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Global nitrous oxide emission factors from agricultural soils after addition of organic amendments: A meta-analysis
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... The water content (94.6 to 96.1%), total NH 4 + -N (1.1 g kg -1 measured at one site, representing 48% of the total N applied), and C:N ratio (varying from 3.6 to 9.4) of the LDM in our study (Table 2) may have further contributed to N 2 O emissions. The high water content (> 95%) and NH 4 + -N (> 10% dry weight) and the low C:N ratio (< 5%) of slurries enhanced N 2 O emissions in Charles et al. (2017) as these factors and the labile C provided with the manure can trigger the microbial activity in the soil and accelerate organic matter decomposition. This was observed in particular at the St-Augustin and Truro sites since the Ottawa site experienced drier soil conditions during corn years when the N fertilizer was applied (Fig. 1), and because the aerobic conditions likely limited N 2 O production by denitrifiers despite high soil inorganic N concentrations and labile C concentrations (Davidson et al. 2000). ...
... Our mean growing season LDM EF in perennial forages (0.36%) was similar to the mean EF of cattle slurry surface-applied or injected on grassland (0.31 to 0.50%; Velthof et al. (2024), but lower than the EF for broadcast spring applied slurry on a UK grassland (0.72%; Thorman et al. (2020). The organic fertilizers composition and their method of application influence the N 2 O emissions, although other management and climate factors will also affect the emissions (Charles et al. 2017;Velthof et al. 2024). Moreover, some species combinations could help mitigate N 2 O emissions in perennial forages as they have a complementary root morphology and greater total biomass productivity (Abalos et al. 2014). ...
... The lower mean EF found from the MIN N fertilizer compared with the LDM in annual crops is in agreement with the EFs from synthetic and organic N sources reported in the meta-analysis of Zhou et al. (2017) and in the Petersen et al. (2023) study on sandy loam soils, but in disagreement with the results obtained by Rochette et al. (2018) in eastern Canada and by Charles et al. (2017) in their meta-analysis. Further, in our study, the mean MIN EF of 0.30 ± 0.19% in annual crops was lower than the IPCC default EF of 1% for synthetic fertilizers and lower than the mean EF of 1.34% (raw data) reported in Charles et al. (2017). ...
Aims
Perennial forages in rotation with annual crops can improve agricultural resilience by increasing soil organic carbon. However, how nitrogen (N) sources interact with rotation diversity to influence soil nitrous oxide (N2O) emissions is not well understood.
Methods
During three snow-free seasons, N2O emissions, crop yields, and ancillary variables were measured at three experimental sites with contrasting soil textures (silty clay and sandy loam) in eastern Canada. Using a split-plot design, we compared a corn (Zea mays L.)-soybean (Glycine max [L.] Merr.)-corn rotation and a mixed perennial grass sward receiving N via: i) mineral fertilizer (MIN), ii) liquid dairy manure (LDM), and iii) inclusion of alfalfa (Medicago sativa L.) to the perennial forages with no additional N (LEG).
Results
When summed across sites over all three years, cumulative N2O emissions were greater for LDM than MIN in annual crops (8.75 ± 1.63 and 5.15 ± 0.96 kg N2O-N ha–1, respectively), but not in perennial grasses (2.95 ± 0.55 and 3.76 ± 0.70 kg N2O-N ha–1, respectively). When comparing N sources within each crop type over the three years, MIN generated greater yields than LDM in annual and perennial crops, but lower yield-scaled N2O emissions than LDM in annual crops only. During forages post-seeding years, area- and yield-scaled N2O emissions induced by LDM and LEG were lower than MIN.
Conclusion
Our results suggest that for a cool humid climate using LDM or LEG in perennial forages and MIN on annual crops can reduce overall N2O emissions, while generating similar or lower yield-scaled emissions.
... It possesses a global warming potential (GWP) 265 times greater than CO 2 [2]. Notably, agricultural land is responsible for 60% of total global anthropogenic N 2 O emissions [3]. According to the Greenhouse Gas Bulletin published by the World Meteorological Organization (WMO) in 2023, N 2 O levels experienced the most considerable year-on-year increase between 2021 and 2022, signifying a critical environmental concern. ...
... For cases lacking both SD and SE values, a regression equation was formulated by linearly fitting SD data with other corresponding mean values from the same study, enabling us to estimate the required SD. In scenarios where pertinent data for these calculations were absent, we assigned SE as 1/10th of the mean value, as per standard practice in statistical analysis [3], and the required data were then calculated. ...
... Our analysis focused on the effects of experimental environmental conditions, such as different climatic factors, soil texture and soil physicochemical properties, on N 2 O emissions from agricultural fields to determine the specific extent of N 2 O emissions. Charles et al. [3] found that the application of organic fertilizer to fine textured soils reduced N 2 O emissions more than sandy soils. This is mainly due to the fact that the main process of N 2 O production in sandy soils undergoes nitrification [60]. ...
Fertilizer application is the basis for ensuring high yield, high quality and high efficiency of farmland. In order to meet the demand for food with the increasing of population, the application of nitrogen fertilizer will be further increased, which will lead to problems such as N2O emission and nitrogen loss from farmland, it will easily deteriorate the soil and water environment of farmland, and will not conducive to the sustainable development of modern agriculture. However, optimizing fertilizer management is an important way to solve this problem. While, due to the differences in the study conditions (geographical location, environmental conditions, experimental design, etc.), leading to the results obtained in the literatures about the N2O emission with different nitrogen fertilizer application strategies have significant differences, which requiring further comprehensive quantitative analysis. Therefore, we analyzed the effects of nitrogen fertilizer application strategies (different fertilizer types and fertilizer application rates) on N2O emissions from the fields (rice, wheat and maize) based on the Meta-analysis using 67 published studies (including 1289 comparisons). For the three crops, inorganic fertilizer application significantly increased on-farm N2O emissions by 19.7–101.05% for all three; and organic fertilizer increased N2O emissions by 28.16% and 69.44% in wheat and maize fields, respectively, but the application of organic fertilizer in rice field significantly reduced N2O emissions by 58.1%. The results showed that overall, the application of inorganic fertilizers resulted in higher N2O emissions from farmland compared to the application of organic fertilizers. In addition, in this study, the average annual temperature, annual precipitation, soil type, pH, soil total nitrogen content, soil organic carbon content, and soil bulk weight were used as the main influencing factors of N2O emission under nitrogen fertilizer strategies, and the results of the study can provide a reference for the development of integrated management measures to control greenhouse gas emissions from agricultural soils.
... Rowlings et al. (2015) indicated that N 2 O emissions were more strongly correlated with the size and distribution of precipitation events than with soil water content, which fluctuates on a seasonal and interannual basis. A meta-analysis by Charles et al. (2017) encompassing 38 studies from 12 countries demonstrated that observed N 2 O EFs were consistently lower than the IPCC's default, with variations driven by amendments, soil properties (texture, drainage, organic carbon (C) and nitrogen (N)), and climatic factors (precipitation). Specifically, N 2 O EFs for organic fertilizers averaged 0.57 ± 0.30%, with fine-textured soils exhibiting 2.80 times higher EFs than coarse-textured soils. ...
... These findings align with earlier reports by Yan et al. (2003) and Albanito et al. (2017), both of which demonstrated that uniform N application across diverse regions leads to significant variation in N 2 O emission. Agricultural practices, including tillage, planting and harvesting methods, fertilization, crop varieties, and irrigation, also play a crucial role in modulating N 2 O emissions, even within similar climatic zones (Charles et al. 2017;Petersen et al. 2023). ...
The default emission factor (EF) of 1.00% for direct nitrous oxide (N2O) emissions, as recommended by the Intergovernmental Panel on Climate Change (IPCC), is often applied in countries that lack region-specific N2O EFs, such as Thailand. However, this approach introduces significant uncertainty due to the spatial variability and complex dynamics governing N2O emissions, potentially leading to inaccurate estimates. This study quantified direct N2O emissions and derived EFs from chemical fertilizer applications at varying rates (0, 100, 150, 200, and 250 kg N ha⁻¹) in sugarcane plantations located in Kanchanaburi (KB) and Ratchaburi (RB) provinces, western Thailand. The results showed that using nitrogen (N) fertilizer significantly stimulated N2O emissions at both study sites, with higher N input correlating to greater emissions. The cumulative N2O emissions for N application rates ranging from 0 to 250 kg N ha⁻¹ varied from 1.16 to 3.85 kg N2O ha⁻¹ in KB and from 1.33 to 3.90 kg N2O ha⁻¹ in RB. The calculated N2O EFs averaged 0.68% (0.66–0.71%) in KB and 0.70% (0.64–0.83%) in RB, with an overall mean EF of 0.69%, representing a 0.31% reduction from the IPCC’s default value. This reduction is relatively attributed to rainfall patterns, soil properties, N application rates, and N utilization by plant in the area. The findings suggest that Thailand’s current national N2O inventory, based on the default EF, may be overestimated if country-specific EFs resemble the area-specific data observed in this study. While chemical fertilizer application increased N2O emissions, its role in enhancing soil nutrient availability is essential for boosting crop productivity. Notably, the highest fertilizer input (250 − 75 − 149 kg N − P − K ha⁻¹) did not result in a proportional increase in yield, suggesting that applying fertilizer beyond crop demand may not maximize productivity. Thus, optimizing fertilizer application to match crop nutrient requirements presents a straightforward and practical strategy to reduce N2O emissions while maintaining food security.
Graphical abstract
... Nitrous oxide is a GHG (Prather et al., 2015), mostly derived from direct and indirect anthropogenic emissions (Tian et al., 2020;IPCC, 2014). In agricultural soils, N 2 O emissions are primarily associated with biological reactions of nitrification and denitrification (Linton et al., 2020;Charles et al., 2017), and are controlled by inorganic N availability (e.g., Glenn et al., 2021;Maaz et al., 2021) and edaphic-climatic factors (Liu et al., 2022b;Machado et al., 2021). The inclusion of pulses in crop sequences can impact soil physical and biochemical properties, which in turn can reduce N 2 O emissions (Li et al., 2021;Oliveira et al., 2021), but increased emissions could also occur if pulse residue decomposition increases soil inorganic N and available carbon. ...
... In addition, crop residues, including from legumes, can result in low N 2 O emissions both in the legume and cereal phases of the rotations (e.g., Li et al., 2021;Machado et al., 2021). Crop residues have been described as a low-risk group for N 2 O emissions, with emission factor of 0.02 ± 0.13% (Charles et al., 2017). This was found in the cereal phases following pulses of our rotations (years 2019 and 2021) that experienced lower cumulative N 2 O emissions than when wheat followed wheat. ...
... In the emission of greenhouse gases (СО2, СН4, N2O), which take part in destruction of ozone layer of atmosphere, the main "supplier" of nitrous oxide (N2O) into the atmosphere is agriculture [13][14][15]. ...
... That is, in agrocenoses under winter wheat, N2O emissions are higher compared to tilled crops -sugar beets and soybeans. 14 In winter wheat crops, increase in the content of mineral forms of nitrogen after foliar fertilizing with mineral and bioorganic fertilizers on the background of calculated doses of phosphorus fertilizers increases the size of nitrous oxide emissions from soil with high correlation coefficient. ...
