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Developing a country specific method for estimating nitrous oxide emissions from agricultural soils in Canada

DOI:10.1007/s10705-020-10058-w
Authors:
B.C. Liang at Environment and Climate Change Canada
B.C. Liang
  • Environment and Climate Change Canada
Douglas Macdonald at Environment Canada
Douglas Macdonald
Dr. Arumugam Thiagarajan at Environment and Climate Change Canada
Dr. Arumugam Thiagarajan
  • Environment and Climate Change Canada
Corey Flemming at Government of Canada
Corey Flemming
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Abstract and Figures

Accurate estimates of nitrous oxide (N2O) emissions from agricultural soils and management factors that influence emissions are necessary to capture the impact of mitigation measures and carry out life cycle analyses aimed at identifying best practices to reduce greenhouse gas emissions. We propose improvements to a country specific method for estimating N2O emissions from agricultural soils in Canada based on a compilation of soil N2O flux data from recent published literature. We provide a framework for the development of empirical models that could be applied in regions where similar data and information on N2O emissions are available. The method considers spatial elements such as soil texture, topography and climate based on a quantitative empirical relationship between synthetic N-induced soil N2O emission factor (EF) and growing season precipitation (P) {N2OEF = e(0.00558P−7.7)}. Emission factors vary from less than 0.0025 kg N2O-N kg N−1 in semi-arid regions of Canada to greater than 0.025 kg N2O-N kg N−1 in humid regions. This approach differentiates soil N2O EFs based on management factors. Specifically, empirical ratio factors are applied for sources of N of 1.0, 0.84, and 0.28 for synthetic N, animal manure N and crop residue N, respectively. Crop type ratio factors where soil N2O EFs from applied manure- and synthetic-N on perennial crops are approximately 19% of those on annual crops. This proposed approach improves the accuracy of the dominant factors that modulate N2O emissions from N application to soils.
Schematic diagram on the processes involved in the calculation of base emission factor (EF_Base) and details of ratio factors (RFs) towards the computation of EFs for soil nitrous oxide emissions
Schematic diagram on the processes involved in the calculation of base emission factor (EF_Base) and details of ratio factors (RFs) towards the computation of EFs for soil nitrous oxide emissions
… 
Average maximal N-induced soil nitrous oxide emission factors for low landscape position of ecodistricts and irrigation derived previously through a linear function of growing season precipitation over potential evapotranspiration and an exponential equation with the growing season precipitation for each province of Canada (AB: Alberta; BC: British Columbia; MB: Manitoba; NB: New Brunswick; NF: Newfoundland and Labrador; NS: Nova Scotia; ON: Ontario; PE: Prince Edward Island; QC: Quebec; SK: Saskatchewan)
Average maximal N-induced soil nitrous oxide emission factors for low landscape position of ecodistricts and irrigation derived previously through a linear function of growing season precipitation over potential evapotranspiration and an exponential equation with the growing season precipitation for each province of Canada (AB: Alberta; BC: British Columbia; MB: Manitoba; NB: New Brunswick; NF: Newfoundland and Labrador; NS: Nova Scotia; ON: Ontario; PE: Prince Edward Island; QC: Quebec; SK: Saskatchewan)
… 
Distribution of synthetic N-induced soil nitrous oxide emission factors (EF_Topo) adjusted for low landscape position of ecodistricts derived previously through a linear function of growing season precipitation over potential evapotranspiration and an exponential equation with the growing season precipitation for each province of Canada
Distribution of synthetic N-induced soil nitrous oxide emission factors (EF_Topo) adjusted for low landscape position of ecodistricts derived previously through a linear function of growing season precipitation over potential evapotranspiration and an exponential equation with the growing season precipitation for each province of Canada
… 
Average synthetic N-induced soil nitrous oxide emission factors (EF_Topo) adjusted for low landscape position of ecodistricts derived previously through a linear function of growing season precipitation over potential evapotranspiration and an exponential equation with the growing season precipitation for each province of Canada (AB: Alberta; BC: British Columbia; MB: Manitoba; NB: New Brunswick; NF: Newfoundland and Labrador; NS: Nova Scotia; ON: Ontario; PE: Prince Edward Island; QC: Quebec; SK: Saskatchewan)
Average synthetic N-induced soil nitrous oxide emission factors (EF_Topo) adjusted for low landscape position of ecodistricts derived previously through a linear function of growing season precipitation over potential evapotranspiration and an exponential equation with the growing season precipitation for each province of Canada (AB: Alberta; BC: British Columbia; MB: Manitoba; NB: New Brunswick; NF: Newfoundland and Labrador; NS: Nova Scotia; ON: Ontario; PE: Prince Edward Island; QC: Quebec; SK: Saskatchewan)
… 
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ORIGINAL ARTICLE
Developing a country specific method for estimating nitrous
oxide emissions from agricultural soils in Canada
Chang Liang .Douglas MacDonald .Arumugam Thiagarajan .
