Pedosphere 15(3): 273--280, 2005
ISSN 1002-0160/CN 32-1315/P
©2005 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Effect of organic acids and protons on release of non-exchangeable NH4+ in flooded paddy soils
ZHANG Yong-Song1, SHAO Xing-Hua1, LIN Xian-Yong1 and H. W. SCHERER2
1 Ministry of Education Key Lab of Environmental Remediation and Ecosystem Health, College of Natural Resources and Environmental Science, Zhejiang University, Hangzhou 310029 (China). E-mail:
2 Institute of Plant Nutrition, university of Bonn, Karlrobert-Kreiten-Str, 13, D-53115 Bonn (Germany)
      In a model experiment, which imitated the rhizosphere of rice, the effect of organic acids (oxalic acid, citric acid) and protons on the release of non-exchangeable NH4+ and the resin adsorption of N was studied in a paddy soil, typical for Zhejiang Province, China. Oxalic and citric acids under low pH conditions, in combination with proton secretion, favored the mobilization of NH4+ ions and increased resin adsorption of N. The release of non-exchangeable NH4+ was associated with less formation of iron oxides. These could coat clay minerals and thus hinder the diffusion of NH4+ ions out of the interlayer. Protons enhanced the release of NH4+, and then they could enter the wedge zones of the clay minerals and displace non-exchangeable NH4+ ions.
Key Words:  ammonium release, exchange resin, non-exchangeable ammonium, paddy soil, root exudates
Citation: Zhang, Y. S., Shao, X. H., Lin, X. Y. and Scherer, H. W. 2005. Effect of organic acids and protons on release of non-exchangeable NH4+ in flooded paddy soils. Pedosphere. 15(3): 273-280.
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