Fertilizer overuse destroying Chinese soil
As usual with cutting edge research, the timing and significance of this is impossible for a layman to accurately access. But this could be bad for China. Yields have already dropped 30-50% in some places.
- A summary of the research by Reuters
- More detailed summaries, in ScienceNow and Nature
- The research, in Science
- For more information from the FM site, and an Afterword
(1) A summary of the research by Reuters
Vivid, for a general audience. “Fertilizer overuse destroying Chinese soil“, Reuters, 11 February 2010 — Excerpt:
Heavy use of nitrogen fertilizers in China since the 1980s has resulted in severe acidification of its soil and some cropland in the south of the country can no longer be used, a Chinese expert said. “In the south, heavy use of fertilizers has pushed the pH to 3 or 4 in some places. Maize, tobacco and tea cannot be grown. This is a long term effect,” said Zhang Fusuo, a professor on plant nutrition at China Agricultural University in Beijing.
… China’s grain production and nitrogen fertilizer use hit 502 million tonnes and 32.6 million tonnes in 2007, up 54 percent and 191 percent compared to 1981, according to Zhang and his colleagues, who published their findings in the journal Science.
… The average pH in all of China has decreased by 0.5 unit in the last 20 years. Left to nature, a single unit change needs hundreds of years or even over 1,000 years, but we have got this change now due to fertilizer overuse,” Zhang said.
(2) A more detailed summary
“Fertilizer Is Acidifying Chinese Land“, Mara Hvistendahl, ScienceNOW, 11 February 2010 — Subscription only. Excerpt:
China has long struggled to feed one-fifth of the world’s population on 7% of the world’s arable land. Adding to the challenge are the side effects of rapid economic development: air pollution, contaminated water, and encroaching urbanization, all of which threaten Chinese farmland. Now, a new study has tacked unnaturally acidic soil onto the list, caused by excessive fertilizer use over the past 30 years.
… The trend has been charted by soil scientist Zhang Fusuo of China Agricultural University in Beijing and colleagues. They compared the results of a national soil survey taken in the 1980s with surveys conducted over the past decade. They also collected data spanning 25 years from the closely monitored agricultural zones the Chinese government maintains throughout the country. For nearly all soil types found in China, soil pH has dropped 0.13 to 0.80 units since the early 1980s, they report online today in Science. A drop on that scale “normally takes hundreds of thousands of years,” Zhang says. Even soils considered resistant to acidification showed a decrease in pH.
Soil acidification can be the result of acid rain. But overuse of certain types of nitrogen fertilizer is another cause, and this is what the researchers identify as the culprit in China. Beginning in the 1970s, Chinese farmers applied ever-increasing amounts of fertilizer with the hope that it would lead to bigger harvests. Instead of high yield, however, they got water and air pollution. Today, agricultural experts estimate that in many parts of China fertilizer use can be slashed by up to 60%.
A drop in pH on the level identified in the study could have some very harmful effects. Acidic soil is paradise for nematodes, parasitic roundworms that destroy crops. And at least one group of Chinese soils is approaching the pH values at which aluminum and manganese start leaching into surface water, with potentially toxic results. …
“Acid soil threatens Chinese farms“, Nature, 11 February 2010 — Subscription only. Excerpt:
“Chinese farmers’ rampant use of fertilizers could soon endanger the nation’s ability to feed itself. A survey of more than 8,000 samples from across the country has shown that overuse of nitrogen fertilizers has caused soil pH to plummet over the past 20 years.”
(3) The research, in Science
“Significant Acidification in Major Chinese Croplands“, J. H. Guo, Science, 11 February 2010 — Subscription only. PDF attached. Abstract:
Soil acidification is a major problem in soils of intensive Chinese agricultural systems. We used two nationwide surveys, paired comparisons in numerous individual sites, and several long-term monitoring-field data sets to evaluate changes in soil acidity. Soil pH declined significantly (P < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. Processes related to nitrogen cycling released 20 to 221 kilomoles of hydrogen ion (H+) per hectare per year, and base cations uptake contributed a further 15 to 20 kilomoles of H+ per hectare per year to soil acidification in four widespread cropping systems. In comparison, acid deposition (0.4 to 2.0 kilomoles of H+ per hectare per year) made a small contribution to the acidification of agricultural soils across China.
(4a) For more information from the FM site
To read other articles about these things, see the FM reference page on the right side menu bar, including About the FM website page. Of esp relevance to this topic:
Posts about the potential food crisis:
- Important news about the global food crisis!, 1 April 2008
- A view from Indonesia of the food crisis, 3 April 2008
- Stratfor warns about the global food crisis, 18 April 2008
- What you probably do not know about China’s food crisis, 21 April 2008
- Higher food prices, riots, shortages – what is going on?, 29 April 2008
- A modest proposal for solving the global food crisis, 30 April 2008
- Weekend reading about the Food Crisis, 17 May 2008
- Teach a man to fish, and you understand what we have done wrong in Haiti, 23 May 2008
- “Food scares are exaggerated, but good copy for the media”, 28 May 2008
- Is global food production peaking?, 13 January 2010
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