Methane mitigation in flooded Louisiana rice fields

Summary A field experiment was conducted to determine whether selected nitrification inhibitors (encapsulated calcium carbide and dicyandiamide) and SO _inf4 ^sup-2 -containing compounds [(NH₄)₂SO₄ and Na₂SO₄] had mitigating effects on CH₄ emissions from flooded rice. Microplots were established within a rice bay drill-seeded with the Texmont rice cultivar and CH₄ fluxes were measured over the main rice cropping season. Methane emissions over the 77-day sampling period were approximately 230, 240, 260, 290, 310, and 360 kg CH₄ ha^-1 from the calcium carbide, Na₂SO₄-rate II, Na₂SO₄-rate I, (NH₄)₂SO₄, dicyandiamide, and urea (control) treatments, respectively. Reductions in CH₄ evolution, compared to the control, ranged from 14 to 35%, depending on treatment. The selected inhibitors and SO _inf4 ^sup-2 -containing compounds appear to be effective in reducing the CH₄ emitted from flooded rice fields.     

Methane emission from paddy fields in Taiwan

 In order to investigate the effect of environmental conditions on CH₄ emission from paddy fields in Taiwan, four locations, two cropping seasons and two irrigation systems were studied. CH₄ emission was high at the active tillering and the booting stages in the first cropping season, whereas it was low at the transplanting and the ripening stages with an intermittent irrigation system. CH₄ emission was high at the transplanting stage in the second cropping season, and decreased gradually during rice cultivation. Daily temperature and light intensity increased gradually during rice growth in the first cropping season (February–June), while it was reversed in the second cropping season (August–December). The seasonal CH₄ emission from paddy fields ranged from 1.73 to 11.70 g m^–2, and from 10.54 to 39.50 g m^–2 in the first and second cropping seasons, respectively. The seasonal CH₄ emission in the second cropping season was higher than that in the first cropping season in all test fields. The seasonal CH₄ emission was 32.65 mg m^–2 in the first cropping season of the National Taiwan University paddy field with continuous flooding, and it was 28.85 mg m^–2 in the second cropping season. The annual CH₄ emission ranged from 12.3 to 49.3 g m^–2 with an intermittent irrigation system, and the value was 61.5 g m^–2 with a continuous flooding treatment. The annual CH₄ emission from paddy fields was estimated to be 0.034 Tg in 1997 from 364,212 ha of paddy fields with an intermittent irrigation system, which was less than the 0.241 Tg calculated by the IPCC method with a continuous flooding treatment Received: 23 February 2000     

Methane emission and entrapment in flooded rice soils as affected by soil properties

Laboratory incubation experiments were conducted to study the effects of soil chemical and physical properties on CH₄ emission and entrapment in 16 selected soils with a pH range of 4.7–8.1, organic matter content of 0.72–2.38%, and soil texture from silt to clay. There was no significant correlation with CH₄ emission for most of the important soil properties, including soil aerobic pH (measured before anaerobic incubation), total Kjeldahl N, cation exchange capacity, especially soil organic matter, and soil water-soluble C, which were considered to be critical controlling factors of CH₄ emission. A lower CH₄ emission was observed in some soils with a higher organic matter content. Differences in soil Fe and Mn contents and their chemical forms contributed to the this observation. A significant correlation between the CH₄ emission and the soil organic C content was observed only after stratifying soils into subgroups according to the level of CH₄ emission in soils not amended with organic matter. The results also showed that the soil redox potential (Eh), anaerobic pH, anerobic pH, and biologically reducible Fe and Mn affected CH₄ emission significantly. Urea fertilization promoted CH₄ emission in some soils and inhibited it in others. This result appeared to be related to the original soil pH. CH₄ entrapment was positively correlated with soil clay content, indicating the importance of soil physical characteristics in reducing CH₄ emissions to the atmosphere.     

