Session 2: Nitrogen, Green House Gasses and Agricultur

CAI  Zucong

YAN  Xiaoyuan

English

紀要類 (bulletin)Session 2: Nitrogen, Green House Gasses and Agriculturedepartmental bulletin pape

YAN, Xiaoyuan

CAI, Zucong

Tohoku University Repository (TOUR) / 東北大学機関リポジトリ

Integrated Greenhouse gas emission from paddyfields in China著者 YAN  Xiaoyuan, CAI  Zucongjournal orpublication titleJournal of Integrated Field Sciencevolume 9page range 100-101year 2012-03URL http://hdl.handle.net/10097/54452100A Great Challenge to Solve Nitrogen Pollution from Intensive AgricultureZucong CAI1 and Xiaoyuan YAN21College of Geography Science, Nanjing Normal University, Nanjing 2100462Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008The huge population and the small arable land area per person determine that intensive agriculture, which is characterized by high ratio of cultivated land to territory, high multiple cropping indices, and large input of agro-chemicals, is an inevitable choice for food security in China. Although the researches were continuously strenthened for good management practices for raising nitrogen use efﬁ ciency (NUE), minimizing N losses from croplands, and thus mitigating adverse impacts of N application on environment and the knowledge on rational application of N fertilizers was improved greatly in China in the last three decades, the total consumption of N fertilizers continuously increased and NUE, on the national average, decreased from about 30-35% in 1980s to around 20-30% in 2000s. This is because the top priority for food security drove the increase in consumption of N fertilizers, thus leading to the decrease in NUE. The driving force for producing food as much as possible will continue and potential is available for enhancing crop production through raising multiple cropping indices and increasing N application in China, while, the NUE is unlikely to reach the levels achieved in some developed countries because it decreases with the increases in multiple cropping indices and nitrogen application rate. All of these factors determines that the N consumption will increase in China in future. Therefore, while we should continue to struggling for higher NUE,  we have to realize that nitrogen pollution from crop production could not be controlled by raising NUE alone under intensive agriculture. In order to protect our environment and sustain development, we have to face a challenge to solve nitrogen pollution under the condition of high nitrogen ap-plication rate. Research should be strengthened for the control of nitrogen pollution through establishedment of theories, principles, technologies, and policies under the intensive agriculture.Session 2: Nitrogen, Green House Gasses and AgricultureIntegrated Greenhouse gas emission from paddy fi elds in ChinaXiaoyuan YAN1 and Zucong CAI21College of Geography Science, Nanjing Normal University, Nanjing 2100462Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008Rice is the crop with the biggest production in China, but the sowing area of rice showed a declining trend since middle 1970s and was outweighed by maize in 2007. The current sowing area is about 29 million ha, with half being single rice, one quarter being early rice and remaining being late rice. Methane (CH4) emission has been measured on over 30 sites, with varying duration since late 1980s. Measured seasonal emissions were ex-tremely variable, ranging from 3.4 to 1274 kg CH4 ha-1. Except the widely acknowledged inﬂ uencing factors such as organic amendment, water regime during rice growing season, it was found that seasonal emission from late rice is higher than that from early rice, and the latter is higher than that from single rice, likely due to the dif-ference in the water regimes before these rice seasons. A number of estimations have been made for the total CH4 emission from Chinese rice ﬁ elds, with more recent ones being around 7.6 Tg CH4 year-1. Nitrous oxide (N2O) emission from paddy ﬁ elds in China has been measured on over 20 sites, with seasonal emissions ranging from 0.02 to 12.6 kg N ha-1. Estimated annual emission ranged from 29 to 37 Gg N. While emitting CH4, paddy ﬁ elds in China acted as a sink of atmospheric carbon dioxide (CO2). Average soil 101organic carbon content of paddy ﬁ elds increased by 2.5% from 1980 to 2007, which translates to a carbon se-questration of 74 Tg for the paddy ﬁ elds nationwide. The sequestrated carbon equals 5.3% of the CH4 emitted during the same time period in terms of global warming potential (GWP). In summary, Chinese paddy ﬁ elds emit CH4 and N2O at 190 and 9.8 Tg CO2-eq year-1, respectively, and seques-trate carbon at 10 Tg CO2-eq year-1. Thus the GWP of paddy ﬁ elds is absolutely dominated by CH4 emission.Analysis of research stocktaking in the Paddy Rice Research Group of theGlobal Research Alliance on Agricultural Greenhouse GasesK. YAGINational Institute for Agro-Environmental SciencesThe Global Research Alliance on Agricultural Greenhouse Gases, which was launched in December 2009, brings countries together to ﬁ nd ways to grow more food without increasing GHG emissions (Global Research Alliance; Shafer et al., 2011). As an initial activity in the Alliance, research stocktaking was conducted within participating countries to identify current research activities, opportunities, gaps and areas of overlap. The results for the Paddy Rice Research Group are presented.A detailed spreadsheet that captures information on each country’s research projects and programmes in ag-ricultural greenhouse gas emissions was prepared and distributed to each contact point of the Alliance member countries. The questions on the spreadsheet include research target, topic, outcome, structure, etc. as well as key equipment, facilities, and databases. As at 1 March 2011, 68 projects from 16 countries (China, Denmark, Ghana, Indonesia, Japan, Korea, Malaysia, Netherlands, Pakistan, Peru, Philippines, Russian Federation, Spain, Thai-land, Uruguay and US) had been listed in the stocktake of the Paddy Rice Research Group.Most of the research is being undertaken into irrigated rice production systems, with little on rain-fed produc-tion systems. The lack of data for rain-fed systems may cause difficulties when one tries to develop country speciﬁ c emission factors. Projects focusing on methane accounted just over 50%, and the percentages for nitrous oxide and soil carbon sinks/sources were 30% and 20%, respectively. This result suggests that possible trade-off between different GHGs and the importance of evaluating the net global warming potential are well understood in many research projects. There were two areas of research that predominated: GHG accounting/life cycle assessment and agronomy. While much smaller, the third focus for research was farming systems. In terms of research outcomes, the key primary outcomes were included: testing of mitigation, low greenhouse gas emitting varieties, improved national inventory and investigation of mitigation options. Most of the current research can be described as “applied” or “tactical” and is primarily funded from governments. The results indicate the general need for research progress on developing mitigation options and improving national inventories for GHG emissions from paddy ﬁ elds in many countries.The Paddy Rice Research Group of the Alliance will continue to compile databases on research projects, ex-perts and literature related to GHG emissions from paddy ﬁ elds in each member country. Those processes will be conducted through the contact point of each country. The Group also plans to develop and publish a manual of standardised measurement techniques for GHG emissions from paddy ﬁ elds through identiﬁ cation of “good practice” and gaps in current methodology. As a plan for longer term action, it is discussing to develop a simple project protocol for evaluating promising mitigation options, such as water management practices, that would be undertaken in a number of rice producing countries.

Integrated Greenhouse gas emission from paddy fields in China

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Integrated Greenhouse gas emission from paddy fields in China

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