2O emissions from a cultivated organic soil located south of Montréal, QC, Canada, drained in 1930 and used since then for vegetable production. Fluxes of N2O were measured weekly from May 2004 to November 2005 when snow cover was absent in irrigated and non-irrigated plots receiving 0, 100 or 150 kg N ha−1 as NH4NO3. Soil mineral N content, gas concentrations, temperature, water table height and water content were also measured to help explain variations in N2O emissions. Annual emissions during the experiment were large, ranging from 3.6 to 40.2 kg N2O-N ha−1 year−1. The N2O emissions were decreased by N fertilizer addition in the non-irrigated site but not in the irrigated site. The absence of a positive influence of soil mineral N content on N2O emissions was probably in part because up to 571 kg N ha−1 were mineralized during the snow-free season. Emissions of N2O were positively correlated to soil CO2 emissions and to variables associated with the extent of soil aeration such as soil oxygen concentration, precipitation and soil water table height, thereby indicating that soil moisture/aeration and carbon bioavailability were the main controls of N2O emission. The large N2O emissions observed in this study indicate that drained cultivated organic soils in eastern Canada have a potential for N2O-N losses similar to, or greater than, organic soils located in northern Europe. [ABSTRACT FROM AUTHOR]

Abstract: Research is ongoing to develop ways to reduce emissions of greenhouse gases (GHGs) from agricultural sources. A convenient technique to estimate emissions is to develop emission factors for a wide range of management practices. Default emission factors such as those given in the Intergovernmental Panel on Climate Change Tier I methodology are often used but these can result in substantial errors when applied to specific geographical regions. In this paper an interface was developed to link soil, climate and agricultural activity data in Canada with the DeNitrification and DeComposition (DNDC) model to create a modeling tool for estimating emission factors for changes in agricultural management. This tool was also designed to calculate country-specific IPCC Tier II emission factors for comparison against modeled results. The DNDC-Management Factor Tool (DNDC-MFT) was developed to automatically generate soil, climate and agricultural management model input data from national databases for estimating emissions factors for any of 462 ecodistricts across Canada. Six ecodistricts were selected across the major climatic regions to test the tool. The emission factors generated by the DNDC model were significantly different from Tier II values. Much variability in N2O emission estimates exist, partly due to limitations in certain biophysical processes in the model and partly due to quality of input data. The DNDC model is very sensitive to climate, size of initial soil C levels, and fertilizer application rates. We should also keep in mind that there is uncertainly associated with Tier II emission factors. The combined N2O and soil C factors estimated by the DNDC model are generally comparable to values that are being used to estimate Canada''s national inventory (Tier II/III) but only the tillage factor was found to be statistically similar. The DNDC-MFT will be useful for testing the ability of the DNDC model to generate GHG emission factors for many management scenarios across varying climatic regions in Canada. The framework can be extended to include improved versions of DNDC and other ecosystem models. [Copyright &y& Elsevier]

Abstract: The characteristic feature of the Prairie Pothole Region is a complex assemblage of mineral soil wetlands embedded in the dominantly agricultural landscape. Soils in these wetlands are loci of high potential greenhouse gas (GHG) emissions, and our objective was to provide estimates of greenhouse gas emissions and the controls on these emissions for typical wetlands of this region. Three years (2004–06) of N2O and CH4 emissions were taken from a large semi-permanent pond and five ephemeral freshwater mineral soil wetlands at the St. Denis National Wildlife Area (SDNWA) near Saskatoon, Saskatchewan, Canada. Methane emissions from the semi-permanent pond were low (ranging from 0.04 to 3.33g CH4 m−2 yr-1) but emissions from landscape elements of the ephemeral ponds were substantially higher, with a maximum of 138.6g CH4 m−2 yr−1 (or approximately 110g CH4 m−2 yr−1 when corrected for mid-day sampling bias) from basin centers of these ponds in 2005. The average annual CH4 emissions averaged across the three elements of the ephemeral ponds at SDNWA were 54.8g CH4 m−2 yr−1 in 2005 and 32.4g CH4 m−2 yr−1 in 2006. Methane emissions were significantly inversely correlated to SO4 2 concentrations of the pond water, which are in turn related to the balance between surface runoff and groundwater inputs into the ponds. The semi-permanent pond consistently had low annual N2O emissions (<0.4kg N2O–N ha−1 yr−1). N2O emissions from landscape elements within the ephemeral ponds showed considerable inter-annual variation, ranging from 0.09 to 1.0kg N2O–N ha−1 yr−1 for riparian grass elements, 0.3 to 0.6kg N2O–N ha−1 yr−1 for riparian tree, and 1.0 to 2.1kg N2O–N ha−1 yr−1 for basin centers. Major N2O emission events in the wetland elements were associated with periods of rapid drainage (i.e., from greater than 80% to less than 60% water-filled pore space) in the upper 15cm of the soil. Within-year patterns of N2O and CH4 emissions from soils of the ephemeral ponds were closely related to a second hydrological control, the area and duration of inundation in the ponds but negligible differences were observed between riparian grass and tree elements. The strong interactions between hydrology, water chemistry, and emissions of N2O and CH4 demonstrate the need for a landscape-scale assessment of GHG processes in these landscapes. [Copyright &y& Elsevier]

