Amount Of N2O Emissions Research Articles

Response of CH4 and N2O emissions to the feeding rates in a pond rice-fish co-culture system.

Feeding rate is an important factor influencing the carbon and nitrogen input and greenhouse gas emission from aquaculture systems. However, the quantitative relationship between feeding rates and GHG emissions is still poorly understood. In this study, we conducted a laboratory-scale experiment to examine the impact of feeding rate (0%, 2%, 4%, 6%, and 8%) on the CH4 and N2O emissions from a pond rice-fish co-culture system. The results showed that the total amount of CH4 emission did not significantly differ when the feeding rate was no more than 6%, but increased more than four times when the feeding rate reach to 8%. The amount of N2O emission showed a linearly increasing trend with the feeding rate. The emission factors of CH4 and N2O was significantly higher for 8% feeding rate than other feeding rates. The variation of CH4 emission was primarily attributed to the ratio of mcrA/pmoA in the sediment and the contents of biological oxygen demand (COD) and dissolved oxygen (DO) in the water; and the variation of N2O was primarily affected by the available nitrogen in the water and sediment and the content of DO in the water. The overall emission of CH4 and N2O showed an exponential relationship with feeding rate. The total yields of fish and rice did not continuously increase when the feeding rate exceeded 4%. The lowest emission intensity per unit yield was reached at the feeding rate of 2.99%. These results can provide a reference for the determination of low-carbon feeding strategy for pond rice-fish co-culture system.

Carbon to Nitrogen Ratio in Forage Plants in South Kalimantan's Oil Palm-Cattle Integration Area

The main cause of climate change is confirmed to originate from greenhouse gas emissions from human activities. Human activities such as burning fossil fuels, land use changes, population growth, and the accumulation of greenhouse gases. This research aims to determine the species of plants, organic C/N content, and to compare N2O emissions in oil palm plantations integrated with cattle farming. The research method used a survey approach in two sampling areas: oil palm plantations integrated with cattle and oil palm plantations without cattle integration. In each location, 5 plots were created, with each plot consisting of 3 subplots as replications from the edge towards the oil palm plantation, resulting in a total of 30 subplots for both locations. Parameters collected included plant species, organic C/N content, and the amount of N2O emissions. The research results showed that there are 5 plant species growing in both integrated and non-integrated oil palm plantation areas: Ageratum conyzoides, Panicum brevifolium , Centotheca longilamina Ohwi, Brachiaria decumbens dan Athyrium filex femina. Integrated and non-integrated land areas significantly affect carbon storage in both leaves and stems. Integrated land has a C/N ratio in leaves of 30.15-40.86%, while in non-integrated areas, it is 27.95-34.15%, and in stems, it ranges from 38.07-55.25% and 32.15-48.46% of total dry biomass. The average N2O gas emissions in non-integrated land are 4.6 N m²/hour, while in integrated oil palm plantations with cattle, it is 5.6 N m²/hour. The difference in N2O values between the two locations is within reasonable limits. In conclusion, oil palm plantations can be integrated with cattle for sustainable agriculture

Effects of Straw Returning and Biochar Addition on Greenhouse Gas Emissions from High Nitrate Nitrogen Soil After Flooding in Rice-vegetable Rotation System in Tropical China

