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Denitrification is one of the most important reactive nitrogen removal pathways in the soil nitrogen cycle. In this process, nitrate is reduced to gaseous nitrogen nitrous oxide（N2O）or nitrogen（N2）, which leaves the soil and enters the atmosphere. The stoichiometric ratio of its gaseous products N2O/N2 is a hot topic in soil denitrification research. Reasonable regulation of this ratio is an important way to reduce greenhouse gas emissions from agricultural sources. In the soil environment, the ratio of denitrification products is affected by many factors. In our view, nitrate content, oxygen, and copper availability are the key factors mediating the change of the product ratio, while electron donors, pH, and moisture are general factors. These factors can directly affect the denitrification process by affecting denitrifying enzyme activity, denitrifying microorganism abundance, and community structure. They can also indirectly affect the ratio by changing the soil microenvironment of denitrification. This paper reviews the progress made toward controlling the factors affecting the soil denitrification gaseous product ratio N2O/N2 in recent years and discusses the response mechanism of the denitrification product ratio to different influencing factors to provide some inspiration for future related research. [ABSTRACT FROM AUTHOR]

Inoculated with normal activated sludge, denitrification and phosphorus removal were successfully achieved in anaerobic/anoxic SBR system after 51 d of domestication, and the denitrification and phosphorus removal efficiency reached (96 ± 2) % and (88 ± 5) %, respectively・ On this basis, anaerobic end activated sludge was taken and the effects of COD concentrations (0,26・ 25.5 mg/L) on the performance of rdtrite type denitrification and phosphorus removal and N2O release were investigated using batch tests. The nitrogen removal efficiency increased from 55. 44% to 63. 50% and 96. 44% with increasing COD concentration; meanwhile, COD was synthesized into PHB and phosphorus release occurred, resulting in a decrease of phosphorus removal efficiency from 33. 54% to 26. 87% and - 0.016%;N2O conversion (N2O-N release/TN removed) decreased from 25. 08% to 22. 96% and 11. 85% ・ High COD concentration is beneficial to enhance denitrification efficiency and reduce N2O release, but it will reduce phosphorus removal e&iciency. [ABSTRACT FROM AUTHOR]

This article introduces the generation pathways, emission mechanisms, and influencing factors of N20 in the denitrification process of wastewater treatment systems, and evaluates the impact of emission strategies based on reduction measures on N20 reduction. Currently, research is primarily focused on controlling aeration and carbon source addition strategies and other process conditions to reduce N20 emis¬sions. With the development of wastewater resource utilization, the article also describes the research pro- greens of mainstream energy recovery processes for N2 0, highlighting quantitative control strategies for gas generation represented by the CAND0 process. Finally, the article provides prospects for novel technolo¬gies for the resource utilization of N20 and discusses the feasibility of utilizing N20 as an electron accep¬tor in the synthesis of polyhydroxyalkanoate, further applying it to biomass synthesis and utilization strate¬gies, thereby providing new insights for the control l reduction, and resource utilization of N20. [ABSTRACT FROM AUTHOR]

Using nitrite denitrification to treat acidic wastewater has the advantages of saving carbon sources and reducing the amount of excess sludge. The start-up and stable operation of denitrification using nitrite as the electron acceptor were successfully achieved by increasing the influent NO2 concentration and reducing the influent pH in a laboratory-scale SBR, and N2O emission in single cycle and change of community was also investigated under long-term acidic conditions. The results showed that when the pH decreased from 6.5 to 5.0, the reduction rate of NO2 slightly increased to 10.88 mg/(h ・ g) VSS， and the N2O production rate remained a low level from 2.07% to 7.17%. In the acidic wastewater treatment system，unclassified _ k _ norrank _d _ Bacillus and Thauera became dominant denitrifying bacteria and they played an important role in reducing N2O emission. [ABSTRACT FROM AUTHOR]

Biochar is widely used as one type of soil amendment to enhance soil properties and carbon sequestration in croplands. But it is still unclear on the influence of rice straw biochar application on CH4 and N2O emissions from paddy fields, especially in Northeast China. The typical rice monoculture region is often used under the alternate regime of wetting and drying (IAWD) with the aging of biochar in soil. This study aims to further investigate the potential of biochar application in IAWD paddy fields. A split-plot field was designed with two irrigation regimes, two biochar additions, and three replications in 2019- 2021. Among them, the irrigation regimes (I) included continuous flooding irrigation (ICF) and IAWD. The sub-plots within each main plot were subjected to two biochar (B) additions (biochar-free control and 20 t ha-1 biochar, represented by B0 and B20, respectively). Prior to the experiment, the surface soil was first sampled in the rice fields and then air-dried to measure the basic physicochemical parameters of the soil. Biochar was applied one day before transplanting in 2019. After that, there was no additional biochar in 2020 and 2021. The opaque static chamber was used to collect the CH4 and N2O emissions over 3-4 days after topdressing, and 7-10 days between rice transplanting and harvesting. Gas samples were finally obtained to measure the CH4 and N2O concentration using gas chromatograph (Agilent 7890B, Agilent Technologies, Inc., USA). Results showed that the IAWD significantly reduced the CH4 emission by 63.03%-78.89%, global warming potential (GWP) by 62.02%-75.21%, greenhouse gas inventory (GHGI) by 62.31%-75.28%, compared with the ICF, although there was an increase in the N2O emission of 100%-122.67%. The B20 treatment reduced the CH4 emission by 21.99% in 2020, and 38.21% in 2021, whereas, there was an increase in the soil organic carbon by 24.03%-28.88%, and N2O emission by 28.26%-33.10% over three years. Moreover, biochar was used to inhibit the negative effect of IAWD on the increase of N2O emissions. A correlation analysis showed that there was a significant negative correlation in the cumulative CH4 emissions with the soil redox potential (Eh) value, and soil organic carbon (SOC), whereas a significant positive correlation was found with the soil temperature. There was a significant negative correlation between the cumulative N2O emission and soil temperature, whereas, a significant positive correlation was between the soil Eh value. A positive effect of rice production was found in the second and third years, although there was a slight decrease in the first year of biochar application. The main reason was that the early straw biochar was more alkaline with a limited effect. A synergy effect was found in the biochar adsorption emission reduction and slow release with the pH value to the normal, indicating the increasing production. Especially, the B20 treatment significantly reduced GWP by 37.50% and GHGI by 42.86% in 2021, whereas there was an increase of 11.02%, compared with the B0. The IAWD B20 treatment reduced the CH4 cumulative emissions by 83.78%, GWP by 77.98%, and GHGI by 78.95%, compared with the ICF B0. It infers that the biochar combined with IAWD can be used to effectively reduce the GWP and GHGI. Anyway, biochar can be expected to reduce carbon sequestration and CH4 and N2O emissions in paddy fields. The finding can also provide a strong theoretical reference to mitigate the CH4 and N2O emissions after the biochar application in rice fields. [ABSTRACT FROM AUTHOR]