To establish the major controls on N2O consumption by forest soils, we conducted laboratory incubations of 16 samples from four soil types, two organic and two mineral, varying in overlying forest vegetation (sugar maple, American beech and eastern hemlock). The fastest potential consumption of N2O occurred under anoxic conditions with little soil nitrate and under elevated headspace N2O concentration. Potential N2O consumption rates were fastest in organic soils under hemlock and beech trees (111 and 75 ng N2O-N g-1 d-1, respectively) compared to mineral soils under beech and maple trees (45 and 41 ng N2O-N g-1 d-1). Organic soils showed faster N2O consumption rates than mineral soils, possibly due to larger organic C levels and higher C:N ratios. Acetylene treatment confirmed that denitrification was the process underlying N2O consumption. These results suggest that soils regularly consume N2O with varying magnitude, most likely in anoxic microsites throughout the soil profile and that the potential for N2O consumption is larger in organic than in mineral forest soils. [ABSTRACT FROM AUTHOR]

In Canada, the piggery industry is an essential part of the agricultural sector, but the main waste product of this industry, swine slurry, is particularly harmful to the environment. The anaerobic storage conditions and the excessive use of slurry for agricultural fertilization contribute, respectively, to the emission of greenhouse gases and to aquatic pollution. This paper provides a review of these environmental concerns and of the existing mitigation technologies. Water pollution from swine slurry is associated with the nutrients it contains, such as nitrogen and phosphorous, while the main greenhouse gases produced by the piggery industry are methane and nitrous oxide. Available technologies can valorize the slurry through agricultural fertilization, reduce greenhouse gas emissions, by limiting nutrient availability for example, or treat the effluents using solid-liquid separation, flaring or biological processes. Specific attention is paid to biofiltration due to its potential to simultaneously treat these two types of pollution. [ABSTRACT FROM AUTHOR]

Abstract: Arctic soils emit nitrous oxide, which is a potent greenhouse gas and also represents an important loss of nitrogen to oligotrophic Arctic ecosystems. However, little is known about the temperature sensitivity of nitrous oxide release in Arctic soils or the organisms mainly responsible for it. We investigated controls on nitrous oxide emissions in an Arctic soil across a typical temperature range (between 4 and 13°C) on Truelove Lowland, Devon Island, Canada (75°40′N 84°35′W) at two different moisture contents. When fertilized with ammonia or nitrate, nitrous oxide emissions and temperature dependence of nitrous oxide emissions were insensitive to soil moisture content but linked to nitrification rates. Stable isotope analysis revealed that nitrous oxide was predominantly released by nitrifiers. However, nitrous oxide emissions were not linked to nitrifier prevalence with an insignificant (P <0.219) increase in amoA genes and a (P <0.01) decrease in archaeal nitrifiers. In contrast, denitrifier nosZ prevalence was 10,000 times greater than that of nitrifiers and was related to nitrous oxide emission potential when soils were fertilized with nitrate. Manipulating water-filled pore space should have changed the pattern of N2O emissions. We used selective inhibitors to further explore why denitrification did not occur under field conditions when we manipulated water-filled pore space or when we used 15N analysis. When fungi were inhibited in the soil, nitrous oxide emissions from denitrifiers increased with no change in nitrous oxide released by nitrifiers. When fungi were active in the soil, there was little available nitrate but when fungi were inhibited, available soil nitrate increased over the incubation period. The dominance of nitrifiers in nitrous oxide emissions from Arctic soils under field conditions is linked to the competition for nitrate between fungi and denitrifiers. [Copyright &y& Elsevier]

The article presents abstracts on dental topics including "Origin of cardiovascular risk in overweight preschool children, a cohort study of cardiometabolic risk factors at the onset of obesity" by B. Shashaj and others, "The hematological effects of nitrous oxide anesthesia in pediatric patients" by A. Duma and others, and "The deterioration of Canadian immigrants’ oral health: analysis of the Longitudinal Survey of Immigrants to Canada" by P. Calvasina and others.

