N2O emission
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Recent papers in N2O emission
This study investigated the effects of biochar and compost, applied individually or together, on soil fertility, peanut yield and greenhouse gas (GHG) emissions on a Ferralsol in north Queensland, Australia. The treatments were (1)... more
This study investigated the effects of biochar and compost, applied individually or together, on soil fertility, peanut yield and greenhouse gas (GHG) emissions on a Ferralsol in north Queensland, Australia. The treatments were (1) inorganic fertilizer only (F) as a control; (2) 10 t ha1 biochar + F (B + F); (3) 25 t compost + F (Com + F) ha1; (4) 2.5 t B ha1 + 25 t Com ha1 mixed on site + F; and (5) 25 t ha1 cocomposted biochar-compost + F (COMBI + F). Application of B and COMBI increased seed yield by 23% and 24%, respectively. Biochar, compost and their mixtures significantly improved plant nutrient availability and use, which appeared critical in improving peanut performance. Soil organic carbon (SOC) increased
from 0.93% (F only) to 1.25% (B amended), soil water content (SWC) from 18% (F only) to over 23% (B amended) and CEC from 8.9 cmol(+)/kg (F only) to over 10.3 cmol(+)/kg (organic amended). Peanut yield was significantly positively correlated with leaf chlorophyll content, nodulation number (NN), leaf nutrient concentration, SOC and SWC for the organic amendments. Fluxes of CO2 were highest for the F
treatment and lowest for the COMBI treatment, whereas N2O flux was highest for the F treatment and all organic amended plots reduced N2O flux relative to the control. Principal component analysis indicates that 24 out of 30 characters in the
first principal component (PRIN1) individually contributed substantial effects to the total variation between the treatments. Our study concludes that applications of B, Com, B + Com or COMBI have strong potential to, over time, improve SOC, SWC, soil nutrient status, peanut yield and abate GHG fluxes on tropical Ferralsols.
from 0.93% (F only) to 1.25% (B amended), soil water content (SWC) from 18% (F only) to over 23% (B amended) and CEC from 8.9 cmol(+)/kg (F only) to over 10.3 cmol(+)/kg (organic amended). Peanut yield was significantly positively correlated with leaf chlorophyll content, nodulation number (NN), leaf nutrient concentration, SOC and SWC for the organic amendments. Fluxes of CO2 were highest for the F
treatment and lowest for the COMBI treatment, whereas N2O flux was highest for the F treatment and all organic amended plots reduced N2O flux relative to the control. Principal component analysis indicates that 24 out of 30 characters in the
first principal component (PRIN1) individually contributed substantial effects to the total variation between the treatments. Our study concludes that applications of B, Com, B + Com or COMBI have strong potential to, over time, improve SOC, SWC, soil nutrient status, peanut yield and abate GHG fluxes on tropical Ferralsols.
Deteriorating soil fertility and the concomitant decline in agricultural productivity are major concerns in many parts of the world. A pot experiment was conducted with a Ferralsol to test the hypothesis that application of biochar... more
Deteriorating soil fertility and the concomitant decline in agricultural productivity are major concerns in many parts of the world. A pot experiment was conducted with a Ferralsol to test the hypothesis that application of biochar improves soil fertility, fertiliser-use efficiency, plant growth and productivity, particularly when combined with compost. Treatments comprised: untreated control; mineral fertiliser at rates of 280 mg nitrogen, 70 mg phosphorus and 180 mg potassium pot–1 (F); 75% F + 40 g compost pot–1 (F + Com); 100% F + 20 g willow biochar pot–1 (F + WB); 75% F + 10 g willow biochar + 20 g compost pot–1 (F +WB+ Com); 100% F + 20 g acacia biochar pot–1 (F + AB); and 75% F + 10 g acacia biochar + 20 g compost pot–1 (F +AB + Com). Application of compost with fertiliser significantly increased plant
growth, soil nutrient status and plant nutrient content, with shoot biomass (as a ratio of control value) decreasing in the order F + Com (4.0) > F +WB+ Com (3.6) > F +WB (3.3) > F +AB+ Com (3.1) > F +AB (3.1) > F (2.9) > control (1.0). Maize shoot biomass was positively significantly correlated with chlorophyll content, root biomass, plant height, and specific leaf weight (r = 0.99, 0.98, 0.96 and 0.92, respectively). Shoot and root biomass had significant correlations with
soil water content, plant nutrient concentration, and soil nutrient content after harvesting. Principal component analysis (PCA) showed that the first component provided a reasonable summary of the data, accounting for ~84% of the total
variance. As the plants grew, compost and biochar additions significantly reduced leaching of nutrients. In summary, separate or combined application of compost and biochar together with fertiliser increased soil fertility and plant growth.
Application of compost and biochar improved the retention of water and nutrients by the soil and thereby uptake of water and nutrients by the plants; however, little or no synergistic effect was observed.
growth, soil nutrient status and plant nutrient content, with shoot biomass (as a ratio of control value) decreasing in the order F + Com (4.0) > F +WB+ Com (3.6) > F +WB (3.3) > F +AB+ Com (3.1) > F +AB (3.1) > F (2.9) > control (1.0). Maize shoot biomass was positively significantly correlated with chlorophyll content, root biomass, plant height, and specific leaf weight (r = 0.99, 0.98, 0.96 and 0.92, respectively). Shoot and root biomass had significant correlations with
soil water content, plant nutrient concentration, and soil nutrient content after harvesting. Principal component analysis (PCA) showed that the first component provided a reasonable summary of the data, accounting for ~84% of the total
variance. As the plants grew, compost and biochar additions significantly reduced leaching of nutrients. In summary, separate or combined application of compost and biochar together with fertiliser increased soil fertility and plant growth.
Application of compost and biochar improved the retention of water and nutrients by the soil and thereby uptake of water and nutrients by the plants; however, little or no synergistic effect was observed.