The article presents the results of studies aimed to identify the effect of foliar treatments of winter wheat, sugar beets and soybeans with mineral and bioorganic fertilizers. Their positive effect on increasing the concentration of mineral forms of nitrogen in soil was revealed. The crop types have a greater influence on the size of nitrous oxide emissions: in winter wheat crops - 679 µg/m3, soybeans - 637.2 µg/m3, sugar beets - 576.8 µg/m3. The amounts of nitrous oxide emissions were lower in the variants without the use of phosphorus-potassium fertilizers. The Ruter AA fertilizer showed the greatest efficiency on winter wheat crops - 42.7 c/ha. Soybean grain yield of 44.2 c/ha was also achieved by using Ruter AA, as well as Geo-humate together with phosphorus-potassium fertilizers. On the background of the actual supply of phosphorus and potassium, maximum yield was obtained when using N30 on the leaf - 39.3 c/ha. Foliar feeding ensured a yield of sugar beet root crops of up to 67.1-77.4 c/ha on the backdrop of the application of phosphorus-potassium fertilizers with the advantage of using Amino turbo. The largest yield of sugar beet roots without use of mineral phosphorus and potassium was ensured by N30 treatment of the leaf in the phases of 4-6 and 8 leaves - 63.2 t/ha. Of the organo-mineral fertilizers and biostimulants, the best result was shown by the use of Ruter A - 62.6 t/ha. We believe that foliar feeding of crops can be a sustainable farming method that can increase crop yields and reduce N2O emissions.
... In one year for example, 6.3% of the total N applied in digested sludge was emitted as N 2 O, as opposed to 0.24% for alkalinestabilized sludge and 0.17% for composted sludge (Obi-Njoku et al. 2022). For comparison, the N 2 O emissions factor for all kinds of sludge, wastewater and animal manure in the IPCC guidelines (Hergoualc'h et al. 2019) is 1%, while a review by Charles et al. (2017) recommends an emissions factor of 1.21 + 0.14% for the same three amendments. However, these N 2 O emissions are highly influenced by other factors like the C:N ratio, moisture content, soil texture and climatic factors like precipitation (Charles et al. 2017). ...
... For comparison, the N 2 O emissions factor for all kinds of sludge, wastewater and animal manure in the IPCC guidelines (Hergoualc'h et al. 2019) is 1%, while a review by Charles et al. (2017) recommends an emissions factor of 1.21 + 0.14% for the same three amendments. However, these N 2 O emissions are highly influenced by other factors like the C:N ratio, moisture content, soil texture and climatic factors like precipitation (Charles et al. 2017). ...
There is growing awareness of the contribution of sanitation systems to greenhouse gas (GHG) emissions globally, and hence to climate change. However, there is a lack of comprehensive insight into emission sources dis-aggregated across the entire sanitation chain. This study presents a detailed review and analysis of emission sources from both sewer-based and non-sewered sanitation systems, with a focus on both fugitive emissions and those related to system operation. Our analysis highlights evidence gaps in several areas in the literature: quantifying emissions from non-sewered sanitation systems, with particular gaps related to technologies like biogas toilets and composting toilets; oversight of contextual factors such as environmental conditions and infrastructure operational status in GHG accounting; a dearth of holistic GHG emission studies across the entire sanitation chain comparable to those in the solid waste management sector; and inconsistencies in GHG measurement methods. By pinpointing these gaps, this review provides a robust reference for planning climate mitigation strategies for sanitation and wastewater management systems, emphasizes the urgent need for the incorporation of climate-smart solutions in the sector e.g. in the design of new and retrofitted infrastructure, and aims to bridge the sustainable development goals related to sanitation and climate action.
... A positive interaction between manure and artificial fertilizer on N 2 O emissions has been noted in the sense that manure amendment increases emission from fertilize. 120 Different manures vary in their effect on N 2 O emission with animal slurries giving a 2.2 kg N ha À1 season À1 increase, solid manure composts and crop residues resulting in a 1.1 kg N 2 O-N ha À1 season À1 increase and composts mediating 0.5 kg N 2 O-N ha À1 season À1 more than control. 120 Hence, application of inorganic N often increases N 2 O emissions from below 1 kg N 2 O-N ha À1 year À1 by further 1-2 kg N 2 O-N ha À1 year À1 . ...
... 120 Different manures vary in their effect on N 2 O emission with animal slurries giving a 2.2 kg N ha À1 season À1 increase, solid manure composts and crop residues resulting in a 1.1 kg N 2 O-N ha À1 season À1 increase and composts mediating 0.5 kg N 2 O-N ha À1 season À1 more than control. 120 Hence, application of inorganic N often increases N 2 O emissions from below 1 kg N 2 O-N ha À1 year À1 by further 1-2 kg N 2 O-N ha À1 year À1 . Application of wet organic fertilizer like slurry may increase emissions even further. ...
In some places, N2O emissions have doubled during the last 2-3 decades. Therefore, it is crucial to identify N2O emission hotspots from terrestrial and aquatic systems. Large variation in N2O emissions occur in managed as well as in natural areas. Natural unmanaged tropical and subtropical wet forests are important N2O sources globally. Emission hotspots, often coupled to human activities, vary across climate zones, whereas N2O emissions are most often a few kg N ha⁻¹ year⁻¹ from arable soils, drained organic soils in the boreal and temperate zones often release 20–30 kg N ha⁻¹ year⁻¹. Similar high N2O emissions occur from some tropical crops like tea, palm oil and bamboo. This strong link between increased N2O emissions and human activities highlight the potential to mitigate large emissions. In contrast, water where oxic and anoxic conditions meet are N2O emission hotspots as well, but not possible to reduce.
... Generally, agriculture accounts for 10 to 14% of total greenhouse gas (GHG) emissions, mainly represented by carbon dioxide (CO 2 ) and nitrous oxide (N 2 O) which alter carbon (C) and nitrogen (N) cycles in agroecosystems (Shakoor et al. 2020). In fact, excessive use of mineral N fertilizers, burning of fossil fuels and intensive tillage are considered major sources of GHG emissions (Charles et al. 2017;Shakoor et al. 2020;Li et al. 2022). These farming practices are widely recognized as unsustainable as they lead to soil degradation and reduced soil fertility across agroecosystems, ultimately causing crop failure in the long-term period (Kopittke et al. 2019). ...
Organic fertilizers have great potential to improve crop production while reducing greenhouse gas (GHG) emissions in agroecosystems. To study their effect on GHG emissions, a field experiment over a two-year period (2021 and 2022) was carried out to quantify carbon dioxide (CO2) and nitrous oxide (N2O) emissions. Experimental treatments included: (i) two types of organic fertilizers [wheat residue (WR) and sheep manure (SM)]; and (ii) three cropping systems [monocropping of maize (Zea mays L., Ma) and mung bean (Vigna radiata (L.) R. Wilczek, Mu), and their intercropping (Ma + Mu)]. Total crop biomass and its carbon (C) and nitrogen (N) content, soil CO2 and N2O emissions, soil temperature and moisture were measured. The results showed that Ma + Mu_WR significantly reduced cumulative CO2 emissions by 36% and 28% compared to the Ma_WR and Mu_WR, respectively. Similarly, Ma + Mu_SM reduced soil CO2 emissions by 38% and 70% compared to Ma_SM and Mu_SM, respectively. In addition, Ma + Mu_WR had 69% and 71% lower cumulative N2O emissions than Ma_WR and Mu_WR, respectively, while Ma + Mu_SM showed 48% and 55% lower emissions than Ma_SM and Mu_SM, respectively. WR application significantly increased C input and the C input/output. In the Mu, WR fertilizer led to a significant reduction in both C output and total C emitted, whereas in Ma + Mu, these parameters were not affected by the type of organic fertilizers. In Ma, C output was higher under WR than SM, but total C emitted remained unaffected. This study suggests that integrating organic fertilizer into an intercropping system provides a sustainable and environmentally friendly approach to effective GHG mitigation.
... Furthermore, optimizing NUE is also essential to minimise N 2 O emissions, a potent greenhouse gas, whose emissions through denitrification can be favoured with organic amendments. In a global meta-analysis, Charles et al. (2017) evaluated effects of organic amendments from 38 studies (422 observations, 43 sites) and were able to classify them into three classes of comparable N 2 O emission factors (high-risk, medium-risk and low-risk), highlighting that organic waste and side streams have the potential to create large sources or even sinks of greenhouse gases when applied to soils. The risk is in particular high when organic amendments are combined with inorganic N fertilizer. ...
The intensification and specialization of global agriculture has led to a nutrient surplus resulting in regional environmental issues such as eutrophication and loss of biodiversity due to nutrient accumulation. Addressing these challenges requires a shift towards regional nutrient circularity, inspired by the principles of a circular economy, to create a more resource-efficient agricultural system. Circular agriculture, particularly in Europe, provides a model for sustainable nutrient management at various scales—local, regional, national and international. Existing technologies enable the production of fertilizers from secondary or waste streams and can improve nutrient use efficiency. The development of a market with transparency of supply and demand dynamics, standardized products, and reliable traceability is essential for the effective implementation of nutrient circularity. However, practical nutrient management takes place on a local level, with significant variability in environmental, economic, and social conditions at the farm and field levels due to differences in nutrient demand by crops or farm management, e.g. organic farming with often lower total nutrient intensity. Therefore, the successful development of a regional circular nutrient economy necessitates a stronger stakeholder perspective, emphasizing the importance of participatory research approaches. In addition to circularity, the efficiency of nutrient use from secondary fertilizers must be enhanced, and the broader food system must evolve towards more nutrient-efficient practices. This transformation will likely require adopting a planetary health diet that promotes both sufficiency and sustainability in nutrient use. Therefore, policy measures need to provide a clear regulatory framework at supranational (e.g. European Union) or national level, targeting environmental and societal goals, while at the same time supporting locally adaptable interventions through economic incentives and innovation support.
... A meta-analysis found that EENF-related N 2 O emission reductions were greater in coarse-textured soils rather than the fine-textured soils (Li et al., 2018). Soil texture affects N 2 O emissions by the likelihood of aerobic and anaerobic conditions to prevail (i.e., fine-textured soil consistent with a more aerobic soil environment), as well as differences in SOC, N availability and microbial populations (Charles et al., 2017;Wang et al., 2021). Thus, the Manitoba studies, conducted on poorly drained, high clay and OM content soils, have a higher potential for N 2 O emissions than lighter-textured sandy loam soils of our site (Burton et al., 2008;Glenn et al., 2012;Rochette et al., 2008). ...
... Organic carbon (C) is usually applied to expedite the process, aming to eliminate soil diseases and pests (Di Gioia et al. 2017;Momma et al. 2013;Zhu et al. 2012). During ASD, the high-temperature and anaerobic environment favor the reduction of accumulated NO₃in the soil through denitrification, resulting in gaseous N emissions, including N₂O and N₂ (Charles et al. 2017). ...
Background and aims
Greenhouse vegetable production (GVP) is expanding globally. High nitrogen (N) fertilizer application causes soil disease and nitrate residues. Anaerobic soil disinfestation (ASD), a common mitigation strategy, involves creating an anaerobic environment through soil flooding, plastic film covering, and greenhouse sealing, typically with organic C addition to expedite the process. These conditions can promote denitrification, causing nitrous oxide (N2O) and dinitrogen (N2) emissions, but this has rarely been reported.
Methods
¹⁵N labeling was used for in situ monitoring of N₂O and N₂ emissions during ASD in a GVP system, in Shouguang, Northern China. Two treatments were implemented: conventional organic fertilization (Fertilizer) and a control (No-fertilizer), with continuous monitoring over 14 days.
Results
Within 14 days, cumulative gaseous N emissions in Fertilizer and No-fertilizer treatments were 0.82, 0.47 kg N ha⁻¹ for N2O, and 40.7 and 25.5 kg N ha⁻¹ for N2, respectively. Organic fertilization significantly increased N2O and N2 emission. In Fertilizer, N emitted as N2O and N2 accounted for 0.3% and 14.5% of organic fertilizer, respectively. From days 1–6, the predominant gaseous N was N2, with an N2O/ (N2O + N2) ratio (RN2O) of 0.007–0.015. From days 7–14, the N2O proportion increased, with RN2O of 0.21–0.75. Isotopic information showed that denitrification contributed to 48.9–51.2% and 27.1–36.7% of total N2O and N2 emissions.
Conclusion
Our findings emphasize the importance of N2 emissions in N loss and provide a basis for studying the fate of N and developing measures to reduce N2O emissions within GVP systems.