This study investigates soil N2O dynamics in forest soils representing early (3-years) and late (>50 years) post-harvest succession in Atlantic Canada over a 9-month snow-free period in order to develop a better understanding of the role of managed forests as sources and sinks of N2O. We couple measurement of surface flux with detailed measurements of subsurface N2O concentrations at four mineral soil depths (0, 5, 20 and 35 cm) at 40 plots located within four sites. Median surface fluxes were similar at all sites regardless of the management stage (−5 to +19 ugN2O–N/m2/day), with all sites behaving as net sinks and sources of N2O over the measurement period. Subsurface mineral soil N2O concentrations at early (3-year) post-harvest succession sites, which ranged from median values of 362 ppbv at 0 cm to 1783 ppbv at 35 cm depth, were significantly higher than late post-harvest succession sites where median concentrations ranged from 329 ppbv at 0 cm to 460 ppbv at 35 cm depth. Examination of relationships between subsurface gas storage and surface flux magnitudes, suggested although recently harvested forest soils may be producing N2O at a greater rate than mature forest soils, observed patterns are consistent with a strong sink for this gas that prevents its conservative transport through the soil profile, and ultimate emission to the atmosphere through the majority of the measurement period. [ABSTRACT FROM AUTHOR]

This paper summarizes greenhouse gas (GHG) emissions measurements obtained during several recent studies conducted by Environment Canada, Emissions Research and Measurement Division (ERMD). A variety of heavy-duty vehicles and engines operating on a range of different fuels including diesel, biodiesel, compressed natural gas (CNG), hythane (20% hydrogen, 80% CNG), and liquefied natural gas (LNG), and with different advanced aftertreatment technologies were studied by chassis dynamometer testing, engine dynamometer testing or on-road testing. Distance-based emission rates of CO2, CH4, and N2O are reported. Fuel consumption calculated by carbon balance from measured emissions is also reported. The measurement results show, for heavy-duty diesel vehicles without aftertreatment, that while CO2 emissions dominate, CH4 emissions account for between 0% and 0.11% and N2O emissions account for between 0.16% and 0.27% of the CO2-equivalent GHG emissions. Both of the aftertreatment technologies (diesel oxidation catalyst and active regeneration diesel particle filter) studied increased N2O emissions compared to engine out emissions while CH4 emissions remain essentially unchanged. No effect on tailpipe GHG emissions was found with the use of up to 20% biodiesel when the engine was equipped with an oxidation catalyst. Biodiesel use did show some reductions in tailpipe GHG emissions as compared to ULSD without aftertreatment and with the use of a diesel particle filter. Natural gas and hythane also offer decreased GHG emissions (10–20%) at the tailpipe when compared with diesel. Emission factors (gL−1 fuel) for CH4 and N2O are suggested for heavy-duty vehicles fueled with diesel-based fuels and natural gas. These emission factors are substantially lower than those recommended for use by IPCC methodologies for developing national inventories. [Copyright &y& Elsevier]

Abstract: Stable 15N isotope dilution and tracer techniques were used in cultivated (C) and uncultivated (U) ephemeral wetlands in central Saskatchewan, Canada to: (1) quantify gross mineralization and nitrification rates and (2) estimate the relative proportion of N2O emissions from these wetlands that could be attributed to denitrification versus nitrification-related processes. In-field incubation experiments were repeated in early May, mid-June and late July. Mean gross mineralization and nitrification rates (10.3 and 3.1mgkg−1 d−1, respectively) did not differ between C and U wetlands on any given date. Despite these similarities, the mean NH4 + pool size in the U wetlands (17.2mgkg−1) was two to three times that of the C wetlands (6.7mgkg−1) whereas the mean NO3 − pool size in U wetlands (2.2mgkg−1) was less than half that of C wetlands (5.8mgkg−1). Mean N2O emissions from the C wetlands decreased from 112.8 to 17.0ngN2Om2 s−1 from May to July, whereas mean U-wetland N2O emissions ranged only from 31.8 to 51.1ngN2Om2 s−1 over the same period. This trend is correlated to water-filled pore space in C wetlands, demonstrating a soil moisture influence on emissions. Denitrification is generally considered the dominant emitter of N2O under anaerobic conditions, but in the C wetlands, only 49% of the May emissions could be directly attributed to denitrification, decreasing to 29% in July. In contrast, more than 75% of the N2O emissions from the U wetlands arose from denitrification of the soil NO3 − pool throughout the season. These land use differences in emission sources and rates should be taken into consideration when planning management strategies for greenhouse gas mitigation. [Copyright &y& Elsevier]

