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1.
GHGs production and emission may vary depending on soil physical properties, water management and fertilization. Two paddy soils characterized by different texture were incubated to evaluate the impact of flooding (permanent or intermittent) and N addition on potential N2O, CH4 and CO2 production and release into atmosphere and soil solution. Relationships with volumetric water content (VWC) and water filled pore space (WFPS) were evaluated. Overall, the finer clayey soil (CL) produced 58% more CH4 than the coarser sandy soil (SA) and showed an earlier sink to source transition; the difference was lower with N addition. Permanent flooding favoured the amount of dissolved CH4. SA produced more N2O emissions than CL under permanent flooding (31.0 vs. 3.7%); an opposite pattern was observed for dissolved N2O (16.4 vs. 52.7%). Fertilization increased N2O emissions under dry conditions in CL and under flooding in SA.

Our findings showed that i) VWC had a larger influence on N2O and CH4 emissions than WFPS, ii) soil type influenced the gas release into atmosphere or soil solution and the timing of sink to source transition in CH4 emissions. Further investigation on timing of fertilization and drainage are needed to improve climate change mitigation strategies.  相似文献   


2.
This study evaluated the effects of rice straw and water regimes on CH4 and N2O emissions from paddy fields for two rice growing seasons (summer 2014 and spring 2015). Water regimes included alternating wet–dry irrigation (AWD) maintained at three levels (–5 cm, – 10 cm and –15 cm) in comparison to continuous flooding irrigation (CF). Rice straw (5 t ha–1) was incorporated into the top soil (0 – 15 cm), distributed and burned in situ. Results showed that using burned in situ rice straw was found to reduce seasonal cumulative CH4 emission (24–34% in summer; 18–28% in spring), N2O emission (21–32% in summer; 22–29% in spring) and lower rice yield (8–9%) than rice straw incorporation into top soil. AWD methods reduced the amount of CH4 production (22.6–41.5%) and increased N2O emission (25–26%) without any decrease in rice yield. Rice straw incorporation into the top soil with AWD had higher water productivity (23–37%) than rice straw when burned in situ with CF. The results conclude that AWD and rice straw management can be employed as mitigation strategy for CH4 and N2O emissions from paddy fields in Central Vietnam.  相似文献   

3.
Winter cover crops are recommended to improve soil quality and carbon sequestration, although their use as green manure can significantly increase methane (CH4) emission from paddy soils. Soil management practices can be used to reduce CH4 emission from paddy soils, but intermittent drainage is regarded as a key practice to reduce CH4 emission and global warming potential (GWP). However, significantly greater emissions of carbon dioxide (CO2) and nitrous oxide (N2O) are expected when large amounts of cover crop biomass are incorporated into soils. In this study, we investigated the effects of midseason drainage on CH4 emission and GWP following incorporation of 0, 3, 6 and 12 Mg/ha of cover crop biomass. Methane, CO2 and N2O emission rates significantly (P < 0.05) increased with higher rates of cover crop biomass incorporation under both irrigation conditions. However, intermittent drainage effectively reduced seasonal CH4 fluxes by ca. 42–46% and GWP by 17–31% compared to continuous flooding. Moreover, there were no significant differences in rice yield between the two water management practices with similar biomass incorporation rates. In conclusion, intermittent drainage and incorporation of 3 Mg/ha of green biomass could be a good management option to reduce GWP.  相似文献   

