Now showing 1 - 10 of 27
  • 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.
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    Matthews, R.B.
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    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.
  • Publication
    Using a crop/soil simulation model and GIS techniques to assess methane emissions from rice fields in Asia. I. Model development
    ( 2000)
    Matthews, R.B.
    ;
    Wassmann, R.
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    Arah, J.
    The development of the MERES (Methane Emissions in Rice EcoSystems) model for simulating methane (CH sub 4) emissions from rice fields is described. The CERES-Rice crop simulation model was used as a basis, employing the existing routines simulating soil organic matter (SOM) decomposition to predict the amount of substrate available for methanogenesis. This was linked to an existing submodel, described elsewhere in this volume (Arah & Kirk, 2000), which calculates steady-state fluxes and concentrations of CH sub 4 and O sub 2 in flooded soils. Extra routines were also incorporated to simulate the influence of the combined pool of alternative electron acceptors in the soil (i. e., NO sub 3 high -, Mn high 4+, Fe high 3+, SO sub 4 high 2-) on CH4 production. The rate of substrate supply is calculated in the SOM routines of the CERES-Rice model from (a) the rate of decomposition of soil organic material including that left from the previous crop and any additions of organic matter, (b) root exudates (modified from the original CERES-Rice model using recent laboratory data), and (c) the decomposition of dead roots from the current crop. A fraction of this rate of substrate supply, determined by the concentration of the oxidized form of the alternative electron acceptor pool, is converted to CO sub 2 by bacteria which outcompete the methanogenic bacteria, thereby suppressing CH sub 4 production. Any remaining fraction of the substrate supply rate is assumed to be potentially available for methanogenesis. The CH sub 4 dynamics submodel uses this potential methanogenesis rate, along with a description of the root length distribution in the soil profile supplied by the crop model, to calculate the steady-state concentrations and fluxes of O sub 2 and CH sub 4. The reduced form of the alternative electron acceptor pool is allowed to reoxidize when soil pores fill with air if the field is drained. The MERES model was able to explain well the seasonal patterns of CH sub 4 emissions in an experiment involving mid- and end-season drainage and additions of organic material at IRRI in the Philippines.
  • Publication
    Crop management affecting methane emissions from irrigated and rainfed rice in Central Java (Indonesia)
    ( 2000)
    Setyanto, P.
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    Makarim, A.K.
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    Fagi, A.M.
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    Wassmann, R.
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    Buendia, L.V.
    Methane (CH sub 4) emissions were determined from 1993 to 1998 using an automated closed chamber technique in irrigated and rainfed rice. In Jakenan (Central Java), the tow consecutive crops encompass a gradient from low to heavy rainfall (wet season crop) and from heavy to low rainfall (dry season crop), respectively. Rainfed rice was characterized by very low emission at the onset of the wet season and the end of the dry season. Persistent flooding in irrigated fields resulted in relatively high emission rates throughout the two seasons. Average emission in rainfed rice varied between 19 and 123 mg Ch sub 4 m high -2 d high -1, whereas average in irrigated rice ranged from 71 to 217 mg CH sub 4 m high -2 d high -1. the impact of organic manure was relatively small in rained rice. In the wet season, farmyard manure (FYM) was completely decomposed before CH sub 4 emission was initiated; rice straw resulted in 40 % increase in emission rates during this cropping season. In the dry season, intensive flooding in the early stage promoted high emissions from organically fertilized plots; seasonal emissions of FYM and rice straw increased by 72 % and 37 %, respectively, as compared with mineral fertilizer. Four different rice cultivars were tested in irrigated rice. Average emission rates differed from season to season, but the total emissions showed a consistent ranking in wet and dry season, depending on season length. The early-maturing Dodokan had the lowest emissions (101 and 52 kg CH sub 4 ha high -1) and the late-maturing Cisadane had the highest emissions (142 and 116 kg CH sub 4 ha high -1). The high-yielding varieties IR64 and Memberamo had moderately high emission rates. These findings provide important clues for developing specific mitigation strategies for irrigated and rainfed rice.
  • Publication
    Mechanisms of crop management impact on methane emissions from rice fields in Los Banos, Philippines
    ( 2000)
    Wassmann, R.
