化肥过量中国土壤酸化恐贻害

choi

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VOA Chinese, Feb. 15, 2010.
http://www1.voanews.com/chinese/news/china/20100215-china-soil-84376312.html

My comment:
(1) The report is based on
(a) Guo JH, Liu XJ, Zhang Y, Shen JL, Han WX, Zhang WF, Christie P, Goulding
KWT, Vitousek PM and Zhang FS, Significant Acidification in Major Chinese
Croplands. Science, published online Feb. 11, 2010.
http://www.sciencemag.org/cgi/content/abstract/science.1182570

The abstract is available to the public. I do not subscribe to the magazine,
and thus have no access to the FULL TEXT.

(b) Based on this report, there is online news and printed news.
(i) Online news:

Mara Hvistendahl, Fertilizer Is Acidifying Chinese Land. ScienceNOW Daily
News, Feb. 11, 2010.
http://sciencenow.sciencemag.org/cgi/content/full/2010/211/2

(ii) Printed news:

Mara Hvistendahl, News: China's Push to Add by Subtracting Fertilizer.
Science, 327: 801 (Feb. 12, 2010).
http://www.sciencemag.org/cgi/content/full/sci;327/5967/801

This news does not deal with acidification, but the notion that merely less
(fertilizer) is better.
   
(c) The latter, (b)(ii), is part of an overview on agriculture.

Ash C, Jasny BR, Malakoff DA and Sugden AM, Introduction to special issue |
Feeding the Future. Science, 327:797 (Feb. 12, 2010).
http://www.sciencemag.org/cgi/content/full/sci;327/5967/797


(3) Prof. Zhang also had a previous Science article about policy, but this
is not it: this particular article did not deal with effect of fertilizers
on acidification.

Vitousek PM, Naylor R,Crews T, David MB, Drinkwater LE, Holland E, Johnes PJ
, Katzenberger J, Martinelli LA, Matson PA, Nziguheba G,  Ojima D, Palm CA,
Robertson GP, Sanchez PA, Townsend AR and Zhang FS,
Policy Forum |  Agriculture: Nutrient Imbalances in Agricultural Development
. Science, 324: 1519 (June 19, 2009).
http://www.sciencemag.org/cgi/content/summary/324/5934/1519


(4) Why nitrogen fertilizers acidify soil? It is concisely explained in

S. Kaan Kurtural and Greg Schwab, Acidification of Vineyard Soils by
Nitrogen Fertilizers. Horticulture Dept, Univ. of Kentucky, undated.
http://www.uky.edu/Ag/HLA/acidification.pdf
(Some, but not all, nitrogen fertilizers acidify, when soil bacteria convert
ammonium (NH4+) to nitrate (NO3-), releasing one H+. Plants can absorb
either form. But when fertilizers are overused and overwhelm plants'
absorption of fertilizer, acidification follows. Under this circumstance,
lime 石灰 (or limestone) should be applied to neutralize acidity. On the
other hand, if instead potassium or calcium nitrate is added as a nitrogen
fertilizer, no acidification results.)

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