... Indeed, it is a common agricultural practice in China to mulch soil surfaces with straw (SM) or plastic film (PM) in maize to increase yields (Fig. 1). Straw decomposition releases large amounts of nutrients, such as C, N, potassium, and other trace elements, which is an effective nutrient supplement to the crop (Charles et al. 2017;Zhou et al. 2020). Straw mulch can also impact soil temperature, further affecting nutrient cycling and organic matter mineralizing Langworthy et al. 2018). ...
Against the backdrop of global warming, the agricultural sector grapples with the dual challenge of safeguarding food security while fulfilling carbon neutrality. Currently, although nitrogen fertilizer and mulch use to enhance maize yields is well-documented, systematic evaluations are lacking in the carbon neutrality potential and holistic benefits, including greenhouse gas (GHG) implications, associated with these strategies. Here, using the calibrated DeNitrification-DeComposition (DNDC) model, we conducted a long-term simulation (1980−2019) incorporating various scenarios of nitrogen fertilizer (N1: conventional nitrogen fertilizer; N0.7: 70% conventional nitrogen fertilizer) and mulch (CK: no-mulch; PM: plastic film mulch; SM: straw mulch), resulting in a baseline scenario (CKN1) and five mitigation scenarios (CKN0.7, PMN1, PMN0.7, SMN1, SMN0.7). We revealed an average net global warming potential during the maize growing season of 5293 kg CO2 eq ha−1, with the most GHG derived from N2O (53%). Considering GHG costs, the net environmental and economic benefits in maize amounted to 5089 CNY ha−1. Presently, Hainan, Henan, Liaoning, and Jilin provinces exhibit a state of low net global warming potential and high net environmental and economic benefits in maize cultivation. Of the mitigation scenarios, only SMN1 concurrently reduced GHG emissions (− 59%) and amplified net environmental and economic benefits (+ 21%) in China. Our results, which provide the first calculation of the combined benefits of mulch and nitrogen fertilizer including GHG costs, not only underscore the immense potential of mulch for enabling carbon neutrality, but also offer valuable insights for policymakers and industry in selecting suitable mulch techniques for agricultural production.
... Эмиссионный фактор варьируется в широком интервале и зависит от почвенно-климатических условий [5], содержания в почвах органических и минеральных форм азота, органического углерода, от внесения в почву разных форм азотных и органических удобрений, растительных остатков, азотсодержащих отходов [6][7][8][9], а также от системы землепользования [10,11]. Кроме того, на секвестрацию углерода и эмиссию закиси азота оказывают влияние известкование и система удобрения (органическая, минеральная, органоминеральная) [12]. ...
The global rise in average environmental temperatures is associated with the emission of greenhouse gases due to human economic activities, including crop production. Current findings indicate the absence of a systematic approach and tools for a comprehensive assessment of greenhouse gas emissions from crop production. ( Research purpose ) The study aims to develop mathematical models and methods to assess greenhouse gas emissions in agricultural production. ( Materials and methods ) The work was carried out based on the analysis of published data from both domestic and international researchers. ( Results and discussion ) The research validates a set of indicators for assessing the level of greenhouse gas emissions during agricultural production. The novelty of the methodology involves the integration of numerous indicators and parameters of the greenhouse gas emission process, taking into account stochastic disturbances in the emission process. Factors such as soil tillage methods, fuel consumption per unit of work performed, the dose, method and ratio of applied fertilizers, content of plant residues and soil texture, as well as other variables, are considered as stochastic factors. Unlike the methodology outlined in the 2006 IPCC Guidelines (Intergovernmental Panel on Climate Change) for calculating greenhouse gas emissions from crop production, the developed methodology addresses more complex scenarios associated with processes containing simultaneously the elements that are both continuous and discrete in nature. As an example, the paper presents calculations for estimating greenhouse gas emissions from potato cultivation using the proposed methodology. ( Conclusions ) The calculated probability coefficient, with a value exceeding 2.21, indicates that the technology used does not meet environmental standards. To reduce greenhouse gas emissions, it is necessary to develop technical and technological solutions that optimize the indicators utilized in this methodology.
... We performed a standard pair-wise meta-analysis to calculate the weighted means of F-Nr (Supplementary Tables 1-5). As the s.d. of F-Nr was rarely reported, the variance of F-Nr (V F-Nr ) was calculated from the s.d. of soil cumulative Nr losses and the number of replicates 49 following equation (6) ...
Maize and wheat are two major staple foods that collectively contribute two-thirds of the world’s grain supply. The extensive use of nitrogen (N) fertilizers during the cultivation of both crops leads to significant losses of reactive nitrogen (Nr) into the environment. Here, using machine learning algorithms, we generate high-resolution maps of crop-specific soil Nr losses based on global field measurements. We estimate that global annual soil Nr losses from the use of synthetic N fertilizer in 2020, including direct emissions of nitrous oxide (N2O), nitric oxide (NO), ammonia (NH3), N leaching and run-off, amount to 0.18, 1.62, 0.09, 1.47 and 1.10 million tonnes N for maize, and 0.12, 1.33, 0.07, 1.21 and 0.95 million tonnes N for wheat, respectively. The annual indirect N2O emissions induced by synthetic N fertilizer use from these soil Nr losses are estimated to be 45,000 and 37,000 tonnes for maize and wheat, respectively, with hydrologic pathways playing a predominant role. Enhancing N use efficiency up to 60% for regions below this value can achieve a total soil Nr loss mitigation potential of 4.00 million tonnes per year for the two crops, thereby reducing indirect N2O emissions by 49%. Our results contribute to constrain global N budgets from the use of fertilizer in agriculture, which then can help to improve projections of nitrogen cycle–climate feedbacks using modelling approaches.
... For N fertilizer input, the EFs associated with manure deposition and application were not considered despite their significant role in N 2 O emissions (Charles et al., 2017;Walling & Vaneeckhaute, 2020). The changes in synthetic fertilizer and manure application rates vary substantially across different policy scenarios, influenced by dietary shifts, and changed NUE. ...
Effective nitrogen fertilizer management is crucial for reducing nitrous oxide (N 2 O) emissions while ensuring food security within planetary boundaries. However, climate change might also interact with management practices to alter N 2 O emission and emission factors (EFs), adding further uncertainties to estimating mitigation potentials. Here, we developed a new hybrid modeling framework that integrates a machine learning model with an ensemble of eight process‐based models to project EFs under different climate and nitrogen policy scenarios. Our findings reveal that EFs are dynamically modulated by environmental changes, including climate, soil properties, and nitrogen management practices. Under low‐ambition nitrogen regulation policies, EF would increase from 1.18%–1.22% in 2010 to 1.27%–1.34% by 2050, representing a relative increase of 4.4%–11.4% and exceeding the IPCC tier‐1 EF of 1%. This trend is particularly pronounced in tropical and subtropical regions with high nitrogen inputs, where EFs could increase by 0.14%–0.35% (relative increase of 11.9%–17%). In contrast, high‐ambition policies have the potential to mitigate the increases in EF caused by climate change, possibly leading to slight decreases in EFs. Furthermore, our results demonstrate that global EFs are expected to continue rising due to warming and regional drying–wetting cycles, even in the absence of changes in nitrogen management practices. This asymmetrical influence of nitrogen fertilizers on EFs, driven by climate change, underscores the urgent need for immediate N 2 O emission reductions and further assessments of mitigation potentials. This hybrid modeling framework offers a computationally efficient approach to projecting future N 2 O emissions across various climate, soil, and nitrogen management scenarios, facilitating socio‐economic assessments and policy‐making efforts.
... Second, the texture of the soil can affect hydroclimate conditions and consequently N 2 O emissions [45][46][47] . In general, soil texture influences N 2 O emissions by determining the likelihood of anaerobic or aerobic soil conditions prevailing 48,49 . Soil texture, for example, can influence water drainage during rainfall and drought, and hence the type of oxic and anoxic microsites of soil 30,50 . ...
... This is unsurprising as the effects on mineral N concentration were small and not signi cant for NO 3 − . Other characteristics of organic fertilisers, such as the C: N ratio, can be signi cant in determining the N 2 O emission factor(Charles et al., 2017). Soil C content and the probable larger contribution to soil mineral N from residues from the ley may have obscured any differences.Although we did measure a reduction in potential NH 3 emissions from the PFM treatments, this was not signi cant, and the reduction was smaller than reported in other studies(Chae et al., 2022;Li et al., 2021). ...
Plastic film mulch (PFM) controls weeds and increases yields, making them attractive to vegetable growers; biodegradable PFMs potentially reduce the harms associated with conventional PFMs. PFMs increase soil biological activity, accelerating the decomposition of soil organic matter and potentially increasing emissions of some greenhouse gases (GHGs). Conversely, they are a barrier to rainfall infiltration and gas exchange, reducing harmful nitrate (NO 3 ⁻ ) leaching and ammonia (NH 3 ) volatilisation. The effects of PFMs on the processes resulting in GHG emissions are not well explored outside conventionally grown commodity crops in major growing regions. To address this, we conducted a field plot-scale experiment on an organic vegetable farm in SW Wales (UK). We measured nitrous oxide (N 2 O), methane (CH 4 ), carbon dioxide (CO 2 ) and potential NH 3 emission from the soil, growing leeks or cabbages, with or without biodegradable PFM and amended with poultry manure or green-waste compost. Averaged across both crops, yield was 26% higher with PFM; potential NH 3 emissions were 18% lower (43% on a yield-scaled basis) in mulched treatments than unmulched; CH 4 emissions were not significantly affected. Yield-scaled N 2 O emissions were 62% higher in mulched leeks than unmulched but 56% lower in mulched cabbages than unmulched; this coincided with higher soil NO 3 ⁻ concentrations in mulched leeks than either unmulched crop or mulched cabbages. Results were not obtained for CO 2 , so partial global warming potential (GWP) and greenhouse gas intensity (GHGI) were determined mainly by N 2 O emissions. Thus, biodegradable PFM is potentially useful in reducing harmful gaseous N emissions in organic horticulture.
... Nitrogen losses as nitrous oxide occur mainly in the anaerobic phase that composes the nitrogen cycle, this natural soil process and is mainly stimulated by effects of chemical or organic nitrogen fertilizations , thus things, according to Coskun et al., (2017), report that agriculture contributes between 60-80% of global anthropogenic N 2 O emissions, and this percentage increases faster than the IPCC's ability to estimate it (Charles et al., 2017). Furthermore, by 2020, FAO estimated a share by agriculture of 89.1% in N 2 O emissions. ...
Nitrous oxide (N 2 O) is a greenhouse gas (GHG) with a global warming potential 277 times stronger than CO 2 , is emitted as a by-product of microbial activity during the anaerobic phase of the nitrogen cycle. The objective of this work was to analyze the influence of the use of nitrification inhibitors during nitrogen fertilization and its relationship with N 2 O emission under specific conditions for sugarcane cultivation typical of the Cauca River valley. A randomized complete block experimental design was used with a 2X3 factorial arrangement with 4 replications, the first factor corresponds to the fractionation of the dose (single or fractionated dose), the second corresponds to the use of inhibitors (without inhibitor; N-[n-butyl] thiophosphoric triamide or mixture of NBPT with dicyandiamide), a total of 7 treatments were evaluated. For monitoring N 2 O emissions, manual stationary cameras were used for field sampling and the gas chromatography technique was used to determine the N 2 O concentration of these samples. Differences between treatments were observed, the N 2 O emissions generated during the application of a fractional dose without inhibitors; single dose + NBPT and single dose without inhibitors were significantly higher compared to the other treatments. This research improves our ability to understand the benefits of using nitrification inhibitors during fertilizer applications on sugarcane crops in this region. N 2 O emissions in most of the treatments with nitrification inhibitor application were lower. Further research is needed on the mechanisms of action of the inhibitors to increase their efficiency and other possible effects on the agroecosystem.