Nitrous oxide (N2O) from agricultural soil is a significant source of greenhouse gas emissions. Biochar amendment can contribute to climate change mitigation by suppressing emissions of N2O from soil, although the mechanisms underlying... more
Nitrous oxide (N2O) from agricultural soil is a significant source of greenhouse gas emissions. Biochar
amendment can contribute to climate change mitigation by suppressing emissions of N2O from soil,
although the mechanisms underlying this effect are poorly understood. We investigated the effect of
biochar on soil N2O emissions and N cycling processes by quantifying soil N immobilisation, denitrification,
nitrification and mineralisation rates using 15N pool dilution techniques and the FLUAZ numerical
calculation model. We then examined whether biochar amendment affected N2O emissions and the
availability and transformations of N in soils.
Our results show that biochar suppressed cumulative soil N2O production by 91% in near-saturated,
fertilised soils. Cumulative denitrification was reduced by 37%, which accounted for 85-95 % of soil
N2O emissions. We also found that physical/chemical and biological ammonium (NH4
þ) immobilisation
increased with biochar amendment but that nitrate (NO3
) immobilisation decreased. We concluded that
this immobilisation was insignificant compared to total soil inorganic N content. In contrast, soil N
mineralisation significantly increased by 269% and nitrification by 34% in biochar-amended soil.
These findings demonstrate that biochar amendment did not limit inorganic N availability to nitrifiers
and denitrifiers, therefore limitations in soil NH4
þ and NO3
supply cannot explain the suppression of N2O
emissions. These results support the concept that biochar application to soil could significantly mitigate
agricultural N2O emissions through altering N transformations, and underpin efforts to develop climate friendly
agricultural management techniques.
amendment can contribute to climate change mitigation by suppressing emissions of N2O from soil,
although the mechanisms underlying this effect are poorly understood. We investigated the effect of
biochar on soil N2O emissions and N cycling processes by quantifying soil N immobilisation, denitrification,
nitrification and mineralisation rates using 15N pool dilution techniques and the FLUAZ numerical
calculation model. We then examined whether biochar amendment affected N2O emissions and the
availability and transformations of N in soils.
Our results show that biochar suppressed cumulative soil N2O production by 91% in near-saturated,
fertilised soils. Cumulative denitrification was reduced by 37%, which accounted for 85-95 % of soil
N2O emissions. We also found that physical/chemical and biological ammonium (NH4
þ) immobilisation
increased with biochar amendment but that nitrate (NO3
) immobilisation decreased. We concluded that
this immobilisation was insignificant compared to total soil inorganic N content. In contrast, soil N
mineralisation significantly increased by 269% and nitrification by 34% in biochar-amended soil.
These findings demonstrate that biochar amendment did not limit inorganic N availability to nitrifiers
and denitrifiers, therefore limitations in soil NH4
þ and NO3
supply cannot explain the suppression of N2O
emissions. These results support the concept that biochar application to soil could significantly mitigate
agricultural N2O emissions through altering N transformations, and underpin efforts to develop climate friendly
agricultural management techniques.
- by Niall McNamara and +1
- •
- Soil Science, BIOCHAR, N2O emission, Nitrogen Cycling
Biogas digestate (BD) is characterised by a lower organic carbon (C) con¬tent, an increased proportion of ammonium as well as an upward shifted pH compared to the undigested precur-sors. Its use may have consequences for N emissions from... more
Biogas digestate (BD) is characterised by a lower organic carbon (C) con¬tent, an increased proportion of ammonium as well as an upward shifted pH compared to the undigested precur-sors. Its use may have consequences for N emissions from soils, e.g. nitrous oxide (N2O), and impacts on soil organic matter (SOM) reproduction, i.e. C sequestra¬tion. Tillage enhances mi-crobial decomposition of SOM in the short-term and, thus, in¬creases soil respiration (SR). Fer-tiliser application generally induces a period of high N2O emissions from agricultural soils. Compared to other fertilisers, BD is additionally loss-prone for ammonia (NH3). To reduce these losses, the injection of BD into soil is recommended.
The treatments amended with BD revealed a distinct C dioxide (CO2) emission pattern com-pared to una¬mended and mineral fertilised treatments during the days after tillage. The in-crease in SR due to tillage-induced mineralisation was significantly lower in BD treatments. Pyrolysis-field ionisation mass spectrometry (Py-FIMS) showed that differences in SOM composition caused by the different fertilisers appeared after only one season in a maize (Zea mays L.) field. The amendment with BD resulted in a lower share of easily decomposable compounds like carbo¬hydrates but a higher share of recalcitrant compounds like lignin com-pared to the mineral fertilised treat¬ment. Additionally, a short-term turnover of lignin-derived substances was detected during the days after tillage. Directly after the application of BD in concentrations typical for injection, the emissions of N2O and N2 were controlled mainly by gas diffusivity. Doubling the amount of applied BD showed no significant effects on the emitted flux rates, probably due to the inhibitory effect of high NH3 concentrations on nitrite oxidisers.
Overall, the BD amended soils were less prone to C losses after tillage. However, the emis-sions of N2O and N2 – and supposedly NO – question the environmental benefits of BD injec-tion into soil.
The treatments amended with BD revealed a distinct C dioxide (CO2) emission pattern com-pared to una¬mended and mineral fertilised treatments during the days after tillage. The in-crease in SR due to tillage-induced mineralisation was significantly lower in BD treatments. Pyrolysis-field ionisation mass spectrometry (Py-FIMS) showed that differences in SOM composition caused by the different fertilisers appeared after only one season in a maize (Zea mays L.) field. The amendment with BD resulted in a lower share of easily decomposable compounds like carbo¬hydrates but a higher share of recalcitrant compounds like lignin com-pared to the mineral fertilised treat¬ment. Additionally, a short-term turnover of lignin-derived substances was detected during the days after tillage. Directly after the application of BD in concentrations typical for injection, the emissions of N2O and N2 were controlled mainly by gas diffusivity. Doubling the amount of applied BD showed no significant effects on the emitted flux rates, probably due to the inhibitory effect of high NH3 concentrations on nitrite oxidisers.
Overall, the BD amended soils were less prone to C losses after tillage. However, the emis-sions of N2O and N2 – and supposedly NO – question the environmental benefits of BD injec-tion into soil.