In rice-vegetable rotation systems in tropical areas, a large amount of nitrate nitrogen accumulates after fertilization in the melon and vegetable season, which leads to the leaching of nitrate nitrogen and a large amount of N2O emission after the seasonal flooding of rice, which leads to nitrogen loss and intensification of the greenhouse effect. How to improve the utilization rate of nitrate nitrogen and reduce N2O emissions has become an urgent problem to be solved. Six treatments were set up [200 mg·kg-1 KNO3 (CK); 200 mg·kg-1 KNO3 + 2% biochar addition (B); 200 mg·kg-1 KNO3+1% peanut straw addition (P); 200 mg·kg-1 KNO3 + 2% biochar + 1% peanut straw addition (P+B); 200 mg·kg-1 KNO3 + 1% rice straw addition (R); 200 mg·kg-1 KNO3 + 2% biochar+1% rice straw addition (R+B)] and cultured at 25℃ for 114 d to explore the effects of organic material addition on greenhouse gas emissions and nitrogen use after flooding in high nitrate nitrogen soil. The results showed that compared with that in CK, adding straw or combining straw with biochar significantly increased soil pH (P<0.05). The B and P treatments significantly increased the cumulative N2O emissions by 41.6% and 28.5% (P<0.05), and the P+B, R, and R+B treatments significantly decreased the cumulative N2O emissions by 14.1%, 24.7%, and 36.7% (P<0.05), respectively. The addition of straw increased the net warming potential of greenhouse gases (NGWP). The addition of coir biochar significantly reduced the effect of straw on NGWP (P<0.05). The combined application of straw and biochar decreased NGWP, and P+B significantly decreased NGWP, but that with R+B was not significant (P>0.05). Adding straw or biochar significantly increased soil microbial biomass carbon (MBC) (P<0.05), and that of P+B was the highest (502.26 mg·kg-1). The combined application of straw and biochar increased soil microbial biomass nitrogen (MBN), and that of P+B was the highest. The N2O emission flux was negatively correlated with pH (P<0.01) and positively correlated with NH4+-N and NO3--N (P<0.01). The cumulative emission of N2O was negatively correlated with MBN (P<0.05). There was a significant negative correlation between NO3--N and MBN (P<0.01), indicating that the reduction in NO3--N was likely to be held by microorganisms, and the increase in the microbial hold of NO3--N also reduced N2O emission. In conclusion, the combined application of peanut straw and coconut shell biochar could significantly inhibit N2O emission and increase soil MBC and MBN, which is a reasonable measure to make full use of nitrogen fertilizer, reduce nitrogen loss, and slow down N2O emission after the season of Hainan vegetables.

Isotopomeric Peak Assignment for N2O in Cross-Labeling Experiments by Fiber-Enhanced Raman Multigas Spectroscopy.

Human intervention in nature, especially fertilization, greatly increased the amount of N2O emission. While nitrogen fertilizer is used to improve nitrogen availability and thus plant growth, one negative side effect is the increased emission of N2O. Successful regulation and optimization strategies require detailed knowledge of the processes producing N2O in soil. Nitrification and denitrification, the main processes responsible for N2O emissions, can be differentiated using isotopic analysis of N2O. The interplay between these processes is complex, and studies to unravel the different contributions require isotopic cross-labeling and analytical techniques that enable tracking of the labeled compounds. Fiber-enhanced Raman spectroscopy (FERS) was exploited for sensitive quantification of N2O isotopomers alongside N2, O2, and CO2 in multigas compositions and in cross-labeling experiments. FERS enabled the selective and sensitive detection of specific molecular vibrations that could be assigned to various isotopomer peaks. The isotopomers 14N15N16O (2177 cm-1) and 15N14N16O (2202 cm-1) could be clearly distinguished, allowing site-specific measurements. Also, isotopomers containing different oxygen isotopes, such as 14N14N17O, 14N14N18O, 15N15N16O, and 15N14N18O could be identified. A cross-labeling showed the capability of FERS to disentangle the contributions of nitrification and denitrification to the total N2O fluxes while quantifying the total sample headspace composition. Overall, the presented results indicate the potential of FERS for isotopic studies of N2O, which could provide a deeper understanding of the different pathways of the nitrogen cycle.

Environmental impact assessment of Finnish feed crop production with methodological comparison of PEF and IPCC methods for climate change impact