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    Buendia, L.V.
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    Lantin, R.S.
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    Bueno, C.S.
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    Lubigan, L.A.
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    Umali, A.
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    Nocon, N.N.
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    Javellana, A.M.
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    Neue, H.U.
    This article comprises 4 yr of field experiments on methane (CH sub 4) emissions from rice fields conducted at Los Banos, Philippines. The experimental layout allowed automated measurements of CH sub 4 emissions as affected by water regime, soil amendments (mineral and organic), and cultivars. In addition to emission records over 24 h, ebullition and dissolved CH sub 4 in soil solution were recorded in weekly intervals. Emission rates varied in a very wide range from 4 to 634 kg CH sub 4 ha high -1, depending on season and crop management. In the 1994 and 1996 experiments, field drying at midtellering reduced CH sub 4 emissions by 15 - 80 % as compared with continuous flooding, without a significant effect on grain yield. The net impact of midtellering drainage was diminished when (i) rainfall was strong during the drainage period and (ii) emissions were suppressed by very low levels of organic substrate in the soil Five cultivars were tested in the 1995 dry and wet season. The cultivar IR72 gave higher CH sub 4 emissions than the other cultivars including the new plant type (IR65597) with an enhanced yield potential. Incorporation of rice straw into the soil resulted in an early peak of CH sub 4 emission rates. About 66 % of the total seasonal emission from rice straw-treated plots was emitted during the vegetative stage. Methane fluxes generated from the application of straw were 34 times higher than those generated with the use of urea. Application of green manure (Sesbania rostrata) gave only threefold increase in emission as compared with urea-treated plots. Application of ammonium sulfate significantly reduced seasonal emission as compared with urea application. Correlation between emissions and combined dissolved CH sub 4 concentrations (from 0 to 20 cm) gave a significant R high2 of 0.95 (urea + rice straw), and 0.93 (urea + Sesbania), whereas correlation with dissolved CH sub 4 in the inorganically fertilized soils was inconsistent. A highly significant correlation (R high 2 is equal 0.93) existed between emission and ebullition from plots treated with rice straw. These findings may stimulate further development of diagnostic tools for easy and reliable determination of CH sub 4 emission potentials under different crop management practices.
  • Publication
    Methane emission from irrigated and intensively managed rice fields in Central Luzon (Philippines)
    ( 2000)
    Corton, T.M.
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    Bajita, J.B.
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    Grospe, F.S.
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    Pamplona, R.R.
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    Asis, C.A.
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    Wassmann, R.
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    Lantin, R.S.
    ;
    Buendia, L.V.
    Methane (CH4) emissions were measured with an automated system in Central Luzon, the major rice producing area of the Philippines. Emission records covered nine consecutive seasons from 1994 to 1998 and showed a distinct seasonal pattern: an early flush of CH4 before transplanting, an increasing trend in emission rates reaching Maximum toward grain ripening, and a second flush after water is withdrawn prior to harvesting. The local practice of crop Management, which consists of continuous flooding and urea application, resulted in 79-184 mg CH4 ma high -2 d high -1 in the dry season (DS) and 269-503 mg CH4 m high -2 d high -1 in the wet season (WS). The higher emissions in the WS may be attributed to more labile carbon accumulation during the dry fallow period before the WS cropping as shown by higher % organic C. Incorporation of sulfate into the soil reduced CH4 emission rates. The use of ammonium sulfate as N fertilizer in place of urea resulted in a 25-36 % reduction in CH4 emissions. Phosphogypsum reduced CH4 emissions by 72 % when applied in combination with urea fertilizer. Midseason drainage reduced CH4 emission by 43 %, which can be explained by the influx of oxygen into the soil. The practice of direct seeding instead of transplanting resulted in a 16-54 % reduction in CH4 emission, but the mechanisms for the reducing effect are not clear. Addition of rice straw compost increased CH4 emission by only 23-30 % as compared with the 162-250 % increase in emissions with the use of fresh rice straw. Chicken manure combined with urea did not increase CH4 emission. Fresh rice straw has wider C/N (25 to 45) while rice straw compost has C/N = 6 to 10 and chicken manure has C/N = 5 to 8. Modifications in inorganic and organic fertilizer management and water regime did not adversely affect grain yield and are therefore potential mitigation options. Direct seeding has a lower yield potential than transplanting but is getting increasingly popular among farmers due to labor savings. Combined with a package of technologies, CH4 emission can best be reduced by (1) the practice of midseason drainage instead of continuous flooding, (2) the use of sulfate-containing fertilizers such as ammonium sulfate and phosphogypsum combined with urea; (3) direct seeding crop establishment; and (4) use of low C/N organic fertilizer such as chicken manure and rice straw compost.