Corey Flemming .Darrel Cerkowniak .Raymond Desjardins
Received: 30 July 2019 / Accepted: 9 March 2020 / Published online: 31 March 2020
ÓCrown 2020
Abstract Accurate estimates of nitrous oxide (N
2
O)
emissions from agricultural soils and management
factors that influence emissions are necessary to
capture the impact of mitigation measures and carry
out life cycle analyses aimed at identifying best
practices to reduce greenhouse gas emissions. We
propose improvements to a country specific method
for estimating N
2
O emissions from agricultural soils in
Canada based on a compilation of soil N
2
O flux data
from recent published literature. We provide a frame-
work for the development of empirical models that
could be applied in regions where similar data and
information on N
2
O emissions are available. The
method considers spatial elements such as soil texture,
topography and climate based on a quantitative
empirical relationship between synthetic N-induced
soil N
2
O emission factor (EF) and growing season
precipitation (P) {N
2
OEF = e
(0.00558P-7.7)
}. Emission
factors vary from less than 0.0025 kg N
2
O-N kg N
-1
in semi-arid regions of Canada to greater than
0.025 kg N
2
O-N kg N
-1
in humid regions. This
approach differentiates soil N
2
O EFs based on man-
agement factors. Specifically, empirical ratio factors
are applied for sources of N of 1.0, 0.84, and 0.28 for
synthetic N, animal manure N and crop residue N,
respectively. Crop type ratio factors where soil N
2
O
EFs from applied manure- and synthetic-N on peren-
nial crops are approximately 19% of those on annual
crops. This proposed approach improves the accuracy
of the dominant factors that modulate N
2
O emissions
from N application to soils.
Keywords Soil N
2
O emissions Synthetic N
Organic N Crop residue N Tillage Perennial/
annual crop
Abbreviations
N
2
O Nitrous oxide
EF Emission factor
NS Sources of N
ON Organic N
CRN Crop residual N
Per Perennial crops
Ann Annual crops
C. Liang (&)R. Desjardins
Ottawa Research and Development Centre, Agriculture
and Agri-Food Canada, Central Experimental Farm, K.W.
Neatby, 960 Carling Ave., Ottawa, ON K1A 0C6, Canada
e-mail: chang.liang@canada.ca
C. Liang D. MacDonald A. Thiagarajan
C. Flemming
Pollutant Inventories and Reporting Division,
Environment and Climate Change Canada, PVM, 7th
Floor, 351 St-Joseph Blvd., Gatineau,
QC K1A 0H3, Canada
D. Cerkowniak
Saskatoon Research and Development Centre, Agriculture
and Agri-Food Canada, 107 Science Place, Saskatoon,
SK S7N 0X2, Canada
123
Nutr Cycl Agroecosyst (2020) 117:145–167
https://doi.org/10.1007/s10705-020-10058-w(0123456789().,-volV)(0123456789().,-volV)
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... In our study, EF area calculated including flux measurements over the potato growing seasons (i.e., ~May to October) were lower than , but our EF area were comparable to EF area magnitudes reported by Chai et al. (2020) under irrigation. By contrast, based on estimations of EF using an exponential equation model proposed by Rochette et al. (2018) and Liang et al. (2020), the growing-season 2-year mean N 2 O EF as a function of total water addition (rainfall + irrigation) was estimated as high as 0.77% and 0.60% at Lethbridge and Brooks, respectively (Table 1). Overall, the context of these comparisons suggest the need for revisions in the model proposed by Rochette et al. (2018) and Liang et al. (2020) to preclude overestimations of the emission factor of N 2 O. ...
... By contrast, based on estimations of EF using an exponential equation model proposed by Rochette et al. (2018) and Liang et al. (2020), the growing-season 2-year mean N 2 O EF as a function of total water addition (rainfall + irrigation) was estimated as high as 0.77% and 0.60% at Lethbridge and Brooks, respectively (Table 1). Overall, the context of these comparisons suggest the need for revisions in the model proposed by Rochette et al. (2018) and Liang et al. (2020) to preclude overestimations of the emission factor of N 2 O. ...
... . Estimated N 2 O EF as a function of total water addition of rainfall and irrigation (EF H2O ) at three different time frames based on exponential equation N 2 O EF % = e (0.00558×H2O−7.701) × 100 (Rochette et al., 2018;Liang et al., 2020). Estimated potato physiological days (P-Days) as well as evapotranspiration from onsite weather stations are also provided. ...
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... In our study, EF area calculated including flux measurements over the potato growing seasons (i.e., ~May to October) were lower than , but our EF area were comparable to EF area magnitudes reported by Chai et al. (2020) under irrigation. By contrast, based on estimations of EF using an exponential equation model proposed by Rochette et al. (2018) and Liang et al. (2020), the growing-season 2-year mean N 2 O EF as a function of total water addition (rainfall + irrigation) was estimated as high as 0.77% and 0.60% at Lethbridge and Brooks, respectively (Table 1). Overall, the context of these comparisons suggest the need for revisions in the model proposed by Rochette et al. (2018) and Liang et al. (2020) to preclude overestimations of the emission factor of N 2 O. ...
... By contrast, based on estimations of EF using an exponential equation model proposed by Rochette et al. (2018) and Liang et al. (2020), the growing-season 2-year mean N 2 O EF as a function of total water addition (rainfall + irrigation) was estimated as high as 0.77% and 0.60% at Lethbridge and Brooks, respectively (Table 1). Overall, the context of these comparisons suggest the need for revisions in the model proposed by Rochette et al. (2018) and Liang et al. (2020) to preclude overestimations of the emission factor of N 2 O. ...
... . Estimated N 2 O EF as a function of total water addition of rainfall and irrigation (EF H2O ) at three different time frames based on exponential equation N 2 O EF % = e (0.00558×H2O−7.701) × 100 (Rochette et al., 2018;Liang et al., 2020). Estimated potato physiological days (P-Days) as well as evapotranspiration from onsite weather stations are also provided. ...