Global climate change caused by excessive greenhouse gas（GHG） emissions has been widely concerned. Agricultural activities are the second largest source of GHGs emissions, so it is urgent to reduce agricultural GHGs emissions. Biochar, which has stable properties, abundant aromatic carbon and pores, is produced by pyrolysis of biomass under high temperature and limited oxygen conditions. The effect of biochar amendment on GHGs mitigation and soil carbon sequestration is excellent, and biochar application has the potential to participate in China’s ongoing carbon trading of voluntary emission reduction（VER）. However, the factors affecting the carbon sequestration and GHGs emission reduction effect of biochar are complicated, so it is necessary to systematically summarize the mitigation effect, influencing factors and research progress of biochar. This paper reviewed researches on the GHGs emission reduction and carbon sequestration effect of biochar through pot and field experiment as well as meta-analysis research. At the same time, CiteSpace software was used for visual analysis to explore the research hotspots and development trends in this field. The opportunities and challenges faced by biochar application projects participating in carbon trading were summarized based on the characteristics of domestic and foreign carbon trading market development and corresponding supporting policies. Corresponding solutions were also provided in this study, which offered scientific guidance and useful reference for the development of carbon sequestration and GHGs emission reduction research of biochar and the successful participation of biochar application projects in carbon trading. [ABSTRACT FROM AUTHOR]

The denitrification activity of catalyst can be improved by adding additives. In this paper, the Nd, Nb co-doped V-Mo/Ti De-NOx catalyst was prepared by impregnation method. The physical and chemical properties of the catalyst were analyzed by XRD, N8 -adsorption and desorption, H8 -TPR, XPS, NH3 -TPD. The results showed that the peak temperature of H 2 reduction of the catalyst modified by Nd and Nb moved to the direction of low temperature, indicating that the addition of Nd and Nb can adjust the dispersion degree of the active components of the catalyst to a certain extent. V-Mo-Nd-Nb/Ti catalyst has the higher Oa content, which is beneficial to its denitrification performance. The overall denitrification activity of Nd and Nb co-doped catalyst is better than that of V-Mo/Ti catalyst. The denitrification efficiency of the catalyst can reach 71. 8% at 210 oC,and the formation of N2O can also be reduced. Moreover, the catalyst also has excellent resistance to SO2 and H2O. After 28 h reaction, the denitration efficiency of the catalyst can still reach about 93 %. [ABSTRACT FROM AUTHOR]

In order to get reasonable water and fertilizer management measures, the effects of different fertigation proportions under the same nitrogen(N)rate on the yield of ratoon and nitrous oxide(N2O)flux and inorganic N content in soil at the different growth stages were studied, the relationships between soil N2O flux and inorganic N content were analyzed. Taking natural rainfall(W0)as the control, two drip irrigation levels, W1(75% of field water capacity)and W2(85% of field water capacity)and four fertigation proportions at the same N rate(N 300 kg·hm-2), F10(100% basal fertilizer), F55(50% basal fertilizer, 50% fertigation topdressing), F37(30% basal fertilizer, 70% fertigation topdressing)and F19(10% basal fertilizer, 90% fertigation topdressing)were designed. Agronomic traits(stalk weight, plant height, stalk diameter and effective stalks per hectare)and yield of sugarcane, the N2O flux and the contents of nitrate, nitrite and ammonium nitrogen in soils at the three growth stages were determined. The results were as follows:(1)The ratoon yields in W1F55 and W2F55 were higher, i.e. 102.4 t·hm-2 and 97.8 t·hm-2, respectively; Soil N2O emission flux in F55 was lower under the same irrigation amount.(2)There was a significant negative correlation between soil N2O flux and ammonium nitrogen content, with a correlation coefficient of -0.497(P<0.05, n=24); A reasonable fertilization proportion with drip irrigation can effectively increase sugarcane yield and reduce soil N2O emission. Therefore, the treatment with a fertigation proportion of 5:5 under the same N rate can not only have a relatively high yield of ratoon, but also reduce the N2O emission from the sugarcane soil. [ABSTRACT FROM AUTHOR]

The Chinese government has planned to hit the carbon emission peak before 2030 and achieve carbon neutrality by 2060. In this case, it is a high demand to reduce emissions, especially greenhouse gas (GHG) emissions. Among them, the livestock industry has been the greatest GHG emission source in agriculture sectors, accounting for 80% of total agricultural non-carbon dioxide emissions. The Emissions Gap Report 2021 has released that the methane emissions can be reduced from fossil fuels and agricultural wastes, further, slowing down global warming in the shortterm. Therefore, a low-carbon livestock industry can also make a great contribution to achieving the carbon neutrality. In this study, a systematic review was made on the agricultural carbon emissions in China, with emphasis on the sources of GHG emissions in animal production systems. Some suggestions were also proposed to reduce the GHG emissions from the livestock and poultry. The carbon emission of the agriculture sector has been the third-largest source of GHG emissions, accounting for about 6.7% of the total emissions in China. The GHG emissions of animal respiration, ruminant intestinal fermentation, and manure are regarded as the direct sources, whereas, the indirect GHG emissions include feed production and processing, the energy consumption of equipment and facilities, as well as animal product processing and transportation. Enteric fermentation has been the largest source of GHG emissions from livestock, according to the global livestock environmental assessment model. Finally, some technologies were also summarized to reduce the GHG emissions from the livestock and poultry. The low-carbon path contained three parts, the source, the process, and the end, according to the whole life cycle of animal husbandry production. Correspondingly, there was a gradual increase in the indirect GHG emissions via energy consumption during the breeding process of livestock and poultry, particularly with the increase in the production and demand of livestock. Moreover, one of the key strategies is necessary to conduct the financial investment and the national incentive mechanism, thereby achieving carbon neutrality. Therefore, this review can greatly contribute to promoting carbon neutrality for the sustainable development of the livestock industry. Four recommendations were made as follows: 1) To monitor the GHG emissions from the livestock industry throughout the entire process and scientifically evaluate GHG emissions and reduction potential of each link; 2) To strengthen the clean production in animal husbandry, including basic and innovative research, further to promote the animal husbandry in a green, low-carbon, and efficient way; 3) To develop the green and low-carbon utilization of manure resources from the livestock and poultry production; and 4) To integrate the modern information technology for the low-carbon emission reduction in the digitally empowered livestock industry. [ABSTRACT FROM AUTHOR]

