Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Shifts in rice farming practices in China reduce greenhouse gas methane

20.12.2002


Changes to farming practices in rice paddies in China may have led to a decrease in methane emissions, and an observed decline in the rate that methane has entered the Earth’s atmosphere over the last 20 years, a NASA-funded study finds.



Changsheng Li, a professor of natural resources in the University of New Hampshire’s Institute for the Study of Earth, Oceans, and Space, and lead author of the study, notes that in the early 1980s Chinese farmers began draining their paddies midway through the rice growing season when they learned that replacing a strategy of continuous flooding would in fact increase their yields and save water. As an unintended consequence of this shift, less methane was emitted out of rice paddies.

Methane is 21 times more potent as a greenhouse gas than carbon dioxide (CO2) over 100 years. At the same time, since 1750, methane concentrations in the atmosphere have more than doubled, though the rate of increase has slowed during the 1980-90s.


"There are three major greenhouse gases emitted from agricultural lands-carbon dioxide, methane and nitrous oxide," said Li. "Methane has a much greater warming potential than CO2, but at the same time, methane is very sensitive to management practices." Currently, about 8 percent of global methane emissions come from the world’s rice paddies.

In an effort to reduce water use, farmers in China found that if they drained the soils, they could get higher yields. That’s because draining stimulates rice root development, and also accelerates decomposition of organic matter in the soil to produce more inorganic nitrogen, an important fertilizer. Methane is produced by soil microbes in paddy soils under anaerobic conditions, or in the absence of air or free oxygen. Midseason drainage aerates the soil again, and hence interrupts methane production.

Li and his colleagues recorded reductions in methane caused by draining practices at several experimental sites in China and the U.S. At the same time, they observed that the amounts of methane reduction varied greatly in space and time due to complex interactions among many factors.

The researchers spent more than 10 years developing a biogeochemical model, called the Denitrification-Decomposition (DNDC) model, which would handle all the major factors relating to methane emissions from rice paddies. These factors included weather, soil properties, crop types and rotations, tillage, fertilizer and manure use, and water management. The model was employed in the study to scale up the observed impacts of water management from the local sites to larger regional scales. Remotely sensed data from the NASA/U.S. Geological Survey Landsat Thematic Mapper (TM) satellite were utilized to locate the geographic distributions and quantify the acreage of all the rice fields in China. A Geographic Information System database amended with this Landsat data was constructed to support the model runs at the national scale and to predict methane emissions from all rice fields in the country.

The researchers adopted 1990 as a mean representative year as they had detailed, reliable data for that year, and then ran the model with two water management scenarios to cover the changes in farming practices from 1980 to 2000. The two scenarios included continuous flooding over each season, and draining of paddy water three times over the course of each season.

When the two model runs were compared, the researchers found that methane emissions from China’s paddy fields were reduced over that time period by about 40 percent, or by 5 million metric tons per year-an amount roughly equivalent to the decrease in the rate of growth of total global methane emissions.

"The modeled decline in methane emissions in China is consistent with the slowing of the growth rate of atmospheric methane during the same period," Li said. "Still, more work will be needed to further verify the relationship demonstrated in this study with limited data points."

Demand for rice in Asia is projected to increase by 70 percent over the next 30 years, and agriculture currently accounts for about 86 percent of total water consumption in Asia, according to a recent report from the International Rice Research Institute. Changes to management practices like this will be more important and likely in the future as the world’s water resources become increasingly limited, Li said.

"Just like the Chinese farmers did, if farmers around the world change management practices, we can increase yields, save water and reduce methane as a greenhouse gas," Li said. "That’s a win-win situation."



The study, which appears in the print version of Geophysical Research Letters in late December, was funded by NASA through grants from the multi-agency Terrestrial Ecosystems and Global Change Program, and also NASA’s Earth Science Enterprise.

Krishna Ramanujan | EurekAlert!
Further information:
http://www.gsfc.nasa.gov/topstory/2002/1204paddies.html
http://www.gsfc.nasa.gov/

More articles from Agricultural and Forestry Science:

nachricht New data unearths pesticide peril in beehives
21.04.2017 | Cornell University

nachricht New rice fights off drought
04.04.2017 | RIKEN

All articles from Agricultural and Forestry Science >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

Im Focus: Quantum-physical Model System

Computer-assisted methods aid Heidelberg physicists in reproducing experiment with ultracold atoms

Two researchers at Heidelberg University have developed a model system that enables a better understanding of the processes in a quantum-physical experiment...

Im Focus: Glacier bacteria’s contribution to carbon cycling

Glaciers might seem rather inhospitable environments. However, they are home to a diverse and vibrant microbial community. It’s becoming increasingly clear that they play a bigger role in the carbon cycle than previously thought.

A new study, now published in the journal Nature Geoscience, shows how microbial communities in melting glaciers contribute to the Earth’s carbon cycle, a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

New quantum liquid crystals may play role in future of computers

21.04.2017 | Physics and Astronomy

A promising target for kidney fibrosis

21.04.2017 | Health and Medicine

Light rays from a supernova bent by the curvature of space-time around a galaxy

21.04.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>