4.
ABSTRACT

Emission of methane (CH4), a major greenhouse gas, from submerged paddy soils is generally reduced by introducing intermittent drainage in summer, which is a common water management in Japan. However, such a practice is not widely conducted in Hokkaido, a northern region in Japan, to prevent a possible reduction in rice grain yield caused by cold weather. Therefore, the effects of intermittent drainage on CH4 emission and rice grain yield have not been investigated comprehensively in Hokkaido. In this study, we conducted a three-year field experiment in Hokkaido and measured CH4 and nitrous oxide (N2O) fluxes and rice grain yield to elucidate whether the reduction in CH4 emission can be achieved in Hokkaido as well as other regions in Japan. Four experimental treatments, namely, two soil types [soils of light clay (LiC) and heavy clay (HC) textures] and two water management [continuous flood irrigation (CF), and intermittent drainage (ID)], were used, and CH4 and N2O fluxes were measured throughout the rice cultivation periods from 2016 to 2018. Cumulative CH4 emissions in 2016 were markedly low, suggesting an initially low population of methanogens in the soils presumably due to no soil submergence or crop cultivation in the preceding years, which indicates a possible reduction in CH4 emission by introducing paddy-upland crop rotation. Cumulative CH4 emissions in the ID-LiC and ID-HC plots were 21–91% lower than those in the CF-LiC and CF-HC plots, respectively, whereas the cumulative N2O emissions did not significantly differ between the different water managements. The amount of CH4 emission reduction by the intermittent drainage was largest in 2018, with a comparatively long period of the first drainage for 12 days in summer. Rice grain yields did not significantly differ between the different water managements for the entire 3 years, although the percentage of well-formed rice grains was reduced by the intermittent drainage in 2018. These results suggest that CH4 emission from paddy fields can be reduced with no decrease in rice grain yield by the intermittent drainage in Hokkaido. In particular, the first drainage for a long period in summer is expected to reduce CH4 emission markedly.  相似文献   

5.
王强盛  刘欣  许国春  余坤龙  张慧 《土壤》2023,55(6):1279-1288
稻田是大气温室气体甲烷(CH4)和氧化亚氮(N2O)的重要排放源, 稻田温室气体减排一直是生态农业研究的热点。目前, 采用水稻品种选择利用、水分控制管理、肥料运筹管理、耕作制度调整以及种养结合模式等方法来减少稻田温室气体排放有较好实践效应, 但不同稻田栽培环境(露地、网室)基础上的稻鸭共作对麦秸全量还田的稻田温室气体排放特征及相关土壤理化特性关联性的影响尚为少见。本研究采用裂区设计, 在两种栽培环境条件下, 以无鸭子放养的常规稻作和麦秸不还田为对照, 在等养分条件下分析麦秸全量还田与稻鸭共作模式对稻田土壤氧化还原电位、CH4排放量、产CH4潜力及CH4氧化能力、N2O排放量及N2O排放高峰期土壤反硝化酶活性、全球增温潜势、水稻产量的影响, 为稻田可持续生产和温室气体减排提供参考。结果表明, 麦秆还田增加了稻田产CH4潜力、提高了CH4排放量, 降低了稻田土壤反硝化酶活性、土壤氧化还原电位和N2O排放量, 整体上导致全球增温潜势上升96.89%~123.02%; 稻鸭共作模式, 由于鸭子的不间断活动提高了稻田土壤氧化还原电位, 降低了稻田产CH4潜力, 增强了稻田CH4氧化能力, 从而降低稻田CH4排放量, N2O排放量虽有提高, 整体上稻鸭共作模式的全球增温潜势较无鸭常规稻田下降8.72%~14.18%; 网室栽培模式显著提高了稻田土壤氧化还原电位, 降低稻田产CH4潜力、CH4氧化能力和土壤反硝化酶活性, 减少了稻田CH4和N2O排放量, 全球增温潜势降低6.35%~13.14%。本试验条件下, 稻田土壤的CH4氧化能力是产CH4潜力的2.21~3.81倍; 相同环境条件下, 稻鸭共作和麦秸还田均能增加水稻实际产量, 网室栽培的所有处理较相应的露地栽培减少了水稻实际产量1.19%~5.48%。本试验表明, 稻鸭共作和网室栽培可减缓全球增温潜势, 稻鸭共作和麦秸还田能够增加水稻实际产量。  相似文献   

6.
Abstract

Methane (CH4) and nitrous oxide (N2O) emissions from an irrigated rice field under continuous flooding and intermittent irrigation water management practices in northern China were measured in situ by the static chamber technique during May to October in 2000. The intermittent irrigation reduced total growing‐season CH4 emission by 24.22% but increased N2O emission by 23.72%, when compared with the continuous flooding. Soil Eh and four related bacterial groups were also measured to clarify their effects on gaseous emissions. Three ranges of soil redox potential were related to gas emissions: below ?100 mV with vigorous CH4 emission, above +100 mV with significant N2O emission, and +100 to ?100 mV with little CH4 and N2O emissions. Intermittently draining the field increased soil oxidation, with a decrease in CH4 emission and an increase in N2O emission. In general the mid‐season drainage slightly increased the populations of methanotrophs, nitrifiers, and denitrifiers but decreased that of methanogens.  相似文献   