In Quebec, most pig slurry is applied to agricultural soils in the spring and fall. A study was initiated to compare the impact of the contrasting spring and fall weather conditions on CO2 and N2O emissions, and on the transformation of pig slurry C and N in a loamy soil cropped to maize (Zea mays L.). Treatments were approximately 200 kg total N ha-1 either as a spring (SPRING) or fall (FALL) application of pig slurry, and 150 kg N ha-1 as NH4NO3 (control). Fluxes of CO2 and N2O, and soil O2, CO2, N2O, NI+, 4NO-3, extractable C and microbial biomass C (MBC) contents were measured 50 times over a 1-yr period. Fluxes of N2O were generally Iow during the experiment but were greatly increased in recently manured soils when soil O2 concentration fell below 0.20 mol mol-1. Soil was warm and well-aerated following spring slurry application. Under these conditions, slurry NH4-N was rapidly nitrified and high N2O emissions attributed to denitrification occurred when soil was rewetted by abundant rainfall. For the fall applied slurry, wet and cool conditions limited net nitrification and resulted in little accumulation of NO3-N, thus limiting potential for subsequent denitrification and N2O emissions. Cumulated N2O emissions during the experiment represented 1.74, 2.73, and 1.14% of added N in the FALL, SPRING, and NH4NO3 plots, respectively. Fluxes of CO2 and cumulated CO2-C losses were also greater for SPRING than for FALL application. Our results clearly show that the impacts of the timing of animal manure application on N2O emissions cannot be generalized, but will vary between years in response to interactions between crop, climatic, and soil factors. [ABSTRACT FROM AUTHOR]

Nitrous oxide fluxes from soils are inherently variable in time and space. An improved understanding of this variability is needed to make accurate estimates of N2O fluxes at a regional scale. The objectives of this work were to (i) characterize the influence of soil landscape combinations and N application rates on N2O emissions and to (ii) determine the contribution of these influences on the estimation of N2O emissions at the field scale. We used static chambers and gas chromatography methods to measure N2O fluxes and collected ancillary data (mineral N, water soluble C, soil water content, soil temperature) in Canada at Mundare (AB) in the aspen parkland ecoregion and at Swift Current (SK) in the short-grass prairie ecoregion. At Mundare, measurements were taken in 1995 and 1996 by landscape position and land use. At Swift Current, data were collected in 1999 and 2000 by landscape position and N rate. At Mundare, landscape position affected N2O emissions but the pattern varied seasonally. During a 46-d period in summer 1995, a flux of 430 g N2O-N ha-1 measured in a backslope was greater than the 60 g N2O-N ha t measured on average in shoulder and depressional areas. The flux pattern changed during a 43-d spring thaw of 1996 when fluxes from depressional areas were greatest (1710 g N2O-N ha-1). Nitrous oxide emissions from natural areas were small. The emission pattern during summer 1996 was similar to that of 1995 but the fluxes were an order of magnitude larger. At Swift Current, N2O fluxes in summer 1999 were affected by topography and N rate. Fluxes were greatest in depressional areas receiving N at 110 kg ha1 (3140 g N2O-N ha-1). Use of the area fraction occupied by each landscape position to calculate N2O flux increased the estimates of N2O fluxes at the field scale in five out of six cases. Further research of N2O fluxes in variable landscapes should help elucidate factors controlling N2O fluxes from pedon to field scale and thus translate into improved flux estimates at regional scales. [ABSTRACT FROM AUTHOR]

Quantifies the effects of pig slurry (PS) application for 19 years on nitrous oxide emissions in loamy soils in Canada. Effect of annual PS application on denitrifying enzyme activity; Increase of nitrous oxide fluxes following PS application; Conformation of emission factors for the PS plots with values for nitrogen-fertilized soils.