An experimental investigation was carried out to study the NOx formation and reduction by primary measures for five types of biomass (straw, peat, sewage sludge, forest residues/Grot, and wood pellets) and their mixtures. To minimize the... more
An experimental investigation was carried out to study the NOx formation and reduction by primary measures for five types of biomass (straw, peat, sewage sludge, forest residues/Grot, and wood pellets) and their mixtures. To minimize the NOx level in biomass-fired boilers, combustion experiments were performed in a laboratory scale multifuel fixed grate reactor using staged air combustion. Flue gas was extracted to measure final levels of CO, CO2, CxHy, O2, NO, NO2, N2O, and other species. The fuel gas compositions between the first and second stage were also monitored. The experiments showed good combustion quality with very low concentrations of unburnt species in the flue gas. Under optimum conditions, a NOx reduction of 50–80% was achieved, where the highest reduction represents the case with the highest fuel-N content. The NOx emission levels were very sensitive to the primary excess air ratio and an optimum value for primary excess air ratio was seen at about 0.9. Conversion of fuel nitrogen to NOx showed great dependency on the initial fuel-N content, where the blend with the highest nitrogen content had lowest conversion rate. Between 1–25% of the fuel-N content is converted to NOx depending on the fuel blend and excess air ratio. Sewage sludge is suggested as a favorable fuel to be blended with straw. It resulted in a higher NOx reduction and low fuel-N conversion to NOx. Tops and branches did not show desirable NOx reduction and made the combustion also more unstable. N2O emissions were very low, typically below 5 ppm at 11% O2 in the dry flue gas, except for mixtures with high nitrogen content, where values up to 20 ppm were observed. The presented results are part of a larger study on problematic fuels, also considering ash content and corrosive compounds which have been discussed elsewhere.
Atmospheric concentration of nitrous oxide (N2O), a greenhouse gas (GHG), is rising largely due to agriculture. At the plot scale, N2O emissions from crops are known to be controlled by local agricultural practices such as fertilisation,... more
Atmospheric concentration of nitrous oxide (N2O), a greenhouse gas (GHG), is rising largely due to agriculture. At the plot scale, N2O emissions from crops are known to be controlled by local agricultural practices such as fertilisation, tillage and residue management. However, knowledge of greenhouse gas emissions at the scale of the cropping system is scarce, notably because N2O monitoring is time consuming. Strategies to reduce impact of farming on climate should therefore be sought at the cropping system level. Agro-ecosystem models are simple alternative means to estimate N2O emissions. Here, we combined ecosystem modelling and field measurements to assess the effect of agronomic management on N2O emissions. The model was tested with series of daily to monthly N2O emission data. It was then used to evaluate the N2O abatement potential of a low-emission system designed to halve greenhouse gas emissions in comparison with a system with high productivity and environmental performance. We found a 29% N2O abatement potential for the low-emission system compared with the high-productivity system. Among N2O abatement options, reduction in mineral fertilizer inputs was the most effective.
NITROUS OXIDE (N2O) IN AQUATIC SYSTEMS: PRODUCTION, REGULATING FACTORS AND FLUXES FROM DIFERENT ENVIRONMENTS. Nitrous oxide (N2O) is one of the three main greenhouse gases, besides being identified as the main destroyer gas of the ozone... more
NITROUS OXIDE (N2O) IN AQUATIC SYSTEMS: PRODUCTION, REGULATING FACTORS AND FLUXES FROM DIFERENT ENVIRONMENTS. Nitrous oxide (N2O) is one of the three main greenhouse gases, besides being identified as the main destroyer gas of the ozone layer in this century. This gas is naturally produced through the processes of nitrification and denitrification in aquatic and terrestrial environments. Rates of N2O emissions have been widely studied in terrestrial ecosystems, but comparatively, they have been neglected in freshwater ecosystems, despite the recent recognition of the importance of these environments in the global cycles of carbon and nitrogen. The objective of this study was to present the main regulating factors on the production of N2O through nitrification and denitrification processes in lakes, reservoirs, rivers, mangroves and estuaries. Rates of N2O emission in such environments exhibit great differences from each other, ranging up to four orders of magnitude. The highest N2O fluxes were observed in estuaries, mangroves and rivers. Lakes and reservoirs are more stable environments than mangroves, estuaries and rivers, and this feature makes the variability of factors, such as pH and nutrient concentrations, are lower, favoring greater stability of processes and consequently a lower production and emission of N2O, since this gas is derived from environmental changes.
The gas mixture N2:SF6 has been used in gas insulated switchgears, gas insulated transmission lines and gas insulated cables for years in order to reduce the use of SF6 gas in electrical system. By taking into account the insulation... more
The gas mixture N2:SF6 has been used in gas insulated switchgears, gas insulated transmission lines and gas insulated cables for years in order to reduce the use of SF6 gas in electrical system. By taking into account the insulation performance and environmental effect, it is advised that the use of N2:SF6 gas mixture in practical to lower the SF6 gas content as far as possible. The present study is undertaken using different N2:SF6 gas mixture ratio to determine the flashover characteristics under AC voltages. In this paper the effect of floating particles, use of different insulating spacers namely PMMA, PP and NYLON and their combination forms hybrid spacers has been studied in non-uniform electric field (needle – plane) electrode configuration. The surface flashover performances of individual and hybrid spacers have been compared in N2:SF6 gas mixture. The experimental results shows that conventional spacer PMMA show better performance than the other spacers (PP and NYLON) at the gas pressure of 0.18MPa. As the gas pressure increases further the flashover voltage values slightly decreases. The hybrid spacer PMMA – PP are more effective at lower pressure than other spacer combinations. With floating particle, PP shows better flashover at lower pressure and the performance of PMMA – NYLON is much better at lower pressure.
