Plant Soil Environ., 2012, 58(7):328-333 | DOI: 10.17221/70/2012-PSE

Potassium release kinetics and its correlation with pinto bean (Phaseolus vulgaris) plant indices

A.R. Hosseinpur, H.R. Motaghian, M.H. Salehi

Department of Soil Science, College of Agriculture, Shahrekord University, Shahrekord, Iran

The rate of potassium (K) release from soils is a dynamic process, and it is important to the evaluation of soil K availability to plant. The objectives of this study were to determine K release characteristics and the correlation of these parameters with bean plant indices in surface soils of 15 calcareous soils. The kinetics of K release was determined by successive extraction with 0.01 mol/L CaCl₂ in a period of 2-2017 h at 25 ± 1°C. The results showed that the cumulative K‏ release ranged from 111 to 411 mg/kg. A plot of cumulative amount of K released showed a discontinuity in slope at 168 h. Thus, two equations were applied to segments of the total reaction time (2 to 168 and 168 to 2017 h). The amounts of K released during 2-168 and 168-2017 h ranged from 55 to 299 and 44 to 119 mg/kg, respectively. Release kinetics of K conformed fairly well to parabolic diffusion, simplified Elovich and power function models in two segments. Potassium released after 2-168 and 168-2017 h and K release rate constants were significantly correlated (P < 0.05) with bean plant indices, while correlation between K extracted by using 1 mol/L NH₄OAc (ammonium acetate) and plant indices was not significant. The results of this research showed that information obtained from K release studies in laboratory and kinetics equation parameters can help to estimate the K supplying power of soils.

Keywords: parabolic diffusion; calcareous soils; kinetics equations; successive extraction

Published: July 31, 2012  Show citation