Fraunhofer-Institut für Atmosphärische Umweltforschung IFU

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  • Publication
    Using a crop/soil simulation model and GIS techniques to assess methane emissions from rice fields in Asia. II. Model validation and sensitivity analysis
    ( 2000)
    Matthews, R.B.
    ;
    Wassmann, R.
    ;
    Buendia, L.V.
    ;
    Knox, J.W.
    The MERES (Methane Emissions from Rice EcoSystems) simulation model was tested using experimental data from IRRI and Maligaya in the Philippines and from Hangzhou in China. There was good agreement between simulated and observed values of total aboveground biomass, root weight, grain yield, and seasonal methane (CH sub 4) emissions. The importance of the contribution of the rice crop to CH sub 4 emissions was highlighted. Rhizodeposition (root exudation and root death) was predicted to contribute about 380 kg C ha high -1 of methanogenic substrate over the season, representing 37 % of the total methanogenic substrate from all sources when no organic amendments were added. A further 225 kg C ha high -1 (22 %) was predicted to come from previous crop residues, giving a total of around 60 % originating from the rice crop, with the remaining 41 % coming from the humic fraction of the soil organic matter (SOM). Sensitivity analysis suggested that the parameter representing transmissivity to gaseous transfer per unit root length (? sub r) was important in determining seasonal CH sub 4 emissions. As this transmissivity increased, more O sub 2 was able to diffuse to the rhizosphere, so that CH sub 4 production by methanogens was reduced and more CH sub 4 was oxidized by methanotrophs. These effects outweighed the opposing influence of increased rate of transport of CH sub 4 through the plant, so that the overall effect was to reduce the amount of CH sub 4 emitted over the season. Varying the root-shoot ratio of the crop was predicted to have little effect on seasonal emissions, the increased rates of rhizodeposition being counteracted by the increased rates of O sub 2 diffusion to the rhizosphere. Increasing the length of a midseason drainage period reduced CH sub 4 emissions significantly, but periods longer than 6 - 7 d also decreased rice yields. Organic amendments with low C/N were predicted to be more beneficial, both in terms of enhancing crop yields and reducing CH sub 4 emissions, even when the same amount of C was applied. This was due to higher rates of immobilization of C into microbial biomass, removing it temporarily as a methanogenic substrate.
  • Publication
    Methane emission from rice fields at Cuttack, India
    ( 2000)
    Adhya, T.K.
    ;
    Bharati, K.
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    Mohanty, S.R.
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    Ramakrishnan, B.
    ;
    Rao, V.R.
    ;
    Sethunathan, N.
    ;
    Wassmann, R.
    Methane (CH4) emission from rice fields at Cuttack (State of Orissa, eastern India) has been recorded using an automatic measurement system (closed chamber method) from 1995-1998. Experiments were laid out to test the impact of water regime, organic amendment, inorganic amendment and rice cultivars. Organic amendments in conjunction with chemical N (urea) effected higher CH4 flux over that of chemical N alone. Application of Sesbania, Azolla and compost resulted in 132, 65 and 68 kg Ch4 ha-1 in the wet season of 1996 when pure urea application resulted in 42 kg Ch4 ha-1. Intermittent irrigation reduced emissions by 15 % as compared to continuous flooding in the dry season of 1996. In the wet season of 1995, four cultivars were tested under rainfed conditions resulting in a range of emissions from 20 to 44 kg Ch4 ha-1. Application of nitrification inhibitor dicyandiamide (DCD) inhibited while Nimin stimulated Ch4 flux from flooded rice compared to that of urea N alone. Wide variation in CH4 production and oxidation potentials was observed in rice soils tested. Methane oxidation decreased with soil depth, fertilizer-N and nitrification inhibitors while organic amendment stimulated it. The results indicate that CH4 emission form the representative rainfed ecosystem at the experimental site averaged to 32 kg Ch4 ha-1 yr-1.
  • Publication
    Simultaneous records of methane and nitrous oxide emissions in rice-based cropping systems under rainfed conditions
    ( 2000)
    Abao, E.B.
    ;
    Bronson, K.F.
    ;
    Wassmann, R.
    ;
    Singh, U.