Soil salinity restricts plant growth, affects soil water balance and nitrous oxide (N 2 O) fluxes and can contaminate surface and groundwater. In this study, the Denitrification Decomposition (DNDC) model was modified to couple salt and water balance equations (SALT-DNDC) to investigate the effect of salinity on water balance and N 2 O fluxes. The model was examined against four growing seasons (2008–11) of observed data from Lethbridge, Alberta, Canada. Then, the model was used to simulate water filled pore space (WFPS), salt concentration and the N 2 O flux from agricultural soils. The results show that the effects of salinity on WFPS vary in different soil layers. Within shallow soil layers (<20 cm from soil surface) the salt concentration does not affect the average WFPS when initial salt concentrations range from 5 to 20 dS/m. However, in deeper soil layers (>20 cm from soil surface), when the initial salt concentration ranges from 5 to 20 dS/m it could indirectly affect the average WFPS due to changes of osmotic potential and transpiration. When AW is greater than 40%, the average growing season N 2 O emissions increase to a range of 0.6–1.0 g-N/ha/d at initial salt concentrations (5–20 dS/m) from a range of 0.5–0.7 g-N/ha/d when the salt concentrations is 0 dS/m. The newly developed SALT-DNDC model provides a unique tool to help investigate interactive effects among salt, soil, water, vegetation, and weather conditions on N 2 O fluxes. Image 1 • SALT-DNDC simulates effects of root zone salinity on water balance and N 2 O fluxes. • The salt leaching patterns depend on soil salinity, rainfall depths and frequency. • Due to soil salinity, plant transpiration and soil evaporation balance each other. • N 2 O emission depends on soil available water, soil moisture and salt concentration. [ABSTRACT FROM AUTHOR]

• Reduced tillage increased growing season N 2 O emissions on fine textured soils. • Fertilization with dairy and pig slurry resulted in similar N 2 O emissions. • Nitrous oxide emissions were lower from the coarse compared to fine textured soil. Reduced tillage is often promoted as a method to sequester carbon (C) in soils and thus mitigate climate change. However, in certain conditions reduced tillage may increase soil nitrous oxide (N 2 O) fluxes, which may negate any climate gains from the potential storage of C in soil. To investigate how long-term applications of different manures interact with tillage effects on N 2 O fluxes during the crop rotation, we established a long-term trial in 2009 in eastern Canada, using two tillage (inversion tillage [IT]; and reduced tillage [RT],) and three fertilizer types (pig slurry, dairy slurry and a 0-N control) arranged in a split-plot design with 3 replications. The experiment was reproduced on two contrasting soil textures (silty clay and sandy loam) located approximately 900 m apart in a wheat-corn-soybean rotation. During 2016 (wheat), 2017 (corn), and 2018 (soybean) we estimated the N 2 O fluxes from each plot using manual static chambers for the growing season (April to November). Mean cumulative fluxes for the growing season ranged from 0.8 kg N 2 O-N ha−1 for the corn/control/IT to 7.6 kg N 2 O-N ha−1 for the wheat/dairy slurry/RT in the silty clay soils and from 0.4 kg N 2 O-N ha−1 for the corn/control/IT to 3.0 kg N 2 O-N ha−1 in the corn/pig slurry/RT in the sandy loam soils. The RT increased soil N 2 O fluxes for both slurry types and the control in the clay soil (mean flux for all fertilizer treatments over both seasons were 5.5 and 2.4 kg N 2 O-N ha−1 season−1 for the RT and IT, respectively), likely because the higher water content in the RT caused greater denitrification; while on the sandy loam the N 2 O flux was similar between the two tillage systems. Manure type had no measurable effect on the growing season N 2 O fluxes in either soil type as both provided sufficient labile N. Application of both slurries however, resulted in greater emissions than the control (P = 0.002). These findings suggest that RT on fine-textured soils in this region may not be an effective strategy to reduce GHG emissions. [ABSTRACT FROM AUTHOR]