The impact of livestock production on the environment is already well acknowledged. When non-ruminants are considered, the major contributors to products' environmental impacts are related to feed crop production. Feed crop production sustainability is therefore especially relevant in addressing the sustainability and mitigation potential of non-ruminant production. Here, the climate change impact and water scarcity (WS) impact of the current Finnish feed crop production was assessed. The impact of methodological differences on the climate change impact of national-, regional-, and farm-level feed crop production were investigated for utilising the European Commission's Product Environmental Footprint (PEF) guidance and the guidelines provided by Intergovernmental Panel on Climate Change (IPCC).Feed crops selected for the assessment were considered as typical for Finnish pork and broiler chicken production, and included wheat (T. aestivum), oat (A. sativa), barley (H. vulgare), turnip rape (B. rapa ssp. oleifera), pea (P. sativum), and faba bean (V. faba). The farmgate climate change impact varied from turnip rape's 1.22 kg CO2 eq./kg to faba bean's 0.37 kg CO2 eq./kg, while cereals resulted in 0.47–0.63 kg CO2 eq./kg, and pea 0.49 kg CO2 eq./kg according to IPCC methods. Similarly, with PEF methods, the results varied from turnip rape's 1.18 kg CO2 eq./kg to 0.31 kg CO2 eq./kg of faba bean, cereals resulted in 0.42–0.58 kg CO2 eq./kg, and pea 0.43 kg CO2 eq./kg. The absolute difference between methods ranged between −0.045 and −0.068 kg CO2 eq./kg. The analysis showed that even if the relative error varied from 3% to 19% between methods, the relative order was the same, independent of the methods. The farmgate WS impact of Finnish feed crops was 0.23 m3 eq./kg for turnip rape, 0.05 m3 eq./kg for faba bean, 0.08 m3 eq./kg for barley, 0.08 m3 eq./kg for oat, 0.09 m3 eq./kg for wheat, and 0.06 m3 eq./kg for pea.It was observed that the PEF and IPCC methods functioned similarly in distinguishing better and worse performing crop production between cases. It was shown that the major contributors to feed crop production in Finland were energy and input production, N2O from N inputs, and peat soil degradation. The amount of N2O emissions from peat soil degradation especially demonstrated high variability and was therefore identified to have high mitigation potential. The investigation demonstrated the importance of including N2O emissions in the widest form when finding production hotspots.

Distinguishing N2O and N2 ratio and their microbial source in soil fertilized for vegetable production using a stable isotope method

Vegetable production systems with excessive nitrogen fertilizer result in severe N2O emission. It is pivotal to identify the source of N2O for reducing N2O emission, but estimating microbial pathways of N2O production is very difficult due to the existence of N2O reduction. A promising tool can address this problem by using δ18O and δ15NSP of N2O to construct a dual isotopocule plot. For ascertaining the microbial pathways of N2O production and consumption in soil fertilized for vegetable production, four treatments were set up: urea (U), half urea and half organic fertilizer (UO), organic fertilizer (O) and no fertilizer (NF), and the experiment was carried out continuously for two years. The δ18O vs. δ15NSP plot method indicated that the nitrification/fungal denitrification was a dominant in N2O emission, and the U treatment was the highest, followed by OU, O and NF in the both years. Among the different treatments, furthermore, the N2O flux had the same trend, whereas the extent of N2O reduction showed an opposite trend. Overall, inorganic fertilizer enhances nitrification/fungal denitrification and hinders reduction of N2O to N2, resulting in a larger amount of N2O emission. However, organic fertilizer increases the contribution of denitrification and greatly improves the extent of N2O reduction, which helps to reduce N2O emission. Therefore, organic fertilizer is crucial to reducing N2O emission by enhancing N2O reduction and should be properly applied in production practice.

Effects of bamboo biochar on nitrogen conservation during co-composting of layer manure and spent mushroom substrate

ABSTRACT Layer manure (LM) and spent mushroom substrate (SMS) are two kinds of nitrogen (N) rich solid wastes generate in the poultry breeding and agriculture production. Composting is an effective way to recycle the LM and SMS. However, a large amount of N in the LM and SMS was lost via volatilisation during composting, with negative environmental and economic consequences. This study investigated the effect of incorporating biochar at the ratio of 5%, 10%, and 15% (w/w) during co-composting of LM and SMS on ammonia (NH3) and nitrogen oxide (N2O) volatilisation and N retention. After the 35-day composting, the results showed that the pile temperature and seed germination index in biochar treatments were significantly improved in comparison with control treatment. The nitrogen in all treatments was lost in the form of N2O (0.05∼0.1%) and NH3 (13.1∼20.2%). Likewise, the total nitrogen loss was 28.9%, 20.3%, and 24.9%, respectively, of which N2O-N accounts for 0.05∼0.10%. Compared with control treatment, the total amount of NH3 volatilisation in biochar treatments of 5%BC, 10%BC and 15%BC was decreased by 21.2%, 33.1%, and 26.1%, respectively. The total amount of N2O emission was decreased by 39.0%, 13.2%, and 1.6%, respectively. Adding 10% and 15% biochar can significantly reduce NH3 volatilisation while adding 5% biochar treatment didn't significantly reduce NH3 emissions but showed the best performance in reducing N2O emission. The addition of 10% biochar in co-composting of LM and SMS is the recommended dosage that exhibited the best performance in improving composting quality and reducing nitrogen loss.