    Rainfed rice (Oryza sativa L.)-based cropping systems are characterized by alternate wetting and drying cycles as monsoonal rains come and go. The potential for accumulation and denitrification of NO3? is high in these systems as is the production and emission of CH4 during the monsoon rice season. Simultaneous measurements of CH4 and N2O emissions using automated closed chamber methods have been reported in irrigated rice fields but not in rainfed rice systems. In this field study at the International Rice Research Institute, Philippines, simultaneous and continuous measurements of CH4 and N2O fluxes were observed, with the highest emissions being in organic residue-amended plots. Nitrous oxide fluxes, on the other hand, were generally nonexistent, except after fertilization events where low N2O fluxes were observed. Slow-release N fertilizer further reduced the already low N2O emissions compared with prilled urea in the first rice season. During the dry seasons, when the field was planted to the upland crops cowpea [Vigna unguiculata (L.) Walp] and wheat (Triticum aestivum L.), positive CH4 fluxes were low and insignificant except after the imposition of a permanent flood where high CH4 fluxes appeared. Evidences of CH4 uptake were apparent in the first dry season, especially in cowpea plots, indicating that rainfed lowland rice soils can act as sink for CH4 during the upland crop cycle. Large N2O fluxes were observed shortly after rainfall events due to denitrification of accumulated NO3?. Cumulative CH4 and N2O fluxes observed during this study in rainfed conditions were lower compared with previous studies on irrigated rice fields.
  • Publication
    Simulation of methane production in anaerobic rice soils by a simple two-pool model
    ( 2000)
    Lu, Y.
    ;
    Arah, J.R.M.
    ;
    Wassmann, R.
    ;
    Neue, H.U.
    Methane (CH sub 4) is produced in flooded rice fields by anaerobic decomposition of applied organic residues, rootderived materials and native soil organic matter (SOM). Since CH sub 4 is an important greenhouse gas it is important to understand, and to be able to model, the processes which produce it. Anoxic incubation of soils employed in the cultivation of irrigated rice, with and without the addition of various potentially-available organic substrates, provides information on potential CH sub 4 emissions which can be incorporated into process-based models. In this study, a simple two-pool model is employed to simulate the CH sub 4 production of a number of anaerobically-incubated rice soils, and their responses to amendment with a variety of organic substrates. The model differs from most accounts of SOM transformation in that kinetics are microbially-mediated rather than first-order. Simulation yields a reproduction of the general trends of CH sub 4 production in response to amendments of acetate, glucose and lice straw.
  • Publication
    Methane transport capacity of rice plants. I. Influence of methane concentration and growth stage analyzed with an automated measuring system
    ( 2000)
    Aulakh, M.S.
    ;
    Bodenbender, J.
    ;
    Wassmann, R.
    ;
    Rennenberg, H.
    A major portion (60 - 90 %) of the methane (CH4) emitted from rice fields to the atmosphere is transported through the aerenchyma of the rice plants. However, a rapid and accurate method to study the CH4 transport capacity (MTC) of rice plants is not available. We developed a gas sampling and analytical device based on a closed two-compartment chamber technique and analyzed the enrichment of the CH4 mixing ratio inside the shoot compartment of cylindrical cuvettes enclosing individual rice plants under ambient conditions. The computer-controlled analytical system consists of a gas chromatograph (GC) and a pressure-controlled autosampler for eight cuvettes (seven for plants and one for CH4-calibration gas). The system automates closure and opening of plant cuvettes using pneumatic pressure, air sample collection and injection into the GC, and CH4 analysis. It minimises sources of error during air sampling by continuously mixing headspace air of each cuvette, maintaining pressure and composition of the headspace inside the cuvettes, purging the dead volumes between the sampler induction tube and GC, and running a reference CH4-calibration gas sample in each cycle. Tests showed that the automated system is a useful tool for accurate sampling of headspace air of cylindrical cuvettes enclosing individual rice plants and enables rapid and accurate fully automated analysis of CH4 in the headspace air samples. A linear relationship was obtained between CH4 transported by rice plants of tow cultivars (IR72, a high-yielding dwarf, and Dular, a traditional tall cultivar) and concentration of CH4 up to 7,500 ppm used for purging the nutrient culture solution surrounding the roots in the root compartment of the chamber. Further increase in CH4 emission by shoots was not observed at 10,000 ppm CH4 concentration in the root compartment of the chamber. The MTC of IR72 was measured at six development stages; it was lowest at seedling stage, increasing gradually until panicle initiation. There was no further change at flowering, but a marked decrease at maturity was noted. These results suggest that the plants have 45 - 246 % greater potential to transport CH4 than the highest Ch4 emission rated reported under field conditions, and plants would not emit CH4 at early growth and at a reduced rate close to ripening.