Objective To study the effect of sevoflurane combined with nitrous oxide inhalation anesthesia on circulatory function, $1008 protein level and angiotensin II expression level in elderly patients undergoing radical rectal cancer surgery. Methods From May 2018 to October 2019.60 elderly patients undergoing radical resection of rectal cancer were selected as the research objects, and they were divided into observation group and control group. with 30 cases in each group. The observation group was anesthetized with sevoflurane combined with nitrous oxide tube intubation and the control group was anesthetized with propofol and remifentanil intravenously. The snack rate, mean arterial pressure (MAP), systolic blood pressure (SBP). diastolic blood pressure (DBP), and serum $1003 protein and angiotensin II levels were compared between the two groups of patients at different times. Results Compared with before anesthesia, the observation group had no significant difference in the changes of heart rate. MAP. SBP and DBP after tracheal intubation. 10 minutes after the start of the operation and catheter extubation (P>0.05). The above indicators in the control group were significantly increased, and they were all higher than the observation group the difference was statistically significant (P<0.05). Compared with before anesthesia, the level of serum S1008 protein in the control group and the observation group was significantly increased at 2 h during the operation and the observation group was significantly lower than the control group, the difference was statistically significant (P<0, 05). At 24 and 72 h after operation, the serum S1008 protein levels of the control group and the observation group dropped sharply and the observation group was significantly lower than the control group, the difference was statistically significant (P<0, 05). Compared with preoperatively, the serum angiotensin II levels in the control group and the observation group increased significantly after 24 hours and the observation group was significantly lower than the control group. the difference was statistically significant (P<0.05). Conclusion Sevoflurane combined with nitrous oxide inhalation anesthesia can effectively improve the circulatory function of elderly patients undergoing radical rectal cancer surgery. regulate the level of serum S1003 protein and reduce the expression of angiotensin II. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) has made a strong contribution to the climate change, particularly on the global warming potential 265 times greater than that of CO2 on a 100-year time horizon. Agricultural soil is an important source of N2O emission, accounting for approximately 33% of the global N2O. Furthermore, nitrogenous fertilizer plays a crucial role in N2O emission in agriculture, accounting for approximately 70% of the agricultural soil N2O emissions. Therefore, the reduced fertilizer can be used to alleviate the soil N2O emission, but it simultaneously can decrease the crop yield. A tradeoff between crop yield and ecological environment has become urgent in the planting link of crops. An application of deep fertilization has the potential to increase the crop yield and the use efficiency of fertilizer. However, there is still lacking the effect of reduced fertilizer on soil N2O emission under deep fertilization. In this study, a field experiment was conducted using the static chamber method and gas chromatography to determine the impacts of fertilizer treatments on soil N2O emission, soil Water-Filled Pore Space (WFPS), soil temperature, and yield of winter rapeseed, from October 2019 to May 2020. Five treatments included: 100% (DF100), 80% (DF80), and 60% (DF60) of the local recommended slow-release fertilizer (N-P2O5-K2O=187.5-52.5-60 kg/hm² ) under deep fertilization, broadcast with the local recommended slow-release fertilizer (BF100), and no fertilizer (F0). The results showed that the soil N2O emission under DF100 was 13.3% greater than that of BF100, but the difference was not significant (P>0.05). The DF100 treatment significantly increased the yield of winter rapeseed by 20.1%, Partial Factor Productivity (PFP) by 20.1%, and Agronomic Efficiency (AE) by 31.9% (P<0.05). The DF100 treatment reduced the yield-scaled N2O emissions (Y-SN2O) by 5.0%, indicating that the increasing rate of rapeseed yield was greater than that of N2O emission under deep fertilization. In addition, the reduced fertilizer significantly decreased the soil N2O emission, winter rapeseed yield, and fertilizer use efficiency (P<0.05). The soil N2O emission under DF100 increased by 22.7%, 42.5%, and 153.7%, compared with the DF80, DF60, and F0 treatment, respectively. The yield of winter rapeseed under the DF100 treatment was 1.30, 2.24, and 3.24 times greater than that of DF80, DF60, and F0, respectively. The PFP under DF100 treatment increased by 3.8% and 34.5% than that of DF80 and DF60, respectively. Meanwhile, the AE under DF100 treatment increased by 19.7% and 201.3% than that of DF80 and DF60, respectively. A trend of an initial increase then decrease in the value of Y-SN2O was observed with the increase of fertilizer amount. The maximum Y-SN2O was 0.293 g/kg under the DF60 treatment, increasing by 23.1%, 48.8%, and 57.4% than that under the F0, DF80, and DF100 treatment, respectively. To balance environmental and economic conditions, the application amount of slow-release fertilizer can be reduced appropriately, according to the local recommendation, but it should be greater than 600 kg/hm². The optimal combination on the amount of slow-release fertilizer and deep fertilization can be used to increase the yield of winter rapeseed and use efficiency of fertilizer, as well as reduce soil N2O emission. This finding can provide a sound reference for the reduction of N2O emission in winter rapeseed fields, and rational fertilization in mechanized direct-seeded rapeseed. [ABSTRACT FROM AUTHOR]

Objective To explore the preventive effect of nitrous oxide(N20) on bradycardia induced by dexmedetomidine in laparoscopic surgery. Methods A total of 145 patients with elective laparoscopic surgery under general anesthesia in the First Affiliated Hospital of Fujian Medical University from March to September 2019 were randomly divided into the nitrous oxide group (n = 72) and the control group (n = 73) by random number table method. The patients were graded grade I - II by the American Association of Anesthesiologists (ASA) , and their ages ranged from 18 to 70 years old. During the maintenance period of general an esthesia, 50% N20 was inhaled in the nitrous oxide group, while no N20 was inhaled in the control group. 10 min before skin inci sion, a loading dose of dexmedetomidine (0. 5 µg/kg) was infused by micro pump for 15 min in both groups. The heart rate, systolic blood pressure, mean blood pressure, diastolic blood pressure were recorded at patients entering the operating room(tBL) and dexmedetomidine infusion immediately (t0) and every 5 min (t5 - t30) within 30 min. The whether bradycardia (heart rate< 5 0 times/ min) occurred intraoperatively, hypotension, hypertension, and use of vasoactive agents were recorded. Results The incidence of bradycardia in nitrous oxide group was significantly lower than that in control group[20. 8% vs. 38. 4%, risk ratio(RR) = O. 543, 95 % confidence interval (95%CJ) O. 318-0. 928, P O. 05) . Conclusion Before dosing dexmedetomidine during laparoscopic surgery under general anesthesia, inhalation of 50 % N20 can prevent bradycardia. [ABSTRACT FROM AUTHOR]