Nitrous oxide emissions and productivity of irrigated potato: Effects of nitrogen fertilization options
Article
  • Sep 2022
Improved nitrogen management is needed in intensive agriculture to mitigate nitrous oxide (N2O) emissions while sustaining high yields. We assessed the effectiveness of polymer‐coated urea (PCU), nitrification inhibitor 2,4‐dimethylpyrazol succinic acid (DMPSA), a biostimulant, and their combinations with granular urea and ammonium sulfate nitrate (ASN) fertilizers to reduce N2O emissions and to improve potato (Solanum tuberosum L.) productivity under irrigation. Sites were located in Lethbridge and Brooks, Alberta, Canada over two growing seasons. Tuber yield, grade and specific gravity, as well as N uptake were quantified. We used the chamber method to measure N2O fluxes from potato hills and furrows. The N2O emissions from furrow positions were at least 2‐fold greater than from hills at the Lethbridge site. Peak N2O emissions as well as increased N concentrations in potato petiole and soils occurred shortly after fertilizer applications. The overall average of N2O emission factor was 0.056% kg N2O‐N kg−1 N fertilizer (accounting for emissions from unfertilized controls). Urea alone commonly exhibited the highest N2O fluxes. Admixing DMPSA with either urea or ASN lowered N2O emissions in only certain cases. For instance, in one growing season at the Brooks site, adding DMPSA to urea reduced the N2O emissions by 57%. Likewise, in one of the four site‐years in the study, 36% higher potato marketable yields were obtained when applying either ASN treated with DMPSA or PCU compared to the unfertilized controls (45 versus 33 Mg ha−1). Results showed that under specific conditions, N application strategies utilizing DMPSA admixed with either urea or ASN can maintain high potato yields while reducing N2O emissions relative to soils receiving these fertilizers without this additive. This article is protected by copyright. All rights reserved Adding the inhibitor DMPSA to urea reduced N2O emissions in only one of four site‐years Potato yield was increased 36% in one site‐year by the fertilizers ASN with DMPSA or PCU Fertilizer options did not influence the overall nitrogen use‐efficiency or harvest indexes Nitrate concentrations in potato petioles were closely associated with availability of soil N N2O emissions from furrow positions were often greater than from potato hills
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... Refined N 2 O EF that incorporate some of the factors inducing variability in emissions such as precipitation, tillage intensity, irrigation, soil texture, and topography have been developed for Canada (Rochette et al., 2008(Rochette et al., , 2018Liang et al., 2020), the UK (Buckingham et al., 2014), China (Shepherd et al., 2015) and Europe (Lesschen et al., 2011). The most recent nationally averaged N 2 O EF for Canada is 0.72 ± 0.43% irrespective of N sources, with large variability between regions due to predominant soil types and precipitation with an EF of 1.3 ± 0.64% for eastern Canada and 0.19 ± 0.064% for the Prairie region (Rochette et al., 2018). ...
... Science of the Total Environment 815 (2022) 152744 2.7. N 2 O emission prediction based on national inventory approaches N 2 O emissions for the study years were estimated using three approaches: 1) default IPCC EF (IPCC, 2019), 2) country specific EF approach proposed by Rochette et al. (2008) and 3) an updated country specific EF approach proposed by Liang et al. (2020) based on Rochette et al. (2018). The disaggregated default EF values suggested by IPCC (2019) are 1.6% of applied synthetic N fertilizer and 0.6% of crop residue or manure N emitted as N 2 O-N for wet regions such as Ontario. ...
... The relationship showed that using data for growing season precipitation, soil texture, type of N fertilizer and crop type results in improved EFs. Building on these relationships Liang et al. (2020) developed an N 2 O emission prediction approach for Canada based on a moisture-or climate (CT) dependent EF (EF_CT i ) for an ecodistrict i: ...
Long-term variability in N2O emissions and emission factors for corn and soybeans induced by weather and management at a cold climate site
Article
Nitrous oxide (N2O) emissions are highly variable in space and time due to the complex interplay between soil, management practices and weather conditions. Micrometeorological techniques integrate emissions over large areas at high temporal resolution. This allows identification of causes of intra- and inter-annual variability of N2O emissions and development of robust emission factors (EF). Here, we investigated factors responsible for variability in N2O emissions during growing and non-growing seasons of corn and soybeans grown in an imperfectly drained silt loam soil, in Ontario, Canada. We used quasi-continuously (at half-hourly to hourly intervals) N2O fluxes measured via the flux-gradient technique over 11 years for corn and 5 years for soybeans and evaluated the uncertainty of default IPCC and Canada-specific EFs. In the growing season, emissions were controlled by soil nitrate content, soil moisture and temperature in the fertilized corn, while moisture and temperature regulated N2O emissions in the unfertilized soybeans. In the non-growing season, nitrogen (N) input from the crop residue did not affect the emissions, pointing to freeze-thaw cycles as mechanisms for enhanced N2O emissions. The non-growing season contribution to annual emissions was 38% in corn and 43% in soybeans. On average, annual emissions were 2.6-fold higher in corn than soybeans. Observed mean N2O EFs were 0.84% (0.12–2.02%) for growing season and 1.69% (0.29–7.32%) for yearly emissions. The growing season EF derived from long-term N2O emissions was 0.9 ± 0.14%. The interannual variability in N2O emissions and EFs can be attributed to management practices and annual weather variability. The default IPCC approach based on overall N input had poorer performance in predicting annual N2O emissions compared to the current Canadian methodology, which includes management and environmental factor in addition to N inputs. The observed emissions were further evaluated with a newly developed growing season N2O emission prediction approach for Canada. However, performance of the approach was poorer than IPCC or the current national Canadian approach. Additional tests of the new national methodology are recommended as well as consideration of non-growing season emissions.
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... Progress towards more accurate estimates is expected when using both the updated default values of emission factors (and other parameters) based on the last available scientific information, and the disaggregation of emission factors by climate according to the IPCC 2019 refinement. This improvement is necessary for encompassing the impact of mitigation measures and designing practices to reduce GHG (Liang et al., 2020). The magnitude of emissions is also essential information for deciding mitigation options. ...
