Rice Fields In China Research Articles

Dynamics of Yeast-like Symbiote and Its Relationship with the Virulence of Brown Planthopper, Nilaparvata lugens Stål, to Resistant Rice Varieties

Abundance of the yeast-like symbiote (YLS) in brown planthopper (BPH), Nilaparvata lugens Stål, collected from rice fields in China and obtained from International Rice Research Institute (IRRI), was monitored. The role of YLS in nymph survival rate, development and adult reproduction, and activities of transaminases in BPH on different resistant rice varieties were examined. Also, the relationship between YLS and virulence shifts of BPH to resistant rice varieties was discussed. The results indicated that the virulence of BPH populations to resistant rice varieties was strongly related to the abundance of YLS in 5th instar nymphs and brachy-pterous females of BPH field populations at Nanning in South China and Hangzhou in East China, showing the more abundance of YLS in BPH, the higher virulence of BPH to resistant rice varieties, while no obvious differences in YLS abundance were monitored between three BPH biotypes. Numbers of YLS reduced significantly in female adult of BPH biotype 1 fed on resistant rice varieties IR26, Mudgo and ASD7, compared with that fed on susceptible rice variety TNI. The lowest YLS abundance of BPH from field population was found in 2nd generation successively fed on resistant varieties, and the number of YLS was resumed at 4th generation when the BPH has adapted the resistant varieties. The markedly lower nymphal survival rate, adult fecundity and activities of alanine and aspartic transminase, and significantly longer nymph duration in the three aposymbiotic biotypes than in the symbiotic ones were recorded on both susceptible and resistant rice varieties. However, the much greater differences between aposymbiotic and symbiotic BPH were found on the inadaptable resistant rice varieties than that on the fitness resistant rice varieties. Those results implied that YLS in BPH should play a crucial role in the virulent shift of BPH populations to resistant rice varieties.

Field validation of the DNDC model for greenhouse gas emissions in East Asian cropping systems

Validations of the DeNitrification‐DeComposition (DNDC) model against field data sets of trace gases (CH4, N2O, and NO) emitted from cropping systems in Japan, China, and Thailand were conducted. The model‐simulated results were in agreement with seasonal N2O emissions from a lowland soil in Japan from 1995 to 2000 and seasonal CH4 emissions from rice fields in China, but failed to simulate N2O and NO emissions from an Andisol in Japan as well as NO emissions from the lowland soil. Seasonal CH4 emissions from rice cropping systems in Thailand were poorly simulated because of site‐specific soil conditions and rice variety. For all of the simulated cases, the model satisfactorily simulated annual variations of greenhouse gas emissions from cropping systems and effects of land management. However, discrepancies existed between the modeled and observed seasonal patterns of CH4 and N2O emissions. By incorporating modifications based on the local soil properties and management, DNDC model could become a powerful tool for estimating greenhouse gas emissions from terrestrial ecosystems.

Effect of soil water status and mulching on N 2 O and CH 4 emission from lowland rice field in China

Cultivation of rice in unsaturated soils covered with mulch is receiving more attention in China because of increasingly serious water shortage; however, greenhouse gas emission from this cultivation system is still poorly understood. A field experiment was conducted in 2001 to compare nitrous oxide (N2O) and methane (CH4) emission from rice cultivated in unsaturated soil covered with plastic or straw mulch and the traditional waterlogged production system. Trace gas fluxes from the soil were measured weekly throughout the entire growth period using a closed chamber method. Nitrous oxide emissions from unsaturated rice fields were large and varied considerably during the rice season. They were significantly affected by N fertilizer application rate. In contrast, N2O emission from the waterlogged system was very low with a maximum of 0.28 mg N2O m−2 h−1. However, CH4 emission from the waterlogged system was significantly higher than from the unsaturated system, with a maximum emission rate of 5.01 mg CH4 m−2 h−1. Our results suggested that unsaturated rice cultivation with straw mulch reduce greenhouse gas emissions.

Methane emission from rice fields in mainland China: Amount and seasonal and spatial distribution