Seed inoculation by plant growth promoting rhizobacteria (PGPRs) is an agronomic practice that stimulates root carbon (C) exudation and nitrogen (N) uptake. Inoculation thus increases and decreases C and N availabilities to denitrifiers... more
Seed inoculation by plant growth promoting rhizobacteria (PGPRs) is an agronomic practice that stimulates root carbon (C) exudation and nitrogen (N) uptake. Inoculation thus increases and decreases C and N availabilities to denitrifiers in the rhizosphere, respectively. Hence, denitrification rates in the rhizosphere can be positively or negatively influenced by root activity depending on the balance between these two processes. We assumed that inoculation effect on denitrifiers could strongly differ according to soil conditions. Would denitrifiers be mostly limited by C, inoculation would increase denitrifier abundance and activity through increased labile C availability. Would denitrifiers be limited by N rather than C, inoculation would decrease denitrifier abundance and activity through increased competition for N. Here we manipulated denitrification limitation by C and N (i) in a field trial through the use of different fertilization levels, and (ii) in a growth chamber experiment by mimicking root exudate inputs. We analyzed how the effects of maize inoculation by the PGPR Azospirillum lipoferum CRT1 on potential gross and net N 2 O production rates and NO 2 −-and N 2 O-reducer abundances were related to C and N limitation levels. An increase in potential gross (up to +113%) and to a lesser extent net (+37%) N 2 O production was observed for soils where denitrification was highly limited by C. This was explained by strong and moderate increases in the abundances of NO 2 −-and N 2 O-reducers, respectively. In contrast, when deni-trification was weakly limited by C, gross and net N 2 O productions were negatively affected by inoculation (−15 and −40%, respectively). Our results show that the inoculation practice should be evaluated in term of possible increased crop yield but also possible modified N 2 O emission, paying much attention to cropland soils where denitrifiers are highly limited by C.
Greenhouse gas (GHG) emissions from soils cause uncertainties within Agricultural LCA. N2O affects global warming and is estimated with IPCC guidelines, agroecosystem models or direct measurements. CERES-EGC model was used to estimate N2O... more
Greenhouse gas (GHG) emissions from soils cause uncertainties within Agricultural LCA. N2O affects global warming and is estimated
with IPCC guidelines, agroecosystem models or direct measurements. CERES-EGC model was used to estimate N2O emissions
from faba bean and winter cereals grown in two trials (ICC and CIMAS) with different climates. Model outputs were compared
with IPCC estimates. Simulated N2O emission patterns showed emissions can be independent from fertiliser application dates or
rates. This was due to soil moisture, rainfall and farming practices. Results showed the IPCC procedure estimated higher annual cereals
emissions of 740 g N2O-N ha-1 y-1 than simulation results and a lower estimation of 304 g N2O-N ha-1 y-1 for faba bean. Results
revealed inclusion of climate, soil properties and management resulted in major variations of N2O emissions which CERES-EGC was
able to capture. Thus, model estimates may increase accuracy of soil GHG emission in Agricultural LCA.
with IPCC guidelines, agroecosystem models or direct measurements. CERES-EGC model was used to estimate N2O emissions
from faba bean and winter cereals grown in two trials (ICC and CIMAS) with different climates. Model outputs were compared
with IPCC estimates. Simulated N2O emission patterns showed emissions can be independent from fertiliser application dates or
rates. This was due to soil moisture, rainfall and farming practices. Results showed the IPCC procedure estimated higher annual cereals
emissions of 740 g N2O-N ha-1 y-1 than simulation results and a lower estimation of 304 g N2O-N ha-1 y-1 for faba bean. Results
revealed inclusion of climate, soil properties and management resulted in major variations of N2O emissions which CERES-EGC was
able to capture. Thus, model estimates may increase accuracy of soil GHG emission in Agricultural LCA.
Maize inoculation by Azospirillum stimulates root growth, along with soil nitrogen (N) uptake and root carbon (C) exudation, thus increasing N use efficiency. However, inoculation effects on soil N-cycling microbial communities have been... more
Maize inoculation by Azospirillum stimulates root growth, along with soil nitrogen (N) uptake and root carbon (C) exudation, thus increasing N use efficiency. However, inoculation effects on soil N-cycling microbial communities have been overlooked. We hypothesized that inoculation would (i) increase roots-nitrifiers competition for ammonium, and thus decrease nitrifier abundance; and (ii) increase roots-denitrifiers competition for nitrate and C supply to denitrifiers by root exudation, and thus limit or benefit denitrifiers depending on the resource (N or C) mostly limiting these microorganisms. We quantified (de)nitrifiers abundance and activity in the rhizosphere of inoculated and non-inoculated maize on 4 sites over 2 years, and ancillary soil variables. Inoculation effects on nitrification and nitrifiers (AOA, AOB) were not consistent between the three sampling dates. Inoculation influenced denitrifiers abundance (nirK, nirS) differently among sites. In sites with high C limitation for denitrifiers (i.e. limitation of denitrification by C > 66%), inoculation increased nirS-denitrifier abundance (up to 56%) and gross N 2 O production (up to 84%), likely due to increased root C exudation. Conversely, in sites with low C limitation (<47%), inoculation decreased nirS-denitrifier abundance (down to −23%) and gross N 2 O production (down to −18%) likely due to an increased roots-denitrifiers competition for nitrate. The rhizosphere provides a peculiar environment where a huge variety of positive, negative and neutral interactions between roots and microorganisms occur 1. Such interactions can significantly influence plant growth as well as the functioning, the abundance and the diversity of rhizospheric microbial communities 2. Beneficial interactions are known to be established by plant growth-promoting rhizobacteria, PGPRs, with host plants through several mechanisms, including associative N 2 fixation, phosphate solubilization or phytosiderophore production 3, 4. This can result in improved root growth 5, 6 , increased number and length of lateral roots 7 , as well as an increased root and shoot biomass 8, 9 and physiology 10. The better root development induced by inoculation can consequently enhance nutrient 11 and water 12 uptake by plant, stimulate ion transport systems in root 13 and increase the amount of root carbon, C, exudation 14, 15. Azospirillum spp. are well-known PGPRs that are able to colonize the roots of many crop plant species including maize 16, 17. These PGPRs produce phytohormones that can promote root growth and improve nutrient and water absorption by plants 18-21. In particular, inoculation of cereal crops by PGPRs like the well-studied Azospirillum lipoferum CRT1 is often expected to improve crop capacity to retrieve mineral nitrogen, N, from soil. This could pave the way for improving the sustainability of these cropping systems under low N inputs conditions 8. However, inoculated plants could differently affect N dynamics in their rhizosphere, thus influencing the levels and types of mineral N forms available and possibly N losses from soil through leaching of nitrate, NO 3 − , or emission of nitrous oxide, N 2 O, a potent greenhouse gas 22 .