... Aside from cropping systems, the type of N fertilizer used may significantly impact GHG emissions (Charles et al. 2017). Urea, known for its rapid denitrification in soil, possesses the highest potential for field-scale GHG emissions among synthetic N fertilizers (Wu et al. 2021). ...
Background and Aim
Continuous monocropping with high nitrogen (N) fertilizer input substantially increases greenhouse gas (GHG) emissions in maize-based agroecosystems in the North China Plain (NCP). Introducing soybeans as an intercrop with maize and partially substituting urea with manure might effectively decrease GHG emissions. The aim of this study was to quantify the synergistic effect of maize-soybean intercropping and manure on soil GHG emissions.
Methods
A two-year field experiment with three cropping systems (maize monocrop, soybean monocrop, and maize-soybean intercrop) and four N treatments (control, urea, manure, and manure + urea) was carried out at Luancheng Agro-Ecosystem Experimental Station in the NCP. All N treatments, except the control, received 150 kg N ha⁻¹season⁻¹, either full dose as a basal application or two equal split applications.
Results
Results showed that all treatments contributed as a net source of N2O and CO2 fluxes but acted as a net sink of CH4 fluxes. In both cropping seasons, intercrops had significantly lower N2O emissions compared to monocropping systems, with 38% and 14% less emissions than maize monocrops in 2018 and 2019, respectively. Additionally, maize monocrops had significantly higher soil CO2 emissions than other systems, while maize-soybean intercropping had 12% and 13% less CO2 emissions than maize monocrops in 2018 and 2019, respectively. Among fertilized treatments, manure-treated soils emit notably lower N2O fluxes compared to sole urea treatments. In this study, N2O and CO2 fluxes had a strong positive correlation with soil mineral N concentrations, soil temperature, and moisture content. Possibly due to more efficient N utilization, intercrop soils exhibited significantly lower NH4⁺ and NO3⁻ concentrations, leading to reduced nitrification and denitrification in the system, resulting in lower N2O emissions from maize-soybean intercrops.
Conclusion
Our findings indicate that intercropping maize and soybean reduces soil NH4⁺ and NO3– concentrations, as well as significantly decreasing soil N2O and CO2 emissions when compared to traditional maize monoculture. Therefore, due to its potential for reducing soil GHG emissions, maize-soybean intercropping can be regarded as an effective alternative cropping system to the prevailing maize-dominant monoculture to develop a sustainable agroecosystem in the NCP region.
... Additionally, a meta-analysis investigating soil N 2 O emission factor (EF) with organic amendments discovered an EF of 0.57-0.3%; lower than the EF of one analysed by the IPCC for synthetic fertiliser [63]. This highlights the need for further investigations of permaculture managed soils with respect to their greenhouse gas emission and, subsequently, mitigation potential that are multiple yearround and conducted in situ to encompass seasonality, crop management, and fertilisation effects. ...
Conventional agricultural practices severely deplete the soil of essential organic matter and nutrients, increasing its vulnerability to disease, drought, and flooding. Permaculture is a form of agroecology adopting a whole ecosystem approach to create a set of principles and design frameworks for enriching soil fertility, but there is little scientific evidence of its efficiency. This study compares two permaculture managed sites with a conventional arable site to investigate the effect of permaculture management on soil fertility. We used phospholipid fatty acid analysis to estimate microbial abundance and diversity and related these to measured soil nutrients and carbon stocks. The potential of permaculture management to mitigate soil greenhouse gas emissions was assessed during a laboratory soil incubation and measurement of greenhouse gases via gas chromatography. Overall, the permaculture managed allotments had three times higher microbial biomass, one and a half times higher nitrogen, and four times higher carbon content than the arable site. Permaculture soils had larger carbon dioxide and nitrous oxide fluxes compared to arable soil, but all sites had a mean negative flux in methane. Permaculture management by use of organic amendments and no-dig practices provides a constant slow release of nutrients and build-up of organic matter and carbon and consequently promotes greater bacterial and fungal biomass within the soil.
... Some processes, such as N20 emissions due to nitrification of ammonium applied, are not considered in this version of the model. However, considering that this process represent usually less than 1% of the nitrogen applied (Charles et al 2017) and that ammonium content in digestate and slurry are similar, this overlooked process is not likely to bias the results. ...
The aim of this study was to assess positive or negative impacts of anaerobic digestion (AD) on water quality using a systemic approach. To this end, we used the agro-hydrological model Topography-based Nitrogen Transfer and Transformation (TNT2), a spatially explicit model that simulates nitrogen and water flows at the watershed scale on a daily time step. Four scenarios were constructed and analyzed: a baseline before the introduction of AD (S0), AD with adjusted fertilization (S1), AD with unadjusted fertilization (S2), and agroecological AD (S3). The results showed that, when spreading practices were similar and an equivalent amount of effective nitrogen was applied, digested pig slurry generally had a predicted amount of nitrate leaching similar to that of undigested pig slurry. In addition, replacing catch crops with energy cover crops had little impact on water quality. Scenario S3 was the most favorable one for water quality and biogas production, but not for soil organic nitrogen storage and food and feed production. This study’s strength is its systemic approach, which considered both environmental and agronomic aspects to assess the scenarios.
... (6) and Eq. (7) (Charles et al., 2017;Du et al., 2023;Ghosh et al., 2022): ...
... N fertilizers are commonly applied to foster straw mineralization and ensure sufficient available N for crop growth. However, N addition not only promotes residue mineralization and crop yield but also significantly increases soil GHG emissions [25,26]. Urea, due to its rapid denitrification in the soil, has the highest potential for fieldscale GHG emissions among synthetic N fertilizers [27]. ...
Incorporating crop residues into the soil is an effective method for improving soil carbon sequestration, fertility, and crop productivity. Such potential benefits, however, may be offset if residue addition leads to a substantial increase in soil greenhouse gas (GHG) emissions. This study aimed to quantify the effect of different crop residues with varying C/N ratios and different nitrogen (N) fertilizers on GHG emissions, yield, and yield-scaled emissions (GHGI) in winter wheat. The field experiment was conducted during the 2018–2019 winter wheat season, comprising of four residue treatments (no residue, maize residue, soybean residue, and maize-soybean mixed residue) and four fertilizer treatments (control, urea, manure, and manure + urea). The experiment followed a randomized split-plot design, with N treatments as the main plot factor and crop residue treatments as the sub-plot factor. Except for the control, all N treatments received 150 kg N ha−1 season−1. The results showed that soils from all treatments acted as a net source of N2O and CO2 fluxes but as a net sink of CH4 fluxes. Soybean residue significantly increased soil N2O emissions, while mixed residue had the lowest N2O emissions among the three residues. However, all residue amendments significantly increased soil CO2 emissions. Furthermore, soybean and mixed residues significantly increased grain yield by 24% and 21%, respectively, compared to no residue amendment. Both soybean and mixed residues reduced GHGI by 25% compared to maize residue. Additionally, the urea and manure + urea treatments exhibited higher N2O emissions among the N treatments, but they contributed to significantly higher grain yields and resulted in lower GHGI. Moreover, crop residue incorporation significantly altered soil N dynamics. In soybean residue-amended soil, both NH4+ and NO3− concentrations were significantly higher (p < 0.05). Conversely, soil NO3− content was notably lower in the maize-soybean mixed residue amendment. Overall, our findings contribute to a comprehensive understanding of how different residue additions from different cropping systems influence soil N dynamics and GHG emissions, offering valuable insights into effective agroecosystems management for long-term food security and soil sustainability while mitigating GHG emissions.
... China is a large agricultural country, and its agricultural activities have major contributions to greenhouse gas emissions. In order to obtain higher crop yields, a large amount of nitrogen fertilizer is applied to the soil, thereby resulting in significant amounts of N 2 O emissions (Charles et al. 2017;Shcherbak et al. 2014). ...
Biochar amendment is widely considered as a potential strategy to mitigate soil acidification and N2O emissions. However, the effect of biochar on N2O emissions from acidic soils remains unclear. This study aims to compare the effects of straw and biochar on N2O emissions from acidic soils in tea fields with different cultivation years in South Central China.
A 48-day microcosm experiment was conducted with soils from two fields after 5 years (pH = 5.8, slightly acidic) and 15 years (pH = 4.5, acidic) of tea cultivation to examine the N2O emissions in response to straw and biochar amendment.
Biochar addition alone significantly increased the soil pH by 1.14 and 0.54 units and further reduced N2O emissions by 28.46% and 68.34%, but straw addition alone increased the cumulative N2O emissions by 141.97% and 127.45% in 5-year and 15-year tea field soils, respectively. Combined application of straw and biochar significantly (p < 0.01) reduced N2O emissions relative to single straw application in both field soils. Furthermore, N2O emissions from the acidic soil (15-year tea cultivation) were 7.12-fold those from slightly acidic soil (5-year tea cultivation) of the control treatment. Correlation analysis indicated that N2O emissions are positively correlated with dissolved organic carbon (DOC), microbial biomass carbon (MBC), and NH4+-N, but negatively correlated with pH.
The results suggested that compared with straw, biochar could increase soil pH and further mitigate N2O emissions from acidic soils, which may be an optimal strategy to reduce soil N2O emissions and alleviate soil acidification.
... DNDC accurately simulated the appearance of most daily N 2 O and NH 3 flux peaks and performed well for the emission of N gases. The N 2 O flux peaks appeared after fertilization, rainfall, and irrigation events where the available N and water-filled pore space (WFPS) (%) changed substantially to offer more resources and favorable settings for both nitrification and denitrification in soils (Charles et al., 2017;Huang et al., 2014;Xu et al., 2019). The WFPS could be a key factor to adjust nitrification and denitrification processes, and it was reported that a WFPS of 60% was the most suitable condition to produce N 2 O with significant microbial activity for nitrification and denitrification processes (Song et al., 2018). ...
Achieving high stable crop yields and minimal environmental damage is crucial to enhance the sustainability of agriculture in China. Process‐based models are indispensable tools to develop agronomy management practices to achieve sustainable agriculture by simulating crop production and emissions of reactive nitrogen (N), particularly in complex climate scenarios. In this study, a long‐term field experiment with an intensive summer maize‐winter wheat rotation system in north‐central China was simulated using the DeNitrification‐DeComposition (DNDC) model. The DNDC model validation and calibration was done by using two‐year monitoring data of crop yields and nitrous oxide emission fluxes and ammonia volatilization. Moreover, the optimal management practices to promote crop production and reduce the reactive N loss under 22 years of climate variability were explored using the calibrated DNDC model in this region. The results showed that the DNDC model effectively simulated wheat and maize yields, N uptake, ammonia volatilization, and nitrous oxide emissions. Sensitivity analyses demonstrated that the agronomic management practices (N rates and ratio of base to topdressing, planting time, and tillage depth) substantially affected crop yields and reactive N losses under long‐term climate variability. Compared with current farming practices, optimal Nutrient Expert (NE) management achieved an increase in high yields and environmental pollution radiation by altering the rate of N application and ratio of base to topdressing. Moreover, the optimal management strategies developed by the DNDC model, such as adjusting the planting date and tillage depth, further increased the average grain yield by 2.9% and reduced the average reactive N losses by 10.5% compared with the NE management implemented in the annual rotation cropping with a 22‐year simulation. This study suggests that the modeling method facilitates the development of most effective agronomic management practices to promote crop production and alleviate the negative impact on environment.
... Необходимость оценки эмиссии парниковых газов из сельскохозяи ственных почв связана с важнеи -шеи ролью, которую играют почвы в образовании этих газов. По разным оценкам от 25 % до 60 % парниковых газов имеют почвенное происхождение, что важно при рассмотрении ключевои позиции почвенного покрова в биосферном круговороте этих газов [6][7][8][9]. ...
