Nitrous oxide emissions from rice farms may speed up global warming – Study

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A global analysis published by the Environmental Protection Fund on Monday showed that emissions of methane and nitrous oxide in rice farms can have the same effect on long-term warming as about 600 coal plants

The study, published on Monday, showed that rice cultivation around the world can be responsible for twice the level of climate impact that scientists evaluated earlier.
It was published in the Proceedings of the National Academy of Sciences.
According to a new study, periodically overcrowded rice farms can give off 30 to 45 times more nitrous oxide than the maximum from constantly flooded farms that predominantly secrete methane.
A global analysis published by the Environmental Protection Fund on Monday showed that emissions of methane and nitrous oxide in rice farms can have the same effect on long-term warming, like about 600 coal plants.
In the short term, this warming can be up to 1200 medium-sized coal-fired power plants, since nitrous oxide in the atmosphere has many decades more than in methane.
The authors also found an inverse correlation between the emissions of methane and nitrous oxide from rice.
The management of water and organic substances that reduce methane emissions can increase nitrous oxide emissions.
This is crucial, since nitrous oxide is a long-lived greenhouse gas that captures several times more heat in the atmosphere than methane over 20 and 100 years.
"The overall climatic effect of rice in agriculture has been significantly underestimated, because up to this point, emissions of nitrogen dioxide from constantly overcrowded farms have not been included," said Crete Crete, a senior researcher at EDF and lead author of the article.
"Increasing pressure on limited water resources in a changing climate can lead to additional rice-growing areas that will seek to intermittently flood to eliminate water restrictions and methane emissions," Crete said.
According to her, water management on rice farms needs to be calibrated in order to balance the problems of water use with the climatic consequences of methane and nitrous oxide emissions.
Rice is the most important source of nutrition for the fast-growing world population, providing more calories for people than any other food.
But growing rice is also resource intensive: rice cultivation covers 11 percent of arable land, consumes one third of irrigation water.
Current climate mitigation strategies for rice production are aimed at reducing methane emissions through alternative wetting and drying or intermittent flooding.
Most rice-producing countries, including the United States and the world's largest rice producers such as China, India, Indonesia, Vietnam and Bangladesh, do not report nitrous oxide emissions associated with rice production within their national greenhouse gas inventories submitted by the United Nations.
Researchers measured greenhouse gas emissions in rice farms in southern India and found that nitrous oxide emissions from rice can be up to 99 percent of the total climate impact on rice cultivation on various farms with intermittent flooding.
According to the study, these emissions contributed significantly to the pollution of global warming, which is much more than the estimate of 10 percent previously proposed by several global research organizations on rice research.
In addition, they found that carefully selected farming practices on individual farms reduced net greenhouse gas emissions in growing rice by as much as 90 percent by integrating shallow flooding with the combined management of nitrogen and organic matter.
If all the irrigated rice farmers used only the alleged small floods, rather than continuous or intense forms of intermittent flooding, estimates showed that rice farms with irrigation could reduce their global climate impact by 60 percent.
Xinhua / NAN.

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