A model for NO and N2O emissions from biomass-fired circulating fluidized bed (CFB) combustors has been developed and evaluated in this study. All the model parameters were chosen for a typical woody biomass–pinewood chips. Both drying... more
A model for NO and N2O emissions from biomass-fired circulating fluidized bed (CFB) combustors has been developed and evaluated in this study. All the model parameters were chosen for a typical woody biomass–pinewood chips. Both drying and devolatilization of biomass particles were modelled with limited rates, which were selected from the literature based on woody biomass fuels. The partition of fuel-nitrogen between volatiles and char was also specifically chosen for pinewood based on available experimental data from the literature. Volatile nitrogen was assumed to consist of NH3, HCN and N2 with the distribution between three species as input parameters to the model. Twenty-five homogenous and heterogeneous global chemical reactions were included in the model, of which 20 reactions represents the global fuel-nitrogen reactions. Both gaseous and solid phase were assumed to be in plug flow. The model has been applied to the modelling of a 12 MWth CFB boiler. The predicted N2O emissions were always less than 5 ppmv for pinewood combustion, which was consistent with the experimental results. The predicted NO emissions increased with the total excess air of the riser and the fuel-N content while the predicted percentage conversion of fuel-N to NO decreased with increasing fuel-N content. The NO emissions were also predicted to decrease with increasing primary zone stoichiometry. These predictions agree with the experimental results. The predicted NO emissions decreased slightly with increasing bed temperature, whereas experiments showed that NO emissions slightly increased with bed temperature for birch chips combustion and did not change with bed temperature for fir chips combustion. Sensitivity analyses reveal that the reaction between NO and char is the key reaction to determine the NO emissions.
A 15 N labeling and lysimeter experiment was conducted with mesocosms of a semi-arid Leymus chinensis grassland. The aim of the study was to evaluate the effects of N fertilization timing (fertilization in fall or spring) and rate (0, 56,... more
A 15 N labeling and lysimeter experiment was conducted with mesocosms of a semi-arid Leymus chinensis grassland. The aim of the study was to evaluate the effects of N fertilization timing (fertilization in fall or spring) and rate (0, 56, and 112 kg-N ha −1 year −1) on ecosystem services (seed yield and forage yield), ecosystem disservices (N leaching surveyed during 1 year and emissions of NH 3 and N 2 O integrated over 76 days after fertilization), and recovery of added fertilizer N in plants and soil. Seed and forage yields increased more under fall than spring N fertilization. Further, N fertilization was linked to higher soil NH 3 and N 2 O emissions, particularly under high N rate for both NH 3 (2.0 and 1.6 kg-N ha −1 under fall and spring N fertilization, respectively) and N 2 O (0.24 and 0.21 kg-N ha −1 , respectively). N leaching was never observed. A significant N fertilization timing × rate interaction effect was observed on plant recovery efficiency of added fertilizer N (Plant-NRE). Plant-NRE was higher for high than moderate N rate, with + 13.2% (from 22.8 to 36%) and + 16.4% (from 28.2 to 44.7%) for fall and spring fertilization, respectively. Fertilizer N recovered in soil was highest for moderate N rate in fall (68% of total N fertilizer) and lowest for high N rate in spring (46%). Our results show synergies among the ecosystem services (seed and forage yields) and among the disservices (NH 3 and N 2 O emissions), and trade-offs between the services and disservices, some of these synergies and trade-offs being modulated by N fertilization timing and rate. Our study is the first one analyzing the possibly interactive effects of the N fertilization timing and rate on this range of ecosystem services and disservices in semi-arid perennial grasslands, which can be useful for N risk: benefit analysis when evaluating N fertilization strategies.
The production of organic wastes tends to increase in a manner that is proportional to human population growth. Currently, applying these wastes to soils is being considered as an alternative solution for the over production of organic... more
The production of organic wastes tends to increase in a manner that is proportional to human population growth. Currently, applying these wastes to soils is being considered as an alternative solution for the over production of organic waste. However, the levels of greenhouse gas (GHG) emissions from organic waste applications in tropical forestry are unknown. The aim of the present study was to quantify soil carbon dioxide (CO 2), nitrous oxide (N 2 O) and methane (CH 4) emissions from a reforestation project, where trees (Calophyllum brasiliense) were fertilized with different mineral and organic waste materials. A randomized trial was established to measure soil GHG emissions from plots fertilized with sewage sludge compost (SSC), sewage sludge (SS), mineral fertilizer (Min Fert) and a control (C). C. brasiliense seedling spaced in 3 m  2 m intervals were place into a planting hole which had fertilizer incorporated for seedling establishment. Soil GHG were measured using the static chamber method, placing chambers on the surface of the soil and taking measurements over time, during 172 days in a dry season. Organic wastes (SS and SSC treatments) had significantly higher soil CO 2 fluxes than mineral fertilizer and control plots, with soil CO 2 fluxes of 6.35 ± 1.17 and 9.33 ± 0.96 g C m À2 day À1 , respectively. The application of organic wastes promoted a drastic increase in soil N 2 O emissions treated with SSC (141.19 mg ± 21 N m À2 day À1 , p < 0.01), which had a higher emission factor (2.11%). Average soil CH 4 flux on collection days was À0.1 ± 0.2 mg C m À2 day À1 , although cumulative soil CH 4 emissions over the 5 months study period was positive for the SS treatment, demonstrating the potential emission of GHG from this treatment. Apparently, the variation in fluxes between treatments with organic residues was influenced by differences in the physical and chemical compositions of the wastes and the amounts of labile carbon added.
