Pedosphere 23(4): 482--492, 2013
ISSN 1002-0160/CN 32-1315/P
©2013 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Application of kinetic models in describing soil potassium release characteristics and their correlations with potassium extracted by chemical methods |
A. R. HOSSEINPUR and H. R. MOTAGHIAN |
| Department of Soil Science, College of Agriculture, Shahrekord University, Shahrekord (Iran) |
| ABSTRACT |
| Potassium (K) release characteristics in soil play a significant role in supplying available K. Information on K-release characteristics in soils of central Iran is limited. The objectives of this study were to determine K release characteristics and correlations of K release rate constants with K extracted by different chemical methods in surface soils of ten calcareous soils of central Iran. The kinetics of K release in the soils was determined by successive extraction with 0.01 mol L-1 CaCl2 in a period of 2--2 017 h at 25±1 oC. Soil K was extracted by distilled water, 0.5 mol L-1 MgNO3, 0.002 mol L-1 SrCl2, 0.1 mol L-1 BaCl2, 0.01 mol L-1 CaCl2, 1 mol L-1 NaCl, 1 mol L-1 boiling HNO3, 1 mol L-1 NH4OAC, Mehlich 1, 0.002 mol L-1 SrCl2 0.05 mol L-1 citric acid, and ammonium bicarbonate-diethylenetriamine pentaacetic acid (AB-DTPA). A plot of cumulative amounts of K released showed a discontinuity in slope at 168 h. Thus, two equations were applied to two segments of the total reaction time (2--168 and 168--2017 h). Cumulative amounts of K released ranged from 55 to 299 mg kg-1 in 2--168 h and from 44 to 119 mg kg-1 in 168--2 017 h. Release kinetics of K in the two time segments conformed fairly well to parabolic diffusion, simplified Elovich, and power function models. There was a wide variation in the K release rate constants. Increasingly higher average concentrations of soil K were extracted by distilled water, Mehlich 1, SrCl2, CaCl2, SrCl2 + citric acid, AB-DTPA, MgNO3, NaCl, NH4OAc, BaCl2 and HNO3. Potassium release rate constants were significantly correlated with K extracted. The results of this study showed that information obtained from mathematical modeling in two reaction time segments can help to estimate the K-supplying power of soils. |
| Key Words: chemical extraction, calcareous soils, mathematical modeling, release rate constant, time segments |
| Citation: Hosseinpur, A. R. and Motaghian, H. R. 2013. Application of kinetic models in describing soil potassium release characteristics and their correlations with potassium extracted by chemical methods. Pedosphere. 23(4): 482-492. |
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