  • Publication
    Characterization of methane emissions from rice fields in Asia. I. Comparison among field sites in five countries
    ( 2000)
    Wassmann, R.
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    Neue, H.U.
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    Lantin, R.S.
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    Buendia, L.V.
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    Rennenberg, H.
    The Interregional Research Program on Methane Emissions from Rice Fields established a network of eight measuring stations in five Asian countries. These stations covered different environments and encompassed varying practices in crop management. All stations were equipped with a closed chamber system designed for frequent sampling and long-term measurements of emission rates. Even under identical treatment - e. g., continuous flooding and no organic fertilizers - average emission rates varied from 15 to 200 kg CH sub 4 ha high -1 season high -1. Low temperatures limited CH sub 4 emissions in temperate and subtropical stations such as northern China and northern India. Differences observed under given climates, (e. g., within the tropics) indicated the importance of soil properties in regulating the CH sub 4 emission potential. However, local variations in crop management superseded the impact o soil- and climate-related factors. This resulted in uniformly high emission rates of about 300 kg CH sub 4 ha high -1 season high -1 for the irrigated rice stations in the Philippines (Maligaya) and China (Beijing and Hangzhou). The station in northern India (Delhi) was characterized by exceptionally low emission rates of less than 20 kg CH sub 4 ha high -1 season high -1 under local practice. These findings also suggest opportunities for reducing CH sub 4 emission through a deliberate modification of cultural practice for most irrigated rice fields.
  • Publication
    Methane transport capacity of rice plants. II. Variations among different rice cultivars and relationship with morphological characteristics
    ( 2000)
    Aulakh, M.S.
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    Bodenbender, J.
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    Wassmann, R.
    ;
    Rennenberg, H.
    Of the total methane (CH4) emitted from a rice field during the growing season, 60 - 90 % is emitted through the rice plants. We determined the methane transport capacity (MTC) of rice plants at different physiological growth stages using an automatic measuring system under greenhouse conditions. A total of 12 cultivars (10 inbred varieties and 2 hybrids) were studied in sets of tow experiments and was distinguished into three groups according to the pattern of MTC development. MTC is generally increasing from seedling stage to panicle initiation (PI), but differs in the development from PI to maturity. While the hybrid showed a gradual increase in MTC, the inbred cultivars showed either minor changes in MTC or a drastic decrease from flowering to maturity. Among tall cultivars, Dular showed the highest MTC, followed by B40; the lowest MTC was found in Intan. High-yielding dwarf cultivars showed MTC in the descending order of IR72 > IR52 > IR64 > PSBRc 20. New plant type cultivars showed very low MTC with IR65600 exhibiting the smallest MTC at PI, flowering, and maturity. Hybrids (Magat and APHR 2) showed the largest MTC that continued to increase with plant growth. The MTC patterns were attributed to growth parameters and the development of morphological characteristics of the aerenchyma. These results suggest that in tall, dwarf, and NPT cultivars, increase in root or aboveground biomass during initial growth determines a corresponding increase in MTC. Once aerenchyma has fully developed, further increase in plant biomass would not influence MTC. However, in the case of hybrids, a positive relationship of MTC with root + shoot biomass (r = 0.672, p > 0.05) and a total plant biomass including grain (r = 0.849, p > 0.01) indicate continuous development of aerenchyma with plant growth, resulting in enhanced MTC. In all cultivars, tiller number, but not height, was linearly related to MTC, indicating that the number of outlets/channels rather than plant size/biomass determines the transport of CH4. These results clearly demonstrate that rice cultivars differ significantly in MTC. Therefore, the use of high-yielding cultivars with low MTC (for example, PSBRc 20, IR65598, and IR65600) could be an economically feasible, environmentally sound, and promising approach to mitigate CH4 emissions from rice fields.