NITROUS OXIDE EMISSION ESTIMATION FROM MANAGED SOILS IN ARGENTINA: DIFFERENCES BETWEEN IPCC 2006 GUIDELINES AND THE IPCC 2019 REFINEMENT
Article
Full-text available
  • Nov 2022
Based on the IPCC 2006 guidelines, the total GHG emission for 2016, in Argentina, were estimated to reach a total net 364 MtCO 2 eq. Particularly, N 2 O emissions from managed soils sector represented 12% of total emissions. The IPCC 2019 refinement to the 2006 guidelines for GHG inventories provides an up-to-date and robust scientific basis to support the preparation and continuous improvement of estimates. The aims of the present work were to carry out a desk study to estimate nitrous oxide emissions from managed soils, using the IPCC 2019 and to compare this methodology with the one currently used for national GHG inventories (IPCC 2006) in Argentina. The nitrogen sources accounted for GHG emissions were: (i) synthetic fertilizer, (ii) crop residues, (iii) mineralization from soil organic matter, (iv) urine and dung from grazing animals, and (v) organic fertilizer. The adoption of the updated emission factors from the 2019 IPCC refinement would have a significant impact on the estimation of nitrous oxide (N 2 O) emissions. Compared to the 2006 IPCC guidelines, the application of these factors in Argentina would lead to decrease emissions from managed soils in 18.95 MtCO 2 eq, representing a 46% reduction for this category. This reduction would be significant in the greenhouse gases (GHG) inventories of Argentina (by approximately 5%), and for other countries with similar economies. These changes might affect the prioritization of mitigation actions for the analyzed categories, when considering cost and benefits. RESUMEN Según las directrices del IPCC de 2006, las emisiones totales de gases de efecto invernadero (GEI) en 2016 se estimaron en 364 MtCO 2 eq en Argentina, representando el óxido nitroso (N 2 O) de los suelos gestionados el 12% de estas emisiones. El refinamiento 2019 de las Directrices del IPCC de 2006 para los inventarios de GEI proporciona una base científica sólida y actualizada para respaldar la preparación y la mejora continua de las estimaciones. El objetivo de este artículo es realizar un estudio teórico para estimar las emisiones de óxido nitroso de suelos gestionados, utilizando el refinamiento del IPCC 2019 y compararlo con la metodología utilizada actualmente para los inventarios nacionales de GEI (IPCC 2006) en Argentina. Las fuentes de nitrógeno contabilizadas que generan emisiones de GEI fueron: (i) fertilizante sintético, (ii) residuos de cultivos, (iii) mineralización de materia orgánica del suelo, (iv) orina y estiércol de animales de pastoreo, (v) fertilizante orgánico. La aplicación de los factores del refinamiento del IPCC 2019 tendría un impacto significativo en la estimación de las emisiones de óxido nitroso (N 2 O). En comparación con las directrices del IPCC 2006, la aplicación de estos factores en Argentina llevaría a disminuir las emisiones de suelos manejados en 18,95 MtCO 2 eq, lo que representa una reducción del 46% para esta categoría. Esta reducción sería significativa en los inventarios de GEI de Argentina (en aproximadamente un 5%), y posiblemente en los inventarios de GEI de otros países con economías similares. Estos cambios podrían afectar la priorización de acciones de mitigación para las categorías analizadas, al considerar costos y beneficios.
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... In the national inventory report (NIR) of Canada, an empirical, country-specific method based on Canadian data provides estimates of soil N 2 O emissions from manure application in agricultural soils (Rochette et al., 2008), and recently this approach has been revised by Liang et al. (2020). However, the impact of manure application on SOC storage from agricultural soils has not been quantified or reported in the NIR. ...
Manure-induced carbon retention measured from long-term field studies in Canada
Article
Accurate estimates of manure-induced carbon retention coefficients (MCR) in soil are required when assessing carbon (C) storage and the C footprint in agricultural production systems. Eight field studies using various types and rates of manure applications on different crop rotations with durations varying from 10 to 74 years were used to quantify MCRs across diverse climatic conditions in Canada. The rate of solid cattle and swine manure had no impact on MCR which averaged 26%, whereas the MCR for liquid manure, including swine and cattle liquid manures, was much smaller, at only 5%. Under semi-arid conditions, irrigation had no impact on MCR. Compared to stockpiled manures, composted manure had a higher MCR (~36%), due to the additional stabilization of C during the composting process. The MCRs can be effectively stratified based on the type of manure affecting soil organic C differently, and the approach has potential application in regional and national estimates of soil C storage in Canada and elsewhere.
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... Most daily CH 4 fluxes were negligible and below 10 g CH 4 -C ha − 1 Table 5 Annual area-based N 2 O emission factors (EF area ) (% kg N 2 O-N kg − 1 N fertilizer), yield-based emission factors (EF yield ) (g N 2 O-N kg − 1 grain DM) and estimated annual N 2 O emission factors (EF) as a function of rainfall only (N 2 O EF % = e (0.00558×H2O− 7.701) × 100 (Rochette et al., 2018;Liang et al., 2020). ‡The numbers inside the parentheses are the P values after the interaction effect was removed. ...