7.
Wheat straw management affects CH4 and N2O emissions from rice fields   总被引：1，自引：0，他引：1  
A 3-year field experiment was conducted in Jiangsu Province, China from 2004 to 2006 to investigate CH4 and N2O emissions from paddy fields as affected by various wheat straw management practices prior to rice cultivation. Five methods of returning wheat straw, no straw, evenly incorporating, burying straw, ditch mulching and strip mulching, were adopted in the experiment. Evenly incorporating is the most common management practice in the region. Results showed that compared with no straw, evenly incorporating increased CH4 emission significantly by a factor of 3.9-10.5, while decreasing N2O emission by 1-78%. Methane emission from burying straw was comparable with that from evenly incorporating, while N2O emission from burying straw was 94-314% of that from evenly incorporating. Compared with evenly incorporating, CH4 emission was decreased by 23-32% in ditch mulching and by 32% in strip mulching, while N2O emission was increased by a factor of 1.4-3.7 in ditch mulching and by a factor of 5.1 in strip mulching. During the rice-growing season, the emitted N2O was negligible compared to that of emitted CH4. No significant difference in grain yield was observed between ditch mulching, burying straw, evenly incorporating and no straw. Compared with no straw, the grain yield was increased by 27% in strip mulching. Based on these results, the best management practice for returning wheat straw to the soil is strip mulching wheat straw partially or completely onto the field surface, as the method reduced CH4 emission from rice fields with no decrease in rice yield.  相似文献   

8.
太湖地区不同水旱轮作方式下稻季甲烷和氧化亚氮排放研究   总被引：15，自引：0，他引：15  
为准确编制我国稻田温室气体排放清单及制定合理减排措施提供基础数据,选择太湖地区典型水稻种植区江苏省苏州市,研究设计了休闲水稻(对照,CK)、紫云英水稻(T1)、黑麦草水稻(T2)、小麦水稻(T3)和油菜水稻(T4)5种水旱轮作方式,采用静态箱气相色谱法,开展了不同水旱轮作方式下水稻生长季田间甲烷(CH4)和氧化亚氮(N2O)排放监测试验。试验结果表明:不同水旱轮作方式下水稻生长季CH4排放通量呈先升高后降低的变化趋势,CH4排放峰值出现在水稻生育前期,移栽至有效分蘖临界叶龄期CH4累积排放量占全生育期排放总量的比例为65%~81%,而N2O仅在水稻烤田期间有明显排放。水旱轮作方式对稻季CH4和N2O排放有极显著(P 0.01)影响,CH4季节总排放量表现为T1(283.2 kg.hm 2)CK(139.5 kg.hm 2)T3(123.4kg.hm 2)T4(114.7 kg.hm 2)T2(100.8 kg.hm 2),N2O季节总排放量顺序为T1 T4 T3 T2 CK,依次为1.06kg.hm 2、0.87 kg.hm 2、0.81 kg.hm 2、0.72 kg.hm 2和0.53 kg.hm 2。T1处理稻季排放CH4和N2O产生的增温潜势最高[7 396 kg(CO2).hm 2],显著(P 0.05)高于其他处理,比CK[3 646 kg(CO2).hm 2]增加103%,T2[2 735kg(CO2).hm 2]较CK减少25%(P 0.05)。紫云英水稻轮作方式增加了太湖地区水稻生长季的温室效应。  相似文献   

9.
Agricultural management significantly affects methane (CH4) and nitrous oxide (N2O) emissions from paddy fields. However, little is known about the underlying microbiological mechanism. Field experiment was conducted to investigate the effect of the water regime and straw incorporation on CH4 and N2O emissions and soil properties. Quantitative PCR was applied to measure the abundance of soil methanogens, methane-oxidising bacteria, nitrifiers, and denitrifiers according to DNA and mRNA expression levels of microbial genes, including mcrA, pmoA, amoA, and nirK/nirS/nosZ. Field trials showed that the CH4 and N2O flux rates were negatively correlated with each other, and N2O emissions were far lower than CH4 emissions. Drainage and straw incorporation affected functional gene abundance through altered soil environment. The present (DNA-level) gene abundances of amoA, nosZ, and mcrA were higher with straw incorporation than those without straw incorporation, and they were positively correlated with high concentrations of soil exchangeable NH4+ and dissolved organic carbon. The active (mRNA-level) gene abundance of mcrA was lower in the drainage treatment than in continuous flooding, which was negatively correlated with soil redox potential (Eh). The CH4 flux rate was significantly and positively correlated with active mcrA abundance but negatively correlated with Eh. The N2O flux rate was significantly and positively correlated with present and active nirS abundance and positively correlated with soil Eh. Thus, we demonstrated that active gene abundance, such as of mcrA for CH4 and nirS for N2O, reflects the contradictory relationship between CH4 and N2O emissions regulated by soil Eh in acidic paddy soils.  相似文献   