Open gas emission sources, such as open dairy lot and manure stockpile, are still challenge to directly measure the gas emissions, due to their fully open nature and the relatively low flux of gas emission, particularly interfering by other emissions sources, such as barns and animals. The detection accuracy of the commonly used static-chamber method depends on the chamber configuration and the different external environment. Four key parameters were evaluated, including the disturbing fan, vent holes, surface wind speed of emission (0.0, 0.5, 1.0, 1.5, and 2.0 m/s) and deployment time (0 to 60 min) in the 300 mm (diameter) × 300 mm (height) (D300×H300) static chamber using nitrous oxide (N2O) as reference gas. The experiment was carried out in a wind tunnel to adjust the wind speed in order to simulate the real environment of open dairy lots. A calibration system was designed to generate a reference flux, and the accuracy of chamber performance was defined based on the difference between the reference fluxes and the calculated fluxes in the static chamber. The results showed that the deviation rates have the similar trends during the deployment time in the static chambers with different configurations. The flux of gas emission that measured by the static chamber was higher at the beginning of process, and then lower compared with that of the reference flux. The measurement accuracy of the static chamber reached the maximum when the deployment time was 50 min, where the deviation rate of the static chamber without the disturbing fan and vent was 1.02%－-20.06%, 12.29% －-47.92% without the disturbing fan and with the vent, -9.71%－-40.92% with the disturbing fan and without the vent, and 4.42%－-25.64% with the disturbing fan and vent. There was no significant difference in the deviation rates of the detected N2O emission fluxes under different wind speeds (P>0.05) using the static chamber with the disturbing fan and with/without vent, indicating these two types of chambers have better detection stability. However, the measurement accuracy of the D300 mm×H300 mm static chamber with the disturbing fan and vent was significantly higher than that with the fan and without vent (P<0.05). When the emission speed of surface wind was 0－2 m/s, the disturbing fan had no significant influence on the measurement accuracy of the static chamber (P>0.05), indicating the emission surface wind was affected by the Venturi effect through the vent. Both the deployment time and emission surface wind speed had significant negative correlation on the deviation rate of the static chambers (P<0.05). However, the correlation between the deployment time and emission surface wind speed was not obvious (P>0.05). This study recommends to use a D300 mm×H300 mm static chamber with the disturbing fan and vent to detect the N2O emission flux in an open gas emission system, such as dairy open lots without manure and emission sources with similar media, with the speed of emission surface wind less than 2 m/s, and the deployment time of 50 min. [ABSTRACT FROM AUTHOR]

Objective To study the effects of different concentrations of N2O on lung function in rabbits with burn combined with inhalation injury. Methods Burn and inhalation injury animal models were established, and the effects of 50%and 70% N2O inhalation on gas exchange (PaO2，PaCO2，pH) and respiratory mechanics (PIP，CL， RL) were evaluated. Results There were significant differences in the levels of PaO2 half an hour after treatment between the 50%-50% N2O- oxygen mixture group (group A) and the 50%-50% nitrogen-oxygen mixture group (group B) ．Compared with those of the 70%-30% nitrogen-oxygen mixture group (group D) ，levels of PaO2 in the 70% -30% N22-oxygen mixture group (group C) showed statistical differences half an hour after treatment. Comparison between group C and group D showed that levels of PaO2 were relatively low at each phase point and the differences showed statistically significance. Meantime，no hypoxemia occurred in either group. Compared with those of group D，levels of PaCO2 in group C were lower at each phase point, with significant differences at 1 h and 2 h after treatment. There was a significant difference in arterial blood pH2, h after treatment and half an hour after injury in group C. Compared with those at half an hour after injury in group C，arterial blood pH showed significant differences in group A after treatment for 15 min and 2 h after treatment. After treatment, lung compliance at different time points in each group was significantly reduced compared with that at half an hour after injury，with significant differences in group A (15 min and 2 h after treatment)，group C (15 min and 1 h after treatment) and group D (1 h and 2 h after treatment)．There was a significant difference between the peak airway pressure 1h after treatment and half an hour after injury in group D.The pulmonary resistance gradually increased after inhalation of the mixed gas for 2 h (2.5 h after treatment). Conclusion Inhalation of high concentration N2O in burned rabbits with inhalation injury did not affect their respiratory function. [ABSTRACT FROM AUTHOR]

Greenhouse gases, such as methane (CH4) and nitrous oxide (N2O) caused by manure storage inside the dairy farms are important contributors of global emissions to atmosphere, which is considered as the primary factor driving global warming. The Intergovernmental Panel on Climate Change (IPCC) guideline (Tier 2 for example) released in 2006 is treated as an authoritative method in estimating CH4 and N2O emissions from the animal manure management of a region, while its accuracy highly depends on the reliabilities of the parameters, including the CH4 and N2O emission factor (EF). While, different manure management modes and climatic conditions will lead to huge difference of the factors, and the estimation based on default factor of IPCC may result in a big deviation in the emissions from the manure management for a country or an area. Using the IPCC method, this paper simulated CH4 and N2O emissions from short-term stacked dairy manures in spring, summer and autumn by the dynamic chamber technique in the laboratory, and the annual emissions of CH4 and N2O from the manure management in Yanqing dairy farms was estimated based on the simulation results, as well as the field investigation on dairy management method and manure production. Finally, CH4 and N2O emission factor of the dairy manure management were calculated and compared with the defaults of IPCC. Results showed that CH4 emissions from the simulated dairy manure stockpiles were 223.97, 4 603.31 and 351.38 mg in spring, summer and autumn, respectively. The total CH4 emission of solid dairy manure management in Yanqing, Beijing was 13 342.50 kg in 2016, or 373.59 t CO2 equivalent. CH4 emission factor of solid manure storage from the simulation was 1.50 kg/(head·yr), which was statistically less than 1.78 kg/(head·yr) calculated from the default values of the relevant parameters in the IPCC guidelines. N2O emission from the simulated dairy manure stockpiles were 5.86, 9.43 and 0.81 mg/kg in spring, summer and autumn, respectively. Total N2O emission of solid dairy manure management in Yanqing, Beijing was 347.87 kg in 2016, or 92.19 t CO2 equivalent. N2O emission factor of solid manure storage from the simulation was 0.0004 kg/kg, which was significantly less than the defaulted value of 0.005 kg/kg in the IPCC guidelines. The difference on the emission factors could be partially explained by the storage period of collected manures from the barns and the open lots of dairy farms in Yanqing, Beijing, which was general less than 4 weeks, and quite differed from the circumstance that the default EFs of CH4 and N2O in IPCC guidelines. Thus, estimating the CH4 and N2O emissions from Yanqing area of Beijing with the default values of CH4 and N2O emission factors in the IPCC guidelines, the flux will be highly overestimated. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is one of the three important greenhouse gases, which has an important impact on atmospheric environment, such as global warming, acid rain formation, ozone layer destruction and so on. As a special artificial aquatic ecosystem, aquaculture, which is rich in nutrients due to the application of a large amount of food, becomes a potential source of nitrous oxide. The total area and increasing rate of aquaculture in the coastal areas of China ranked first in the world, and the emission of N2O from the aquaculture attracted more and more attention. In order to differentiate the production process of N2O and its contribution to the total N2O production of sediment, this study took the reclamation shrimp ponds of Min River estuary in the southeast coast of China as the research object and adopted the laboratory-incubated experiments by means of inhibited process. On this basis, the influence of physicochemical properties on N2O production of sediment was analyzed and the measures to reduce N2O emission from the aquaculture were put forward. Results showed that the average N2O production rate of sediment from the shrimp pond was 1.80, 5.95 and 8.70 nmol/( kg·h) in the early, middle and final stages of the aquaculture, respectively. The shrimp pond was the N2O sources and the production rate increased with the time of aquaculture. The mean contribution of nitrification, denitrification, nitrifier denitrification and abiotic effect in the three aquaculture period was -162.04%, 327.52%, -239.45% and 90.27%, respectively. The N2O production of the sediments from the shrimp ponds in Min River estuary was generated from the denitrification and abiotic effect, while nitrification and nitrifier denitrification played a negative role. Nitrification was negatively correlated with denitrification and nitrifier denitrification, while nitrifier denitrification was negatively correlated with abiotic effect. The total N2O production rate of sediments in the shrimp ponds increased with temperature and decreased with salinity in general, which reached the maximum under the high-temperature and low-salinity condition and the minimum under the low-temperature and high-salinity condition. Salinity had a significant effect on the total N2O production and the four different production processes, while the interaction of temperature and salinity had a significant effect on the nitrifier denitrification and abiotic effect. The correlation analysis showed that the total N2O production rate was significantly positively correlated with the content of total carbon (TC), soil organic carbon (SOC), NH4+-N and the ratio of C: N. There was only abiotic processes significantly affected by TC and SOC in the four N2O production processes. In order to decrease the production and emission of N2O in the coastal aquaculture ecosystem, the salinity of aquaculture ecosystem would be increased and the contents of organic carbon and inorganic nitrogen would be reduced by increasing the exchange frequency between aquaculture water and seawater. [ABSTRACT FROM AUTHOR]

