Zinc Release Kinetics from different Soils of Golestan Province using Diethylene triamine pentaacetic acid (DTPA)

Release of Zinc (Zn) is an important factor in determining Zn availability in calcareous soils. The kinetics of soil Zn release were investigated using 15 different soil samples collected from Golestan province by diethylene triamine pentaacetic acid (DTPA) solution. Different kinetic equations (Zero-and first order, parabolic diffusion, simplified Elovich and power function) were used to describe the rate of release of soil Zn. Comparisons of coefficient of determination (R2) and standard errors of estimate (SE) indicated that the power function, simplified Elovich and first order equations adequately described Zn release, whereas the zero-order equation did not. However, the first order kinetic equation inadequately described the release data at short reaction times.The Zinc release pattern based on the parabolic diffusion equation revealed that the rate of Zn release was higher in the first 2 hours followed by a slower release rate, which suggests that two different mechanisms are involved. The soil available Zn (released in rapid step) was included 40.5-83.3% of total Zn released in 192 hours.