10.
The effect of controlled drainage on methane (CH4) and nitrous oxide (N2O) emissions from a paddy field under controlled irrigation (CI) was investigated by controlling the sub-surface drainage percolation rate with a lysimeter. CI technology is one of the major water-saving irrigation methods for rice growing in China. Water percolation rates were adjusted to three values (2, 5, and 8 mm d?1) in the study. On the one hand, the CH4 emission flux and total CH4 emission from paddy fields under CI decreased with the increase of percolation rates. Total CH4 emissions during the growth stage of rice were 1.83, 1.16, and 1.05 g m?2 in the 2, 5, and 8 mm d?1 plots, respectively. On the other hand, the N2O emission flux and total N2O emissions from paddy fields under CI increased with the increase of percolation rates. Total N2O emissions during the growth stage of rice were 0.304, 0.367, and 0.480 g m?2 in the 2, 5, and 8 mm d?1 plots, respectively. The seasonal carbon dioxide (CO2) equivalent of CH4 and N2O emissions from paddy fields under CI was lowest in the 2 mm d?1 plot (1364 kg CO2 ha?1). This value was 1.4% and 19.4% lower compared with that in the 5 and 8 mm d?1 plots, respectively. The joint application of CI and controlled drainage may be an effective mitigation strategy for reducing the carbon dioxide equivalents of CH4 and N2O emissions from paddy fields.  相似文献   

11.
Recently, large areas of tropical peatland have been converted into agricultural fields. To be used for agricultural activities, peat soils need to be drained, limed and fertilized due to excess water, low nutrient content and high acidity. Water depth and amelioration have significant effects on greenhouse gas (GHG) production. Twenty-seven soil samples were collected from Jabiren, Central Kalimantan, Indonesia, in 2014 to examine the effect of water depth and amelioration on GHG emissions. Soil columns were formed in the peatland using polyvinyl chloride (PVC) pipe with a diameter of 21 cm and a length of 100 cm. The PVC pipe was inserted vertically into the soil to a depth of 100 cm and carefully pulled up with the soil inside after sealing the bottom. The treatments consisting of three static water depths (15, 35 and 55 cm from the soil surface) and three ameliorants (without ameliorant/control, biochar+compost and steel slag+compost) were arranged using a randomized block design with two factors and three replications. Fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from the soil columns were measured weekly. There was a linear relationship between water depth and CO2 emissions. No significant difference was observed in the CH4 emissions in response to water depth and amelioration. The ameliorations influenced the CO2 and N2O emissions from the peat soil. The application of biochar+compost enhanced the CO2 and N2O emissions but reduced the CH4 emission. Moreover, the application of steel slag+compost increased the emissions of all three gases. The highest CO2 and N2O emissions occurred in response to the biochar+compost treatment followed by the steel slag-compost treatment and without ameliorant. Soil pH, redox potential (Eh) and temperature influenced the CO2, CH4 and N2O fluxes. Experiments for monitoring water depth and amelioration should be developed using peat soil as well as peat soil–crop systems.  相似文献   