Greenhouse gas emissions, nitrogen dynamics and barley productivity as impacted by biosolids applications
Article
Land application of biosolids is recognized as a sustainable disposal approach, as it enables the recycling of nutrients that can be used by plants. However, the emissions of greenhouse gases (GHG) from such a practice is an environmental concern that needs to be addressed. We evaluated the fluxes of nitrous oxide (N2O), methane (CH4), and carbon dioxide (CO2); soil available N; barley (Hordeum vulgare L.) for silage biomass productivity; and N use efficiency (NUE) as a function of the application of three contrasting types of biosolids (mesophilic anaerobic digested [BM], composted [BC], and alkaline-stabilized [BA]) and granular urea in Central Alberta, Canada, over two experimental years. The combination of each biosolid with urea was also evaluated. All N source treatments were assessed with both surface (S) and incorporation (I) placements. Concurrent increases in soil moisture and available N triggered high N2O emissions during the growing season and spring thaw. Emissions during thawing accounted for 42% of the total annual cumulative. Incorporation of the N source increased N2O emissions by at least 22% compared with surface-applied N. In general, CO2 fluxes followed similar patterns to the N2O fluxes, whereas CH4 fluxes were minimal. Overall, BMI showed the highest N2O, CO2, and CH4 emissions. On the basis of field fluxes, annual N2O emission factor (EFarea) from urea-amended soils (0.62 ± 0.14%) were fivefold higher than those from soils receiving only BA or BC (0.12 ± 0.04% or 0.12 ± 0.03%, respectively, P < 0.05), but EFarea from soils amended with only BM (1.33 ± 034%) was more than double the EFarea from urea-amended soils (P > 0.05). We calculated a partial GHG balance in which field N2O emissions were the main contributor, accounting for up to 96% of the budget. The GHG footprint of urea manufacturing also made a considerable contribution to the GHG balance (up to 49%), which offset the comparatively low field N2O emissions from the urea-amended fields, leading to CO2 equivalents even higher than the BA- and BC-amended fields. Incorporating the N sources enhanced barley biomass by 12% based on the 2-year mean. In certain cases, the combination of biosolids and urea (e.g., BMURI, BMURS, BCURS) showed even higher biomass and NUE, as well as lower N2O emissions. Our findings will help to improve predictions and mitigation strategies for GHG emissions, particularly for N2O, from agricultural soils receiving biosolids applications.
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... Conceivably, from a crop management perspective, frequent applications are more feasible on sandier soils to reduce leaching losses in fields that are accessible by equipment (i.e., less saturated soils). While texture was not an important factor in our analysis, studies in Canada indicate very strong effects of soil texture on N 2 O emission(Liang et al., 2020;Rochette et al., 2018). Alternatively,Huang et al. (2016) reported increases in yield and reductions in NH 3 volatilization with split applications, which may contribute to pollution swapping if crop recovery is low.In their meta-analysis,Fernandez et al. (2020) reported that later applications of fertilizer in maize improved yields only for plants with heightened N uptake during the reproductive stages. ...
Meta‐analysis of yield and nitrous oxide outcomes for nitrogen management in agriculture
Article
Full-text available
  • Apr 2021
Improved nitrogen (N) use is key to future food security and environmental sustainability. While many regions still experience N shortages, agriculture is the leading global emitter of N2O due to losses exacerbated by N surpluses in other regions. In order to sustainably maintain or increase food production, farmers and their advisors need a comprehensive and actionable understanding of how nutrient management affects both yield and N2O emissions, particularly in tropical and subtropical agroecosystems. We performed a meta‐analysis to determine the effect of N management and other factors on N2O emissions, plant N uptake, and yield. Our analysis demonstrates that performance indicators—partial N balance and partial factor productivity—predicted N2O emissions as well as or better than N rate. While we observed consistent production and environmental benefits with enhanced‐efficiency fertilizers, we noted potential trade‐offs between yield and N2O emissions for fertilizer placement. Furthermore, we observed confounding effects due to management dynamics that co‐vary with nutrient application practices, thus challenging the interpretation of the effect of specific practices such as fertilization frequency. Therefore, rather than providing universally prescriptive management for N2O emission reduction, our evidence supports mitigation strategies based upon tailored nutrient management approaches that keep N balances within safe limits, so as to minimize N2O emissions while still achieving high crop yields. The limited evidence available suggests that these relationships hold for temperate, tropical, and subtropical regions, but given the potential for expansion of N use in crop production, further N2O data collection should be prioritized in under‐represented regions such as Sub‐Saharan Africa.
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... Inter-annual variability in precipitation at the site (Table 3), particularly in June (i.e., early growing season), was a key factor in both the findings and execution of the study. Soil N 2 O emissions have been found to be dependent on cumulative rainfall (Liang et al., 2020;Rochette et al., 2018) or the ratio of cumulative rainfall to ET Schelde et al., 2012) and soil water content (Fisher et al., 2018;Sehy et al., 2003;Taki et al., 2018;Vilain et al., 2010), so having a range in growing season precipitation between years adds information to reported findings examining the influence of variable rate N management. Conversely, excessive rainfall during the late spring and early summer of 2014 caused crop failure and resulted in the loss of a study year. ...