China is the largest rice producer in the world. Methane (CH4) emission from its rice fields has been widely measured since the late 1980s. This study collected the results of available field research, totaling 204 season‐treatment measurements conducted on 23 sites. Analysis of these data shows that input of organic material, such as green manure, animal waste, and crop straw, increases CH4 emission by a factor of 2. Average CH4 flux from intermittently irrigated rice fields is 53% of that from continuously flooded rice fields; and average CH4 emission flux from late rice fields is 1.6 and 2.3 times greater than flux from early and single rice fields, respectively. There are regional differences in emission factors and a trend of decreasing emission from south to north. On the basis of earlier estimates of CH4 emission from Chinese rice fields, and recent reports on the use of crop residue and green manure, it is presumed that half of the rice fields in China receive organic input. From the frequency of various water management events indicated in the surveyed field experiments, as well as from specific statements in individual reports, it is presumed that 2/3 of irrigated rice fields have been intermittently flooded. On the basis of these assumptions, the region‐specific emission factors, and 1995 data on rice cultivation area, CH4 emission from growing‐season rice fields in Mainland China was estimated to be 7.67 Tg yr−1, ranging from 5.82 to 9.57 Tg yr−1, due to uncertainties in the areas receiving organic inputs, and intermittent irrigation. Generalized seasonal flux patterns were developed for early, late, and single rice. Monthly distributions of emission were estimated from these patterns and rice calendars. The highest emission rate occurred in August. Spatially, emission hot spots included the plains of Dongting Lake in Hunan Province, Boyang Lake in Jiangxi Province, the delta region of Qiantang River in Zhejiang Province, and the Sichuan Basin. Nearly 90% of all Mainland China CH4 emission occurred between 23°N and 33°N.

CH 4 emission and oxidation in Chinese rice paddies

In the paper, the characteristics of CH4 emission from the rice paddies, its temporary and spatial variations as well as factors regulating CH4 emission and oxidation are reviewed with an emphasis on CH4 emission from rice paddies in China. The observed four types of diel variation and two type of seasonal variation can be explained by the variations of methane production in the soil and the transport efficiencies of the three transport routs. The inter-annual variation of CH4 emission from rice fields is significant, but the process causing this change is very complicated and unclear based on the available data at present. The large special variation, more than 10 times difference, of the total season methane emissions observed in various rice fields in China, is largely attributed to soil type difference although both soil physics and chemistry are important. Rice growing activities regulate the diel and seasonal variation patterns of the methane emissions. Drainage of flooded water may significantly reduce the emission. Organic fertilizer may enhance the emission, while some of the chemical fertilizers may reduce the emission. Local climate conditions, average temperature and annual rainfall, may be responsible for part of the observed year to year differences of the total season emission. Estimates of total emissions of CH4 from Chinese rice fields, based on field measurement and model calculation, are 9.7–12.7 Tg/year and 8.17–10.52 Tg/year respectively, for the year of 1994. Oxidation of CH4 reduces the emission of CH4 produced in the soil of rice field to the atmosphere. The most likely sites for CH4 oxidation in rice fields are the water–soil interface and the rhizosphere. When the flood water dries up in irrigated fields, the oxidation of CH4 in the soil is more important and can partially explain the lower emission rates during the last period before harvest in most experiments. The magnitude of oxidation in the rhizosphere is not well known. Good correlation between methane reduction and O2 mixing ratio in the soil has been found in most soil types. Methane oxidation rate is mainly controlled by the gas transport resistance in the soil. The oxidation rate increases with the increase of temperature in the temperature range of 5–36 °C.

New estimates of methane emissions from Chinese rice paddies

In this paper, a new method had been developed, which is suitable to estimate methane emissions from rice fields in China at present. The method is developed based upon the methane models developed in China, different from those recommended by OECD/IPCC. The influences of climate conditions, field water management, organic fertilizers and soil types on methane emission from rice fields are considered. The methane model has been tested with field measurement data. Methane emissions from Chinese rice fields are estimated to be 9.67–12.66 Tg/yr in 1990. These values are lower than previous estimates and are more nearly to the measured data, because of the improved method extrapolations of field measurements.

Importance of water regime during the non-rice growing period in winter in regional variation of CH4 emissions from rice fields during following rice growing period in China

Rice fields are either continuously flooded or drained in China in the winter (non-rice growth season). Due to great spatial variation of precipitation and temperature, there is a spatial variation of soil moisture in the fields under drained conditions during the winter season. The effect of water regime in winter on CH4 emissions during the following rice growing period and their regional variation were investigated. Soil moisture in the winter was simulated by DNDC model with daily precipitation and temperature as model inputs. Under the same management during the rice growing period, CH4 emissions was higher from rice fields flooded, compared to those from fields drained during winter. CH4 emission from rice fields correlated significantly with simulated soil moisture and with mean precipitation of the preceding winter season. Spatial variation of precipitation in winter and corresponding variations of soil moisture regimes control the regional and annual variation of CH4 emissions from rice fields in China. Keeping soils drained as much as possible during winter seems to be a feasible option to reduce CH4 emissions during the following rice growing seasons.

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.