• At economically optimal nitrogen rates (EONR), N management did not affect yield. • Broadcasting N, particularly as urea, increased the EONR, relative to incorporation. • Application timing did not affect EONR, but in-season applications decreased leaching. • Yield-scaled N losses were never minimized at the EONR. • Mean yield-scaled N loss at the EONR was 4 kg N Mg−1 and N surplus was 28 kg N ha−1. The goal of most fertilizer decision support tools is to help maize farmers estimate the most profitable nitrogen (N) rate for a given fertilizer N/grain price ratio, known as the economically optimum N rate (EONR). While maximizing profitability, to our knowledge the environmental performance of the EONR has not been fully assessed using a process-based model that can jointly predict yield, N uptake, and multiple N loss pathways (leaching, nitrous oxide emissions, volatilization). The objective of this study was to construct a full N budget when the EONR is applied, and to measure how N management influences both grain yield and the environmental performance of the EONR. The DeNitrification and Decomposition model (DNDC) was calibrated and validated using measurements from a long-term N rate trial from Elora, ON, Canada (2009–2016). DNDC was then used to simulate N applications at the EONR when two different N sources (urea and urea ammonium-nitrate), two N placements (broadcast or incorporated) and four N timings (100 % at planting, 100 % at V6, 50 % at planting and 50 % at V13, and 50 % at V6 and 50 % at V13) were used. Depending on N management, mean EONR (2009–2016) was highly variable, ranging from 158 to 185 kg N ha−1 while grain yield was stable across N management choices. The use of urea over urea ammonium-nitrate (UAN), and the decision to broadcast versus incorporate, increased the EONR, yield-scaled N/ losses at the EONR, and N surplus. When applied in-season, N applications modestly reduced leaching N losses at the EONR but did not significantly impact the amount of N applied at the EONR or yield-scaled N losses. In all 16 management combinations, simulated mean (2008–2016) N surplus never exceeded 50 kg N ha−1, and yield-scaled N losses never exceeded 8 kg N Mg−1 grain. In conclusion, the EONR delivers strong environmental performance relative to established benchmarks for N surplus and yield-scaled N losses, while N management decisions such as N source and N placement will still affect in-season N losses and consequently the amount of N applied at the EONR. [ABSTRACT FROM AUTHOR]

The widely used Denitrification-Decomposition (DNDC) model does not explicitly account for the influence of microbes in organic fertilizer. However, applying organic fertilizers to soils may increase N 2 O emissions because organic fertilizers can contain appreciable levels of the plant-available nitrogen (N), and contain many types of microbes including denitrifiers. In this study, the DNDC model was extended to include a microbial factor to account for the enhancement of microbial contents by the organic fertilizer input, and applied to two organically fertilized (digestate and manure) soils planted with barley in Lethbridge, Alberta, Canada. The growing season cumulative N 2 O emissions at the recommended N rate of digestate and manure were used to calibrate the model, while the emissions at the double recommended N loadings were used for validation. The results show that the growing season cumulative N 2 O emissions at recommended N loadings were calculated to be 1.90, 1.62, 3.50, and 2.55 kg-N ha−1 for digestate, and 0.45, 0.17, 0.35, and 0.74 kg-N ha−1 for manure in 2008, 2009, 2010, and 2011 respectively. The corresponding emission factors (EFs) are 0.937, 0.444, 1.947, and 0.510, as well as 0.095, 0.035, 0.072, and 0.083 for manure in 2008, 2009, 2010, and 2011 respectively. The average four-year relative errors of N 2 O emissions and EFs of validated cases are 32.3% and 34.3% for digestate, as well as 66.9% and 126% for manure, respectively. Two-factor hyperbolic and quadratic models of emissions and EFs correlating N loadings and weather conditions were developed and applied to N 2 O emission data at recommended N loadings. The coefficients of determination of modeled EFs to measured values are 0.887 and 0.982 for digestate and manure, respectively. The two-factor hyperbolic model predicted that N 2 O EFs would range from 0.085% to 1.1% for digestate with N loadings ranging from 100 to 800 kg-N ha−1, and product of average precipitation and air temperature during the growing season ranging from 18 to 36 mm × oC. The corresponding emissions ranged from 1.0 to 5.1 kg-N ha−1. We conclude that N 2 O emissions and EFS could be effectively modeled by a two-factor hyperbolic equation for digestate, and quadratic equation for manure. Unlabelled Image • DNDC model is extended by a factor representing microbes in organic fertilizers. • Average 4-year relative errors of N 2 O emissions of validated cases is about 32.3%. • Two-factor models of N 2 O and emission factors are correlated to N loadings and weather. • A five-factor exponential model of N 2 O emissions and emission factors was developed. • A two-factor hyperbolic model effectively modeled N 2 O emissions and emission factors. [ABSTRACT FROM AUTHOR]