Soil nitrous oxide emissions from no-till canola production under variable rate nitrogen fertilizer management
Article
Full-text available
Precision farming methods such as variable rate or site-specific nitrogen (N) fertilizer application based on field management zones may represent a mechanism to mitigate soil nitrous oxide (N2O) emissions. To investigate the impact of site-specific N fertilization on soil N2O fluxes a study was conducted from spring 2013 through summer 2015 on no-till cropland under canola (Brassica napus) production near Brandon, Manitoba, Canada. The static chamber method was used to measure soil N2O fluxes across three management zones (low yield, average yield, and high yield) with three N application rates (50%, 100%, and 150% of target seed yields for each management zone) and unfertilized control treatments. A machine-learning approach (random forest analysis) for analyzing soil N2O fluxes confirmed conditions related to soil temperature, moisture, and nitrate availability were the most important predictors of individual flux events. Similarly, soil N availability and moisture content were found to be the most important variables in regression models of cumulative growing season emissions. Nitrogen fertilizer-induced N2O emission factors were lower for the high yield management zone (≈0.1% both growing seasons) compared to the low yield management zone (0.9% in 2013 and 0.2% in 2015) confirming that variable rate application can mitigate N2O fluxes from cropland soils. The high yield zones had the lowest emission factors despite receiving 50% more fertilizer than field average target yields suggesting more efficient crop N use in these areas with greater production potential. Conversely, the low yield zones had higher emission factors despite receiving 50% less fertilizer than field average target yields indicating a greater environmental burden associated with annual cropping these portions of the agricultural landscape. More studies are required to investigate the generality of these findings for different crops, soils and climatic conditions.
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... On the basis of the available data, Rochette et al. (2018) established a Tier 2 EF of 0.33% for synthetic N fertilizer specifically in Black Chernozem soils in the Canadian Prairies. Recently, Liang et al. (2020) proposed instead implementing a nonlinear approach to estimate EF as a function of growing-season cumulative rainfall (May-October) while modifying the Canadian Tier 2 inventory methodology. When embracing such nonlinear approach in our two study years, we calculated an annual N 2 O EF of 0.30% (Supplemental Table S5). ...
Nitrous oxide emissions and nitrogen use efficiency in wheat: N fertilization timing and formulation, soil N, and weather effects
Article
  • Sep 2020
Improving N fertilization in croplands could minimize soil emissions of nitrous oxide (N2O) and mitigate climate change. This study investigated the effects of spring vs. fall N applications of conventional vs. enhanced efficiency N fertilizers (EENFs) on N2O emissions and N use efficiency (NUE) in spring wheat (Triticum aestivum L.) over 2.5 yr in Alberta, Canada. Fertilizers were anhydrous ammonia and urea, and the EENF formulations included urease and nitrification inhibitors and a polymer coating. We measured a fertilizer N2O emission factor of 0.31±0.04%. Irrespective of N fertilizer and timing options, peak N2O emissions were evident following soil thawing and major rainfalls. Because most of the annual N2O emissions were associated with soil thawing, spring‐applied N emitted half the N2O of the fall‐applied N during the second study year (P< 0.001). Conversely, the opposite was observed for the first study year, when overall N2O emissions were 36% larger for spring‐ than fall‐applied N (P = 0.031), as major rainfalls occurred shortly after the spring N fertilization. Nevertheless, within this first study year, EENFs significantly reduced N2O emissions (by 26% on average; P = 0.019), with a tendency for 11% higher grain yield across springtime EENFs than for conventional fertilizers. Concomitantly, spring‐applied N doubled the fertilizer N recovery efficiency (NRE) in the same year (P = 0.023). The soil at the study site inherently had high N availability (NH4 and NO3) and this probably moderated the beneficial effects of EENFs on N2O emissions and grain yields. Results suggest that spring EENFs can mitigate the risk for N2O emissions while sustaining high yields even under scenarios with high availability of native soil N. This article is protected by copyright. All rights reserved
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Nitrous oxide emissions from northern barley croplands after injections of liquid manure and nitrification inhibitors
Preprint
Full-text available
  • Sep 2022
Increasing contributions of nitrous oxide (N 2 O) from agriculture to the atmosphere is a concern. We quantified N 2 O emissions from barley fields after repeated injections of liquid manure in Central Alberta, Canada. Manure alone was injected in the fall or spring, and we also evaluated two nitrification inhibitors (NIs: nitrapyrin and DMPP) admixed with the manure. Flux measurements were done with surface chambers from soil thawing to freezing. Soil moisture, ammonium and nitrate were repeatedly measured. Across all manure treatments, annual N 2 O emissions ranged broadly from 1.3 up to 15.8 kg N 2 O–N ha − 1 , and likewise, the direct emission factor (EF d ) varied widely from 0.23 up to 2.91%. When comparing the manure injections without NIs, spring-manure had higher annual N 2 O EF d than fall-manure. The effectiveness of NIs on reducing emissions manifested only in moist soils. The spring thaw after the last manure injections was very wet, and this generated high N 2 O emissions from soils that had received repeated manure injections in the previous years. We interpreted this result as an increased differential residual effect in soils amended with spring-manure in the previous growing season. This outcome supports the need to account for emissions in succeeding springs when estimating N 2 O EF d of manure injections. Neglecting this residual spring-thaw N 2 O emission would lead to a substantial underestimation of year-round EF d . Across all treatment combinations, increased spring-thaw N 2 O emissions were associated with increases in both moisture and postharvest nitrate in these heavily-manured soils.
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Dry matter partitioning and residue N content for 11 major field crops in Canada adjusted for rooting depth and yield
Article
Full-text available
To improve the estimates of C and N inputs to soil, we developed new estimates of partitioning between the harvested portion, aboveground residue, and belowground residue for 11 major crops based on depth-adjusted root/shoot ratios and grain yield-adjusted harvest indices. We updated the mean N concentration of each partition.