Spatial and seasonal distribution of organic amendments affecting methane emission from Chinese rice fields

The effect of fertilizers on methane emission rates was investigated using an automated closed chamber system in Chinese rice fields (Human Province). Each of three experiments compared two fields treated with a first uniform fertilizer dose and a second fertilizer dose which was different for each of the two fields. The uniform fertilizer doses for both fields in each experiment comprised mineral (experiment 1), organic (experiment 2) and combined mineral plus organic components (experiment 3). In all three experiments the second fertilizer dose comprised organic amendments for field 1 and no organic amendments for field 2. The rate of increase in methane emission with a given amount of organic manure was found to depend on the total amount of organic manure applied. A single dose of organic manure increased the emission rates by factors of 2.7 to 4.1 as compared to fields without organic manure (experiment 1). In rice fields that had already been treated with organic manure, the application of a second dose of organic manure only slightly enhanced the emission rates in experiment 2 by factors of 1.1 to 1.5 and showed no detectable increase in experiment 3. The net reduction achieved by separation of organic and mineral fertilizers was maximized by concentrating the organic amendments in the season with low emission rates, i.e. early rice, and using exclusively mineral fertilizers on late rice when emission rates were generally higher. This distribution pattern, which was not associated with significant yield losses, resulted in an annual methane emission corresponding to only 56% of the methane emitted from fields treated with blended fertilizers.     

Potassium application reduces methane emission from a flooded field planted to rice

In a field study, potassium (K) applied as muriate of potash (MOP) significantly reduced methane (CH₄) emission from a flooded alluvial soil planted to rice. Cumulative emission was highest in control plots (125.34 kg CH₄ ha⁻¹), while the lowest emission was recorded in field plots receiving 30 kg K ha⁻¹ (63.81 kg CH₄ ha⁻¹), with a 49% reduction in CH₄ emission. Potassium application prevented a drop in the redox potential and reduced the contents of active reducing substances and Fe²⁺ content in the rhizosphere soil. Potassium amendment also inhibited methanogenic bacteria and stimulated methanotrophic bacterial population. Results suggest that, apart form producing higher plant biomass (both above- and underground) and grain yield, K amendment can effectively reduce CH₄ emission from flooded soil and could be developed into an effective mitigation option, especially in K-deficient soils.     

Effect of the herbicide butachlor on methane emission and ebullition flux from a direct-seeded flooded rice field

 Application of a commercial formulation of the herbicide butachlor (N-butoxymethyl-2-chloro-2′,6′-diethyl acetanilide) at 1 kg a.i. ha^–1 to an alluvial soil planted with direct-seeded flooded rice (cv. Annada), significantly inhibited both crop-mediated emission and ebullition fluxes of methane (CH₄). Over a cropping period of 110 days, the crop-mediated cumulative emission flux of CH₄ was lowered by ∼20% in butachlor-treated field plots compared with that of an untreated control. Concurrently, ebollition flux of CH₄ was also retarded in butachlor-treated field plots by about 81% compared with that of control plots. Significant relationships existed between CH₄ emission and redox potential (E _h) and Fe²⁺ content of the flooded soil. Application of butachlor retarded a drop in soil redox potential as well as accumulation of Fe²⁺ in treated field plots. Methanogenic bacterial population, counted at the maturity stage of the crop, was also low in butachlor-treated plots, indicating both direct and indirect inhibitory effects of butachlor on methanogenic bacterial populations and their activity. Results indicate that butachlor, even at field-application level, can effectively abate CH₄ emission and ebollition from flooded soils planted to rice whilst maintaining grain yield. Received: 15 March 2000     

Methane emission from two Indian soils planted with different rice cultivars

In a greenhouse study, methane emissions were measured from two diverse Indian rice-growing soils planted to five rice cultivars under similar water regimes, fertilizer applications and environmental conditions. Significant variations were observed in methane emitted from soils growing different cultivars. Total methane emission varied between 8.04 and 20.92gm^–2 from IARI soil (Inceptisol) and between 1.47 and 10.91gm^–2 from Raipur soil (Vertisol) planted to rice. In all the cultivars, emissions from IARI soil were higher than from Raipur soil. The first methane flux peak was noticed during the reproductive phase and the second peak coincided with the grain-ripening stage of the rice cultivars. Received: July 7, 1996     

水稻油菜轮作稻田甲烷排放及其总量估算

利用静态箱/气相色谱法对川中丘陵区水稻油菜轮作稻田进行水稻全生长季CH4排放观测。结果表明,稻田CH4排放有明显的季节变化,呈“前低后高”的变化趋势,CH4排放峰出现在水稻抽穗扬花期;测定期内稻田CH4平均排放通量为6.20mg/m2.h。对影响稻田CH4排放的因素分析发现,淹水条件下水稻移栽到抽穗初期,水稻植株生长是影响稻田CH4排放的关键因素;水稻抽穗期到成熟期,温度是影响稻田CH4排放的关键因素。水稻油菜轮作稻田在水稻生长季中CH排放总量为173.96kg/hm2。     