• Flux-gradient N 2 O emissions were monitored over 4 agricultural fields for 11 years. • 50% of emissions followed spring fertilizer application and 15–20% occurred during spring thaw. • N application rate and time integrated nitrate concentration were more important than environmental factors to N 2 O. • Emissions were less during inclusion of a 4-year perennial legume phase in an annual crop rotation. • Over 11-years, emissions were not reduced with inclusion of the perennial phase because of large emissions following its termination. • Net CO 2 equivalent emissions based on partial life cycle analysis showed both treatments to be a similar source. Nitrous oxide (N 2 O) emissions were measured over 4 fields in Manitoba, Canada, continuously from 2006 to 2016 using the micrometeorological flux-gradient technique. The fields were divided into 2 treatments: 2 fields with a rotation of annual crops (corn, faba bean, spring wheat, rapeseed, barley, spring wheat, corn, soybean, spring wheat, soybean, soybean); while 2 fields had a four-year period with a leguminous perennial crop in the rotation (corn, faba bean, alfalfa/grass, alfalfa/grass, alfalfa/grass, alfalfa/grass, corn, soybean, spring wheat, soybean, soybean). Nitrogen fertilizer was applied according to local practice, and was typically not applied in years when a legume was planted. N 2 O was emitted from the field in episodes during spring thaw and following nitrogen fertilizer application. Emissions were less during the perennial phase of the comparison (mean 1 kg N ha−1 y−1 from perennial fields; 4.7 kg N ha−1 y−1 from the annual fields; P < 0.001). However, over the 11-year period, the treatments were not different (P = 0.3), averaging 5 kg N ha−1 y−1 because of large emissions of about 20 kg N ha−1 y−1 in the year following termination of the perennial crop. Nitrogen fertilizer application rate explained 69% of the variability in emissions (P < 0.001), with only a marginal advantage including other environmental variables such as soil nitrate exposure or soil ammonium concentrations. The N 2 O flux data were combined with carbon dioxide flux measurements, fertilizer N manufacturing, and potential product end uses to estimate the net greenhouse gas budget. Net emissions were a source of 1.7 Mg CO 2 equivalents ha−1 y−1, driven by 3 Mg CO 2 equivalents ha-1 y-1 source from N 2 O emissions, net carbon exchange of 3 to 5 Mg CO 2 equivalents ha-1 y-1 sink, and a consumption source of 6 to 7 Mg CO 2 equivalents ha-1 y-1. High inter-annual variability in fluxes resulted in no significant difference (P = 0.87) in overall greenhouse gas emissions between treatments over the full period including N fertilizer inputs and end uses of crop products. [ABSTRACT FROM AUTHOR]

Agriculture is targeted to make a substantial contribution to Canada's greenhouse gas reduction targets under the Kyoto Protocol. To achieve a net reduction in emissions any gains in soil organic carbon storage cannot come at the expense of enhanced nitrous oxide emissions from the soil. In non-level agricultural landscapes of the Canadian Prairies the potential for significant soil organic carbon gain due to adoption of soil conserving practices is greatest on convex upper slope positions, which have experienced major losses of soil organic carbon due to cultivation. The potential for soil organic carbon gain in lower slope positions is limited due to their high soil organic carbon contents, but targeted wetland and riparian vegetation restoration programs could lead to significant above ground carbon gains. Several studies have shown that emissions of nitrous oxide from lower slope positions are significantly higher than the convex slope positions, and that improvements in nitrogen fertilizer use efficiency through site-specific management has the potential to significantly reduce nitrous oxide (N2O) emissions from these positions. Because of the close relationship between landform position and the key carbon and nitrogen processes, quantitative landform segmentation procedures can be used to delineate precision conservation management zones in these landscapes. Site-specific management practices such as reduced or no-till, seeding to grass, wetland restoration, and site-specific nitrogen (N) management can then be implemented to simultaneously increase soil organic carbon stores on eroded upper slope segments while preserving existing stores of soil organic carbon and reducing N2O emissions from lower slope segments. Close cooperation between precision conservation professionals and agronomists is required to ensure that information required by producers is available to guide them in their decision making and implementation of precision conservation for co-management of carbon and nitrogen. [ABSTRACT FROM AUTHOR]