Temporal Patterns of N2O Fluxes From a Rainfed Maize Field in Northeast China

Rainfed agriculture is one of the most common farming practices in the world and is vulnerable to global climate change. However, only limited studies have been conducted on rainfed agriculture, mainly using low-frequency manual techniques, which caused large uncertainties in estimating annual N2O emissions. In this study, we used a fully automated system to continuously measure soil N2O emissions for two years (April 2017 to March 2019) in a typical rainfed maize field in Northeast China. The annual N2O emissions were 2.8 kg N ha−1 in year 1 (April 2017 to March 2018) and 1.8 kg N ha−1 in year 2 (April 2018 to March 2019), accounting for 1.9 and 1.2% of the nitrogen fertilizer applied, respectively. The inter-annual variability was mainly due to different weather conditions encountered in years 1 and 2. A severe drought in year 1 reduced plant N uptake, leaving high mineral N in the soil, and the following moderate rainfalls promoted a large amount of N2O emissions. The seasonal pattern of N2O fluxes was mainly controlled by soil temperature and soil nitrate concentration. Both soil moisture and the molar ratio of NO/N2O indicate that N2O and NO were mainly derived from nitrification, resulting in a significant positive correlation between N2O and NO flux in the intra-rows (where nitrogen fertilizer was applied). Moreover, we observed that the N2O emissions during the freeze–thaw periods were negligible in this region for rainfed agriculture. Our long-term and high-resolution measurements of soil N2O emissions suggest that sampling between LST 9:00 and 10:00 is the best empirical sampling time for the intermittent manual measurements.

Gaseous Nitrogen Losses from Tropical Soils with Liquid or Granular Urea Fertilizer Application

Gaseous loss of N leads to lower nitrogen use efficiency (NUE) of applied urea and N content of the soil. This laboratory study was conducted to compare the nitrogen losses from two tropical soil series (Bungor sandy clay loam and Selangor clay) incubated with either liquid urea (LU) or granular urea (GU) at 0, 300, 400, or 500 mg/kg of soil for thirty days. The NH3 volatilization, N2O emission, and N content in the soils were measured throughout the incubation period. For the same application rate, the total NH3 volatilization loss was higher in GU-treated soils than the LU-treated soils. NH3 volatilization loss continued up to the 15th day in the Selangor soil, while in the Bungor soil series it continued up to the 26th day. Higher amounts of N2O emissions were recorded in GU-treated soils than the LU-treated soils, and N2O emission increased with increasing rate of GU and LU applications in both soils. The N2O emission was higher only in the first few days and then tapered off at the seventh and eighth day in Bungor and Selangor soil series, respectively. The total N2O emission was higher in the Selangor soil series than that of Bungor soil series. The total N content that remained in the LU-treated soils after 30 days of incubation was higher than the GU-treated soils. The total N loss from applied urea was higher in the sandy clay loam Bungor soils than that of clayey Selangor soil series. The results suggest that the LU may be a better N fertilizer source than GU due to lower N loss from NH3 volatilization and N2O emission.

Effects of the nitrification inhibitor nitrapyrin and tillage practices on yield-scaled nitrous oxide emission from a maize field in Iran