Emissions of methane, nitrous oxide, and other trace gases from rice fields in China

We measured the emissions of methane, nitrous oxide, and other environmentally important trace gases from rice fields in China. The experiments were conducted near Beijing, representing temperate latitude rice agriculture, and at Guangzhou, representing tropical and subtropical agriculture. These studies complement our intensive research at Tu Zu in China (subtropical) and the work near Bogor, Indonesia, representing tropical rice agriculture. The experiments described here span 5 years between 1992 and 1996. The seasonally averaged methane emissions from Beijing were about 9 (5–16) mg m−2 h−1. Emissions from the first crop of the year at Guangzhou were about 5 (2–8) mg m−2 h−1 and about 30 (18–54) mg m−2 h−1 from the second crop. Measurements of nitrous oxide fluxes from the same rice fields show that emissions are confined to events that consist of high fluxes decaying to zero within a few days. Some of the events appear to be triggered by fertilizer applications. It is apparent that rice fields using nitrogen‐based fertilizers are a source of N2O, but a robust estimate of whole season average emission rate is still not possible. The composite of all the N2O fluxes we observed gives a geometric mean of about 70 μg m−2 h−1. These rates are high enough to suggest that the rice fields could be a globally important source of N2O. As the agricultural practices change from use of organic fertilizers to nitrogen‐based fertilizers, the role of N2O emissions from rice fields may become more important in its global budget. We also observed that chloroform and carbon monoxide were emitted from all fields studied. The flux of CO is not large enough to be important on the global scale, but the emissions of chloroform may be.

Measurements of methane emissions from rice fields in China

Rice fields have always been regarded as one of the largest anthropogenic sources of atmospheric methane. Here we report the results of a 7‐year study of methane emissions from rice fields in the Sichuan Province of China. In this region, there is one crop of rice per year, the fields are continuously flooded from transplanting to harvest, and there is heavy use of organic fertilizers. Emissions over the entire growing season were measured from each of up to 24 plots. Environmental variables were measured and relevant supporting data on the agricultural practices were recorded. The fields were studied under prevailing agricultural practices of the local farmers. The results represent emissions under standard agricultural practices and the year to year variability of climate, fertilizers, available irrigation water, and cultivars. Based on some 5000 flux measurements, the average emission rates between 1988 and 1994 were 30 mg/m2/h for a growing season of between 100 and 120 days. This emission rate is comparable to other published data from similar rice fields but somewhat on the high side of the range. There were no systematic trends of emissions during the 7 years of our experiment, but there was substantial year to year variability. The data have been subjected to exhaustive analyses for validity, accuracy, and reliability. From this, a high‐quality, spatially averaged data set has been constructed representing average emissions from the rice fields for each day when measurements were taken. We describe here the main observational results and document the spatial and temporal variability observed on timescales ranging from a day to several years and on spatial scales ranging from 0.5 m2 to 16 m2.

Using ambient concentrations as proxy for methane flux measurements from rice fields

Ambient concentrations of trace gases near their sources carry precise information about the emission rates. In this paper we use ambient measurements of methane near rice fields to estimate the emissions and compare them to actual flux measurements. The data are from a seven-year study of rice fields in China when both emissions and ambient concentrations were measured. The calculations are based on an empirical model of the dilution factor that relates emissions from the rice fields to the ambient concentrations caused by these emissions. The relationship is derived from the first year of the experiment (base year — 1988) and then applied to subsequent years (1989–1994) using only ambient measurements near the rice fields, to estimate methane emissions. The ambient data are about an order of magnitude fewer than the data for the direct flux measurements. Yet, the results of the ambient proxy calculations of flux are in agreement with the seasonal patterns and whole season emissions measured from the direct flux measurements. The seasonally averaged fluxes for each year agree to within ± 25%. There is a close agreement between the actual flux measurements and the proxy estimates of the seasonal pattern of emissions in the composite of all years of data (± 10 %). The seasonally averaged emissions over all seven years are nearly the same between the proxy] and actual measurements at about 30 mg/m=/hr (within 2%).These results are an independent validation of the direct flux measurements taken at this site.

Balancing the rice carbon budget in China using spatially-distributed data

Rice paddies are a source of food for over half of the world population and also the source of a very potent greenhouse gas, methane. We used the FAO soil map of the world to produce a high-resolution rice location map. Using published GIS-linked climate-based and yield-based empirical models, we calculated the net primary production (NPP) of rice fields in China. Values varied between 136·10 12 g C using climate drivers from digital maps to 222·10 12 g C using published grain production figures for 1988. We assumed that either 5% of NPP or 30% of the organic matter added to the soil during rice cultivation was transformed into methane, adding up to a total emission of 7 to 16·10 12 g C. We also gathered published data on fertilizer inputs and management practices and, using linear regression techniques, calculated the correlation between methane emission and carbon inputs to obtain a total emission value of 10·10 12 g C. Using the results for NPP (135–222·10 12 g C), methane emission (7–16·10 12 g C) and published grain production figures, we balanced the carbon budget of rice paddies estimating soil respiration at 51·10 12 g C for all Chinese rice fields or 159 g C m −2 y −1 for an average Chinese rice field, a number which agrees with published values for similar systems. This result confirmed our assumption that rice soils in China, where rice cultivation has occurred for several thousand years, were neither losing nor accruing carbon. However, any changes in the hydrology of these soils may transform them into significant carbon sources. Using the Food and Agricultural Organization (FAO) digital map of the soils of the world, we estimated soil carbon content for the rice-growing regions of China and quantified the potential carbon losses that would occur if these soils were drained.