Keywords: Denitrification nirK nirS nosZ Soil nitrate Soil organic carbon A B S T R A C T Increasing attention has been paid to microorganisms able to produce nitrous oxide (N 2 O), a potent greenhouse gas, or reduce it to harmless N 2.... more
Keywords: Denitrification nirK nirS nosZ Soil nitrate Soil organic carbon A B S T R A C T Increasing attention has been paid to microorganisms able to produce nitrous oxide (N 2 O), a potent greenhouse gas, or reduce it to harmless N 2. Based on previous studies, niche differentiation could exist between nirK-and nirS-nitrite reducers and nosZI-and nosZII-N 2 O reducers, and nosZII-bacteria would have a key role for N 2 O reduction in soils. Most previous studies have been performed for agricultural systems but never in the moist savanna zone which covers half a million km 2 in West Africa and whose soils are among the poorest in nitrogen (N) on earth. Here, we quantified potential gross and net N 2 O production rates along with the abundances of nirK-, nirS-, nosZI-and nosZII-harbouring bacteria for soils under six agricultural practices with maize rotations (slash-and-burn, chemical fertilization, mulching with or without inclusion of crop legumes, and without any input) after 4 and 5 crop cycles at nine sites in Ivory Coast. Sites and practices influenced denitrifier abundances and activities, the ratio of total abundances of nitrite-toN 2 O reducers being highest and lowest for the mulching + green soya and slash-and-burn practices, respectively. Using structural equation modelling, we showed that nirS-and nosZI-bacteria both strongly depended on nitrate availability whereas nirK-and nosZII-bacteria were related to soil organic carbon and pH. Furthermore, potential gross and net N 2 O production rates depended strongly and only on the abundances of nirS-and nosZI-bacteria. Our results support the view of a clear niche differentiation between these four microbial groups but invalidate the assumption of a prominent functional role of soil nosZII-N 2 O reducers.
Biogas digestate (BD) is increasingly used as organic fertilizer, but has a high potential for NH3 losses. Its proposed injection into soils as a countermeasure has been suggested to promote the generation of N2O, leading to a potential... more
Biogas digestate (BD) is increasingly used as organic fertilizer, but has a high potential for NH3 losses. Its proposed injection into soils as a countermeasure has been suggested to promote the generation of N2O, leading to a potential trade-off. Furthermore, the effect of high nutrient concentrations on N2 losses as they may appear after injection of BD into soil has not yet been evaluated. Hence, we performed an incubation experiment with soil cores in a helium–oxygen atmosphere to examine the influence of soil substrate (loamy sand, clayey silt), water-filled pore space (WFPS; 35, 55, 75 %) and application rate (0, 17.6 and 35.2 mL BD per soil core, 250 cm3) on the emission of N2O, N2 and CO2 after the usage of high loads of BD. To determine the potential capacity for gaseous losses, we applied anaerobic conditions by purging with helium for the last 24 h of incubation. Immediate N2O and N2 emissions as well as the N2 / (N2O+N2) product ratio depended on soil type and increased with WFPS, indicating a crucial role of soil gas diffusivity for the formation and emission of nitrogenous gases in agricultural soils. However, emissions did not increase with the application rate of BD. This is probably due to an inhibitory effect of the high NH4+ content of BD on nitrification. Our results suggest a larger potential for N2O formation immediately following BD injection in the fine-textured clayey silt compared to the coarse loamy sand. By contrast, the loamy sand showed a higher potential for N2 production under anaerobic conditions. Our results suggest that short-term N losses of N2O and N2 after injection may be higher than probable losses of NH3 following surface application of BD.
Soil, climate and management practices make greenhouse gas (GHG) emission estimates associated with crop production highly uncertain. Biophysical modelling provides reliable reactive nitrogen (Nr) estimates for environmental assessment.... more
Soil, climate and management practices make greenhouse gas (GHG) emission estimates associated with crop production highly uncertain. Biophysical modelling provides reliable reactive nitrogen (Nr) estimates for environmental assessment. In this paper LCA and ecosystem modelling are combined to improve GHG estimation from cropping systems in the Paris (France) area, and to compare environmental impacts of two cropping systems at regional level. A cropping system aimed at productivity with high environmental performance (PHEP), while the other one aimed to reduce (GHG) emissions by half (50%GHG). Model-derived GHG estimates for crop production were at least 7% lower than estimates from the standard methodology applied to LCA, emphasizing the importance of regional factors in agricultural LCAs. The 50%GHG cropping system appears promising (184% reduction in the life-cycle GHG emissions) for climate mitigation of arable crops, pending trade-offs with other impact categories.
- by Pietro Goglio and +1
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- Spatial Analysis, Cropping Systems, N2O emission, LCA
The objective of this study was to determine the changes in N2O emissions in two contrasting soils, well-drained Andosol and poorly drained Fluvisol, after the application of urea or coated urea fertilizers. Coated urea is a new attempt... more
The objective of this study was to determine the changes in N2O emissions in two contrasting soils, well-drained Andosol and poorly drained Fluvisol, after the application of urea or coated urea fertilizers. Coated urea is a new attempt to mitigate soil-N2O emissions through microbial processes by slowly releasing the N substrates and therefore reducing the N-availability for microorganisms. However, there is evidence that the reduction of N2O emissions due to coated urea strongly depends on the used soil type. I hypothesized that changes in nitrification and/or denitrification rates after urea/coated urea application can explain the variability in N2O emissions from coated urea in different soils. Thus, nitrification and denitrification rates were determined using a 15N-tracer technique at 3 timings, before, 1 week and 1 month after urea/coated urea application, in Andosol and Fluvisol. When compared to N2O emissions from soils with urea, a reduction of N2O emissions of around 30% was achieved using coated urea in Andosol. However, in Fluvisol no significant difference was observed between N2O emissions after urea and coated urea application. For Fluvisol, nitrification and denitrification contributed equally to N2O emissions when urea was applied, whereas the contribution of nitrification to N2O production was enhanced after coated urea application. For Andosol, nitrification was the major contributor of N2O emissions regardless to the sampling timings and to the fertilizer types. Consequently, the efficiency of coated urea in terms of N2O mitigation depended on the soil type and the magnitude of the enhancement of soil processes (nitrification and denitrification) determined this efficiency.