Methane (CH4) and nitrous oxide (N2O) are two of the most important greenhouse gases. The concentrations of CH4 and N2O in the atmosphere have been increasing since the industrial revolution. The paddy field N2O emissions account for 7%-11% of the farmland N2O emissions. Therefore, it is important to research the origin and dynamic of CH4 and N2O emissions under which different fertilization conditions are applied. To investigate the effects of the same carbon level of organic fertilizer applications on methane and nitrous oxide emissions in paddy soils, various organic manures were used in a three-year (2010-2012) study. They were: chemicals fertilizer (CF), pig manure +chemicals fertilizer (PM), chicken manure + chemicals fertilizer (CM), and rice straw + chemicals fertilizer (RS). Control was paddy field without fertilizer (NF). The greenhouse gas emission was measured by using the static chamber-gas chromatography method. The results showed that the CH4 seasonal emission of CF treatment was 202.1, 279.9 and 332.5 kg/hm2. There was no significant difference (P>0.05) between CF and NF in CH4 seasonal emission, and significant difference (P<0.05) between CF and CM, RS. N2O emission from CF treatment was 1.12, 1.26 and 1.29 kg/hm2. There were no significant differences (P>0.05) among CF and the other three organic manures in N2O seasonal emission. Furthermore, the CH4 emission was effected by paddy soil Eh value, temperature, and organic carbon contents, such as the readily oxidizable organic carbon. The CH4 emissions had a negative correlation with soil Eh value, but a positive correlation with soil temperature at 5 cm soil depth. The liable carbon contents in the organic manures ranged from 18.4 to 114.5 g/kg. ROC167 (ROC167 is defined as carbon that can be readily oxidized by 167 mmol/L of potassium permanganate in manures) had a significant impact on CH4 emission and showed a positive correlations between CH4 emission and ROC167 content with a correlation coefficient of 0.872 (P<0.05). The average yields of rice production were increased by 14.3% (P<0.05) in fields applied with organic fertilizers for the third years than those applied with CF only. Among the three different organic manure treatments, global warming potential (GWP) and greenhouse gas intensity (GHGI) are the lowest in the PM treatment, which may be due to low content of ROC167 in the PM. There were no significant differences among PM, CF and NF in GWP and GHGI. In summary, PM could balance the relationship between environmental concerns of CH4 and N2O emissions and rice production concern of increasing yield. Treatment of PM could be recommended as a valuable CH4-limiting organic fertilizer for future use in rice paddy fields. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) has been recognized as one of the most important trace gases in the atmosphere that causes global warming and stratospheric ozone depletion. Nitrogen (N) fertilizer is considered as the primary source of N2O emissions from agricultural soils. N2O production and emission processes are influenced by a number of soil and environmental variables, interacting of soil water and N processes, crop uptake and management practices. As a large agricultural country, China consumes the greatest amount of synthetic N fertilizer which accounts for 30% of the world consumption. Therefore, quantifying N2O emissions from agricultural soils and seeking suitable mitigation measures have become a relatively hot issue in international global climate change studies. It is a great challenge to guarantee high crop yields while reducing N2O emissions under high input of N fertilizers (e. g., N fertilizer application rate can be as high as 600 kg/hm2 in the North China Plain). However, few field data sets are available for the exploration of the effects of fertilizer N regimes on soil N2O emission in Beijing suburb, one of the regions with the most intensive agriculture in North China Plain. The main objectives of this research were to identify the characteristics of N2O emission from winter wheat - summer maize rotation land in Beijing suburb, and to seek a way that could decrease N2O emission and increase or keep crop yield. N2O exchange fluxes from the intensively cultivated winter wheat - summer maize rotation system in Beijing suburb, Fangshan District, were measured by the static chamber technique under 8 levels of N treatments from October 13, 2012 to September 28, 2013. Eight treatments with 3 replications (each micro-plot was 80 cm in diameter and 0.5 m2 in area) were contained in the experiment: N0 (0 kg/hm2), N1 (50 kg/hm2), N2 (100 kg/hm2), N3 (150 kg/hm2), N4 (200 kg/hm2), N5 (250 kg/hm2), N6 (300 kg/hm2), and N7 (400 kg/hm2) respectively for each crop field. The results indicated that the cumulative emissions of N2O from 8 levels of N treatments were 0.08-0.52 kg/hm2 (winter wheat) and 0.26-3.70 kg/hm2 (summer maize), respectively. The N2O emission during the wheat growing season from 8 levels of N fertilization treatments accounted for 0.05%-0.13% of the total N loss, and during the maize growing season were 0.78%-1.02%, which indicated that the emission of N2O mainly occurred during the maize growing season. It was obvious that the application of existing chemical fertilizers showed significantly seasonal and diurnal variation on the N2O emissions in wheat-maize rotation system in the suburbs of Beijing. Considering fertilizer rates, N2O emission and crop yield, it was concluded that the fertilization rate of N4 (200 kg/hm2) for each crop was very reasonable, which could provide the basis for applying fertilizer rationally, reducing farm production costs, estimating greenhouse gas emissions from cropland and compiling national greenhouse gases emission inventory. [ABSTRACT FROM AUTHOR]

Difengjiang Jasmine Garden of Fuzhou was chosen as the study site. Methane, nitrous oxide and carbon dioxide production were in the control, and shell, gypsum, slag, biochar and straw addition treatments were determined by experiment incubation-gas chromatogram method. The results showed ： During the whole observation period, averaged methane production were 0. 014，0. 012，0. 012，0. 012，0. 013，0. 014 μg/(g • d), respectively. All addition treatment were decreased by 16. 7%, 16.7%, 15. 2k，7. 25%，2. 17% comparison with the control，respectively. Averaged nitrous oxide production were 0.008，0.014，0.030，0.015，0.009，0.019 μg/(g • d)，respectively. All addition treatments were not decreased nitrous oxide production comparison with that of the control, respectively. Averaged carbon dioxide production were 58. 7，79.5，86.5，51.0，44.7，1050 μg/( g • d), respectively. Slag, biochar addition treatment were decreased by 13. 1%，23. 8% comparing with the control, respectively. Shell, gypsum addition inhibited the jasmine soil methane production. Slag, biochar addition inhibited the jasmine soil methane and carbon dioxide production, however, all addition could not inhibit the jasmine soil nitrous oxide production. [ABSTRACT FROM AUTHOR]