中国常年淹水稻田CH4排放量估算

A special kind of rice field exists in China that is flooded year-round. These rice fields have substantially large CH4 emissions during the rice-growing season and emit CH4 continuously in the non-rice growing season. CH4 emission factors were used to estimate the CH4 emissions from year-round flooded rice fields during the rice-growing season in China.The CH4 emissions for the year-round flooded rice fields in China for the rice growing season over a total area of 2.66 Mha were estimated to be 2.44 Tg CH4 year^-1. The uncertainties of these estimations are discussed as well. However,the emissions during the non-rice growing season could not be estimated because of limited available data. Nevertheless,methane emissions from rice fields that were flooded year-round could be several times higher than those from the rice fields drained in the non-rice-growing season. Thus, the classification of “continuously flooded rice fields”in the IPCC (International Panel on Climate Change) Guidelines for National Greenhouse Gas Inventories is suggested to be revised and divided into “continuously flooded rice fields during the rice growing season” and “year-round flooded rice fields”.     

Effect of rice variety on methane emission from an Indonesian paddy field

Variations in CH₄ emission from a Sumatra paddy field in which 8 popular modern varieties in Indonesia were grown were compared in the 1994/1995 rainy season. Total amounts of CH₄ emitted during the period of rice growth were in the ranges of 32.6-41.7 and 51.3–64.6 g CH₄ m^-2 for the plots amended with chemical fertilizer only and those amended with both rice straw and chemical fertilizer, respectively. The mean CH₄ emission rate was highest in the plot with the variety Bengawan solo and lowest in the plots with the varieties Atomita-4 and Way seputih among the plots which received chemical fertilizer, while highest in the plot with Way seputih and lowest in the plot with Bengawan solo among the plots amended with both rice straw and chemical fertilizer. The increase in the mean CH₄ emission rates by rice straw application was higher for the plots planted with Way seputih (1.98 times) and Atomita-4 (1.77 times) than for the plots with Bengawan solo (1.23 times) and IR-64 (1.35 times). The plots with Walanai and Cisanggarung recorded intermediate mean emission rates and the increase in CH₄ emission by rice straw application was also intermediate (1.57–1.64 times). It was noteworthy that Way seputih and Atomita-4 were derived from the variety Cisadane, Bengawan solo and IR-64 from the variety IR-54, and Walanai and Cisanggarung from the varieties IR-36 and Pelita 1-1, respectively.

The amounts of CH. emitted for 1 kg grain production ranged from 53 (Atomita-4) to 74 (Kapuas and Walanai) and from 89-93 (IR-64, Bengawan solo, and Atomita-4) to 121 (Kapuas) g CH₄ kg^-1 of grain for the plots amended with chemical fertilizer and those amended with rice straw and chemical fertilizer, respectively.     

Fluxes of methane from rice fields and potential for mitigation

Abstract. Methane (CH₄) is an important greenhouse gas. Flooded rice fields (paddies) are a significant source of atmospheric CH₄; estimates of the annual emission from paddies range from less than 20 to 100 million Tg, with best estimates of 50 × 20 Tg. The emission is the net result of opposing bacterial processes: production in anaerobic microenvironments, and consumption and oxidation in aerobic microenvironments, both of which occur sequentially and concurrently in flooded rice soils. With current technologies, CH₄ emission from rice fields will increase as production increases. Over the next 25 years rice production will have to increase by 65% from the present 460 Mt/y to 760 Mt/y in 2020. The current understanding of the processes controlling CH₄ fluxes, rice growth and rice production is sufficient to develop mitigation technologies. Promising candidates are changes in water management, rice cultivars, fertilization, and cultural practices. A significant reduction of CH₄ emission from rice fields, at the same time that rice production and productivity increase at the farm level, is feasible, although the regions where particular practices can be applied, and the trade-offs that are possible, have still to be identified.     