Keywords: Soil-N2O Emissions, N2O Production Processes, 15N-Tracers, Coated Urea
Keywords: Soil-N2O Emissions, N2O Production Processes, 15N-Tracers, Coated Urea
Urine deposition on grassland causes significant N2O losses, which in some cases may result from increased denitrification stimulated by labile compounds released from scorched plant roots. Two 12-day experiments were conducted in... more
Urine deposition on grassland causes significant N2O losses, which in some cases may result from increased denitrification stimulated by labile compounds released from scorched plant roots. Two 12-day experiments were conducted in 13C-labelled grassland monoliths to investigate the link between N2O production and carbon mineralization following application of low rates of urine-N. Measurements of N2O and CO2 emissions from the monoliths as well as d13C signal of evolved CO2 were done on day)4,)1, 0, 1, 2, 4, 5, 6 and 7 after application of urine corresponding to 3.1 and 5.5 g N m)2 in the first and second experiment, respectively. The d13C signal was also determined for soil organic matter, dissolved organic C and CO2 evolved by microbial respiration. In addition, denitrifying enzyme activity (DEA) and nitrifying enzyme activity (NEA) were measured on day)1, 2 and 7 after the first urine application event. Urine did not affect DEA, whereas NEA was enhanced 2 days after urine application. In the first experiment, urine had no significant effect on the N2O flux, which was generally low ()8 to 14 lg N2ON m)2 h)1). After the second application event, the N2O emission increased significantly to 87 lg N2ON m)2 h)1 and the N2O emission factor for the added urine-N was 0.18%. However, the associated 13 C signal of soil respiration was unaffected by urine. Consequently, the increased N2O emission from the simulated low N-urine patches was not caused by enhanced denitrification stimulated by labile compounds released from scorched plant roots.
Global environmental changes are expected to alter ecosystem carbon and nitrogen cycling, but the interactive effects of multiple simultaneous environmental changes are poorly understood. Effects of these changes on the production of... more
Global environmental changes are expected to alter ecosystem carbon and nitrogen cycling, but the interactive effects of multiple simultaneous environmental changes are poorly understood. Effects of these changes on the production of nitrous oxide (N2O), an important greenhouse gas, could accelerate climate change. We assessed the responses of soil N2O fluxes to elevated CO2, heat, altered precipitation, and enhanced nitrogen deposition, as well as their interactions, in an annual grassland at the Jasper Ridge Global Change Experiment (CA, USA). Measurements were conducted after 6, 7 and 8 years of treatments. Elevated precipitation increased N2O efflux, especially in combination with added nitrogen and heat. Path analysis supported the idea that increased denitrification due to increased soil water content and higher labile carbon availability best explained increased N2O efflux, with a smaller, indirect contribution from nitrification. In our data and across the literature, single-factor responses tended to overestimate interactive responses, except when global change was combined with disturbance by fire, in which case interactive effects were large. Thus, for chronic global environmental changes, higher order interactions dampened responses of N2O efflux to multiple global environmental changes, but interactions were strongly positive when global change was combined with disturbance. Testing whether these responses are general should be a high priority for future research.
A review is presented on trace gas exchange of CH₄, CO, N₂O, and NOx arising from agriculture and natural sources in the world’s semiarid and arid zones due to soil processes. These gases are important contributors to the radiative... more
A review is presented on trace gas exchange of CH₄, CO, N₂O, and NOx arising from agriculture and natural sources in the world’s semiarid and arid zones due to soil processes. These gases are important contributors to the radiative forcing and the chemistry of the atmosphere. Quantitative information is summarized from the available studies. Between 5 and 40% of the global soil–atmosphere exchange for these gases (CH₄, CO, N₂O, and NOx) may occur in semiarid and arid zones, but for each of these gases there are fewer than a dozen studies to support the individual estimates, and these are from a limited number of locations. Significant differences in the biophysical and chemical processes controlling these trace gas exchanges are identified through the comparison of semiarid and arid zones with the moist temperate or wet/dry savanna land regions. Therefore, there is a poorly quantified understanding of the contribution of these regions to the global trace gas cycles and atmospheric chemistry. More importantly, there is a poor understanding of the feedback between these exchanges, global change, and regional land use and air pollution issues. A set of research issues is presented.
Methane (CH₄) and nitrous oxide (N₂O) emission estimates were made for Vigna mungo and Vigna radiata legumes. The affecting soil parameters like redox potential, soil temperature were studied to evaluate CH₄ and N₂O emissions. The CH₄ was... more
Methane (CH₄) and nitrous oxide (N₂O) emission estimates were made for Vigna mungo and Vigna radiata legumes. The affecting soil parameters like redox potential, soil temperature were studied to evaluate CH₄ and N₂O emissions. The CH₄ was negative and N₂O was positive for Vigna mungo, almost throughout the cropping period. The redox potential was more than +100 mV during the entire cropping period with a maximum N₂O flux of 11.67 μg m–2 h–1. The raise in soil temperature and the redox potential during harvest further increased the N₂O flux to 18.38 μg m–2 h–1. The seasonally integrated flux E(SIF) for CH₄ and N₂O for Vigna mungo was calculated to be –4.06 g.m–2 and 3.38 mg m–2 respectively. Similarly E(SIF) values estimated for Vigna radiata cropping season were 0.009 g m–2 and –7.6 mg m–2, whereas for the post harvesting period the fluxes were 0.02 g m–2 and 4.06 mg m–2 for CH₄ and N₂O respectively. The soil parameters like organic carbon and nutrients such as ammonia, nitrate and nitrite during the cropping season were evaluated. The emission of greenhouse gases (GHG) was also correlated to various physico-chemical parameters of soil.
El metano, producido mayoritariamente en la degradación microbiana de compuestos orgánicos bajo condiciones anaeróbicas, es el segundo gas en importancia que interviene en el efecto invernadero del planeta. Su potencial de absorción de... more
El metano, producido mayoritariamente en la degradación microbiana de compuestos orgánicos bajo condiciones anaeróbicas, es el segundo gas en importancia que interviene en el efecto invernadero del planeta. Su potencial de absorción de rayos infrarrojos procedentes de la tierra es 11 veces superior a la del CO₂. Por este motivo, a pesar de su baja concentración en la atmósfera (1.7 ppm frente a 334 ppm de CO₂), el CH₄ contribuye en aproximadamente 17 % al calentamiento actual del planeta (Intergo-vernamental Panel on Climate Change, 1990).