The article presents the results of studies on the impact of bioorganic fertilizers on the cultivation of winter wheat, sugar beet, and soybeans in irrigated light sierozems of southeastern Kazakhstan. The study focuses on the effects of these fertilizers on the mineral forms of nitrogen content and the size of N 2 O emissions from the soil. When applying leaf treatments of mineral and bioorganic fertilizers to cultivated crops, the nitrogen content in light sierozems is enhanced. The main sources of nutrition are easily hydrolyzable and nitrate nitrogen, which accounts for more than 80 %. The contribution of ammonium forms to plant nutrition is insignificant. The size of nitrous oxide emissions was recorded at the beginning of the experiment and after the initial leaf treatment. Under winter wheat crops, the initial concentration of nitrous oxide was 440.3 µg/m³. In the field prepared for sowing sugar beet and soybean in 2023, the concentrations were 373.7 µg/m³ and 557.7 µg/m³, respectively. After the initial treatment, the vegetation on the leaves showed that, on average, the indicator in the different experimental variants for winter wheat crops was 679 µg/m³, for sugar beet crops was 576.8 µg/m³, and for soybean crops was 637.2 µg/ m³. In agroecosystems, N 2 O emissions are higher under winter wheat compared to row crops such as sugar beet and soybean.
... Zhang, Huang, et al. (2021) and Zhang, Meng, et al. (2021) found that the average N fertilizer input 378 kg N ha À1 , which was obviously higher than the national average. Optimizing the N rate is a practical method to maintain soil fertility, improve crop yield and reduce reactive C and N loss (Charles et al., 2017;Guo et al., 2020). ...
With the rapid expansion of agriculture on saline–alkaline soils, environmental problems such as increased greenhouse gas (GHG) emissions, eutrophication and soil degradation are becoming increasingly serious. To clarify the characteristics of carbon (C) and nitrogen (N) cycling and their loss mechanisms in cultivated saline–alkaline soils, an undisturbed soil column experiment was conducted to analyse C and N leaching and GHG emissions by applying different fertilizer rates. The experiment had six treatments using N‐(NH 4 )SO 4 over a 40‐day seedling stage, with and without maize. Treatments were: no N with maize (0N maize : 0 kg N ha ⁻¹ ), reduced N with maize (RN maize : 63 kg N ha ⁻¹ ), conventional N with maize (CN maize : 160 kg N ha ⁻¹ ) and their equivalents without maize (0N soil : 0 kg N ha ⁻¹ ; RN soil : 63 kg N ha ⁻¹ ; CN soil : 160 kg N ha ⁻¹ ). The results indicated that reduced N with maize reduced the N 2 O emission by 21%, with N leaching (TN: 41%, NO 3 ⁻ –N: 19%, NH 4 ⁺ − N: 63%) within 15 days after fertilization, but had no significant effect on CH 4 emission compared to conventional N with maize. Therefore, reduced N with maize had the smallest N loss, which accounted for 1.5% of the relative percentage of N flow including N 2 O (0.3%), N leaching (2%), aboveground biomass N (76%) and root biomass N (22%). Compared to conventional N with maize, reduced N with maize significantly reduced N leaching by 40% because conventional N with maize greatly exceeded the crop N uptake when maize root length was only within 20 cm. Reduced N without maize reduced CO 2 emission (19%) compared to conventional N without maize. Uncultivated saline–alkaline soils face greater N overuse and leaching risk because higher NO 3 ⁻ –N leaching (6.9 mg L ⁻¹ ) that occurred in bare soils without fertilization, which increased by 2.6–3.6 times when the N input increased from 63 to 160 kg N ha ⁻¹ compared to control. In conclusion, reducing conventional N fertilizer inputs by 60% is not only an effective strategy to reduce CO 2 and N 2 O emission and N leaching but also effectively absorbs C, and the N retained in the soil tillage layer can help to meet maize seedling growth requirements in Solonchaks.
... Simulation models are useful tools in this context (Hénault et al., 2005;Plaza-Bonilla et al., 2017;Wang et al., 2021), as they allow us to predict the dynamics of the control variables of N 2 O emissions and the different interacting processes that affect N 2 O emissions. N 2 O emissions from soil result mainly from nitrification and denitrification processes (Butterbach-Bahl et al., 2013;Mei et al., 2018), which are strongly affected by substrate availability (NH 4 and NO 3 contents, soluble C), environmental conditions (soil temperature and moisture) and soil characteristics (pH, soil texture) (Charles et al., 2017). Surface residues can affect N 2 O emissions directly during their decomposition by increasing soil N and labile C availability to soil microbes (Chen et al., 2013) and indirectly by affecting soil moisture and temperature . ...
In no-tillage systems, crop residues are left on the soil surface and form a mulch, which can result in the stimulation of N2O emissions through various processes. As a consequence, the accurate description of mulch decomposition and the associated N2O emissions by soil-crop models is essential to help manage the potential impacts of mulches on the environmental performances of these agroecosystems. Here, we combined the use of a soil-crop model (STICS) and published experimental data to develop a new model representation of mulches (with various masses and qualities) and their decomposition, the carbon (C) and nitrogen (N) dynamics, and effects on N2O emissions. We used a published dataset from southern Brazil combining two residues with distinct chemical characteristics (vetch, Vicia sativa L., and wheat Triticum aestivum L.) and four rates of mulch addition (0, 3, 6 and 9 Mg dry matter (DM) ha-1) decomposing over one year. The STICS model with its default parameterization overestimated the remaining mulch masses, particularly at high DM inputs, and underestimated the N2O emissions. The evolution of the STICS soil and decomposition modules led to two major results: i) we modified the mulch module parameterization, by representing that the whole mulch is accessible to decomposers, whatever its initial mass and thickness; ii) a new potential denitrification function was proposed, which uses simulated CO2 fluxes associated from both soil humus and residue decomposition as proxy for C readily available to denitrifiers. With these new representation and parameterization, the model then accurately reproduced the very large range of magnitudes and the temporal variability of C and N fluxes observed for the two residues and the four mulch masses. These results are promising and the conceptual formalisms generic enough to be potentially developed in other soil-crop models. The next step is now to extend and generalize them to other conditions.
... These processes can occur simultaneously in soils, albeit in different micro-habitats, and are among others dependent on the oxygen availability (Butterbach-Bahl et al., 2013;Skinner et al., 2014;Tian et al., 2020). The use of organic amendments can lead to increased N 2 O emissions, as the mineral nitrogen input can be nitrified and subsequently denitrified (Charles et al., 2017). However, as yet, no consistent effect of sustainable agricultural management strategies has been found on soil N 2 O emissions (Bayer et al., 2016;Gregorich et al., 2005;Meng et al., 2005;Skinner et al., 2019), indicating the variable nature of agricultural soil N 2 O fluxes. ...
... On the contrary, previous studies had detected higher N2O emission rates from digestate compared to mineral fertilizers (Buchen-Tschiskale et al., 2020;Köster et al., 2011). Furthermore, we did not observe any effect of the quality of the different EOMs as reported by Charles et al. (2017), lower N2O emission rates with digestate than with undigested slurry as found by Köster et al. (2015), Möller (2015) and Nkoa (2014), or any decrease in N2O emissions as a result of phase separation as published by Askri et al. (2016) and Möller 620 (2015). We hypothesize that the effect of soil mineral N content, soil moisture levels, and air temperature may have masked some or all of these effects. ...
On-farm anaerobic digestion is used as a means of producing biogas, with the resulting digestates serving as organic fertilizers. However, such digestates have different fertilizer properties than undigested animal effluents, and are associated with different degrees of N loss. We conducted a field experiment in which cattle slurry and farmyard manure were co-digested with urban and agro-industrial wastes, which represented slightly more than two-thirds of the total. We managed a three-year crop succession (wheat – rapeseed – wheat) with five fertilization systems: no fertilization, mineral fertilizers, cattle manure and slurry, raw digestate, or separated solid and liquid digestates. An exogenous organic matter (EOM) (cattle slurry, liquid or raw digestates) or mineral fertilizer was applied five times in winter and spring. A different type of EOM (cattle manure, solid or raw digestates) was applied twice in summer. After each fertilizer application, we measured ammonia volatilization and N2O emissions, along with crop N uptake and soil mineral N stocks. Across the three-year rotation, the NH3 volatilization rate was the lowest in the plot treated with mineral fertilizers (2 % of applied total N, TN), followed by cattle effluents (7 % TN), liquid and solid digestates (9 % TN), and raw digestate (18 % TN). Seasonal cumulative N2O emissions were similar between mineral fertilizers and digestates, and were lower with cattle effluent, mainly because of lower ammoniacal N inputs. Compared to unfertilized crops, the surplus crop N uptake strongly reflected the mineral N content of fertilizers, ammonia volatilization, and the decomposition of EOM in the soil. Liquid digestate and cattle slurry had similar N use efficiencies (37 % to 60 % depending on the cropping season), while values for raw digestate were lower (25 to 41 %), likely due to its larger NH3 volatilization. Overall, digestates served as an effective N fertilizer but require particular attention to NH3 volatilization.
Organic materials returned to the field have a significant effect on N2O emissions from agricultural fields, but the knowledge about the relationship between soil denitrifying microorganisms and N2O emissions is limited. Hence, we delved deeper into the significance of denitrifying microorganisms in N2O emissions by examining the soil N2O emissions, gene copy numbers, and community structures of denitrifying microorganisms during the wheat harvest season, three years after the partial substitution of chemical nitrogen fertilizers with various organic materials, including straw, pig manure, and biogas residues. The results showed that compared with chemical fertilizer, straw return did not change N2O emission, and pig manure and biogas residue, especially pig manure return, significantly reduced N2O emission (62 % and 45 %). Organic materials return did not change the gene copy number of denitrifying microorganisms, but had a significant effect on the community structure. The relative abundance of genera in the three organic materials treatments differed significantly from the chemical fertilizer treatment. The pig manure treatment had marker genera in the nosZ gene. Among the nirK, nirS, and nosZ genes, Sinorhizobium, norank_p_environment_samples, and unclassified_k_norank_d_bacteria, respectively, had the greatest effect on N2O emissions. The results of the RDA and the minimum depth method indicated that K, pH, and SOC were the key environmental factors influencing the structural changes of nirK, nirS and nosZ communities. Overall, organic materials, especially pig manure, effectively suppressed N2O emissions by changing the relative abundance and community structure of the dominant genera of denitrifying microorganisms.
Silicate rock dust and manure admixtures are increasingly considered to improve crop growth and soil health. Soil application of silicate rock dust can capture and store atmospheric CO2 as inorganic carbon but could also have the potential to stabilize manure-derived organic matter when combined. However, synergies between rock dust and manure have been rarely investigated, while identifying the optimal combination rate remains elusive. Here, we set up a field trial in two contrasting kaolinitic soil (coarse-textured sandy loam and medium-textured silt loam) amended with a modest realistic rate of broiler manure (10 Mg ha 1) [100 %], finely ground silicate rock dust (granite) (10 Mg ha 1) [100 %], and a combination of manure (7 Mg ha 1) + rock dust (3 Mg ha 1) [70:30 %], manure (5 Mg ha 1) + rock dust (5 Mg ha 1) [50:50 %] and an un-amended control to investigate their effects on a leafy vegetable plant (Amaranthus cruentus) and metrics of soil health, and an incubation
experiment to monitor soil heterotrophic CO2 emission. Despite a reduction in manure input, the manure-rock dust mixture outperformed sole manure by increasing vegetable fresh herbage yield (by 19 %) and enhancing all soil health metrics, as revealed by the decrease in soil acidity, increased soil EC and soil total C, enhanced N availability and retention, increased bioavailable P, decreased soil dissolved organic C losses, increased soil microbial activity, and improved soil physical properties (viz., soil aggregate, bulk density, porosity, and water infiltration). Soil texture modulates the effects of manure-rock dust, as demonstrated by the better response from coarse-textured sandy loam than medium-textured silt loam soil. Manure-rock dust admixture [50:50] ratio decreased soil CO2 emissions by 26 % and 54 %, respectively, in sandy loam and silt loam soil texture compared to sole manure. The synergistic performance of manure-rock dust admixture at 70:30 and 50:50 ratios was similar; however, to reduce nutrient limitation in the soil towards a more nutrient-equilibrated system while enhancing soil functioning and mitigating CO2 emissions, we adjudged the manure-rock dust [70:30] ratio to be optimal.
