Haruo Tsuruta

Methane and nitrous oxide emissions from rice paddy fields as affected by nitrogen fertilisers and water management

Methane and N2O emissions affected by nitrogen fertilisers were measured simultaneously in rice paddy fields under intermittent irrigation in 1994. Ammonium sulphate and urea were applied at rates of 0 (control), 100 and 300 kg N ha-1. The results showed that CH4 emission, on the average, decreased by 42 and 60% in the ammonium sulphate treatments and 7 and 14% in the urea treatments at rates of 100 and 300 kg N ha-1, respectively, compared to the control. N2O emission increased significantly with the increase in the nitrogen application rate. N2O emission was higher from ammonium sulphate treatments than from the urea treatments at the same application rate. A trade-off effect between CH4 and N2O emission was clearly observed. The N2O flux was very small when the rice paddy plots were flooded, but peaked at the beginning of the disappearance of floodwater. In contrast, the CH4 flux peaked during flooding and was significantly depressed by mid-season aeration (MSA). The results suggest that it is important to evaluate the integrative effects of water management and fertiliser application for mitigating greenhouse gas emissions in order to attenuate the greenhouse effect contributed by rice paddy fields.

Effect of water management on methane emission from a Japanese rice paddy field: Automated methane monitoring

The effect of differing water management schemes on the emission of methane (CH4) from rice paddies to the atmosphere was studied in a Japanese paddy field. Using an automated sampling and analyzing system, the test site was divided into two plots: a continuously flooded plot which was maintained flooded by constant irrigation from May to August, and an intermittently drained plot in which short-term draining practices were performed several times during the flooding period . The draining practice had a strong effect on CH4 emission. A large flush of CH4 emission was observed in the intermittently drained plot immediately after each drainage. It was followed by a rapid decrease in CH4 flux in most of the cases. A large flush of CH4 was observed after the final drainage at the end of August in the continuously flooded plot, accounting for about 7% of the total CH4 emitted in the plot. Total emission rates of CH4 during the cultivation period were 14.8 and 8.63 g m−2 for 1991 and 9.49 and 5.18 g m−2 for 1993 in the continuously flooded and intermittently drained plots, respectively. Companion N2O flux measurements showed that almost no N2O was emitted from either plot until the final drainage. These results indicate that short-term draining practices strongly reduce CH4 emission from rice paddy fields, and that improvement in water management can be one of the most important mitigation strategies for CH4 emission from rice paddy fields.

Overview of the Atmospheric Brown Cloud East Asian Regional Experiment 2005 and a study of the aerosol direct radiative forcing in east Asia

2005 which is smaller in magnitude than in the APMEX region, mainly because of large cloud fraction in this region (0.70 at Gosan versus 0.51 at Hanimadhoo in the ISCCP total cloud fraction). We suggest there may be an underestimation of the forcing due to overestimation of the simulated cloudiness and aerosol scale height. On the other hand, the possible error in the simulated surface albedo may cause an overestimation of the magnitude of the forcing over the land area. We also propose simple formulae for shortwave radiative forcing to understand the role of aerosol parameters and surface condition to determine the aerosol forcing. Such simple formulae are useful to check the consistency among the observed quantities.

Possible options for mitigating methane emission from rice cultivation

Studies focused on mitigating CH4 emission from rice paddy fields are summarized and the possibilities and limits that the options might be applied to worlds rice cultivation are discussed. The mitigation options are water management, soil amendments, organic matter management, different tillage, rotation, and cultivar selection. Altering water management, in particular promoting midseason aeration by short-term drainage, is one of the most promising strategies, although these practices may be limited to the rice paddy fields where the irrigation system is well prepared. Improving organic matter management by promoting aerobic degradation through composting or incorporating into soil during off-season drained period is another most promising candidate. There are several formidable obstacles to adopt the mitigation options into local rice farming, including limited applicability to different types of rice fields, increasing cost and labor, negative effects on rice yield and soil fertility, and time requirement for practical application. Further studies to verify the mitigation options should focus on the feasibility for local farmers.

Methane emission from rice fields in China: Measurements and influencing factors

Methane emissions from rice fields in China were measured at eight sites in five provinces under conditions representative of local practices for rice cultivation. Methane emission rates during the rice growth period varied greatly from site to site and with treatments at the same site, ranging from 0.3 to 205 g CH4/m2. Flooded or waterlogged rice fields in the nonrice growth season continuously emitted CH4 substantially. The average CH4 emission rate from a rice field in Chongqing was as high as 36.2 g CH4/m2 in the nonrice growing season. Furthermore, flooding in the nonrice growth season also significantly stimulated CH4 emission during the rice growth period in the next year. Increases in the rate of CH4 flux after rice transplanting were less when the number of consecutive upland crops grown before rice transplanting was greater. CH4 emissions from rice fields located on downslope was larger than from those on midslope and upslope in hilly areas due to poor drainage of the former. Application of rice straw in fall when winter wheat was sown did not increase CH4 emission significantly during the following rice growth period. CH4 emission was depressed by the application of ammonium sulfate but was, in general, not significantly affected by urea application.

Measurements of CH4 and N20 emissions from rice paddies in Fengqiu, China

Abstract Methane emissions were measured by a closed chamber method in rice plots with sandy, loamy, and clayey soil, respectively, under a water regime consisting of a flooding and draining cycle in Fengqiu, Henan Province, China in 1993 and 1994. Nitrous oxide emissions were measured for every two measurements of CH4 flux in 1994. The results showed that CH4 emissions were low compared with those recorded in previous reports and the means of CH4 fluxes ranged from 0.16 to 1.86 mg CH4 m-2 h-1 in the growing season (108 d). The lowest mean flux of CH4 was observed in the clayey plot in both years. Statistically, soil temperature and soil Eh at 5 em depth significantly affected the fluctuations of the CH4 flux measured in the morning and afternoon, but they were not the main factors controlling the seasonal variation of the CH. flux. Flooding and draining cycle, as well as high rate of water percolation and low organic matter content of the soils resulted in low emissions of CH4. In contrast, the studied p...