  • Publication
    Characterization of methane emissions from rice fields in Asia. II. Differences among irrigated, rainfed, and deepwater rice
    ( 2000)
    Wassmann, R.
    ;
    Neue, H.U.
    ;
    Lantin, R.S.
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    Makarim, K.
    ;
    Chareonsilp, N.
    ;
    Buendia, L.V.
    ;
    Rennenberg, H.
    Methane (CH sub4) emission rates were recorded automatically using the closed chamber technique in major rice-growing areas of Southeast Asia. The three experimental sites covered different ecosystems of wetland rice -irrigated, rainfed, and deepwater rice - using only mineral fertilizers (for this comparison). In Jakenan (Indonesia), the local water regime in rainfed rice encompassed a gradual increase (wet season) and a gradual decrease (dry season) in floodwater levels. Emissions rates accumulated to 52 and 91 kg CH sub 4 ha high -1 season high -1 corresponding to approximately 40 % of emissions from irrigated rice in each season. Distinct drainage periods within the season can drastically reduce Ch sub 4 emissions to less than 30 kg CH sub 4 ha high -1 season high -1 as shown in Los Banos (Philippines). The reduction effect of this water regime as compared with irrigated rice varied from 20 % to 80 % from season to season. Methane fluxes from deepwater rice in Prachinburi (Thailand) were lower than from irrigated rice but accumulated to equally high seasonal values, i. e., about 99 kg CH sub 4 ha high -1 season high -1, due to longer seasons and assured periods of flooding. Rice ecosystems with continuous flooding were characterized by anaerobic conditions in the soil. These conditions commonly found in irrigated and deepwater rice favored CH sub 4 emissions. Temporary aeration of flooded rice soils. which is generic in rainfed rice, reduced emission rates due to low CH sub 4 production and high CH sub 4 oxidation. Based on these findings and the global distribution of rice area, irrigated rice accounts globally for 70 - 80 % of CH sub 4 from the global rice area. Rainfed rice (about 15 %) and deepwater rice (about 10 %) have much lower shares. In turn, irrigated rice represents the most promising target for mitigation strategies. Proper water management could reduce CH sub 4 emission without affecting yields.
  • Publication
    Dynamics of dissolved organic carbon and methane emissions in a flooded rice soil
    ( 2000)
    Lu, Y.H.
    ;
    Wassmann, R.
    ;
    Neue, H.U.
    ;
    Huang, C.Y.
  • Publication
    Methane emissions from irrigated rice fields in northern India (New Delhi)
    ( 2000)
    Jain, M.C.
    ;
    Kumar, S.
    ;
    Wassmann, R.
    ;
    Mitra, S.
    ;
    Singh, S.D.
    ;
    Singh, J.P.
    ;
    Singh, R.
    ;
    Yadav, T.
    ;
    Gupta, S.
    Methane (CH4) emission fluxes from rice fields as affected by water regime, organic amendment, and rice cultivar were measured at the Indian Agricultural Research Institute, New Delhi, using manual and automatic sampling techniques of the closed chamber method. Measurements were conducted during four consecutive cropping seasons (July to October) from 1994 to 1997. Emission rates were very low (between 16 and 40 kg CH4 m high -1 season high -1) when the field was flooded permanently. These low emissions were indirectly caused by the high percolation rates of the soil; frequent water replenishment resulted in constant inflow of oxygen in the soil. The local practice of intermittent flooding, which encompasses short periods without standing water in the field, further reduced emission rates. Over the course of four seasons, the total CH4 emission from intermittently irrigated fields was found to be 22 % lower as compared with continuous flooding. The CH4 flux was invariably affected by rice cultivar. The experiments conducted during 1995 with one cultivar developed by IRRI (IR72) and two local cultivars (Pusa 169 and Pusa Basmati) showed that the average CH4 flux from the intermittently irrigated plots without any organic amendment ranged between 10.2 and 14.2 mg m high -2 d high -1. The impact of organic manure was tested in 1996 and 1997 with varieties IR72 and Pusa 169. Application of organic manure (FYM + wheat straw) in combination with urea (1 : 1 N basis) enhanced CH4 emission by 12 - 20 % as compared with fields treated with urea only. The site in New Delhi represents one example of very low CH4 emissions from rice fields. Emissions from other sites in northern India may be higher than those in New Delhi, but they are still lower than in other ricegrowing regions in India. The practice of intermittent irrigation-in combination with low organic inputs-is commonly found in northern India and will virtually impede further mitigation of CH4 emissions in significant quantities. In turn, the results of this study may provide clues to reduce emissions in other parts of India with higher baseline emissions.
