A decrease in Eh in a subtropical swamp was accompanied by a reduction in soil N 2 O concentrations that could directly reduce the emissions of N 2 O to the atmosphere[ 74 ]. Previous studies have also reported higher emissions of N 2 O during the day than at night as a result of higher dissolved O 2 concentrations, which indirectly supported the findings of a positive correlation between soil Eh and N 2 O emission[ 43 , 44 ].
This study provides results indicating that both models of CH 4 emissions and management strategies to reduce CH 4 emissions should take into account the trade-off between N 2 O and CH 4 emissions.
For instance, some previous studies claim that the use of sulphate N-fertilization reduced CH 4 emissions[ 11 ], however, as commented this could increase N 2 O emissions.
The limited number of available observations of CH 4 N 2 O emissions in relation to environmental variables under field conditions have constrained the parameterization and validation of process-based biogeochemistry models [ 15 , 16 ]; this study can thus contribute to improve models of CH 4 and N 2 O emissions. Moreover, the results of this study indicate the interest of management strategies that can reduce methane emission by decreasing the production or transportation or increasing the oxidation.
Methanogenesis and plant-related CH 4 transport are the two main processes governing the overall CH 4 emission from paddy fields. The reduction of CH 4 production in soil is thus critical for any attempt to mitigate CH 4 emissions from paddy fields. The sulfate concentrations were negatively correlated with CH 4 emissions, so the amendment with sulfate fertilizers may be a viable option to reduce CH 4 emission from the soil.
Acid and sulfate deposition by rainwater are increasing in this part of China, so CH 4 production and emissions would likely be suppressed to some extent due to an increase in sulfate availability. Our results, however, suggest that the use of sulfate fertilizer may increase N 2 O emissions from paddy fields. The stepwise regression analysis showed that plant-related parameters, such as stem and leaf biomasses, were the most important factors controlling CH 4 and N 2 O emissions with significant, positive correlations.
Rice cultivars with low biomasses should thus be selected for reducing the plant-mediated transport of CH 4 and N 2 O through the aerenchymatous tissue. CH 4 emission was positively correlated with DOC concentration, so our results suggest that the addition of carbon substrates such as straw could be an option for mitigating the GHG emissions from paddy fields.
All the data used in this study is available in the submitted supplementary information. National Center for Biotechnology Information , U. PLoS One. Published online Jan Chun Wang , 1, 2 Derrick Y. Derrick Y. Spain Find articles by Jordi Sardans. Dafeng Hui, Editor. Author information Article notes Copyright and License information Disclaimer. Competing Interests: he authors have declared that no competing interests exist. Received Jul 27; Accepted Dec This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
This article has been cited by other articles in PMC. Abstract Paddy fields are major sources of global atmospheric greenhouse gases, including methane CH 4 and nitrous oxide N 2 O. Introduction Climate change is a major environmental problem of the 21 st century caused mainly by increasing emissions of anthropogenic greenhouse gases GHGs.
Open in a separate window. Fig 1. Measurement in situ of rates of CH 4 production and oxidation The rates of CH 4 production and oxidation were measured once every two weeks using acetylene C 2 H 2 inhibition, which has been successfully used in both laboratory incubations and field-based studies [ 26 — 29 ].
Measurement in situ of CH 4 transport in the paddy field The CH 4 transport pathways were measured once every two weeks following the method of Wang and Shangguan[ 32 ]. Sampling of porewater and soil samples Porewater was sampled in situ once every two weeks from April to July Measurement in situ of porewater and soil properties Before analysis, the vials were first thawed at room temperature and were then vigorously shaken for 5 min to equilibrate the CH 4 concentrations between the porewater and the headspace.
Statistical analysis The data were checked for normality and homogeneity of variance, and if necessary, were log-transformed. Fig 2. Fig 3. Changes in soil, porewater, weather, and plant parameters during the experimental period Ambient air temperature increased steadily over the period of rice growth from Fig 4. Fig 5. Fig 6. Fig 7. Relationships of CH 4 production, oxidation, and transport with emissions The rate of CH 4 production was low early in the season Fig 8 but had become significantly higher by 71 DAT.
Fig 8. Table 1 Pearson correlation coefficients between CH 4 emission, production, oxidation, and transport and the concentration of dissolved CH 4.
Table 2 Pearson correlation coefficients between CH 4 metabolism, N 2 O emission, and various environmental factors. Table 3 Equations of stepwise regression analysis for CH 4 metabolism and N 2 O emission with environmental factors. Relationships of N 2 O emission with environmental variables Table 2 presents the Pearson correlation coefficients between N 2 O emissions and the environmental factors. Influence of environmental factors on CH 4 and N 2 O emission: clues for mitigation Both CH 4 production and emission in this subtropical paddy field were predominantly controlled by the soil concentrations of sulfate and DOC and the biomass of the rice plants.