12.
Understanding the greenhouse gas(GHG)emission from rice paddy fields is essential to come up with appropriate countermeasure in response to global warming.However,GHG emissions from paddy fields in South Korea are not well characterized.The objectives of this study were to estimate the carbon dioxide(CO2)and methane(CH4)emissions from rice paddy fields in South Korea,under the Representative Concentration Pathway 8.5(RCP-8.5)climate change scenario using the DNDC(i.e.,DeNitrification-DeComposition)model at 1-km2resolution.The performance of the model was verified with field data collected using a closed chamber,which supports the application of the model to South Korea.Both the model predictions and field measurements showed that most(>95%)GHG emissions occur in the cropping period,between April and October.As a baseline(assuming no climate change),the national sums of the CO2and CH4emissions for the 2020 s and 2090 s were estimated to be 5.8×106and 6.0×106t CO2-equivalents(CO2-eq)year-1for CO2and 6.4×106and 6.6×106t CO2-eq year-1for CH4,respectively,indicating no significant changes over 80 years.Under RCP-8.5,in the 2090 s,CH4emissions were predicted to increase by 10.7×106and 14.9×106t CO2-eq year-1,for a 10-or 30-cm tillage depth,respectively.However,the CO2emissions gradually decreased with rising temperatures,due to reduced root respiration.Deep tillage increased the emissions of both GHGs,with a more pronounced effect for CH4than CO2.Intermittent drainage in the middle of the cropping season can attenuate the CH4emissions from paddy fields.The findings of this work will aid in developing nationwide policies on agricultural land management in the face of climate change.  相似文献   

13.
Combination of a pre-season wet soil condition and rice straw incorporation just before transplanting, which is typical for a tropical rice double cropping, can induce a flash of methane (CH4) emission shortly after the transplanting. The conventional practice of alternate wetting and drying (AWD) irrigation technique that typically starts at 21 days after transplanting (DAT) can hardly reduce this emission because the soil become methanogenic before the onset of AWD treatment. Field experiments were conducted in Central Luzon, Philippines, during the 2014–2017 dry rice seasons to examine the effects of the timing of rice straw/stubble incorporation on the efficacy of AWD in reducing the CH4 emission. Two treatments of the timing of stubble incorporation were stubbles incorporated during the start of wet land preparation (S1) and stubbles incorporated during the dry fallow tillage (S2). For the water management, we compared two treatments: continuous flooding (CF) and AWD with – 15 cm threshold for irrigation. The AWD under S2 was implemented earlier at 10 DAT. We observed a significant interaction (p < 0.01) between effects of AWD and straw management on CH4 emissions; the seasonal total CH4 emission was reduced by AWD compared with CF by 73% under S2, while the reduction was <20% under S1. The AWD significantly (p < 0.05) increased the nitrous oxide (N2O) emissions by 47 and 48% relative to CF under S1 and S2, respectively. The global warming potential (GWP, CH4 + N2O) and yield-scaled GWP were still substantially lower by 62 and 59%, respectively, in AWD than in CF under S2, but the reduction was not realized under S1 due to the relatively smaller CH4 reduction and increased N2O emission. The results confirm that pre-season aerobic stubble decomposition and earlier implementation of AWD enhanced AWD’s mitigation potential in reducing substantially the CH4 emission from the tropical rice double-cropping system.  相似文献   

14.
Elevated CO2(eCO2) and rice cultivars can strongly alter CH4 and N2 O emissions from paddy fields.However,detailed information on how their interaction affects greenhouse gas fluxes in the field is still lacking.In this study,we investigated CH4 and N2 O emissions and rice growth under two contrasting rice cultivars(the strongly and weakly responsive cultivars) in response to eCO2,200 μmol mol-1 higher than the ambient ...  相似文献   

15.
Adding easily decomposable organic materials into flooded nitrate-rich soils can effectively decrease the soil nitrate concentration and repair nitrate-rich soil. However, nitrate reduction is usually accompanied with an increase in N2O emission. This study was conducted to reduce N2O emission in a nitrate-rich vegetable soil flooded for remediation and amended with biochar. Nitrate-rich vegetable soil was placed in five treatment groups: flooding (F); flooding with rice straw (F?+?RS); flooding with rice straw and 1% biochar (F?+?RS?+?1% biochar); flooding with rice straw and 3% biochar (F?+?RS?+?3% biochar); flooding with rice straw and CaO (F?+?RS?+?CaO). Biochar and CaO reduced the N2O emission levels relative to the F?+?RS group, with the former being more effective than the latter, achieving reduction of 40.70% (3% biochar) and 17.35% (CaO) of cumulative N2O emission. The 3% biochar was more effective than the 1% biochar. Regression analysis showed a positive correlation between the abundance of NO reductase gene (norB) and soil N2O emission flux. In general, biochar and CaO could effectively reduce N2O emissions from a nitrate-rich vegetable soil during flooding remediation, duo to elevating soil pH and altering denitrifying activity. The norB gene was the most important denitrifying gene driving soil N2O emission in the remediation.  相似文献   