Nitrification inhibitors can effectively decrease nitrification rates and nitrous oxide (N2O) emission while increasing crop yield under certain conditions. However, there is no information available on the effects of nitrification inhibitors and tillage practices on N2O emissions from maize cropping in Iran. To study how tillage practices and nitrapyrin (a nitrification inhibitor) affect N2O emission, a split factorial experiment using a completely randomized block design with three replications was carried out in Northeast Iran, which has a cold semiarid climate. Two main plots were created with conventional tillage and minimum tillage levels, and two nitrogen (N) fertilizer (urea) management systems (with and without nitrapyrin application) were created as subplots. Tillage level did not have any significant effect on soil ammonium (NH4+) and nitrate (NO3–) concentrations, cumulative amount and yield-scaled N2O emission, and aboveground biomass of maize, whereas nitrapyrin application showed significant effect. Nitrapyrin application significantly reduced the cumulative amount of N2O emission by 41% and 32% in conventional tillage and minimum tillage practices, respectively. A reduction in soil NO3– concentration by nitrapyrin was also observed. The average yield-scaled N2O emission was 13.6 g N2O-N kg–1 N uptake in both tillage systems without nitrapyrin application and was significantly reduced to 7.9 and 8.2 g N2O-N kg–1 N uptake upon the application of nitrapyrin in minimum tillage and conventional tillage practices, respectively. Additionally, nitrapyrin application increased maize biomass yield by 4% and 13% in the minimum tillage and conventional tillage systems, respectively. Our results indicate that nitrapyrin has a potential role in reducing N2O emission from agricultural systems where urea fertilizers are broadcasted, which is common in Iran due to the practice of traditional farming.

Responses of CO2 and N2O emissions from soil-plant systems to simulated warming and acid rain in cropland

Climate warming is anticipated to change the terrestrial carbon/nitrogen cycle through its impact on the fluxes of greenhouse gases such as CO2 and N2O. This study investigated the effect of diurnal warming and acid rain on CO2 and N2O emissions from soil-plant systems in a winter wheat–soybean rotation cropland. Field rotational experiments of winter wheat and soybean were conducted by simulating diurnal warming and acid rain. Manipulated experiments included the control (CK), diurnal warming (T, + 2 °C), acid rain (AR, pH = 2.5), and the combined treatment (TAR, + 2 °C and acid rain). CO2 and N2O fluxes from soil-plant systems were measured using a static chamber-gas technique. The results showed that in the winter wheat and soybean growing seasons, compared with CK treatment, T, AR, and TAR treatments did not change the accumulative amount of CO2 emission (AAC) across the full growth period (p ˃ 0.05), although T treatment significantly increased soil AAC (p < 0.05) at the grain filling-maturity stage. On the contrary, T and AR treatments significantly increased the accumulative amount of N2O emission (AAN) in winter wheat and soybean croplands (p < 0.05), which was attributed to leaf nitrate reductase activity, total biomass, and soil NO3−–N content. In addition, there was a significant interaction between warming and acid rain on N2O flux. The AAN from the winter wheat cropland under treatments was in the order: TAR ˃ AR ˃ T ˃ CK. Our findings suggest that diurnal warming and acid rain had no significant effect on CO2 emissions from soil-plant systems, but significantly increase N2O emissions in winter wheat and soybean growing seasons. Moreover, diurnal warming would strengthen the positive effect of acid rain on N2O emissions from soil-plant systems in winter wheat farmland.

Bryophytes impact the fluxes of soil non-carbon dioxide greenhouse gases in a subalpine coniferous forest

Terrestrial bryophytes substantially regulate ecosystem processes in high latitude and high elevation ecosystems; however, the role of these plants in mediating soil emissions of non-CO2 greenhouse gases (GHGs) (N2O and CH4) in these ecosystems remains poorly understood. A removal experiment was conducted to investigate the influence of bryophytes on soil non-CO2 GHGs emission in a subalpine coniferous forest on the eastern edge of the Tibetan Plateau. Bryophyte removal decreased the average N2O emission rate, but did not significantly alter the CH4 flux rate. The cumulative amount of N2O emission and CH4 uptake was decreased by bryophyte removal. Compared to bryophyte-removal plots, soil in the control plots had higher concentrations of soil organic C (SOC), total N (TN), dissolved organic C (DOC), dissolved N (DN), and exchangeable NH4+. The control plots also had higher cumulative N2O emission and CH4 uptake compared to plots with bryophytes removed. Bryophyte-removal significantly changed the relationship between soil non-CO2 GHGs flux rates and soil water content, induced a linear decreasing relationship between the N2O emission rate and soil water content and a quadratic relationship between CH4 flux rate and soil water content in the bryophyte-removal plots. Results from this study indicate that bryophytes may regulate non-GHG emissions from subalpine coniferous soils and demonstrate that in the presence of bryophytes, these soils may act as a greater N2O source and CH4 sink in southwestern China.

