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Fertilizer overuse destroying Chinese soil

18 February 2010

 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.

  1. A summary of the research by Reuters
  2. More detailed summaries, in ScienceNow and Nature
  3. The research, in Science
  4. 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:

(4b)  Afterword

Please share your comments by posting below.  Per the FM site’s Comment Policy, please make them brief (250 word max), civil and relevant to this post.  Or email me at fabmaximus at hotmail dot com (note the spam-protected spelling).

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5 Comments leave one →
  1. jon (layman) permalink
    18 February 2010 12:11 am

    I don’t see them laying off the juice anytime soon, what with the booming and all. Maybe they could import more. Maybe we could settle the ~$800 billion debt we’ve got with them by selling some of California’s excess once the water issues get figured out.
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    FM reply: I suggest you not make any bets assuming China’s farmers are fools.

    Like

  2. Grimgrin permalink
    18 February 2010 1:35 am

    Chinese farmers may not be stupid (anyone who farms/ranches successfully rarely is) but agricultural policy is not set by farmers, and agribuisness is not noted for caring about long term consequences.

    That said a reduction of arable land in China is likely to accelerate the drive for leased agricultural land in Africa, which to me looks like its setting the stage for one serious drought or crop failure being a continent wide replay of the Irish potato famine. Or it may lead to the government subsidizing Calcium Hydroxide to kick the problem down the road while trying to maintain yields and food security.
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    FM reply: My understanding (which could easily be wrong) is that China’s farmers usually work with little direction from business or government supervisors, as a result of the first post-Mao reforms (although they lack title to the land). Do you have any information on this?

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  3. Grimgrin permalink
    18 February 2010 3:20 am

    Here’s a USDA report on China’s agricutural subsidies: “China’s New Farm Subsidies“, US Dept of Ag, February 2005
    And the USDA Economic Research Service webpage “Summary of China’s agricultural policy measures
    Here’s an OECD report: “Agricultural Policy Reform in China“, October 2005

    Farming inputs, seeds, equipment and fertilizers are directly subsidized, as well as being supported by loans, and government purchasing. While this isn’t the same as direct control over production, any subsidy regime is going to influence what’s produced and how it’s produced.
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    FM reply: Agreed. Thanks for the links! But as they learn what’s happening, a subsidy regime will not induce farmers to lower yields through fertilizer overuse. They’re not stupid, which was my original reply to comment #1.

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  4. 18 February 2010 3:54 pm

    There is a radio speech by Governor Alfred E. Smith of New York, back in 1925 or so, in which he said “The best cure for evils of democracy is. . .more democracy.” Jerry Pournelle paraphrases it to say “The best cure for the evils of technology is more technology.” I agree.

    If farmers anywhere are losing yield because the soil has grown too acidic, then adding some cheap base to raise the pH would seem a reasonable second step. Using fertilizer of any kind (“night soil”) has been done for millenia. Using chemical fertilizers will produce a large jump in yields. Then you get more sophisticated and bring the pH back into balance, and add a “cocktail” of micronutrients. . . As you said, they are not fools.
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    FM reply: Did you read the articles? They are overapplying fertilizer. Most drugs have doses beyond which there are long-term side-effects. That seems to be what’s happening here. No new input of technology needed, except over longer-term horizons — when better fertilizers might appear.

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  5. PC Scipio permalink
    18 February 2010 5:50 pm

    Ave, Quintus Fabius.

    Perhaps the Chinese agricultural sector is undergoing something akin to the U.S. in the “Great Plains” (once referred to as the “Great American Desert”) during the first part of the 20th Century. At that time, marginal lands were intensely cultivated to the point that when drought came, the soils and cover were too weak to hold themselves to the earth. We know what happened next.

    Now I am sure that the Chinese powers-that-be will not want a replication of the American experience. However, they do have competing needs and wants. The Chinese people need food, and increasingly that means something beyond just rice. Also, China is suffering from desertification in the West, thus reducing available farmable land (in addition to rapid urbanization which may be even a bigger factor in the reduction of agricultural lands.) So, the farmers may be forced to push their farms to and beyond their sustainable limits to (a) take advantage of prices, and/or (b) meet quotas set by regional and central government.

    Vale

    Publius Cornelius
    Amicus

    Like

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