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Globally important nitrous oxide emissions from croplands induced by freeze–thaw cycles
Article
Full-text available
  • Mar 2017
Seasonal freezing induces large thaw emissions of nitrous oxide, a trace gas that contributes to stratospheric ozone destruction and atmospheric warming. Cropland soils are by far the largest anthropogenic source of nitrous oxide. However, the global contribution of seasonal freezing to nitrous oxide emissions from croplands is poorly quantified, mostly due to the lack of year-round measurements and difficulty in capturing short-lived pulses of nitrous oxide with traditional measurement methods. Here we present measurements collected with half-hourly resolution at two contrasting cropland sites in Ontario and Manitoba, Canada, over 14 and 9 years, respectively. We find that the magnitude of freeze–thaw-induced nitrous oxide emissions is related to the number of days with soil temperatures below 0 °C, and we validate these findings with emissions data from 11 additional sites from cold climates around the globe. Based on an estimate of cropland area experiencing seasonal freezing, reanalysis model estimates of soil temperature, and the relationship between cumulative soil freezing days and emissions that we derived from the cropland sites, we estimate that seasonally frozen cropland contributes 1.07 ± 0.59 Tg of nitrogen as nitrous oxide annually. We conclude that neglecting freeze–thaw emissions would lead to an underestimation of global agricultural nitrous oxide emissions by 17 to 28%.
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Current inventory approach overestimates the effect of irrigated crop management on soil-derived greenhouse gas emissions in the semi-arid Canadian Prairies
Article
Greenhouse gas (GHG) emissions from agricultural soils in the Canadian Prairie region are generally low and, due to dry, well aerated soil conditions, can be quite variable. Compared to dryland (rainfed) crop production, irrigated cropping has potential to contribute greater quantities of soil derived nitrous oxide (N2O), carbon dioxide (CO2), and methane (CH4) to the atmosphere as producers target higher yields by minimizing soil moisture limitations and applying greater amounts of nitrogen fertilizers. However, the actual GHG dynamics from irrigated soils in this region are not well understood as there have been few field-based studies in the semi-arid prairies of western Canada. The goal of this study was to identify how emissions of soil derived N2O, CO2, and CH4 are influenced by changes in soil temperature, water status, and nitrogen rates brought about by irrigated crop management. This was achieved through continuous, in-situ monitoring of soil conditions and chamber-based measurements of soil GHG flux. The most notable change in soil conditions brought about by irrigation was elevated moisture levels, which appeared to influence the flux dynamics of all three agricultural greenhouse gases—specifically, a reduction in CH4 uptake and periodic increases in CO2 and N2O emissions. Despite the reduced soil moisture limitation, annual N2O emissions from the irrigated cropping system were much lower than those calculated using the current Canadian National GHG Inventory Reporting. This suggests that annual emissions are limited more by N availability rather than moisture deficits, as the current method for emissions accounting assumes. Consequently, our results indicate that emissions from irrigated cropping systems in the semi-arid Canadian Prairies are overestimated by the current inventory approach. Moreover, because irrigated crop production involves more than just the application of water, our results demonstrate that a more systems-oriented approach to GHG accounting is required to capture the combined effects of water-soil-crop management on GHG emissions from irrigated cropping systems.
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Changes in snow cover alter nitrogen cycling and gaseous emissions in agricultural soils
Article
Climate change-related increases in winter temperatures and precipitation, as predicted for eastern Canada, may alter snow cover, with consequences for soil temperature and moisture, nitrogen cycling, and greenhouse gas fluxes. To assess the effects of snow depth in a humid temperate agricultural ecosystem, we conducted a two-year field study with (1) snow removal, (2) passive snow accumulation (via snow fence), and (3) ambient snow treatments. We measured in situ N2O and CO2 fluxes and belowground soil gas concentration, and conducted denitrification and potential nitrification laboratory assays, from November through May. Snow manipulation significantly affected winter N2O dynamics. In the first winter, spring thaw N2O fluxes in snow removal plots were 31 and 48 times greater than from ambient snow and snow accumulation plots respectively. Mid-winter soil N2O concentration was also highest in snow removal plots. These effects may have been due to increased substrate availability due to greater soil frost, along with moderate gas diffusivities facilitating N2O production, in snow removal plots. In the second winter, spring thaw N2O fluxes and soil N2O concentration were greatest for ambient snow plots. Peak fluxes in ambient snow plots were 19 and 24 times greater than in snow accumulation and snow removal plots, respectively. Greater soil moisture in ambient snow plots overwinter could have facilitated denitrification both through decreased O2 availability and increased disruption of soil aggregates during freeze-thaw cycles. Overall, results suggest that effects of changing snow cover on N cycling and N2O fluxes were not solely a direct effect of snow depth; rather, effects were mediated by both soil water content and temperature. Furthermore, the fact that treatments with greatest mid-winter belowground N2O accumulation also had greatest spring thaw N2O fluxes in both years suggests the hypothesis that high spring thaw fluxes were due not only to spring soil conditions, but also to an effect of soil conditions in frozen soils that had facilitated N2O production throughout winter.
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Streaming Urea Ammonium Nitrate with or without Enhanced Efficiency Products Impacted Corn Yields, Ammonia, and Nitrous Oxide Emissions
Article
  • Mar 2018
Surface streaming urea ammonium nitrate (UAN) into corn (Zea mays L.) at side-dress (v4–v6) or later in the season (v12–v14) is an emerging N fertilizer application method as it is rapid, reduces soil disturbance, and allows for flexible application times. In 2013 and 2014, side-dress N application (130 kg N ha–1) using three streaming UAN sources was evaluated for their ability to maintain grain yield, reduce ammonia (NH3) volatilization, and mitigate nitrous oxide (N2O) emissions. The products included streaming of urea ammonium nitrate (StrUAN), urea ammonium nitrate with a urease inhibitor (StrUAN-UI), urea ammonium nitrate with urease inhibitor plus nitrification inhibitor (StrUAN-UI+NI), and a control (no N). The efficacy of streaming relative to traditional shal-low-injected urea ammonium nitrate (InjUAN) was also assessed. Delayed NH3 sampling related to wind-tunnel installation in 2013 and 2014 led to additional NH3 measurements in 2015 and 2016. Average yields from StrUAN were 11% lower relative to InjUAN. The use of inhibitors did not improve yields relative to StrUAN. Ammonia volatilization was not significantly different between StrUAN and InjUAN losing 14 and 20% of applied N (2-yr average), respectively. However in 2015 and 2016, NH3 volatilization from StrUAN was 3.6-fold greater than InjUAN when measurements were started immediately after application. Hence lower yields in 2013 and 2014 from StrUAN likely reflect N loss to rapid volatilization during or shortly after application. The StrUAN-UI treatment increased 2-yr average N2O emissions by 17.3 to 18.7% relative to StrUAN or StrUAN-UI+NI. For humid-temperate clay loam soil, UAN streaming with/without inhibitors was not effective for maintaining yields or reducing NH3 volatilization.