  • Publication
    Using a crop/soil simulation model and GIS techniques to assess methane emissions from rice fields in Asia. IV. Upscaling to national levels
    ( 2000)
    Matthews, R.B.
    ;
    Wassmann, R.
    ;
    Knox, J.W.
    ;
    Buendia, L.V.
    The process-based crop/soil model MERES (Methane Emissions from Rice EcoSystems) was used together with daily weather data, spatial soil data, and rice-growing statistics to estimate the annual methane (CH sub 4) emissions from China, India, Indonesia, Philippines, and Thailand under various crop management scenarios. Four crop management scenarios were considered: (a) a 'baseline' scenario assuming no addition of organic amendments or field drainage during the growing season, (b) addition of 3,000 kg DM ha high -1 of green manure at the start of the season but no field drainage, (c) no organic amendments but drainage of the field for a 14-d period in the middle of the season and again at the end of the season, and (d) addition of 3,000 kg DM ha high -1 of green manure and field drainage in the middle and end of the season. For each scenario, simulations were made at each location for irrigated and rainfed rice ecosystems in the main rice-growing season, and for irrigated rice in the second (or 'dry') season. Overall annual emissions (Tg CH sub 4 yr high -1) for a province/district were calculated by multiplying the rates of CH sub 4 emission (kg CH sub 4 ha high -1 yr high -1) by the area of rice grown in each ecosystem and in each season obtained from the Huke and Huke (1997) database of rice production. Using the baseline scenario, annual CH sub 4 emissions for China, India, Indonesia, Philippines, and Thailand were calculated to be 3.73, 2.14, 1.65, 0.14, and 0.18 Tg CH sub 4 yr high -1, respectively. Addition of 3,000 kg DM ha high -1 green manure at the start of the season increased emissions by an average of 128 % across the five countries, with a range of 74 - 259 %. Drainage of the field in the middle and at the end of the season reduced emissions by an average of 13 % across the five countries, with a range of -10 % to -39 %. The combination of organic amendments and field drainage resulted in an increase in emissions by an average of 86 % across the five countries, with a range of 15 - 176 %. The sum of CH sub 4 emissions from these five countries, comprising about 70 % of the global rice area, ranged from 6.49 to 17.42 Tg CH sub 4 yr high -1, depending on the crop management scenario.
  • Publication
    Using a crop/soil simulation model and GIS techniques to assess methane emissions from rice fields in Asia. III. Databases
    ( 2000)
    Knox, J.W.
    ;
    Matthews, R.B.
    ;
    Wassmann, R.
    As part of a series of papers describing the use of a simulation model to extrapolate experimental measurements of methane (CH4) emissions from rice fields in Asia and to evaluate the large-scale effect of various mitigation strategies, the collation and derivation of the spatial databases used are described. Daily weather data, including solar radiation, minimum and maximum temperatures, and rainfall were collated from 46 weather stations from the five countries in the study, namely China, India, Indonesia, Philippines, and Thailand. Quantitative soil data relevant to the input requirements of the model were derived by combining data from the World Inventory of Soil Emissions (WISE) database, the ISIS database, and the FAO Digital Soil Map of the World (FAO-DSMW). These data included soil pH; organic carbon content; sand, silt, and clay fractions; and iron content for top and subsoil layers, and average values of bulk density and available water capacity for the whole profile. Data on the areas allocated to irrigated, rainfed, upland, and deepwater rice at the province or district level were derived from the Huke & Huke (1997) database developed at IRRI. Using a geographical information system (GIS), a series of georeferenced data sets on climate, soils, and land use were derived for each country, at the province or district level. A summary of the soil-related derived databases is presented and their application for use in global change modeling discussed.