Conclusions Methanogenesis and plant-related CH 4 transport are the two main processes governing the overall CH 4 emission from paddy fields. Supporting Information S1 Appendix Field data used in this study. DOC Click here for additional data file. Data Availability All the data used in this study is available in the submitted supplementary information. References 1. Eur J Agron 14 : — Science : — Agr Ecosyst Environ : 6— Plant Soil : — J Geophys Res 97 : — Soil Sci Soc Am J 75 : — Biogeochemistry 51 : 91— Le Mer J, Roger P Production, oxidation, emission and consumption of methane by soils: a review.
Eur J Soil Biol 37 : 25— Soil Biol Biochem 43 : — Global Change Biol 17 : — Biogeosciences 10 : — Global Change Biol 19 : — Biogeosciences 13 : — Lai DYF Methane dynamics in northern peatlands: a review. Pedosphere 19 : — Ro S, Seanjan P, Tulaphitak T Sulfate content influencing methane production and emission from incubated soil and rice-planted soil in Northeast Thailand.
Soil Sci Plant Nutr 57 : — Geomicrobiol J 24 : 65— J Environ Sci Heal A 45 : — Atmos Environ 3 : — J Environ Manage 88 : — Atmos Environ 66 : — Watanabe I, Takada G, Hashimoto T, Inubushi K Evaluation of alternative substrates for determining methane-oxidizing activities and methanotrophic populations in soils. Biol Fert Soils 20 : — Appl Environ Microb 64 : — Soil Biol Biochem 32 : — Nutr Cycl Agroecosyst 64 : 71— Atmos Environ 38 : — Biogeochemistry : — Springer-Verlag, Berlin, 69— Lu RK Analytical methods of soil agrochemistry.
Chemosphere 51 : — J Geophys Res D15 : — Atmos Environ 89 : — Lu Y, Watanabe A, Kimura M Contribution of plant-derived carbon to soil microbial biomass dynamics in a paddy rice microcosm. Biol Fert Soils 36 : — Biogeosciences 8 : — Paddy Water Environ 10 : — Agric Ecosyst Environ : 64— Estuar Coast 36 : — Soil Biol Biochem 39 : — J Environ Qual 40 : — Freshwater Biol 57 : — Boose U, Frenzel P Methane emissions from rice microcosms: the balance of production, accumulation and oxidation , Biogeochemistry 41 : — J Geophys Res G00A07 : 1—6.
Dise NB, Verry ES Suppression of peatland methane emission by cumulative sulfate deposition in simulated acid rain. Biogeochemistry 53 : — Which of the following country is the largest producer of wheat in the world?
Which of the following countries accounts for about two thirds of earning of its total export from rice trade? Which of the following is not an endospermic seed? Which of the following is not a cash crop? Which among the following countries is the largest producer of rice? Suggested Test Series. Suggested Exams. More Agriculture Officer Questions Q1. The age of the first calf of a hybrid heifer is. Considering the large CH 4 emission from paddy fields, it is important to understand the CH 4 chemistry, mechanisms of CH 4 production and emission.
Moreover, the reduction of CH 4 emission from rice paddy fields has become increasingly important. Therefore, the main objectives of this research are to discuss CH 4 cycling in the paddy soil and global warming, the basic understandings of methane chemistry, production, oxidation, transportation, calculation, the mechanisms of CH 4 exchange between rice paddy field and atmosphere, final emission and try to give some mitigation options of CH 4 emissions from paddy soils to slow down the global warming.
Global warming is a serious problem nowadays. CH 4 is one of the vital greenhouse gases that contribute to global warming. The main sources of anthropogenic CH 4 emissions are the oil and gas industries, agriculture, landfills, wastewater treatment, and emissions from coal mines.
Globally, about million tons of CH 4 converted in terms of carbon are emitted annually [ 17 ]. Rice fields are contributing to global warming, but it is a far bigger problem than previously thought. The conventional paddy field with continuous flooding irrigation is known as a major source of CH 4 emission [ 18 ].
It is expected that economic activities will become more active in the next future mainly in Asia. The paddy area in was 10,, ha in Thailand, 4,, ha in the Philippines, 7,, ha in Vietnam and 12,, ha in Indonesia [ 19 ]. So a hues amount of population needs more rice, more rice growing mean more CH 4 adding to the atmosphere.
During 1 kg of rice grain production, paddy field contributes g of CH 4 to the atmosphere. The default methane baseline emission factor is 1. Part of the CH 4 produced in the rice soil is consumed in the oxidized rhizosphere of rice roots or in the oxidized soil-floodwater interface.
Soil bacteria also can consume CH 4 [ 22 ]. CH 4 is also leached to ground water, as a small part dissolves in water and most of it escapes from the soil into the atmosphere see Figure 1. The important thing is most of the CH 4 is staying in the atmosphere for 10 years as it is or the increasing CH 4 abundance leads to a longer lifetime for CH 4 [ 23 ]. After a certain time later, the CH 4 is broken down into CO 2.