Nitrous oxide (N2O) is a long-lived greenhouse gas that mainly originates from agricultural soils. More and more studies have explored the sources, influencing factors and effective mitigation measures of N2O in recent decades. However, the hierarchy of factors influencing N2O emissions from agricultural soils at the global scale remains unclear. In this study, we carry out correlation and structural equation modeling analysis on a global N2O emission dataset to explore the hierarchy of influencing factors affecting N2O emissions from the nitrogen (N) and non-N fertilized upland farming systems, in terms of climatic factors, soil properties, and agricultural practices. Our results show that the average N2O emission intensity in the N fertilized soils (17.83 g N ha−1 d−1) was significantly greater than that in the non-N fertilized soils (5.34 g N ha−1 d−1) (p< 0.001). Climate factors and agricultural practices are the most important influencing factors on N2O emission in non-N and N fertilized upland soils, respectively. For different climatic zones, without fertilizer, the primary influence factors on soil N2O emissions are soil physical properties in subtropical monsoon zone, whereas climatic factors are key in the temperate zones. With fertilizer, the primary influence factors for subtropical monsoon and temperate continental zones are soil physical properties, while agricultural measures are the main factors in the temperate monsoon zone. Deploying enhanced agricultural practices, such as reduced N fertilizer rate combined with the addition of nitrification and urease inhibitors can potentially mitigate N2O emissions by more than 60% in upland farming systems.
Agricultural production is crucial for maintaining the normal functioning of human society and promoting environmental sustainability. Agricultural production encompasses various components. In this chapter, we categorize agricultural production system into crop production system and animal production system. Crop production system is composed of fertilizer production and crop cultivation. Animal production system is composed of crop feed cultivation, breeding, and manure management. In recent years, there has been a growing concern about the environmental impacts of material flows in agricultural production. The material flows dominated by carbon, N, and P have been found to have the most significant impacts on the environment, regardless of whether they are in crop production system or in livestock production system. We aim to illustrate the environmental impacts of material flows (such as N flows and P flows) in agricultural production with some examples. We will apply life cycle assessment (LCA) method to demonstrate the nutrient flows in agricultural production.
Global potent greenhouse gas nitrous oxide (N2O) emissions from soil are accelerating, with increases in the proportion of reactive nitrogen emitted as N2O, i.e., N2O emission factor (EF). Yet, the primary controls and underlying mechanisms of EFs remain unresolved. Based on two independent but complementary global syntheses, and three field studies determining effects of acidity on N2O EFs and soil denitrifying microorganisms, we show that soil pH predominantly controls N2O EFs and emissions by affecting the denitrifier community composition. Analysis of 5438 paired data points of N2O emission fluxes revealed a hump-shaped relationship between soil pH and EFs, with the highest EFs occurring in moderately acidic soils that favored N2O-producing over N2O-consuming microorganisms, and induced high N2O emissions. Our results illustrate that soil pH has a unimodal relationship with soil denitrifiers and EFs, and the net N2O emission depends on both the N2O/(N2O + N2) ratio and overall denitrification rate. These findings can inform strategies to predict and mitigate soil N2O emissions under future nitrogen input scenarios.
Background and Aims: Greenhouse vegetable production (GVP) is expanding worldwide. The high application of nitrogen (N) fertilizers has caused soil diseases and nitrate residue. Farmers usually adopt anaerobic soil disinfestation (ASD), involving organic carbon addition, extensive irrigation, plastic films laying, and greenhouse sealing during the summer fallow. These conditions may promote denitrification, causing nitrous oxide (N2O) and dinitrogen (N2) emissions. However, this is rarely reported.
Methods: We used ¹⁵N labeling for in situ monitoring of N₂O and N₂ emissions during ASD in a GVP system in Shouguang, Northern China. Two treatments were implemented: conventional organic fertilization (Fertilizer) and a control (No-fertilizer), with continuous monitoring over 14 days.
Results: Within 14 days, cumulative gaseous N emissions in Fertilizer and No-fertilizer treatments were 0.82, 0.47 kg N ha⁻¹ for N2O, and 40.7 and 25.5 kg N ha⁻¹ for N2, respectively. Organic fertilization significantly increased N2O and N2 emission. From days 1–6, the predominant gaseous N was N2, with an N2O/ (N2O + N2) ratio (RN2O) between 0.007 and 0.015. From days 7–14, N2O proportion increased, with RN2O ranging from 0.21 to 0.75. Isotopic information showed that denitrification contributed to 48.9%–51.2% and 27.1%–36.7% of total N2O and N2 emissions. The structural equation model showed that high soil temperature during ASD significantly reduced N2O emissions.
Conclusion: Our findings emphasize the importance of N2 emissions in N loss and provide a basis for studying the fate of N, as well as developing measures to reduce N2O emissions within GVP systems.
Nitrous oxide (N2O) is an important greenhouse gas. N2O emissions from soils vary with fertilization and cropping practices. The response of N2O emission to fertilization of agricultural soils plays an important role in global N2O emission. The objective of this study was to assess the seasonal pattern of N2O fluxes and the annual N2O emissions from a rain-fed winter wheat ( Triticum aestivum L.) field in the Loess Plateau of China. A static flux chamber method was used to measure soil N2O fluxes from 2006 to 2008. The study included 5 treatments with 3 replications in a randomized complete block design. Prior to initiating N2O measurements the treatments had received the same fertilization for 22 years. The fertilizer treatments were unfertilized control (CK), manure (M), nitrogen (N), nitrogen + phosphorus (NP), and nitrogen + phosphorus + manure (NPM). Soil N2O fluxes in the highland winter wheat field were highly variable temporally and thus were fertilization dependent. The highest fluxes occurred in the warmer and wetter seasons. Relative to CK, M slightly increased N2O flux while N, NP and NPM treatments significantly increased N2O fluxes. The fertilizer induced increase in N2O flux occurred mainly in the first 30 days after fertilization. The increases were smaller in the relatively warm and dry year than in the cold and wet year. Combining phosphorous and/or manure with mineral N fertilizer partly offset the nitrogen fertilizer induced increase in N2O flux. N2O fluxes at the seedling stage were mainly controlled by nitrogen fertilization, while fluxes at other plant growth stages were influenced by plant and environmental conditions. The cumulative N2O emissions were always higher in the fertilized treatments than in the non-fertilized treatment (CK). Mineral and manure nitrogen fertilizer enhanced N2O emissions in wetter years compared to dryer years. Phosphorous fertilizer offset 0.78 and 1.98 kg N2O ha−1 increases, while manure + phosphorous offset 0.67 and 1.64 kg N2O ha−1 increases by N fertilizer for the two observation years. Our results suggested that the contribution of single N fertilizer on N2O emission was larger than that of NP and NPM and that manure and phosphorous had important roles in offsetting mineral N fertilizer induced N2O emissions. Relative to agricultural production and N2O emission, manure fertilization (M) should be recommended while single N fertilization (N) should be avoided for the highland winter wheat due to the higher biomass and grain yield and less N2O flux and annual emission in M than in N.
Nitrous oxide (N2O) emissions were monitored using the micrometeorological eddy covariance technique from manure-fertilized cropland on a large dairy farm in New York State in 2006 to 2009. Nitrous oxide emissions demonstrated episodic behavior with intermittent short-duration peak fluxes up to 39.7 mg N2O-N m(-2) d(-1), whereas most of background fluxes during the annual agricultural cycle were below 6.5 mg N2O-N m(-2) d(-1). This paper discusses temporal variability of measured N2O emissions using a "hot moment" approach. To identify and quantify peak events as potential hot moments and to determine whether or not they could be treated statistically as outliers, N2O daily fluxes were analyzed by the box plot method using multiple thresholds. Peak events exceeding outlier thresholds contributed up to 51% of cumulative annual N2O emissions, although they represented <7% of the total observation time. Individual N2O peaks were also categorized by their duration, as single day spikes and multiday events. The highest contributing instances were multiday N2O peaks during summer precipitation and early spring thaw, largely enhanced by manure fertilization. These high-intensity emission events demonstrated repetitive seasonal responses to a combination of environmental factors and were therefore identified as hot moments. Abrupt rises in both temperature and soil moisture appeared to trigger major hot moments, whereas the availability of manure N controlled their magnitude. In the absence of strong correlations between time-series of individual environmental factors and N2O emissions, the hot moment approach can be a promising tool for the integrated analysis of most significant N2O events in cultivated fields receiving manure applications.
Lignin plus cutin (LIC) content and biological stability index (BSI) are well-recognized indexes of potentially recalcitrant carbon (C) in organic products, and C / nitrogen (N) and lignin/N ratios have been related to potentially mineralizable N (PMN). Our objective was to use Fourier-transform near-infrared (FT-NIR) spectroscopy to estimate PMN and BSI of plant residues, composts, and manures. We also evaluated FT-NIR for determining the C/N, LIC/N, and BSI/N ratios as indexes of N mineralization in selected organic products. We analyzed 148 organic products for biochemical composition and total C and N. A subset of 10 products was incubated in a sandy soil to determine PMN. The FT-NIR successfully determined lignin and cutin (LIC) and BSI from r, the ratio of prediction to standard deviation, and the ratio error range criteria. The PMN was less closely related to the C/N ratio (r = 0.64) than the BSI/N (r = 0.84) and LIC/N (r = 0.87) ratios. There was some N immobilization at an early stage of incubation when C/N, LIC/N, and BSI/N ratios exceeded 14, 10, and 15, respectively. There is a need to characterize a larger number of organic compounds in the soluble and LIC fractions to improve the BSI equation.
In the USA, swine operations produce more than 14 Tg of manure each year. About 30% of this manure is stored in anaerobic lagoons before effluent applications to land. Although land application is the preferred means of disposal and can supply nutrients for crop production, it leads to gaseous emissions of ammonia (NH3) and nitrous oxide (N2O), both of which can be detrimental to the environment. Our objectives were to quantify gaseous emissions of NH3 and N2O from effluent applications under field conditions and to relate N2O fluxes to soil water content. Three applications of swine effluent were applied to oat (Avena sativa 'GA-Mitchell') starting at heading stage. Gaseous fluxes were determined from gas concentration profiles and the momentum balance transport coefficient. About 13% of the ammonium (NH4-N) was lost through drift or volatilization of NH3 during irrigation. An additional 69% was volatilized within 24 h of application. Nitrous oxide emissions were low before effluent applications (19 mg N2O-N ha-1 d-1) and increased to 0.25 to 0.38 kg N2O-N ha-1 d-1 after irrigation. Total N2O emissions during the measurement period were 4.7 kg N2O-N ha-1, which was about 13% of total N applied. The large losses of NH3 and N2O illustrate the difficulty of basing effluent irrigation schedules on N concentrations and the data indicate that compared to N2O, NH3 emissions made greater contributions to N enrichment of the environment.
The influence of crop residues with different C: N ratios on the N2O emission from differently managed loamy sand soddy-podzolic soils was studied in a 50-day laboratory experiment. The application of crop residues into the soil increased the N2O emission from the soil. The N2O emission was lower from the poorly managed soil as compared to the soil with the high degree of cultivation. The crop residues form the following decreasing sequence in terms of their effect on the cumulative N2O flow: cabbage > red clover > perennial grasses > straw of spring wheat. The composting of crop residues with a wide C: N ratio for 50 days did not exceed the critical value of the emission factor (1.25%), whereas, in the composting of crop residues with a narrow C: N ratio, the critical value of the emission factor was 1.3–2.0 times higher.