The effect of phenyl phosphorodiamidate on urease activity and ammonia volatilization in flooded rice

Summary The behaviour of urease activity, ammoniacal N concentrations and pH in flood water and that of ammonia flux was investigated in a water-logged soil either in the presence or in the absence of rice and with three different treatments (control, urea and urea + phenyl phosphorodiamidate). In the presence of the phenyl phosphorodiamidate (PPD), that is a urease inhibitor, increases in ammoniacal N concentrations and in ammonia evolution were delayed but not eliminated. The degradation and/or the inactivation of PPD might have occurred, thus removing the inhibition of the enzyme activity.     

Effect of rice straw application on CH4 emission from paddy fields

The effect of rice straw (RS) incorporated at the time of plowing in the previous cr–p season on CH₄ emission from rice paddies was investigated in a pot experiment. Rice straw that incorporated just before transplanting of rice seedlings (June) into a paddy field was collected after the harvest (October) and at the beginning of the next cropping period (May). Methane emission rates from the rice-planted pots with the application of fresh RS, RS collected in October. and RS collected in Mayas well as the pots without RS application were measured using the chamber method. The composition of organic constituents in the three kinds of RS was estimated by the proximate analysis. The cumulative amount of CH₄ emitted during the first 50–d period was lower in the order of the pots with RS collected in May, pots with RS collected in October, and pots with fresh RS. The cumulative amount of CH₄ emitted throughout the rice growth period from the pots with fresh RS and with RS collected in October was significantly larger while that from the pots with RS collected in May did not differ statistically compared with the total CH₄ emission from the pots without RS. These results suggested that there was an overall decrease in the amount of organic constituents in RS based on the large differences in T-C content and similar composition of organic constituents between the fresh RS and RS collected in May. Significant effect of RS continuously applied during the previous cropping period on the increase in CH₄ emission was discussed.     

CO2/heat fluxes in rice fields: Comparative assessment of flooded and non-flooded fields in the Philippines

The seasonal fluxes of heat, moisture and CO₂ were investigated under two different rice environments: flooded and aerobic soil conditions, using the eddy covariance technique during 2008 dry season. The fluxes were correlated with the microclimate prevalent in each location. This study was intended to monitor the environmental impact, in terms of C budget and heat exchange, of shifting from lowland rice production to aerobic rice cultivation as an alternative to maintain crop productivity under water scarcity.The aerobic rice fields had higher sensible heat flux (H) and lower latent heat flux (LE) compared to flooded fields. On seasonal average, aerobic rice fields had 48% more sensible heat flux while flooded rice fields had 20% more latent heat flux. Consequently, the aerobic rice fields had significantly higher Bowen ratio (0.25) than flooded fields (0.14), indicating that a larger proportion of the available net radiation was used for sensible heat transfer or for warming the surrounding air.The total C budget integrated over the cropping period showed that the net ecosystem exchange (NEE) in flooded rice fields was about three times higher than in aerobic fields while gross primary production (GPP) and ecosystem respiration (R_e) were 1.5 and 1.2 times higher, respectively. The high GPP of flooded rice ecosystem was evident because the photosynthetic capacity of lowland rice is naturally large. The R_e of flooded rice fields was also relatively high because it was enhanced by the high photosynthetic activities of lowland rice as manifested by larger above-ground plant biomass. The NEE, GPP, and R_e values for flooded rice fields were −258, 778, and 521 g C m⁻², respectively. For aerobic rice fields, values were −85, 515, and 430 g C m⁻² for NEE, GPP, and R_e, respectively. The ratio of R_e/GPP in flooded fields was 0.67 while it was 0.83 for aerobic rice fields.This short-term data showed significant differences in C budget and heat exchange between flooded and aerobic rice ecosystems. Further investigation is needed to clarify seasonal and inter-annual variations in microclimate, carbon and water budget of different rice production systems.     