Discrepancies in N2O emissions between household waste and its food waste and non-food waste components during the predisposal stage

Nitrous oxide (N2O) is a greenhouse gas (GHG) and an ozone-depleting substance. Municipal solid waste (MSW) management and treatment activities are some of the sources of GHG emissions. However, the biogenic GHG emissions during the predisposal stage of MSW management, during which waste is transferred to garbage cans and then transported to disposal sites, have received little attention. In this study, household waste was divided into food and non-food waste, and the effects of these types of waste and different oxygen concentrations (21%, 10%, and 1%) on N2O emissions were investigated. A15N-labeled isotope experiment was conducted over three days to determine the contributions of nitrification and denitrification to N2O emissions. The results showed that the N2O fluxes first increased and then decreased during the three-day tests at different O2 concentrations. The maximum N2O flux of 1469.59 ± 1004.32 μg N·kg−1 wet waste·h−1 occurred during the predisposal of food waste at an O2 concentration of 21%, with the total N2O emissions reaching 20.26 ± 10.87 mg N·kg−1 wet waste, which exceeds the emissions from some waste disposal processes, such as composting and landfills. The N2O emissions decreased in the following order: food waste > household waste > non-food waste. For food waste, the peak value and total amount of N2O emissions decreased significantly as the O2 concentration decreased. In contrast, the N2O emissions from non-food waste increased as the O2 concentration decreased. Denitrification was the predominant biogenic source of N2O emissions; it accounted for over 60% of N2O production in all treatments. Nitrification also played an important role in N2O emissions during the early predisposal stage.

Mitigating nitrous oxide emission using nanoclay-polymer composites in rice-wheat cropping system

ABSTRACT A study was conducted in lab for synthesizing and characterizing the behavior of the nanoclay-polymer composites (NCPCs). Furthermore, greenhouse experiments carried out to investigate the effects of NCPCs application on crop yield, nutrient uptake, soil nitrogen availability and N2O emission. Wheat flour (WF), sodium alginate (Na-Alg) and acrylic acid (AA)+ acrylamide (Am) (AA+Am) NCPCs were synthesized via free radical polymerization and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), SEM-energy dispersive X-ray (SEM-EDX) and transmission electron microscopy (TEM). At lower dose NCPCs, resulted in significantly equal grain yield in rice and wheat with 100% urea treatment with reduced amount of N2O emissions. Yield-scaled N2O emissions of rice and wheat under T9 [NCPC (AA+AM+Clay) (75% N of RDF) + PK (full dose)] treatment was respectively 19.8 and 25.5% lower than urea treatment. These findings demonstrate that there is a great potential to increase crop yields with lower N2O emissions through use of innovative fertilizer technique in India.

Characteristics of CO2 and N2O Emissions Under Two Land Use Types in the Loess Plateau of China

To evaluate the emission characteristics of carbon dioxide (CO2) and nitrous oxide (N2O) in the Loess Plateau, a field in situ study was conducted from July 2017 to July 2018 under two land-use types (15 year old apple orchard and wheat field) using static chamber-gas chromatographic techniques. Four treatments were conducted in this experiment as follows:apple orchard with fertilization (AF), apple orchard without fertilization (ACK), wheat field with fertilization (WF), and wheat field without fertilization (WCK). The results showed that CO2 and N2O emissions varied significantly with the season, and the emission peaks appeared after rainfall and fertilization. The cumulative amount of CO2 and N2O emissions from the AF treatment were 7.14% and 461.4% higher than that of the WF treatment, respectively. However, the cumulative amount of CO2 emissions under the ACK treatment was 10.41% lower than that of the WCK treatment, whereas the cumulative amount of N2O emissions was 109.5% higher than that of the WCK treatment. The N2O emission flux from the orchard was significantly positively correlated with soil temperature and moisture (P<0.01). The CO2 emission fluxes from the orchard and wheat field were significantly positively correlated with topsoil temperature (P<0.05) but were not correlated with topsoil moisture. Thus, the combination of field management and environmental factors affected soil CO2 and N2O emissions. The fertilizer regime and soil hydrothermal conditions were the main factors influencing the characteristics of CO2 and N2O emissions under different land-use types.

