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 Back to Nature: Palm oil plantations are being turned back into protected rainforest
21.03.2019 | Forschungsverbund Berlin e.V.

nachricht The inner struggle of the evening primrose: Chloroplasts are caught up in an evolutionary arms race
14.03.2019 | Max-Planck-Institut für Molekulare Pflanzenphysiologie

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: Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

A stellar flare 10 times more powerful than anything seen on our sun has burst from an ultracool star almost the same size as Jupiter

  • Coolest and smallest star to produce a superflare found
  • Star is a tenth of the radius of our Sun
  • Researchers led by University of Warwick could only see...

Im Focus: Quantum simulation more stable than expected

A localization phenomenon boosts the accuracy of solving quantum many-body problems with quantum computers which are otherwise challenging for conventional computers. This brings such digital quantum simulation within reach on quantum devices available today.

Quantum computers promise to solve certain computational problems exponentially faster than any classical machine. “A particularly promising application is the...

Im Focus: Largest, fastest array of microscopic 'traffic cops' for optical communications

The technology could revolutionize how information travels through data centers and artificial intelligence networks

Engineers at the University of California, Berkeley have built a new photonic switch that can control the direction of light passing through optical fibers...

Im Focus: A long-distance relationship in femtoseconds

Physicists observe how electron-hole pairs drift apart at ultrafast speed, but still remain strongly bound.

Modern electronics relies on ultrafast charge motion on ever shorter length scales. Physicists from Regensburg and Gothenburg have now succeeded in resolving a...

Im Focus: Researchers 3D print metamaterials with novel optical properties

Engineers create novel optical devices, including a moth eye-inspired omnidirectional microwave antenna

A team of engineers at Tufts University has developed a series of 3D printed metamaterials with unique microwave or optical properties that go beyond what is...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

Fraunhofer FHR at the IEEE Radar Conference 2019 in Boston, USA

09.04.2019 | Event News

 
Latest News

New automated biological-sample analysis systems to accelerate disease detection

18.04.2019 | Life Sciences

Explosion on Jupiter-sized star 10 times more powerful than ever seen on our sun

18.04.2019 | Physics and Astronomy

New eDNA technology used to quickly assess coral reefs

18.04.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>