Possibilities for Reducing Methane Emission From Ricefields in China

Possibilities for Reducing Methane Emission From Ricefields in China

Methane emissions from rice fields in China

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMethane emissions from rice fields in ChinaM. A. K. Khalil, R. A. Rasmussen, Ming Xing Wang, and Lixin RenCite this: Environ. Sci. Technol. 1991, 25, 5, 979–981Publication Date (Print):May 1, 1991Publication History Published online1 May 2002Published inissue 1 May 1991https://doi.org/10.1021/es00017a023RIGHTS & PERMISSIONSArticle Views575Altmetric-Citations118LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (310 KB) Get e-Alerts Get e-Alerts

Patterns of Trace Gases Near Sources of Global Pollution

Many trace gases are increasing in the earth's armosphere and may couase global environmental changes in the future. Consequently there has been growing interest in the cycles of the long-lived gases that are likely to contribute the most to global change. At present there are four such gases: methane (CH{sub 4}), nitrous oxide (N{sub 2}0), trichlorofluoromethane (CCl{sub 3}F,F-11), and dichlorodifluoromethane (CCl{sub 2}F{sub 2},F-12). Methane and N{sub 2}O are involved mostly in adding to the greenhouse effect with some role in the stratospheric ozone cycle, and the two main fluorocarbons (F-11 and F-12) are involved in the depletion of the ozone layer with some role in global warming. This paper is about the patterns of these trace gases near regions of global scale pollution. Our purpose is to provide a synthesis of observations from diverse environments and ecosystems of the world and to provide readers with intuitive connections between sources and concentrations. We will consider four types of regions: rice fields in CHina that are a major source of methane, urban areas of the United States and China that are sources of fluorocarbons and other gases, rivers and surrounding wetlands, specifically the Yangtze in China and the Amazon in Brazil, andmore » finally the environment of Boola Boola National Forest in Australia populated by many speices of termites that are a source of methane to the atmosphere. Eventually these patterns can be translated into estimeates of fluxes from the various sources of global pollution.« less

Water-air transfer resistance for ammonia from flooded rice

Vertical flux densities of ammonia, water vapour and sensible heat were measured over a flooded rice field in China following the application of ammonium bicarbonate fertilizer. Aqueous and gaseous phase transfer resistances for ammonia were deduced from these measurements. The aqueous phase resistance was maximal in the morning and least in the afternoon. Stable stratification of the floodwater immediately adjacent to the air-water interface was observed during the morning when evaporation rates were low, and may be responsible for inhibiting the transfer of ammonia to the atmosphere.

A Veteran Goes to College

EYVEN in the most remote part of the world, wherever there are American soldiers, news of educational planning and benefits during the postwar era has been disseminated. The question is whether educators at home will have a thorough understanding of the problems of the American soldier unless some of them have shared at least a few of the trying experiences which soldiers meet at the fighting front. Obviously, it is not practicable to ask our educators at home to visit the battle areas of the Burma jungle, the hot spots in India, the rice fields in China, or the firing lines of Italy and France. Nevertheless, on all of the fighting fronts there are many teachers who are also good soldiers. These teachers have led youth in peace and are now leading men in war. Their hope is to return to teaching, in a free world. Their experience on the fighting fronts has proved a dynamic and challenging re-inforcement of their formal university training. They have shared in the experiences of their future students, thereby establishing a common basis for understanding the problems and the needs of the veterans in the postwar years. The proposal made here is that a representation of educators who have served with the armed forces in various combat areas be called upon to aid in the planning of curriculum and in determining the aims and methods of instruction in higher education, both general and specialized. These educators, working with experts at home, would find surveys of the opinions of military personnel of great value in determining their postwar needs and facilitating their postwar adjustments. If general education is to be fostered in the American colleges, the traditional isolated series of courses distributed among various departments will not suffice. The purpose of general education, as stated by Mr. Kellv of the United States Office of Education, is to advance the public welfare. The public welfare cannot be advanced nor can the needs of the veterans be fulfilled by giving a series of lectures in English, social studies, science, mathematics, and languages. Instead, the college curriculum should be integrated to offer study of vital problems and their solutions whenever possible. This type of curriculum construction would unite professors from all departments in a concerted attack