To investigate the rule of dissolved N2O concentration and N2O flux diffused from river water and its influential factors, a one-year (from April 2014 to April 2015) monitoring was conducted in Tuojia watershed of Xiangjiang River, which is located in the red soil hilly area of subtropical China. The double-layer-diffusion model was used to measure the diffusion of N2O flux from river water and the environmental factors of water were monitored by a portable multi-parameter meter. Four reaches of Tuojia watershed with the upstream, middle stream and downstream were employed in this study. The results indicated that there was significant spatial difference in the N2O flux between each reach. The annual dissolved N2O concentration and the diffusion flux of N2O from four reaches of Tuojia River varied from 0.006 to 1.38 μmol/L (0.15±0.26 μmol/L) and from -0.88 to 337.94 μg/(m2·h) (32.60±56.41 μg/(m2·h)), respectively. And the corresponding range of the concentration of ammonia nitrogen, nitrate nitrogen and dissolved organic carbon varied from 0.004 to 8.32, from 0.01 to 3.05, and from 0.92 to 6.72 mg/L, respectively, ((1.29±1.49), (1.43±0.63), and (2.99±1.25) mg/L respectively). And the annual conductivity from 4 reaches of Tuojia River varied from 50.36 to 248.43 μS/cm (138.37±47.56 μS/cm). Generally speaking, the totally transfer of N2O was increased with the pollution loading of the river water. However, the temporal variation of N2O flux between 4 reaches was not significant (2 >4 >3 >1 for the 4 reaches). Except several sites in headwater region during winter period where we found negative N2O fluxes, others expressed the continuous positive fluxes. Winter period (from January to April in 2015) showed the highest N2O flux and summer period (from July to October in 2014) outputted the smallest N2O flux. By the correlation analysis, we found there were significant and positive correlations between dissolved N2O concentration and inorganic N (NH4 +-N and NO3 --N) concentration (r=0.44, P<0.05; r=0.52, P<0.05), dissolved organic carbon (r=0.49, P<0.05) and conductivity (r=0.45, P<0.05) respectively, while there were no significant relationships between stream dissolved N2O concentration and water temperature (r=-0.10), dissolved oxygen (r=0.03), water pH value (r=0.08) and redox potential (r=-0.09). And at the same time, there were significant and positive correlations between N2O flux and inorganic N (NH4 +-N and NO3 --N) concentration (r=0.50, P<0.05; r=0.58, P<0.05), dissolved organic carbon (r=0.46, P<0.05) and conductivity (r=0.50, P<0.05), while water temperature (r=-0.10, P<0.05) showed negative correlation with N2O flux in some cases, and additionally, dissolved oxygen (r=0.10), water pH value (r=0.11) and redox potential (r=-0.08) showed no significant relationships with stream N2O flux. For the N2O production from river water, the nitrification process controlled the fashion. The results of our study indicated that waste and sewage produced by agricultural non-point source pollution, livestock breeding and human activities were the main reasons leading to the increase of river pollution loading, which gave rise to more stream N2O transportation. Our findings may provide important reference for further understanding and research on the assessment of global N2O budget of rivers in subtropical region. [ABSTRACT FROM AUTHOR]

Effects of the availability of nitrate nitrogen and different carbon sources on N20 and C02 emission from soil of typical farmland in the North China were studied. The static culture systems were adopted in an indoor experiment. The results illustrated that, compared with single nitrate nitrogen fertilizer, combined different carbon sources and nitrate nitrogen fertilizer increased the emission of N20 from soil, except for cellulose; combined different carbon sources and nitrate nitrogen fertilizer increased the accumulated emission of C02 from soil. The emission flux of N20 by treatment of pectin peaked 1 383.42 μg N ·kg-1 ·d-1 on day l.The emission flux of C02 by treatment of glucose peaked 370.13 mg C ·kg-1 ·d-1 on day 1, and the accumulated emission of C02 order was：glucose>pectin>straw>cellulose>starch>lignin. It showed a highly signifcant positive conrelation between the content of N〇2-N and emission of N20. Overall, combined cellulose and nitrate nitrogen fertilizer suppressed the N20 emission, improved the C02 emission, and increased NO3-N content; combined other carbon sources and nitrate nitrogen fertilizer promoted the N20 and C02 emission. [ABSTRACT FROM AUTHOR]

Greenhouse gas emissions from paddy field in China have aroused widespread attention. Northeast China is the most important marketable grain base in China, and the paddy fields acreage of northeast China is increasing rapidly in nearly a decade. It has only scattered reports in regard to paddy greenhouse gas emissions in the northeast cold region. The winter of northeast is very cold and long, and organic matter of farmland soil is relatively high. Nitrous oxide (N2O) emissions from fields in cold region of northeast China may play an role in climate change. In this study, a field experiment was conducted to investigate the N2O emissions from rice paddy field in cold region under different irrigation modes and its response to environmental factors. The experiment was set up in Rice Irrigation Experimental Center of Heilongjiang located in Heping town of Qing'an county in 2014 with four treatments including control irrigation, wet irrigation, intermittent irrigation and flood irrigation. The For all the treatments, drainage and drying were conducted in the lateral tillering stage and yellow ripe stage. In addition, under the control irrigation system, the soil water content was controlled at 0.7 or 0.8 times of saturated moisture content except for seeding establishment when water layer was 0-30 mm; Under the intermittent irrigation system, water layer was arranged at 0-30 or 0-40 mm for stages other than the lateral tillering stage and yellow ripe stage; Under the wet irrigation system, water layer was arranged at 0-20 or 0-30 mm for stages other than the lateral tillering stage and yellow ripe stage; Under the flood irrigation, most of stages had water layer of 0-40 mm. Each treatment was repeated three times. During the experiment, the N2O emission was measured at 10:00-14:00 using the method of static chamber-gas chromatographic techniques. Additionally, rice yield was determined at harvest. The results showed that the N2O emissions fluxes had same trend in the seasonal variation under different treatments. The peak of emissions appeared in the stage when water alteration was frequent. The N2O emission was low in the early stage of rice growth and small amounts of N2O emissions occurred in steeping field stage. Compare to flood irrigation, the total amount of N2O emissions under intermittent irrigation increased by 47.3%, but that of control and wet irrigation treatments reduced by 40.7% and 39.6%. The N2O emission flux from cold rice paddies was closely related to soil NO3 --N content and soil 10-cm temperature (P<0.05). The N2O emission from rice yield would increase with soil temperature and NO3 --N content. For rice yield, the treatment of wet irrigation was worse than the others and the other treatments had no significant difference. The N2O emissions per unit yield of control and wet irrigation were 40% and 30% lower than the flood irrigation. However, the rice yield of control irrigation treatment was significantly higher than wet irrigation. Therefore, the control irrigation was best irrigation mode to increase rice yield and reduce N2O emission among the four treatments. It should be heavily emphasized in future in the cold regions of China. The results can provide valuable information for selection of water-saving irrigation method in Heilongjiang cold region. [ABSTRACT FROM AUTHOR]

