Pedosphere 14(1): 85--92, 2004
ISSN 1002-0160/CN 32-1315/P
©2004 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Effect of organic ligands on biological availability of inorganic phosphorus in soils
FENG Ke1, LU Hai-Ming1, SHENG Hai-Jun1, WANG Xiao-Li1 and MAO Jian
Agricultural College, Yangzhou University, Yangzhou 225009 (China). E-mail: fengke55@yahoo.com
ABSTRACT
      Citrate, oxalate, tartrate and malate were added into soils during the growth period of ryegrass to study the effect of different organic ligands on the release of various inorganic P (Pi) fractions in a yellow-brown soil and a paddy soil. The results showed that oxalate was most effective in promoting the release of total Pi in the yellow-brown soil and tartrate in the paddy soil. The dominant Pi fractions released from the yellow-brown soil were calcium phosphate (Ca-P) and aluminum phosphate (Al-P) and those from the paddy soil were iron phosphate (Fe-P) and reductant soluble phosphate (O-P) mobilized by tartrate. Phosphorous-mobilizing capability of organic acids in the yellow-brown soil revealed the following order: oxalate > citrate > malate > tartrate. In the paddy soil, the order was tartrate > citrate ≈ oxalate > malate. It was demonstrated that organic ligands were different in their capabilities of mobilizing Pi and the same organic ligand showed also a discrepancy in mobilizing P in different soils. Although the addition of organic ligands into soils could increase the amount of P taken up by ryegrass, the more uptake of P, however, was not only due to the more release of Pi, but also partly from organic P. In many cases, organic ligands promoted the release of the total Pi, while different fractions showed different trends: some increased and others decreased.
Key Words:  biological availability, inorganic P release, organic ligands, ryegrass
Citation: Feng, K., Lu, H. M., Sheng, H. J., Wang, X. L. and Mao, J. 2004. Effect of organic ligands on biological availability of inorganic phosphorus in soils. Pedosphere. 14(1): 85-92.
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