The impact of fire on soil fluxes of CO₂, CH₄ and N₂O was investigated in a tropical grassland in Congo Brazzaville during two field campaigns in 2007–2008. The first campaign was conducted in the middle of the dry season and the second... more
The impact of fire on soil fluxes of CO₂, CH₄ and N₂O was investigated in a tropical grassland in Congo Brazzaville during two field campaigns in 2007–2008. The first campaign was conducted in the middle of the dry season and the second at the end of the growing season, respectively one and eight months after burning. Gas fluxes and several soil parameters were measured in each campaign from burned plots and from a close by control area preserved from fire. Rain events were simulated at each campaign to evaluate the magnitude and duration of the generated gas flux pulses. In laboratory experiments, soil samples from field plots were analysed for microbial biomass, net N mineralization, net nitrification, N₂O, NO and CO₂ emissions under different water and temperature soil regimes. One month after burning, field CO₂ emissions were significantly lower in burned plots than in the control plots, the average daily CH₄ flux shifted from net emission in the unburned area to net consumption in burned plots, no significant effect of fire was observed on soil N₂O fluxes. Eight months after burning, the average daily fluxes of CO₂, CH₄ and N₂O measured in control and burned plots were not significantly different. In laboratory, N₂O fluxes from soil of burned plots were significantly higher than fluxes from soil of unburned plots only above 70% of maximum soil water holding capacity; this was never attained in the field even after rain simulation. Higher NO emissions were measured in the lab in soil from burned plots at both 10% and 50% of maximum soil water holding capacity. Increasing the incubation temperature from 25 °C to 37 °C negatively affected microbial growth, mineralization and nitrification activities but enhanced N₂O and CO₂ production. Results indicate that fire did not increase postburning soil GHG emissions in this tropical grasslands characterized by acidic, well drained and nutrient-poor soil.
This study aimed to quantify the carbon dioxide emissions from an Oxisol under degraded pasture located in Sorocaba, São Paulo State, Brazil. The treatments were: sewage sludge (LE), sewage sludge compost (CLE), mineral fertilizer (AM)... more
This study aimed to quantify the carbon dioxide emissions from an Oxisol under degraded pasture located in Sorocaba, São Paulo State, Brazil. The treatments were: sewage sludge (LE), sewage sludge compost (CLE), mineral fertilizer (AM) and no fertilization (T0). The experiment was conducted in a completely randomized block design with analysis of the effect of the four treatments (CLE, LE, and AM T0) with four replications. The application of sewage sludge, sewage sludge compost, mineral fertilizer and no fertilizer was statistically significant for the variables of height increase and stem height of Guanandi seedlings (Calophyllum brasiliense Cambessèdes-Calophyllaceae). Treatments showed significant differences in terms of CO 2 emissions from soil. The CLE exhibited the highest CO 2 fluxes, reaching a peak of 9.33±0.96 g C m –2 day –1 (p<0.0001), as well as the LE with a maximum CO 2 flux of 6.35±1.17 C m –2 day –1 (p<0.005). The AM treatment (4.96±1.61 g C m –2 day –1) had the same statistical effect as T0 (5.33±0.49 g C m –2 day –1). CO 2 fluxes were correlated with soil temperature in all treatments. However, considering the period of 172 days of evaluation, the total loss of C as CO 2 was 2.7% for sewage sludge and 0.7% for the sewage sludge compost of the total C added with the application on soil.
At most sites the magnitude of soil-atmosphere exchange of nitrous dioxide (N₂O), carbon dioxide (CO₂) and methane (CH₄) was estimated based on a few chambers located in a limited area. Topography has been demonstrated to influence the... more
At most sites the magnitude of soil-atmosphere exchange of nitrous dioxide (N₂O), carbon dioxide (CO₂) and methane (CH₄) was estimated based on a few chambers located in a limited area.
Topography has been demonstrated to influence the production and consumption of these gases in temperate ecosystems, but this aspect has often been ignored in tropical areas. In this study, we investigated spatial variability of the net fluxes of these gases
along a 100 m long slope of a evergreen broadleaved forest in southern China over a whole year. We expected that the lower part of slope would release more N₂O and CO₂, but take up less atmospheric CH₄ than the upper part due to different availability of water and nutrients. Our results showed that the soil moisture (Water Filled Pore Space, WFPS) decreased along the slope from bottom to top as we expected, but among the three gases only N₂O emissions followed this pattern. Annual means of WFPS ranged from 27.7% to 52.7% within the slope, and annual emissions of N₂O ranged from 2.0 to 4.4 kg N ha¯¹ year¯¹, respectively. These two variables were highly and positively correlated across the slope. Neither potential rates of net N mineralization and nitrification, nor N₂O emissions in the laboratory incubated soils varied with slope positions. Soil CO₂ release and CH₄ uptake appeared to be independent on slope position in this study. Our results suggested that soil water content and associated N₂O emissions are likely to be influenced by topography even in a short slope, which may need to be taken into account in field measurements and modelling.
Topography has been demonstrated to influence the production and consumption of these gases in temperate ecosystems, but this aspect has often been ignored in tropical areas. In this study, we investigated spatial variability of the net fluxes of these gases
along a 100 m long slope of a evergreen broadleaved forest in southern China over a whole year. We expected that the lower part of slope would release more N₂O and CO₂, but take up less atmospheric CH₄ than the upper part due to different availability of water and nutrients. Our results showed that the soil moisture (Water Filled Pore Space, WFPS) decreased along the slope from bottom to top as we expected, but among the three gases only N₂O emissions followed this pattern. Annual means of WFPS ranged from 27.7% to 52.7% within the slope, and annual emissions of N₂O ranged from 2.0 to 4.4 kg N ha¯¹ year¯¹, respectively. These two variables were highly and positively correlated across the slope. Neither potential rates of net N mineralization and nitrification, nor N₂O emissions in the laboratory incubated soils varied with slope positions. Soil CO₂ release and CH₄ uptake appeared to be independent on slope position in this study. Our results suggested that soil water content and associated N₂O emissions are likely to be influenced by topography even in a short slope, which may need to be taken into account in field measurements and modelling.
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