A new study by the Chinese Academy of Sciences recommends a 60 percent
reduction in fertilizer use in areas that are already ‘over-fertilized.’
AsianScientist (Nov. 5, 2012) – A new study by the Chinese Academy of Sciences
recommends a 60 percent reduction in fertilizer use in areas that are already
‘over-fertilized.’
Halving the amount of nitrogen
fertilizer used in certain areas of China would substantially decrease
greenhouse gas emissions without affecting crop productivity and the area’s
natural carbon sink, it says.
The study, which was published
this month in the journal Environmental Research Letters, also
pinpointed areas of heavy nitrogen fertilizer use as the North China Plain and
middle and lower reaches of the Yangtze River Basin.
China is currently tasked with
meeting the food demands of 22 percent of the world’s population; however, its
over-reliance on nitrogen-based fertilizer has dramatically increased its
emissions of nitrous oxide – the third highest contributor to climate change
behind carbon dioxide and methane.
According to the study, since
2002, the warming effect caused by nitrous oxide emissions has been
significantly greater than the cooling effects from the croplands storing
carbon dioxide, resulting in overall warming.
Looking at the past six decades,
the researchers found that between 1949 and 1990 nitrogen fertilizer increased
the rates of crop production and the storage of soil carbon; however, from 1990
onward, they found that the rate of soil carbon storage stopped and the rate of
crop production slowed.
In the 1990s, nitrogen fertilizer
was contributing to 53 percent of the crop production but since then has
contributed to 49 percent, even though more of it was being used, suggesting it
had become less effective.
Nitrogen fertilizer can be
beneficial to the climate, providing crops with essential nutrients so they can
grow and create a larger natural carbon sink in soils, taking in excess carbon
dioxide that is released into the atmosphere. When there is a balance between
nitrous oxide release and carbon dioxide intake, the warming effects of nitrous
oxide can be negated.
“Nitrogen fertilizers have become
less efficient in recent years as the nitrogen input has surpassed nitrogen
demands of plants and microbes. Excess nitrogen is not stimulating plant growth
but leaving the system through leaching and nitrous gas emissions,” said Dr.
Hanqin Tian, a co-author on the study.
Chinese farmers need to be
educated on the economic and environmental costs of excessive nitrogen
fertilizer use, says Tian.
“Effective management practices
such as compound fertilizer use and optimized irrigation and tillage should be
advanced to increase nitrogen use efficiency,” he advised.
The article can be found at: Tian H et al. (2012) Food benefit and climate
warming potential induced by nitrogen fertilizer uses in China.
Source: Institute of Physics
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