Effects of Plastic Film Mulching Patterns and Irrigation on Yield of Summer Maize and Greenhouse Gas Emissions Intensity of Field

In order to evaluate the effect of different treatments on yield and greenhouse gas emissions during the summer maize growing season, a two-year film mulching experiment was conducted in 2014 and 2015. In this experiment, the two main experimental factors were rainfed treatment (R) and irrigated treatment (I), and the secondary experimental factors included control treatment (CK), half film mulching treatment (HM), and full film mulching treatment (FM). The emissions of soil greenhouse gases (CO2, CH4, and N2O) were monitored using a static opaque chamber and chromatography method. Moreover, the greenhouse gas emissions intensity (GHGI) was used to evaluate the effect of carbon sequestration in different treatments. The results of this study showed that the yields of the RHM and RFM treatments did not differ significantly in 2014, but increased by 19.6% and 26.8%, respectively, in 2015 compared with that of RCK. The yield of IHM was not improved, and that of IFM significantly increased by 14.1% and 55.8% in 2014 and 2015, respectively, compared with that of ICK. The irrigated treatments only promoted CO2 emissions in 2015 (P<0.01), and all film mulching treatments (regardless of HM and FM treatments) had no effect on CO2 emissions under rainfed and irrigated conditions (P>0.05). Irrigated treatments had no effect on the absorption of CH4 (P>0.05), whereas the film mulching treatments had an inhibitory effect. Compared with values of RCK, the amount of seasonal N2O emissions for ICK showed a significant difference in 2015 with a decrease of 22.3%. Compared with values of RCK, the amounts of N2O emissions for RHM and RFM had no significant differences in 2014, but significantly decreased by 50.7% and 51.4% in 2015, respectively. Compared with ICK, IHM and IFM significantly decreased the amounts of N2O emissions by 47.5% and 54.2% in 2014, and by 9.6% and 52.2% in 2015, respectively. The GHGIs of RHM and RFM were significantly reduced by 60.1% and 61.7% in 2015, respectively, compared with values of RCK, and the GHGIs of IHM and IFM were significantly reduced by 39.7% and 53.2% in 2014, and reduced by 22.2% and 67.5% in 2015, respectively, compared with that of ICK. This means that the effect of FM on reducing GHGI was better than that of HM. It was also found that the significantly reduced GHGI in irrigated treatments may be attributed to the increased yields. Therefore, FM under irrigation conditions was recommended for summer maize for stabilizing the yield and reducing the GHGI.

Hyperthermophilic composting significantly decreases N2O emissions by regulating N2O-related functional genes

This study reported for the first time that hyperthermophilic composting (HTC) could mitigate 90% of the cumulative amount of N2O emissions compared to traditional composting (TC) in a full-scale experiment. The concentrations of NO2−-N and NO3−-N in HTC were significantly lower than those in TC, which may be the main reason for the reduced N2O emissions. Furthermore, this study found that the decrease in N2O emissions in HTC compared to TC was mainly due to the inhibition of the abundance of the bacterial amoA and norB genes, which could decrease the nitrification rate and control N2O formation, respectively. Partial least squares path modeling revealed that a high temperature was the key factor in lowering N2O emissions in HTC, while physicochemical properties were the dominant factor in enhancing N2O emissions in TC. These results suggested that HTC is a promising technique for reducing N2O emissions in manure composting.

A simulation–optimization modeling approach for watershed-scale agricultural N2O emission mitigation under multi-level uncertainties