The increment of greenhouse gas emissions is considered as the main reason for global warming, and paddy field is an important source of greenhouse gas emissions. While rice production increases at the same time, and selected an effective method to mitigate greenhouse gas emissions is necessary. Wufeng Experiment Station of Fujian Rice Research Institute was chosen as the study site. Methane and nitrous oxide production potential in the control, and slag, straw, biochar and slag + biochar addition treatments were determined by indoor cultivation-gas chromatogram. The results showed that during the whole observation period, averaged methane production potential were 0. 007 1, 0. 004 9, 1.505 1, 0. 079 0, 0. 080 0 μg/( g • d), respectively. Slag addition treatment was decreased by 31 % comparison with the control, and the other treatments were not decreased methane production comparison with that of the control. Averaged nitrous oxide production potential were 0. 003 5, 0. 001 6, 0. 001 1, 0. 002 1, 0. 002 9 μg/( g • d), respectively. Slag, straw, biochar, and slag + biochar addition treatment were decreased by 54 %, 69 %, 40 %, 17% comparison with the control. Slag addition could inhibit the soil methane and nitrous oxide production from paddy fields, and straw, biochar, and and slag + biochar could effectively suppress the nitrous oxide production, however not suppress the methane production. [ABSTRACT FROM AUTHOR]

Climate change, as one of the most important environmental issues, has become an increasing global concern to scientists, policy makers, and the public. Paddy soils are a dominant source of N2O emissions. Agricultural management practices (e.g., water regime, fertilizers management, tillage) have important impacts on N2O emissions due to the changing microenvironment of paddy fields that can affect the processes of soil nitrification and denitrification. This paper summaried current literatures on the influence of these practices on N2O production and emission and their corresponding mechanisms in rice fields. At present, the generation and the pathway of N2O emission from paddy soils are clarified. Nevertheless, the current information on the action of farming management practices on N2O indirect emission is limited. The fertilizer application rate, the various types of fertilizers, and the varying timing and placement of application have a significant effect on the N2O emissions of paddy fields due to the different supplementation of nitrate and ammonium substrate in the processes of nitrification and denitrification. Generally, N2O emissions increase with increasing nitrogen (N) fertilizer rate. Previous studies showed that applying N fertilizer deeper can decrease N2O emissions compared to surface application. Water regime exerts substantial influence on N2O emission through the changes in oxidation and reduction in paddy soil layers during rice cropping. The mid-season aeration and drying-wetting alternation can stimulate N2O generation and emissions from paddy soils. Tillage and residue management practices can also affect nitrification and denitrification due to the change of soil characteristics. However, cultivation patterns do not have significant impacts on N2O emissions from paddy fields in current studies. Further research is needed to study the long-term effects of cultivations on N2O emissions. Most studies showed that N2O emissions decrease by incorporating biochar into paddy soils, but inconsistent results have also been reported. In addition, models (e.g., DNDC, CENTURY) are good options to simulate the effects of alternative agricultural practices on N2O emission from paddy fields and to identify potential strategies for climate change mitigation. In addition, the different effect of farming management practices on N2O emission may be presented based on the difference of many factors (e.g., climate conditions, soil types). An immense challenge to find ways to reduce N2O emission from paddy soils lies ahead for the scientific community and policy makers. Researchable priorities should be: 1) to implement exhaustive research on mechanisms that new agricultural management practices affect N2O generation and its emission pathways; 2) to assess effect of agricultural practices on the direct and indirect N2O emissions from paddy fields and their mechanisms; 3) to make in-depth studies on characteristics of N2O emission in technologies with integration of various farming practices; and 4) to simulate and forecast impacts of agricultural practices on N2O emissions in paddy ecosystems. Integrated farming approaches that exert a crucial role in the reduction of N2O emissions from paddy soils are necessary to be explored to mitigate the consequences of climate change on our planet. [ABSTRACT FROM AUTHOR]

[Objectives] Biochar has been proposed as a potent tool for greenhouse gas mitigations. The distribution characteristics of methane(CH4)and nitrous oxide(N20)in the soil profiles can provide detailed information on the mechanisms of greenhouse gas production and emissions. [ Methods] Four treatments were installed as follows, no nitrogen ( N ) and biochar ( B) as the control (N0B0) ,single N fertilization( N1B0) ,single biochar amendment( N0B1) ,and N fertilizer with biochar amendment( N1B1). Nitrous oxide( N20) and methane(CH4)concentration dynamics in soil profile at the depths of 7,15,30,and 50 cm in the paddy fields under both flooding and drainage conditions were monitored through a special soil gas collection device. [Results] All the soil N20 concentration exhibited a sharp peak after N fertilizer application. N application has significantly promoted the soil CH4 concentrations throughout the rice season and N20 concentrations during the entire rice-wheat rotation (P< 0.05) compared with no N application. The CH4 and N20 concentrations in top soil profiles were higher than those in deep soil profiles with N fertilization application. The biochar effects were dependent on the N fertilization. When N was applied, the CH4 concentrations were reduced following biochar amendment by 24.8% from the N1B1 compared with the N1B0 in the depths of 7 cm and 15 cm in the rice season(P<0.05) while the N20 concentrations were reduced by 33.2% at all soil depths in the wheat season (P< 0.05). When no nitrogen was applied, the CH4 concentrations of N0B1 were higher than those of N0B0 at soil depth of 7 and 15 cm(P<0.05). [ Conclusions] Together with N fertilization, biochar amendment significantly reduced both CH4 and N20 concentrations within the top soil profiles while N fertilization promoted both CH4 and N20 concentrations within the top soil profiles in the rice-wheat annual rotations. [ABSTRACT FROM AUTHOR]

