Effect of rhizosphere on release rate of zinc in selected calcareous soils of Chaharmahal-va-Bakhtiari province

Rhizosphere is a small zone with different biological and chemical properties from bulk soil. In this research، kinetics of zinc (Zn) release was compared in wheat (Rowshan Back Cross) rhizosphere and bulk soil in 10 calcareous soils by using rhizobox at greenhouse conditions. The rhizosphere and bulk soil samples were extracted with DTPA-TEA for 1 to 504 h at 25±1 0C. In addition، available Zn was evaluated by chemical extractions (DTPA-TEA، AB-DTPA and Mehlich 3). Results showed that the amount of available Zn، cumulative released Zn and rate of Zn release in the rhizosphere soils were significantly (p<0. 05) higher than the bulk soils. Power equation was the best descriptive of Zn release in rhizosphere and bulk soils. In addition، parabolic diffusion، first order and simple Elovich equations could be used to describe kinetics of Zn release. The obtained correlation coefficients between wheat responses and characteristics of Zn release showed that higher significant correlations in the rhizosphere soils were found as compared to the bulk soils.