In this research, an integrated simulation–optimization modeling approach (ISOMA) was developed for supporting agricultural N2O emission mitigation at the watershed scale. This approach can successfully combine soil N2O emission simulation and the consequential mitigation management within a general modeling framework. Also, uncertainties associated with the key soil parameter can be effectively reflected and addressed through adoption of Monte Carlo analysis for the simulation results. The Monte Carlo simulated results were then used to generate fuzzy membership functions that can be consequentially used for emission mitigation management, reflecting the combined uncertainties for N2O emission simulation and mitigation management. The developed ISOMA was then applied to a reservoir watershed in Miyun county of Beijing municipality. In the studying watershed, the simulation model was calibrated and verified. Then, N2O emission from multiple agricultural land-use patterns were predicted. The amounts of N2O emission of four land use patterns (i.e., cash tree, orchard, cropland, and natural forest) were (536.9, 590.8, 653.1), (237.7, 254.4, 275.9), (79.5, 100.7, 105.1), (33.0, 47.3, 61.1) kg CO2 eq ha−1 year−1, respectively. Two scenarios (i.e., G1 and G2) were set up according to development priorities of local economy and society. Meanwhile, multiple credibility levels were considered according to the risk of N2O emission. The land use patterns could be adjusted according to solutions of ISOMA. The developed methods could help regional manager choose various production patterns with cost-effective agriculture N2O emission management schemes in the Miyun reservoir watershed. The manager also can obtain deeply insights into the tradeoffs between agricultural benefits and system reliabilities.

Effect of Organic Manure Substitution of Synthetic Nitrogen on Crop Yield and N2O Emission in the Winter Wheat-Summer Maize Rotation System

Controlling agricultural greenhouse gas emissions, such as N2O, is important in mitigating global climate warming. Through monitoring the dynamics of N2O emission fluxes, we investigated the effect of organic nitrogen (N) substitution of synthetic N on N2O emissions and the yield of winter wheat and summer maize in the Guanzhong Plain of Shaanxi Province, China. The study involved six treatments, consisting of no fertilizer (CK), synthetic N, phosphorus (P), and potassium (K) fertilizers alone (NPK), 75% NPK+25% organic N through manure (25%M), 50% NPK+50% organic N (50%M), 25% NPK+75% organic N (75%M), 100% organic N (100%M). The results showed that the peak value of the N2O emission flux appeared after fertilization, rainfall, and irrigation. In the wheat season, the emission flux of N2O varied from -1.33 to 144.2 μg·(m2·h)-1, with the highest peak value in the NPK treatment. In the maize season, the emission flux of N2O varied from 88.2 to 1800.1 μg·(m2·h)-1, and the 50%M treatment showed the highest peak value. The range in the total amount of N2O emissions from the different treatments in the wheat-maize rotation system was 429.8-2632.1 g·hm-2, and the amount for the treatments decreased in order as follows:50%M > 25%M > NPK > 75%M > 100%M > CK. The yields of wheat, maize, or wheat plus maize were significantly higher in the fertilized treatments compared to the CK. Organic substitution treatments significantly increased wheat yield by 26.1% to 50.0% relative to the NPK treatment. While the maize yield in 50%M and 75%M treatments was similar to that in the NPK treatment, the 25%M and 100%M treatments showed significantly lower yields than with the NPK treatment. The total yield of wheat plus maize varied from 9166 to 17496 kg·hm-2, of which total yield was significantly higher with 50%M and 75%M compared to NPK. Overall, the 75%M treatment is the best measure to guarantee crop yield and to reduce N2O emissions in the wheat-maize rotation system based on a one year study in the Guanzhong plain of Shaanxi Province.

Nitrogen Removal and Nitrous Oxide Emission in an Anaerobic/Oxic/Anoxic Sequencing Biofilm Batch Reactor

Abstract An anaerobic/oxic/anoxic sequencing batch biofilm reactor (A/O/A SBBR) was tested to treat carbon-limited wastewater without external carbon addition. Simultaneous nitritation–denitritation in the oxic period and poly-hydroxybutyrate (PHB)-driven denitritation in the anoxic period were implemented in the A/O/A SBBR. A high total nitrogen (TN) removal efficiency of 95.97 ± 2.85% was achieved, in which 57.62 ± 4.43% was removed during the aerobic period and 39.00 ± 4.07% was removed during the anoxic period. Simultaneously, 15.47 ± 2.65% of the removed TN was emitted as nitrous oxide (N2O), and 72.25 ± 4.86% of total N2O was produced during the anoxic period. As a result, PHB-driven denitritation improved TN removal efficiency while stimulating high amounts of N2O emission. High-throughput pyrosequencing analysis revealed an abundance of the genera Thauera and Denitratisoma as potential denitrifiers that improved TN removal efficiency. N2O was primarily produced by betaproteobacterial microorganism...