16.
Drainage of peatlands affects the fluxes of greenhouse gases (GHGs). Organic soils used for agriculture contribute a large proportion of anthropogenic GHG emissions, and on-farm mitigation options are important. This field study investigated whether choice of a cropping system can be used to mitigate emissions of N2O and influence CH4 fluxes from cultivated organic and carbon-rich soils during the growing season. Ten different sites in southern Sweden representing peat soils, peaty marl and gyttja clay, with a range of different soil properties, were used for on-site measurements of N2O and CH4 fluxes. The fluxes during the growing season from soils under two different crops grown in the same field and same environmental conditions were monitored. Crop intensities varied from grasslands to intensive potato cultivation. The results showed no difference in median seasonal N2O emissions between the two crops compared. Median seasonal emissions ranged from 0 to 919?µg?N2O?m?2?h?1, with peaks on individual sampling occasions of up to 3317?µg?N2O?m?2?h?1. Nitrous oxide emissions differed widely between sites, indicating that soil properties are a regulating factor. However, pH was the only soil factor that correlated with N2O emissions (negative exponential correlation). The type of crop grown on the soil did not influence CH4 fluxes. Median seasonal CH4 flux from the different sites ranged from uptake of 36?µg CH4?m?2?h?1 to release of 4.5?µg?CH4?m?2?h?1. From our results, it was concluded that farmers cannot mitigate N2O emissions during the growing season or influence CH4 fluxes by changing the cropping system in the field.  相似文献   

17.
Elevated CO2 stimulates N2O emissions in permanent grassland   总被引：1，自引：1，他引：0  
To evaluate climate forcing under increasing atmospheric CO2 concentrations, feedback effects on greenhouse gases such as nitrous oxide (N2O) with a high global warming potential should be taken into account. This requires long-term N2O flux measurements because responses to elevated CO2 may vary throughout annual courses. Here, we present an almost 9 year long continuous N2O flux data set from a free air carbon dioxide enrichment (FACE) study on an old, N-limited temperate grassland. Prior to the FACE start, N2O emissions were not different between plots that were later under ambient (A) and elevated (E) CO2 treatments, respectively. However, over the entire experimental period (May 1998–December 2006), N2O emissions more than doubled under elevated CO2 (0.90 vs. 2.07 kg N2O-N ha−1 y−1 under A and E, respectively). The strongest stimulation occurred during vegetative growth periods in the summer when soil mineral N concentrations were low. This was surprising because based on literature we had expected the highest stimulation of N2O emissions due to elevated CO2 when mineral N concentrations were above background values (e.g. shortly after N application in spring). N2O emissions under elevated CO2 were moderately stimulated during late autumn–winter, including freeze–thaw cycles which occurred in the 8th winter of the experiment. Averaged over the entire experiment, the additional N2O emissions caused by elevated CO2 equaled 4738 kg CO2-equivalents ha−1, corresponding to more than half a ton (546 kg) of CO2 ha−1 which has to be sequestered annually to balance the CO2-induced N2O emissions. Without a concomitant increase in C sequestration under rising atmospheric CO2 concentrations, temperate grasslands may be converted into greenhouse gas sources by a positive feedback on N2O emissions. Our results underline the need to include continuous N2O flux measurements in ecosystem-scale CO2 enrichment experiments.  相似文献   

18.
To evaluate the impacts of organic cropping system on global warming potentials (GWPs), field measurements of CH4 and N2O were taken in conventional and organic rice (Oryza sativa L.) cropping systems in southeast China. Rice paddies were under various water regimes, including continuous flooding (F), flooding–midseason drainage–reflooding (F-D-F), and flooding–midseason drainage–reflooding and moisture but without waterlogging (F-D-F-M). Nitrogen was applied at the rate of 100 kg N ha?1, as urea-N or pelletized, dehydrated manure product in conventional or organic rice paddies, respectively. Seasonal fluxes of CH4 averaged 4.44, 2.14, and 1.75 mg m?2 h?1 for the organic paddy plots under the water regimes of F, F-D-F and F-D-F-M, respectively. Relative to conventional rice paddies, organic cropping systems increased seasonal CH4 emissions by 20%, 23%, and 35% for the plots under the water regimes of F, F-D-F, and F-D-F-M, respectively. Under the water regimes of F-D-F and F-D-F-M, seasonal N2O-N emissions averaged 10.85 and 13.66 μg m?2 h?1 in organic rice paddies, respectively, which were significantly lower than those in conventional rice paddies. The net global warming potentials (GWPs) of CH4 and N2O emissions from organic rice paddies relative to conventional rice paddies were significantly higher or comparable under various water regimes. The greenhouse gas intensities were greater, while carbon efficiency ratios were lower in organic relative to conventional rice paddies. The results of this study suggest that organic cropping system might not be an effective option for mitigating the combined climatic impacts from CH4 and N2O in paddy rice production.  相似文献   