It is still not clear exactly how much of the CH 4 is finally converted to CO 2 and how much might remain as other intermediate carbon-containing compounds without a significant direct effect on the climate [ 25 ]. CH 4 also creates ground-level ozone in the atmosphere. And ozone is not only harmful to human health but also contributes to climate change. Global temperatures in and were warmer than at any other time in the modern temperature record after And carbon emissions are the central cause of that rise.
Rising temperatures and changes in rainfall have a significant effect on enhancing microbial activity and create ideal conditions for microbial CH 4 production of flooded rice fields. If it is actually going to happen, most of the agricultural plants cannot grow; it will make severe starvation for the world population.
On the other hand, sea level will rise. The consequences will be so devastating, most of the low lands will go underneath the water and it will increase homeless people all over the world. CH 4 is a very special kind of molecule. CH 4 is an end product of the organic carbon decomposition under anoxic conditions and the simplest organic compound and member of the paraffin series of hydrocarbons [ 27 ]. It is colorless, odorless gas that occurs abundantly in nature and as a product of anthropogenic activities.
Its chemical formula is CH 4 Figure 2. CH 4 is lighter than air, having a specific gravity of 0. It is slightly soluble gas in water and burns readily in air, forming carbon dioxide and water vapor; the flame is pale, luminous and very hot. Chemical formula of methane. The production of CH 4 is a microbiological process, which is predominantly controlled by the absence of oxygen and the amount of easily degradable actions [ 29 ].
Methanogens produce CH 4 under anaerobic conditions [ 30 , 31 ]. Methanogens are prokaryotic microorganisms and belong to the domain of archaea. They are living in an anaerobic environment e. Acetate and hydrogen are formed by fermentation from hydrolyzed organic matter [ 29 ].
However, flooding of rice fields cuts off oxygen supply from the atmosphere to the soil, which leads to anaerobic fermentation of organic matter in the soil, resulting in the production of CH 4 [ 33 ]. In flooded rice paddies, straw incorporation usually stimulates CH 4 production [ 34 ]. Root exudates and degrading roots are also important sources of CH 4 production, especially at the later growth stages of paddy. There are two major pathways of CH 4 production e. Acetoclastic methanogens use ATP to convert acetate to acetyl phosphate and then remove the phosphate ion via a reaction catalyzed by coenzyme A [ 12 ].
CH 4 is formed gradually by processes involving oxidized ferredoxin, tetrahydrosarcinapterin, coenzyme M, and coenzymes B. Taking account of all, CH 4 emissions from paddy soil are the net result of CH 4 production, oxidation and transportation. The total CH 4 emission process consists of three ways from soil to atmosphere e. CH 4 transports via the plant starts in the roots; CH 4 enters by diffusion through the epidermis and during the water uptake. It is likely that dissolved CH 4 is directly gasified in the root cortex and further diffuses upwards to the root-shoot transition zone traveling through intercellular spaces and aerenchyma.
The aerenchyma system is developed by the plant to transport the oxygen necessary for respiration from leaves towards the roots. Just like CH 4 diffuses from the soil into the root system, oxygen diffuses from the root into the soil, creating a relative oxygen-rich zone in the rhizosphere. CH 4 is partly oxidized in the rhizosphere to CO 2 by methanotrophic bacteria. Methanogenesis in the rhizosphere itself is suppressed by oxygen. The transport of CH 4 to the atmosphere depends on the properties of the rice plant.
The flux of gases in the aerenchyma depends on permeability coefficients, concentration gradients of roots and the internal structure of the aerenchyma. Temperature is one of the major determining factors on the biological process e.
Previous studies showed that increased soil temperature leads to an increase in CH 4 production [ 35 ]. There is a lot of qualitative evidence showing that CH 4 production from rice field increase with the increasing temperature [ 35 ]. The paddy soil temperature could control the amount of CH 4 production and there is a positive and strong correlation in both soil temperature and CH 4 production pattern [ 37 ]. Effects of temperature on CH 4 production in paddy soil shown in each figure.
Periods of soil sampling: A continuous flooding B intermittent irrigation C from harvest to winter [ 38 ]. Soil pH is another influential factor in CH 4 production. The pH effects on CH 4 production in a flooded rice soil. Methanogenic bacteria are acid sensitive. Generally, the optimum pH for methanogenesis is 7. Introducing the acidic materials frequently results in a decrease in CH 4 production [ 39 ]. A slight decrease in soil pH can cause decreases in CH 4 production. A slight increase in soil pH about 0.
These results suggested that a small reduction of soil pH could be obtained a decrease in CH 4 production in paddy soil. The decomposition of organic matter by methanogens under anaerobic condition leads to the production of CH 4.
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