Nitrous oxide emissions from three rice paddy fields in China

Nitrous oxide (N2O) fluxes from rice paddy fields were measured in Nanjing, Yingtan and Fengqiu, using closed chamber method in 1994. The results showed that N2O fluxes varied temporally, spatially and geographic regionally, with the total amounts of N2O emissions during the period of rice growth ranged from 13.66 to 98.11mg/m2 in Nanjing, 1.73 to 3.65mg/m2 in Yingtan and 178.04 to 472.26mg/m2 in Fengqiu, respectively. Soil water regime and soil texture had significant effects on N2O production and emission from rice paddy fields. The mean N2O fluxes from sandy, loamy and clayey rice paddy fields were 182.2,82.8 and 68.7 µg N2O-N/m2/h, respectively. High N2O fluxes occurred when rice paddy fields were imposed by alternation of irrigation and drainage and almost no N2O emitted when the fields were submerged continuously. The rice paddy field applied with ammonium sulphate emitted more N2O than with urea and N2O-N losses of applied ammonium sulphate and urea ranged from 0.038 to 0.28% and 0.033 to 0.16%, respectively.

Carbon monoxide, hydrogen, and methane uptake by soils in a temperate arable field and a forest

CO, H2, and CH4 uptake by the soil of an arable field and a forest soil (360 m apart) was measured by a closed-chamber method in temperate Japan for about 1 year. CO production observed was exponentially dependent on top soil temperature. CO production was greater in the forest soil than in the soil of the arable field at the same soil temperature. (Gross) CO, H2, and CH4 deposition velocities ranged from 0 to 7×10−2, from 0 to 9×10−2, and from 0.05 to 0.1×10−2 cm s−1 in the arable field and from 1.5 to 4.5×10−2, 5 to 8×10−2, and from 0.3 to 0.6×10−2 cm s−1 in the forest, respectively. Variations in the deposition velocities were smaller in the forest than in the arable field and corresponded to variations in soil moisture in the top soil. Seasonal trends caused by the variation in temperature were observed only for CH4 deposition, reflecting the clear dependence on soil temperature. Application of dead plant material to the arable field led to acceleration of CO and H2 deposition onto the soil. The deposition velocities of CO and H2 were positively correlated (n =36, R2* = 0.881, p<0.0001; R2* is the coefficient of determination adjusted by degrees of freedom) in the arable field and (n = 37, R2* = 0.408, p<0.0001) in the forest, suggesting diffusion control on their deposition velocities.

Greenhouse gas emissions from tropical peatlands of Kalimantan,Indonesia

Greenhouse gas emissions were measured from tropical peatlands of Kalimantan, Indonesia. The effect of hydrological zone and land-use on the emission of N2O, CH4 and CO2 were examined. Temporal and annual N2O, CH4 and CO2 were then measured. The results showed that the emissions of these gases were strongly affected by land-use and hydrological zone. The emissions exhibited seasonal changes. Annual emission of N2O was the highest (nearly 1.4 g N m−2y−1) from site A-1 (secondary forest), while there was no signi.cant difference in annual N2O emission from site A-2 (paddy field) and site A-3 (rice-soybean rotation field). Multiplying the areas of forest and non-forest in Kalimantan with the emission of N2O from corresponding land-uses, the annual N2O emissions from peat forest and peat non-forest of Kalimantan were estimated as 0.046 and 0.004 Tg N y−1, respectively. The emissions of CH4 from paddy field and non-paddy field were estimated similarly as 0.14 and 0.21 Tg C y−1, respectively. Total annual CO2 emission was estimated to be 182 Tg C y−1. Peatlands of Kalimantan, Indonesia, contributed less than 0.3 of the total global N2O, CO2 or CH4 emission, indicating that the gaseous losses of soil N and C from the study area to the atmosphere were small.

Influence of soil physical properties, fertiliser type and moisture tension on N2O and NO emissions from nearly saturated Japanese upland soils

In Japan, upland soils are an important source of nitrous oxide (N2O) and nitric oxide (NO) gas emissions. This paper reports on an investigation of the effect of soil moisture near saturation on N2O and NO emission rates from four upland soils in Japan of contrasting texture. The aim was to relate these effects to soil physical properties. Intact cores of each soil type were incubated in the laboratory at different moisture tensions after fertilisation with NH4-N, NO3-N or zero N. Emissions of N2O and NO were measured regularly over a 16–20 day period. At the end of the incubation, soil cores were analysed for physical properties. Moisture and N fertiliser significantly affected rates of emissions of both N2O and NO with large differences between the soil types. Nitrous oxide emissions were greatest in the finer-textured soils, whereas NO emissions were greater in the coarser-textured soils. Emissions of N2O increased at higher moisture contents in all soils, but the magnitude of increase was much greater in finer-textured soils. Nitric oxide emissions were only significant in soils fertilised with NH4-N and were negatively correlated with soil moisture. Analysis of soil properties showed that there was a strong relationship between the magnitude of emissions and soil physical properties. The importance of soil wetness to gas emissions was mainly through its influence on soil air-filled porosity, which itself was related to gas diffusivity. From the results of this research, we can now estimate likely effects of soil texture on emissions through the influence of soil type on soil aeration and soil drainage. This is of particular value in modelling N2O and NO emissions from soil moisture status and land use inputs.