  • Publication
    Methane emissions and mitigation options in irrigated rice fields in southeast China
    ( 2000)
    Lu, W.F.
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    Chen, W.
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    Duan, B.W.
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    Guo, W.M.
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    Lu, Y.
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    Lantin, R.S.
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    Wassmann, R.
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    Neue, H.U.
    Methane (CH sub 4) emissions from rice fields were monitored in Hangzhou, China, from 1995 to 1998 by an automatic measurement system based on the "closed chamber technique." The impacts of water management, organic inputs, and cultivars on CH sub 4 emission were evaluated. Under the local crop management system, seasonal emissions ranging from 53 to 557 kg CH sub 4 ha high -1 were observed with an average value of 182 kg CH sub 4 ha high -1. Methane emission patterns differed among rice seasons and were generally governed. by temperature changes. Emissions showed an increasing trend in early rice and a decreasing trend in late rice. In a single rice field, CH sub 4 emissions increased during the first half of the growing period and decreased during the second half. Drainage was a major modifier of seasonal CH sub 4 emission pattern. The local practice of midseason drainage reduced CH sub 4 emissions by 44 % as compared with continuous flooding; CH sub 4 emissions could further be reduced by intermittent irrigation, yielding a 30 % reduction as compared with midseason drainage. The incorporation of organic amendments promoted CH sub 4 emission, but the amount of emission varied with the type of organic material and application method. Methane emission from fields where biogas residue was applied was 10 - 16 % lower than those given the same quantity (based on N content) of pig manure. Rice straw applied before the winter fallow period reduced CH sub 4 emission by 11 % as compared with that obtained from fields to which the same amount of rice straw was applied during field preparation. Broadcasting of straw instead of incorporation into the soil showed less emission (by 12 %). Cultivar selection influenced CH sub 4 emission, but the differences were smaller than those among organic treatments and water regimes. Modifications in water regime and organic inputs were identified as promising mitigation options in southeast China.
  • Publication
    Characterization of methane emissions from rice fields in Asia. III. Mitigation options and future research needs
    ( 2000)
    Wassmann, R.
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    Lantin, R.S.
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    Neue, H.U.
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    Buendia, L.V.
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    Corton, T.M.
    ;
    Lu, Y.
    Methane (CH sub 4) emissions from rice fields were determined using automated measurement systems in China, India, Indonesia, Thailand, and the Philippines. Mitigation options were assessed separately for different baseline practices of irrigated rice, rainfed, and deepwater rice. Irrigated rice is the largest source of CH sub 4 and also offers the most options to modify crop management for reducing these emissions. Optimizing irrigation patterns by additional drainage periods in the field or an early timing of midseason drainage accounted for 7 - 80 % of CH sub 4 emissions of the respective baseline practice. In baseline practices with high organic amendments, use of compost (58 - 63 %), biogas residues (10 - 16 %), and direct wet seeding (16 - 22 %) should be considered mitigation options. In baseline practices using prilled urea as sole N source, use of ammonium sulfate could reduce CH sub 4 emission by 10 - 67 %. In all rice ecosystems, CH sub 4 emissions can be reduced b fallow incorporation (11 %) and mulching (11 %) of rice straw as well as addition of phosphogypsum (9 - 73 %). However, in rainfed and deepwater rice, mitigation options are very limited in both number and potential gains. The assessment of these crop management options includes their total factor productivity and possible adverse effects. Due to higher nitrous oxide (N sub 2 O) emissions, changes in water regime are only recommended for rice systems with high baseline emissions of CH sub 4. Key objectives of future research are identifying and characterizing high-emitting rice systems, developing site-specific technology packages, ascertaining synergies with productivity, and accounting for N sub 2 O emissions.
  • Publication
    Methane emission from rice fields at Cuttack, India
    ( 2000)
    Adhya, T.K.
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    Bharati, K.
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    Mohanty, S.R.
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    Ramakrishnan, B.
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    Rao, V.R.
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    Sethunathan, N.
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    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.