Although it is well established that soils are the dominating source for atmospheric nitrous oxide (N2O), we are still struggling to fully understand the complexity of the underlying microbial production and consumption processes and the links to biotic (e.g. inter- and intraspecies competition, food webs, plant-microbe interaction) and abiotic (e.g. soil climate, physics and chemistry) factors. Recent work shows that a better understanding of the composition and diversity of the microbial community across a variety of soils in different climates and under different land use, as well as plant-microbe interactions in the rhizosphere, may provide a key to better understand the variability of N2O fluxes at the soil-atmosphere interface. Moreover, recent insights into the regulation of the reduction of N2O to dinitrogen (N2) have increased our understanding of N2O exchange. This improved process understanding, building on the increased use of isotope tracing techniques and metagenomics, needs to go along with improvements in measurement techniques for N2O (and N2) emission in order to obtain robust field and laboratory datasets for different ecosystem types. Advances in both fields are currently used to improve process descriptions in biogeochemical models, which may eventually be used not only to test our current process understanding from the microsite to the field level, but also used as tools for up-scaling emissions to landscapes and regions and to explore feedbacks of soil N2O emissions to changes in environmental conditions, land management and land use.
The microbial processes of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two important nitrate reducing mechanisms in soil, which are responsible for the loss of nitrate (NO3−) and production of the potent greenhouse gas, nitrous oxide (N2O). A number of factors are known to control these processes, including O2 concentrations and moisture content, N, C, pH, and the size and community structure of nitrate reducing organisms responsible for the processes. There is an increasing understanding associated with many of these controls on flux through the nitrogen cycle in soil systems. However, there remains uncertainty about how the nitrate reducing communities are linked to environmental variables and the flux of products from these processes. The high spatial variability of environmental controls and microbial communities across small sub centimeter areas of soil may prove to be critical in determining why an understanding of the links between biotic and abiotic controls has proved elusive. This spatial effect is often overlooked as a driver of nitrate reducing processes. An increased knowledge of the effects of spatial heterogeneity in soil on nitrate reduction processes will be fundamental in understanding the drivers, location, and potential for N2O production from soils.
Information from 846 N2O emission measurements in agricultural fields and 99 measurements for NO emissions was used to describe the influence of various factors regulating emissions from mineral soils in models for calculating global N2O and NO emissions. Only those factors having a significant influence on N2O and NO emissions were included in the models. For N2O these were (1) environmental factors (climate, soil organic C content, soil texture, drainage and soil pH); (2) management-related factors (N application rate per fertilizer type, type of crop, with major differences between grass, legumes and other annual crops); and (3) factors related to the measurements (length of measurement period and frequency of measurements). The most important controls on NO emission include the N application rate per fertilizer type, soil organic-C content and soil drainage. Calculated global annual N2O-N and NO-N emissions from fertilized agricultural fields amount to 2.8 and 1.6 Mtonne, respectively. The global mean fertilizer-induced emissions for N2O and NO amount to 0.9 and 0.7, respectively, of the N applied. These overall results account for the spatial variability of the main N2O and NO emission controls on the landscape scale.
Animal manures may differ strongly in composition and as a result may differ in the emission of N2O following application to soil. An incubation study was carried out to assess the effects of type of mineral N fertilizer and manure, application technique and application rate on N2O emission from a sandy soil with low organic matter content. Fluxes of N2O were measured 30 times over a 98-day period. The total N2O emission from mineral N fertilizer ranged from 2.1 to 4.0% of the N applied. High emissions were associated with manures with high contents of inorganic N, easily mineralizable N and easily mineralizable C, such as liquid pig manure (7.3-13.9% of the N applied). The emission from cattle slurries ranged from 1.8 to 3.0% and that of poultry manures from 0.5 to 1.9%. The total N2O emission during the experimental period tended to increase linearly with increasing N application rate of NH4NO3 and liquid pig manure. The N2O emission from surface-applied NH4NO3 was significantly smaller than that following the incorporation of NH4NO3 in the soil. The N2O emission from pig manure placed in a row at 5 cm depth was significantly higher than from surface-application and other techniques in which manure was incorporated in the soil. The results show that modification of the composition and application technique may be tools to mitigate emission of N2O.
Bacterial denitrification plays an important role in the global nitrogen cycle and is a principal contributor of nitrous oxide (N2O) to the atmosphere. The influence of simple (glucose) and complex (red clover and barley residue) carbon (C) sources on the amount of denitrification, N2O molar ratio (N2O:(N2 + N2O)), and abundance of soil total bacterial and denitrifier communities was investigated using repacked soil cores. Quantitative PCR was used to determine the abundance of the total bacterial community (16S rRNA gene) and components of the denitrifier community, cnorBP (Pseudomonas mandelii and related species), cnorBB (Bosea/Bradyrhizobium/Ensifer spp.) and nosZ gene bearing communities. The relationship between the supply of, and demand for, terminal electron acceptors (TEAs), as determined by the relative availability of C and nitrate (NO3−), influenced the amount of denitrification and the N2O molar ratio for both simple and complex C sources. Addition of glucose and red clover to the soil increased microbial activity, leading to NO3− depletion and an increased consumption of N2O, whereas in soil amended with barley straw, there was not sufficient stimulation of microbial activity to create sufficient TEA demand to cause a measurable increase in emissions. This resulted in a higher N2O molar ratio at the end of the incubation for the barley straw amended soil. A significant relationship (R2 = 0.83) was found between respiration and cumulative denitrification, suggesting that the available C increased microbial activity and O2 consumption, which led to conditions favorable for denitrification. The source of C did not significantly affect the total bacterial community or the nosZ copy numbers with an average of 4.9 × 107 16S rRNA gene copies g−1 dry soil and 4.6 × 106nosZ gene copies g−1 dry soil, respectively. The addition of red clover plus NO3− significantly increased the cnorBP denitrifier community in comparison with the unamended control while the density of the cnorBP denitrifier community increased from 3.9 × 104 copies g−1 dry soil to a maximum of 8.7 × 105 copies g−1 dry soil following addition of glucose plus NO3− to soil. No significant correlations were found between the denitrifier community densities and cumulative denitrification or N2O emissions, suggesting that the denitrification activity was decoupled from the denitrifier community abundance.
Research in animal sciences, especially nutrition, increasingly requires processing and modeling of databases. In certain areas of research, the number of publications and results per publications is increasing, thus periodically requiring quantitative summarizations of literature data. In such instances, statistical methods dealing with the analysis of summary (literature) data, known as meta-analyses, must be used. The implementation of a meta-analysis is done in several phases. The first phase concerns the definition of the study objectives and the identification of the criteria to be used in the selection of prior publications to be used in the construction of the database. Publications must be scrupulously evaluated before being entered into the database. During this phase, it is important to carefully encode each record with pertinent descriptive attributes (experiments, treatments, etc.) to serve as important reference points for the rest of the analysis. Databases from literature data are inherently unbalanced statistically, leading to considerable analytical and interpretation difficulties; missing data are frequent, and data structures are not the outcomes of a classical experimental system. An initial graphical examination of the data is recommended to enhance a global view as well as to identify specific relationships to be investigated. This phase is followed by a study of the meta-system made up of the database to be interpreted. These steps condition the definition of the applied statistical model. Variance decomposition must account for inter- and intrastudy sources; dependent and independent variables must be identified either as discrete (qualitative) or continuous (quantitative). Effects must be defined as either fixed or random. Often, observations must be weighed to account for differences in the precision of the reported means. Once model parameters are estimated, extensive analyses of residual variations must be performed. The roles of the different treatments and studies in the results obtained must be identified. Often, this requires returning to an earlier step in the process. Thus, meta-analyses have inherent heuristic qualities.
The use of various animal manures for nitrogen (N) fertilization is often viewed as a viable replacement for mineral N fertilizers. However, the impacts of amendment type on NO production may vary. In this study, NO emissions were measured for 2 yr on two soil types with contrasting texture and carbon (C) content under a cool, humid climate. Treatments consisted of a no-N control, calcium ammonium nitrate, poultry manure, liquid cattle manure, or liquid swine manure. The N sources were surface applied and immediately incorporated at 90 kg N ha before seeding of spring wheat ( L.). Cumulative NO-N emissions from the silty clay ranged from 2.2 to 8.3 kg ha yr and were slightly lower in the control than in the fertilized plots ( = 0.067). The 2-yr mean NO emission factors ranged from 2.0 to 4.4% of added N, with no difference among N sources. Emissions of NO from the sandy loam soil ranged from 0.3 to 2.2 kg NO-N ha yr, with higher emissions with organic than mineral N sources ( = 0.015) and the greatest emissions with poultry manure ( < 0.001). The NO emission factor from plots amended with poultry manure was 1.8%, more than double that of the other treatments (0.3-0.9%), likely because of its high C content. On the silty clay, the yield-based NO emissions (g NO-N kg grain yield N) were similar between treatments, whereas on the sandy loam, they were greatest when amended with poultry manure. Our findings suggest that, compared with mineral N sources, manure application only increases soil NO flux in soils with low C content.
Nitrous oxide (N2O) is an important greenhouse gas. N2O emissions from soils vary with fertilization and cropping practices. The response of N2O emission to fertilization of agricultural soils plays an important role in global N2O emission. The objective of this study was to assess the seasonal pattern of N2O fluxes and the annual N2O emissions from a rain-fed winter wheat (Triticum aestivum L.) field in the Loess Plateau of China. A static flux chamber method was used to measure soil N2O fluxes from 2006 to 2008. The study included 5 treatments with 3 replications in a randomized complete block design. Prior to initiating N2O measurements the treatments had received the same fertilization for 22 years. The fertilizer treatments were unfertilized control (CK), manure (M), nitrogen (N), nitrogen + phosphorus (NP), and nitrogen + phosphorus + manure (NPM). Soil N2O fluxes in the highland winter wheat field were highly variable temporally and thus were fertilization dependent. The highest fluxes occurred in the warmer and wetter seasons. Relative to CK, m slightly increased N2O flux while N, NP and NPM treatments significantly increased N2O fluxes. The fertilizer induced increase in N2O flux occurred mainly in the first 30 days after fertilization. The increases were smaller in the relatively warm and dry year than in the cold and wet year. Combining phosphorous and/or manure with mineral N fertilizer partly offset the nitrogen fertilizer induced increase in N2O flux. N2O fluxes at the seedling stage were mainly controlled by nitrogen fertilization, while fluxes at other plant growth stages were influenced by plant and environmental conditions. The cumulative N2O emissions were always higher in the fertilized treatments than in the non-fertilized treatment (CK). Mineral and manure nitrogen fertilizer enhanced N2O emissions in wetter years compared to dryer years. Phosphorous fertilizer offset 0.50 and 1.26 kg N2O-N ha−1 increases, while manure + phosphorous offset 0.43 and 1.04 kg N2O-N ha−1 increases by N fertilizer for the two observation years. Our results suggested that the contribution of single N fertilizer on N2O emission was larger than that of NP and NPM and that manure and phosphorous had important roles in offsetting mineral N fertilizer induced N2O emissions. Relative to agricultural production and N2O emission, manure fertilization (M) should be recommended while single N fertilization (N) should be avoided for the highland winter wheat due to the higher biomass and grain yield and lower N2O flux and annual emission in m than in N.