19.
The incorporation of straw with a microbial inoculant (a mixture of bacteria and fungi, designed to accelerate straw decomposition) is being increasingly adopted within the agricultural sector in China. However, its effects on N and C trace gas emissions remain unclear. We conducted a field experiment to investigate the effects of different straw incorporation methods (with and without microbial inoculant) in the wheat season on nitrous oxide (N2O) and methane (CH4) emissions from a wheat-rice rotation system in China. The treatments comprised N, P, and K fertilizers only (NPK), NPK plus rice straw (NPKS), NPKS plus Ruilaite microbial inoculant (NPKSR), and NPKS plus Jinkuizi microbial inoculant (NPKSJ). Rice straw incorporation before wheat sowing significantly decreased N2O emissions during the wheat season and stimulated N2O and CH4 emissions during the subsequent rice season. Compared with the NPKS treatment, the NPKSR and NPKSJ treatments decreased N2O emissions during the wheat season, but had no effect on N2O or CH4 emissions during the subsequent rice season. Annually, the two treatments were comparable regarding N2O emissions. Although the global warming potentials of the NPKSR and NPKSJ treatments were lower than that of the NPKS treatment during the wheat season, no significant differences were observed during the subsequent rice season, or over the entire rotation cycle. The annual greenhouse gas intensity was slightly lower in the NPKSR and NPKSJ treatments than in the NPKS treatment. Overall, these results suggest that the incorporation of rice straw with a microbial inoculant in the wheat season was the best strategy tested for managing straw resources within the wheat-rice rotation system.  相似文献   

20.
Agricultural fields, including rice (Oryza sativa L.) paddy fields, constitute one of the major sources of atmospheric methane (CH4) and nitrous oxide (N2O). Organic matter application, such as straw and organic fertilizer, enhances CH4 emission from paddy fields. In addition, rice straw management after harvest regulates CH4 emissions in the growing season. The interaction of tillage times and organic fertilizer application on CH4 and N2O emissions is largely unknown. Therefore, we studied the effects of fallow-season tillage times and fertilizer types on CH4 and N2O emissions in paddy fields in Ehime, southwestern Japan. From November 2011 to October 2013, four treatments, two (autumn and spring) or one (spring) in the first year, or two (autumn and spring) or three (autumn, winter, and spring) in the second year times of tillage with chemical or organic fertilizer application, were established. Gas fluxes were measured by the closed-chamber method. Increasing the number of tillage times from one to two decreased succeeding CH4 emission and the emission factor for CH4 (EFCH4) in the rice-growing season, suggesting that the substrate for CH4 production was reduced by autumn and spring tillage in the fallow season. Higher EFCH4 [1.8–2.0 kg carbon (C) ha?1 d?1] was observed when more straw was applied (6.9–7.2 Mg ha?1) in the second year. Organic fertilizer application induced higher CH4 emission just after the application as basal and supplemental fertilizers, especially at a lower straw application rate. This indicated that EFCH4 in the organically managed fields should be determined individually. Organic fertilizer application with two tillage times induced N2O efflux during the rice-growing season in the second year, but N2O emissions were not affected by winter tillage. Although paddy fields can act as an N2O sink because of reduced soil conditions when straw application was high, application of organic C and nitrogen as fertilizer can enhance N2O production by the denitrification process during the growing season, especially in the ripening stage when soil anaerobic conditions became moderate. These results suggest that negative emission factors for N2O (EFN2O) can be applied, and EFN2O of organic fertilizer should be considered during the estimation of N2O emission in the paddy field.  相似文献   

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