Pedosphere 17(4): 457--466, 2007
ISSN 1002-0160/CN 32-1315/P
©2007 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Effect of oxalic acid on potassium release from typical Chinese soils and minerals
TU Shu-Xin1, GUO Zhi-Fen2 and SUN Jin-He2
1 College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China). E-mail: atu@mail.hzau.edu.cn
2 Institute of Nuclear Agricultural Sciences, Zhejiang University, Hangzhou 310029 (China)
ABSTRACT
      Oxalic acid plays an important role in improving the bioawilability of soil nutrients. Batch experiments were employed to examine the influences of oxalic acid on extraction and release kinetics of potassium (K) from soils and minerals along with the adsorption and desorption of soil K+. The soils and minerals used were three typical Chinese soils, black soil (Mollisol), red soil (Ultisol), and calcareous alluvial soil (Entisol), and four K-bearing minerals, biotite, phlogopite, muscovite, and microcline. The results showed that soil K extracted using 0.2 mol L-1 oxalic acid was similar to that using 1 tool L-1 boiling HNO3. The relation between K release (y) and concentrations of oxalic acid (c) could be best described logarithmically as y=a+blogc, while the best-fit kinetic equation of K release was y=a+b√t, where a and b are the constants and t is the elapsed time. The K release for minerals was ranked as biotite>phlogopite ≥ muscovite>microcline and for soils it was in the order:black soil>calcareous alluvial soil>red soil. An oxalic acid solution with low pH was able to release more K from weathered minerals and alkaline soils. Oxalic acid decreased the soil K+ adsorption and increased the soil K+ desorption, the effect of which tended to be greater at lower solution pH, especially in the red soil.
Key Words:  Chinese soils, K+ adsorption and desorption, K-bearing minerals, K release, oxalic acid
Citation: Tu, S. X., Guo, Z. F. and Sun, J. H. 2007. Effect of oxalic acid on potassium release from typical Chinese soils and minerals. Pedosphere. 17(4): 457-466.
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