Treatment of liquid swine manure (LSM) offers opportunities to improve manure nutrient management. However, N2O fluxes and cumulative emissions resulting from application of treated LSM are not well documented. Nitrous oxide emissions were monitored following band-incorporation of 100 kg N ha(-1) of either mineral fertilizer, raw LSM, or four pretreated LSMs (anaerobic digestion; anaerobic digestion + flocculation: filtration; decantation) at the four-leaf stage of corn (Zea mays L.). In a clay soil, a larger proportion of applied N was lost as N2O with the mineral fertilizer (average of 6.6%) than with LSMs (3.1-5.0%), whereas in a loam soil, the proportion of applied N lost as N2O was lower with the mineral fertilizer (average of 0.4%) than with LSMs (1.2-2.4%). Emissions were related to soil NO3 intensity in the clay soil, whereas they were related to water-extractable organic C in the loam soil. This suggests that N2O production was N limited in the clay soil and C limited in the loam soil, and would explain the interaction found between N sources and soil type. The large N2O emission coefficients measured in many treatments, and the contradicting responses among N sources depending on soil type, indicate that (i) the Intergovernmental Panel on Climate Change (IPCC) default value (1%) may seriously underestimate N2O emissions from fine-textured soils where fertilizer N and manure are band-incorporated, and (ii) site-specific factors, such as drainage conditions and soil properties (e.g., texture, organic matter content), have a differential influence on emissions depending on N source.
Information from 846 N2O emission measurements in agricultural fields and 99 measurements for NO emissions was summarized to assess the influence of various factors regulating emissions from mineral soils. The data indicate that there is a strong increase of both N2O and NO emissions accompanying N application rates, and soils with high organic-C content show higher emissions than less fertile soils. A fine soil texture, restricted drainage, and neutral to slightly acidic conditions favor N2O emission, while (though not significant) a good soil drainage, coarse texture, and neutral soil reaction favor NO emission. Fertilizer type and crop type are important factors for N2O but not for NO, while the fertilizer application mode has a significant influence on NO only. Regarding the measurements, longer measurement periods yield more of the fertilization effect on N2O and NO emissions, and intensive measurements (≥1 per day) yield lower emissions than less intensive measurements (2–3 per week). The available data can be used to develop simple models based on the major regulating factors which describe the spatial variability of emissions of N2O and NO with less uncertainty than emission factor approaches based on country N inputs, as currently used in national emission inventories.
Unwelcome Dominance
Stratospheric ozone is depleted by many different chemicals; most prominently, chlorofluorocarbons (CFCs) responsible for causing the Antarctic ozone hole. Nitrous oxide is also an ozone-depleting substance that has natural sources in addition to anthropogenic ones. Moreover, unlike CFCs, its use and emission are not regulated by the Montreal Protocol, which has helped to reverse the rate of growth of the ozone hole. Surprisingly, Ravishankara et al. (p. 123 , published online 27 August; see the Perspective by Wuebbles ) now show that nitrous oxide is the single greatest ozone-depleting substance that, if its emissions are not controlled, is expected to remain the dominant ozone-depleting substance throughout the 21st century. Reducing nitrous oxide emissions would thus enhance the rate of recovery of the ozone hole and reduce the anthropogenic forcing of climate.
The aims of this study were to (i) assess N fluxes (mineralization, volatilization, denitrification, leaching) caused by spreading various organic wastes from food-processing industries during a field experiment, and (ii) to identify the main factors affecting N transformation processes after field spreading. Experimental treatments including the spreading of six types of waste and a control soil were set up in August 2000 and studied for 22 mo under bare soil conditions. Ammonia and nitrous oxide emissions, and nitrogen mineralization were measured in experimental devices and extrapolated to field conditions or computed in calculation models. The ammonia emissions varied from 80 to 580 g kg(-1) NH4+-N applied, representing 0 to 90 g N kg(-1) total N applied. Under these meteorologically favorable conditions (dry and warm weather), waste pH was the main factor affecting volatilization rates. Cumulated N2O-N fluxes were estimated at 2 to 5 g kg(-1) total N applied, which was quite low due to the low soil water content during the experimental period; water-filled pore space (WFPS) was confirmed as the main factor affecting N2O fluxes. Nitrogen mineralization from wastes represented 126 to 723 g N kg(-1) organic N added from the incorporation date to 14 May 2001 and was not related to the organic C to organic N ratio of wastes. Nitrogen lost by leaching during the equivalent period ranged from 30 to 890 g kg(-1) total N applied. The highest values were obtained for wastes having the highest inorganic N content and mineralization rates.
Swine operations are important sources of greenhouse gases, primarily methane (CH4) and nitrous oxide (N2O). The objective of the study was to provide a systematic review of the literature on GHG emissions from land following swine manure application through a meta-analysis that integrates results of individual previous studies. Results showed that, for CH4 emissions, land applied swine manure generate more emissions than land with no N added or land applied commercial N fertilizer. For N2O emissions, there was no significant difference between land applied with swine manure and that applied with commercial fertilizer of the same N amount. The CH4 and N2O emissions from swine manure land applications were commonly of the similar scale. Generally N2O emissions deserve more attention than CH4 emissions in swine manure land application, considering that the global warming potential of N2O is about 12 times higher than that of CH4 while CH4 and N2O emissions from swine manure land applications were commonly of the similar scale. The wide variations in reported N2O emission factors (0.7 to 2.2%, 95% CI in North American studies) indicate great potential in mitigating N2O emissions through optimized management practices. The N2O emissions from land applications can be affected by many factors, while factors affecting CH4 emissions were less studied. Results of meta-analysis indicated that CH4 emissions had an increasing trend with increasing annual average temperature and a deceasing trend with increasing annual precipitation.
IntroductionIndividual studiesThe summary effectHeterogeneity of effect sizesSummary points
There is a growing concern that greenhouse gas (GHG) emissions during agricultural energy crop production might negate GHG emission savings which was not intended when promoting the use of renewable energy. Nitrous oxide (N2O) is a major GHG, and in addition, it is the most powerful ozone-depleting compound that is emitted by human activity. The use of N fertilizers and animal manures is the main anthropogenic source of N2O emissions. In spite of their high relevance, we still have limited understanding of the complex underlying microbial processes that consume or produce N2O and their interactions with soil types, fertilizers (rate and types), plants, and other environmental variables. In a 2-year field experiment, we compared two important biogas crops in two different agro-ecological regions of northern Germany for their productivity and GHG emissions, using the closed-chamber technique and high time-resolution sampling. Silage maize, which is currently the most widespread crop grown for biogas fermentation purposes in Germany, was compared with an alternative bioenergy crop at each site. The three forms of nitrogen fertilizers/manures were given: calcium ammonium nitrate, cattle/pig slurry, and biogas residue. The greatest N2O flux activity occurred in the period of May–July in all crops and at both sites. Flux patterns indicated pronounced effects of soil moisture-soil mineral-N interactions which were also seen as causation of the higher N2O fluxes in the bioenergy crop maize compared to the other tested energy crops. However, the N2O emission per unit methane production (specific N2O emission) was clearly lower in soils planted with maize due to significantly higher methane hectare yield of maize. Our data suggest a linear relationship between increasing N input and increases in N2O emission in both years at site with sandy loam texture where highest N2O fluxes were measured. At sandy loam site, the percentage of applied N being emitted as N2O was 1.9 and 1.1 % in soils cropped with maize and 0.9 and 0.8 % in soils cropped with wheat during the investigation period 2007–2008 and 2008–2009, respectively. In contrast, at site with sandy soil texture, the percentage of applied N emitted as N2O was only 0.6 and 0.7 % in maize soils and 0.4 and 0.3 % in grassland during 2007–2008 and 2008–2009 period, respectively. Higher daily and annual N2O emissions at the sandy loam site were attributed to the finer soil texture and higher denitrification activity. The present study provides a very good basis for the assessment of direct emissions of greenhouse gases from relevant biogas crops in North-West Europe.
The objectives of the study were to quantify N2O and NO emissions from poultry litter and urea applications to Bermuda grass (Cynodaon dactylon L.) and examine the seasonal variations in emissions. Soil N2O and NO emissions were measured in a Bermuda grass pasture treated with two sources of poultry litter, composted poultry litter (CPL) and fresh poultry litter (FPL) and urea (URE). Nitrogen (N) was applied to supply 336 kg available N ha-1 in four split applications made during the period from April to August 1995. An automated closed chamber system was employed to monitor N2O and NO emissions. The seasonal N2O emission patterns were characterized by several peaks occurring in phase with intermittent rain events and increasing soil N and organic carbon (C) associated with fertilizer application. The cumulative N2O emissions over the season (May to mid September) from the various treatments were, 3.87 kg N ha-1 from FPL, 2.96 kg N ha-1 from URE, and 1.64 kg N ha-1 from CPL. These seasonal N2O losses accounted for 1.0, 0.73 and 0.32% of the added available N for the, FPL, URE and CPL treatments, respectively. Denitrification was suggested as the primary source of N2O following rain events when inorganic N and C soil concentrations were highest and soil water-filled-pore-space (WFPS) was elevated. Peaks in NO emissions were observed primarily immediately after the addition of N sources. The seasonal NO emissions were smaller and ranged from 1.36 kg N ha-1 for URE, and 0.97 kg N ha-1 for FPL, to 0.47 kg N ha-1 for CPL. The seasonal NO emissions accounted for 0.36, 0.24 and 0.09% of the added N for the URE, FPL, and CPL treatments, respectively.
National and international requirements for greenhouse gas emissions
demand the development of more accurate inventories and mitigation
options that are effective in reducing emissions. The UK government set
a target for the year 2050 of an 80% reduction in greenhouse gas
emissions compared to the 1990 baseline. Estimate of UK national
emissions is based on IPCC default methodology and as agriculture
contributes about 7% of total GHG emissions of which 60% is
N2O, efforts to improve the inventory and assess mitigation
options are needed. Models can be used to derive N2O emission
factors providing high spatial and temporal resolution. In this study,
we used two models, the UK-DNDC, a mechanistic model to estimate
N2O emissions from soils and the NITCAT model to estimate the
fraction of N applied that is leached and causes indirect emissions,
both at county level for the UK. Four mitigation options were assessed
and the results showed there were differences in the emission factors
according to location. Average emission factors for N2O from
soils for inorganic fertiliser did not differ from the IPCC default
value but for organic fertiliser the model gave much lower values.
FracLEACH for arable land was higher than that for grassland
(UK averages of 0.28 and 0.09 respectively) and the national average
value was 0.18. For N2O, the most effective mitigation
measure was adjusting fertiliser rates to account for crop available
manure N. For N leaching, the most effective measure was implementation
of a manure closed period.
International initiatives such as the United Nations Framework Convention on Climate Change and the Kyoto Protocol require that countries calculate national inventories of their greenhouse gas emissions. The objective of the present study was to develop a country-specific (Tier II) methodology to calculate the inventory of N2O emissions from agricultural soils in Canada. Regional fertilizer-induced emission factors (EFreg) were first determined using available field experimental data. Values for EFreg were 0.0016 kg N2O-N kg-1 N in the semi-arid Brown and 0.008 kg N2O-N kg N-1 in the sub-humid Black soil zones of the Prairie region, and 0.017 kg N2O-N kg-1 N in the humid provinces of Quebec and Ontario. A function relating EFreg to the "precipitation to potential evapotranspiration" ratio was determined to estimate annual emission factors (EFeco) at the ecodistrict scale (≈150 000 ha) in all agricultural regions of Canada. Country-specific coefficients were also developed to account for the effect of several additional factors on soil N2O emissions. Emissions from fine-textured soils were estimated as being 50% greater than from coarse- and medium-textured soils in eastern Canada; emissions during winter and spring thaw corresponded to 40% of emissions during the snow-free season in eastern Canada; increased emissions from lower (wetter) sections of the landscape and irrigated areas were accounted for; emissions from no-till soils were 10% greater in eastern, but 20% lower in western Canada than from those under conventional tillage practices; emissions under summerfallow were estimated as being equal to those from soils under annual cropping. This country-specific methodology therefore accounts for regional climatic and land use impacts on N2O emission factors, and includes several sources/offsets that are not included in the Intergovernmental Panel on Climate Change (IPCC) default approach.