不同水稻、小麦品种对N2O排放的影响

Plant species of cropping systems may affect nitrous oxide (N2O) emissions. A field experiment was conducted to investigate dynamics of N2O emissions from rice-wheat fields from December 2006 to June 2007 and the relationship between soil and plant parameters with N2O emissions. The results indicated that N2O emissions from different wheat varieties ranged from 12 to 291 μg N2O-N m-2 h-1 and seasonal N2O emissions ranged from 312 to 385 mg N2O-N m-2. In the rice season, it was from 11 to 154 μg N2O-N m-2 h-1 with seasonal N2O emission of 190--216 mg N2O-N m-2. The seasonal integrated flux of N2O differed significantly among wheat and rice varieties. The wheat variety HUW 234 and rice variety Joymoti showed higher seasonal N2O emissions. In the wheat season, N2O emissions correlated with soil organic carbon (SOC), soil NO3--N, soil temperature, shoot dry weight, and root dry weight. Among the variables assessed, soil temperature followed by SOC and soil NO3--N were considered as the important variables influencing N2O emission. N2O emission in the rice season was significantly correlated with SOC, soil NO3--N, soil temperature, leaf area, shoot dry weight, and root dry weight. The main driving forces influencing N2O emission in the rice season were soil NO3--N, leaf area, and SOC.     

Release of silicon from rice straw under flooded conditions

It is estimated that nearly 20 kg of SiO₂ is removed from the soil by rice plants for producing 100 kg brown rice (Takahashi 1987). Although there is a large amount of silicon in soil, little is available to the rice plant. To supply a sufficient amount of silicon to the rice plant for healthy growth, therefore, it is nccessary to supply various silicon materials to the soil. Rice straw application to the soil is one of the means.     

太湖地区不同集约化栽培模式下稻田CH4排放

采用静态暗箱—气相色谱法对太湖地区水稻生态系统甲烷(CH4)排放进行田间原位观测,共设置无氮(NN)、常规(FP)、增产增效(YE)(增产10%～15%,氮肥利用率(NUE)提高20%～30%)、再增产(HY)(增产30%～40%)、再增效(HE)(NUE提高30%～50%)和保产增效(IE)(产量不变,NUE提高20%～30%)六种不同的栽培模式。结果表明,稻田CH4排放具有明显的季节变化,在水稻生长期间先升高后降低,从水稻移栽至抽穗期CH4排放通量占全生育期的93%～98%。不同栽培模式间CH4累积排放量差异显著(p<0.05),HY处理高达258.8 kg hm-2,显著高于未施有机肥各处理;单位稻谷产量CH4排放量差异不显著,平均为CO2 0.60 kg kg-1,提高稻谷产量的模式不会显著影响CH4排放;其中YE处理单位稻谷产量CH4排放量最低,为CO2 0.49 kg kg-1,可以同时实现增产、增效和减排,值得推广。     

长期施肥对湖南稻田甲烷排放的影响

采用静态箱-气相色谱法对长期不同施肥处理的稻田甲烷排放进行了手动观测。结果表明，不同施肥处理的稻田甲烷排放具有一致的规律，混施有机肥的处理甲烷排放大于单施氮肥的处理，同施用稻草相比，发酵猪粪处理的甲烷排放较少。文章还对影响稻田甲烷排放的因素进行了讨论。     

Methane emissions from paddy fields in Bali Island,Indonesia

Abstract

Methane emission rates from plots with and without fertilizer and rice straw application, and growth of two rice varieties (an improved variety, IR74 or IR64, and a local variety, Krueng Aceh) in two Indonesian paddy fields (Inceptisol and Alfisol soils of volcanic ash origin) were measured every week throughout the growth period in the first and the second cropping seasons, 1994. The CH₄ emission rates from the fields were similar between the two varieties. The effect of chemical fertilizer on the increase of the emissions was observed only in the Tabanan paddy field for the plots treated with rice straw. Application of rice straw increased the CH₄ emission rates. The mean rates of CH₄ emission were 1.37-2.13 mg CH₄?C m^?2 h^?1 for the plots without rice straw and 2.14–3.62 mg CH₄?C m^?2 h^?1 for the plots with rice straw application in the Alfisol plots, and 2.32–3.32 mg CH₄ -C m-2 h-1 for the plots without rice straw and 4.18–6.35 mg CH₄?C m^?2 h^?1 for the plots with rice straw application in the Inceptisol plots, respectively. Total amounts of CH₄ emitted during the growth period were 3.9–6.8 and 2.6–3.3 g CH₄?C m^?2 for the Alfisol plots and 6.9–10.7 and 4.2–5.8 g CH₄?C m^?2 for the Inceptisol plots with and without rice straw application, respectively. These findings suggested that CH₄ emission from tropical paddy fields with soils of volcanic ash origin is low.