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Soil nitrous oxide emissions from agricultural soils in Canada: Exploring relationships with soil, crop and climatic variables
Article
National scale emissions of nitrous oxide (N2O) from agricultural soils are often estimated using a unique fertilizer-induced emission factor (EF); thereby neglecting how factors other than nitrogen input could impact emissions. In the present study, we compiled soil N2O flux data collected since 1990 on agricultural soils in Canada, to identify key soil and climate factors, and management practices that explain variations in N2O emissions and in EF. Stepwise regression analysis showed that the growing season precipitation was the most important factor impacting N2O emissions, and that cumulative N2O fluxes and EFs could be predicted using equations (R² from 0.68 to 0.85) including two to five of the following variables: growing season precipitation, ratio of growing season precipitation to potential evapotranspiration, mean annual air temperature, crop type (annual or perennial), soil pH, texture and organic carbon content. We conclude that N2O EFs could be effectively stratified based on growing season precipitation, soil texture (coarse, medium and fine), type of N (synthetic and organic), and crop type (perennial and annual). We propose EFs that account for the dominant factors that modulate the nitrogen fertilizer-induced emissions and should improve regional and national estimates in Canada. They may also provide useful information for guiding the development of soil N2O emission quantification in other countries.
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Combining Urease and Nitrification Inhibitors with Incorporation Reduces Ammonia and Nitrous Oxide Emissions and Increases Corn Yields
Article
  • Sep 2017
Less than 50% of applied nitrogen (N) fertilizer is typically recovered by corn (Zea mays L.) due to climatic constraints, soil degradation, overapplication, and losses to air and water. Two application methods, two N sources, and two inhibitors were evaluated to reduce N losses and enhance crop uptake. The treatments included broadcast urea (BrUrea), BrUrea with a urease inhibitor (BrUrea+UI), BrUrea with a urease and a nitrification inhibitor (BrUrea+UI+NI), injection of urea ammonium nitrate (InjUAN), and injected with one or both inhibitors (InjUAN+UI, InjUAN+UI+NI), and a control. The BrUrea treatment lost 50% (64.4 kg N ha⁻¹) of the applied N due to ammonia volatilization, but losses were reduced by 64% with BrUrea+UI+NI (23.0 kg N ha⁻¹) and by 60% with InjUAN (26.1 kg N ha⁻¹). Ammonia losses were lower and crop yields were greater in 2014 than 2013 as a result of the more favorable weather when N was applied in 2014. When ammonia volatilization was reduced by adding a urease inhibitor, N2O emissions were increased by 30 to 31% with BrUrea+UI and InjUAN+UI compared with BrUrea and InjUAN, respectively. Pollution swapping was avoided when both inhibitors were used (BrUrea+UI+NI, InjUAN+UI+NI) as both ammonia volatilization and N2O emissions were reduced, and corn grain yields increased by 5% with BrUrea+UI+NI and by 7% with InjUAN+UI+NI compared with BrUrea and InjUAN, respectively. The combination of two N management strategies (InjUAN+UI+NI) increased yields by 19% (12.9 t ha⁻¹) compared with BrUrea (10.8 t ha⁻¹). © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. 5585 Guilford Rd., Madison, WI 53711 USA.
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Harvest index–yield relationship for estimating crop residue in cold continental climates
Article
Soil carbon (C) balance largely depends on the amount of crop residue inputs into soils and those inputs are affected by harvest index (HI), the ratio of harvested product to total shoot dry matter. The objective of this study was to establish the relationship between HI and yield for major crops to improve the estimation of aboveground crop residue inputs to agricultural soils in cold continental climates. We analyzed yield and HI data for 11 major crops from published field studies in a cold continental climate. Significant linear relationships between HI and crop yield were determined for wheat (Triticum aestivum L.), maize (Zea mays L.), oat (Avena sativa L.), barley (Hordeum vulgare L.), pea (Pisum sativum L.), chickpea (Cicer arietinum L.), lentil (Lens culinaris L.), soybean (Glycine max L.), canola (Brassica napus L.), and flax (Linum usitatissimum L.) (R² = 0.19–0.65, P < 0.05), while HI of potato (Solanum tuberosum L.) did not change with yield. The HI increased by 0.015 for wheat and maize to 0.110 for flax for each Mg ha⁻¹ yield increase. Results for wheat, lentil, flax, and maize showed that crop HI was significantly influenced by grain yield (P < 0.01) but not significantly (P > 0.05) affected by cultivar when the grain yield effect was included. These results indicated that cultivar effect appears to be largely captured through crop yield, so it does not appear to be essential to know the cultivar to estimate the HI for an annual series of regional yields from different cultivars. The developed relationships between HI and crop yield allow improved estimation of residue inputs in cold continental climates.
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