Maize production inevitably generates greenhouse gas (GHG) emissions which contribute to global warming. The greenhouse gas intensity (GHGI) of maize production was controlled by various management techniques. Fuel, fertilizer production, herbicide production, seed consumption, transportation, and on-farm energy consumption all result in GHG emissions. Life cycle assessment (LCA) methodology was adopted in this study to calculate GHG emissions under different fertilization treatments aiming at comprehensively evaluating the effects of different fertilization treatments on GHG emissions and selecting the options with both economic benefits and GHG mitigation. Four different fertilization treatments are: local traditional fertilization; urea treatment; sulfur coated urea; and urea added with dicyandiamide treatment. Static chamber and gas chromatography (GC) systems were used to continuously monitor N2O emissions from maize cropland. N2O emissions under different fertilization treatments were calculated. Data on the amount and type of fertilizer applied, energy consumption for the tillage, herbicide consumption, irrigation area and Diesel consumption, for tillage, electricity consumption for irrigation, and seed consumption were collected. Total GHG emissions from fertilizer production, energy consumption, seed production were estimated. GHG emission intensity based on grain yield and economic benefit were also calculated. The result showed that N2O emissions from fertilization, total GHG emission of the whole life cycle, emission intensities based on yield and output were all ranked as local traditional fertilization>urea treatment>urea added with dicyandiamide treatment>sulfur coated urea treatment. N2O emissions from the local traditional fertilization treatment was very significantly higher than that from the other three treatments (P<0.01). N2O emissions from the sulfur coated urea treatment was significantly lower than that from the urea treatment (P<0.05) and was not significantly different from that in the urea added with dicyandiamide treatment (P>0.05). Total GHG emissions from the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 4.11, 2.71, 2.56, and 2.61 t/(hm2.a) respectively. Emission per unit of yield for the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 364.1, 238.3, 216.6, and 223.4 kg/t maize, respectively. Emission per 10 000 yuan for the treatments of local traditional fertilization, urea, sulfur coated urea, and urea added with dicyandiamide were 2.19, 1.32, 1.15, and 1.18 t /10 000 yuan respectively. Compared with a traditional fertilization treatment, sulfur coated urea could reduce total GHG emissions, GHG emission per unit of yield and per 10 000 yuan net output by 37.8%, 40.5%, and 47.3% respectively, while the urea added with dicyandiamide treatment could reduce total GHG emissions, GHG emission per unit of yield, and per 10 000 yuan by 36.5%, 38.6%, and 45.9% respectively. Production of fertilizers, especially nitrogen fertilizer, makes the greatest contribution to total GHG emissions for maize cultivation, accounting for 42.4%-55.0% of the total GHG emissions from the four treatments, followed by fertilizer application, accounting for 20.8%-26.1% of the total GHG emissions from the four treatments. In order to ensure grain output and economic benefits, two fertilization treatments, sulfur coated urea treatment and urea added with dicyandiamide treatment, resulted in relatively low total emissions and emission intensity. They can be recommended as options to mitigate GHG emissions from maize production. [ABSTRACT FROM AUTHOR]

Biochar application to the paddy field may be an effective method to deal with global climate change for the mankind. The effect of four different application rates of biochar made from bamboo added to the paddy field on soil quality, rice yield and trace greenhouse gas emissions was investigated by a field experiment to provide a scientific basis for biochar agricultural application. The experiment was carried out in a rice farm from Tai Lake Region and consisted of four treatments, biochar at 10 t/hm2 (T1), biochar at 20 t/hm2 (T2), biochar at 40 t/hm2 (T3), and paddy field without biochar application as a control (T0). Each treatment had three replicates arranged in a completely randomized block design. Changes in soil chemical and physical properties, rice yield and trace greenhouse gases (CH4, N2O) emissions with biochar addition were investigated during a whole rice growing season of 2013. The results showed that, comparing with the control treatment, soil pH value and organic carbon content were significantly increased (P<0.05) after biochar application, and the increase of organic carbon content was proportional to biochar application amount (r=0.78, P<0.01). Soil bulk density was significantly decreased with the increasing biochar application rate (P<0.05). Biochar application had no significant effect on soil cation exchange capacity, total nitrogen, available phosphorus and quick-acting potassium content (P>0.05). Rice yields of four treatments were respectively (8 120.6±468.2), (8 313.5±221.8), (8 505.4±381.2) and (7 996.8±285.6) kg/hm2, and had no significant difference with biochar application amount (P>0.05), and the same result was obtained by the experiment of 2014, which showed biochar application cannot increase rice yield effectively, but can stable rice yield sustainably. CH4 emission flux decreased gradually with the increase of biochar application amount. Meanwhile, CH4 cumulative emission decreased effectively with biochar application. There was a negative correlation between CH4 cumulative emission and biochar application amount (r=-0.24, P<0.01).However, CH4 cumulative emission cannot decrease significantly by excessive biochar application (P>0.05). Comparing with the control (T0), N2O emission flux decreased significantly within a week after biochar application (P<0.05), and rose slightly during the drainage of the paddy field, and finally reached a steady value (about 9.80 mg/(m2·h)) for three biochar application treatments (T1, T2 and T3). However, there was no significant difference with CH4 cumulative emission between the treatments of biochar at 20 t/hm2 (T2) and 40 t/hm2 (T3) (P>0.05), implying that CH4 cumulative emission cannot decrease effectively by excessive biochar application (>20 t/hm2 for the purple clay soil in the Tai Lake region). N2O cumulative emission decreased significantly with biochar application (P<0.05), but there was no significant difference among the treatments with different biochar application rates (P>0.05). CH4 and N2O emission fluxes and cumulative emissions showed the similar changes according to the preliminary experiment results of 2014. In this experiment, considering the effect and cost comprehensively, biochar application amount at 20 t/hm2 could be a technical option to reach low carbon emission intensity and stable rice producitivity in the rice paddy agriculture. It also provided a viable way to realize the enhancement of carbon sequestration and the mitigation of greenhouse emissions in the Tiaoxi Watershed of Tai Lake region. [ABSTRACT FROM AUTHOR]

Global warming is a critical issue today. The increment of greenhouse gas emission is important cause for the change, nitrous oxide is one of the main greenhouse gas. It is necessary to carry out research on its emission characteristics and reduction methods. In order to clarify the effect of iron slag adding on nitrous oxide fluxes of different pathways in paddy field, the nitrous oxide fluxes of different pathways of control, 2,4, and 8 mg/hm² iron slag application were determined by static chamber gas chromatogram. The results showed; plant pathway nitrous oxide fluxes were -0. 020 4 ~ 0. 033 4, - 0. 038 9 ~ 0. 052 3, - 0. 062 3 ~ 0. 094 4, -0. 035 1 ~0. 080 2 mg/(m² ⋅ h), and the averaged values were 0.005 9, -0.013 9, 0.017 7, -0.000 1 mg/(m² ⋅ h). Diffusion pathway nitrous fluxes were -0.032 3 -0.069 9, - 0. 015 5 ~ 0. 037 2, - 0. 023 1 ~ 0. 067 1, - 0. 035 2 ~ 0. 032 4 mg/(m² ⋅ h), and the averaged values were 0.020 6, -0.003 1, 0.005 3, -0.001 6 mg/(m² ⋅ h). Bubble pathway nitrous oxide fluxes were -0. 073 6 ~ 0. 033 4, - 0. 025 7 ~ 0.084 2, - 0. 045 6 ~ 0. 068 9, -0. 080 1 ~0. 080 2 mg/(m² ⋅ h), and the averaged values were -0.014 7, 0.000 2, 0. 012 5, -0. 011 7 mg/(m² ⋅ h). The effects of iron slag addition on nitrous oxide fluxes of different pathways were different in the same patterns. [ABSTRACT FROM AUTHOR]