| Abstract: | The primary factor that influences release of zinc (Zn) for plants is the rhizosphere. However, information about Zn-desorption characteristics in the rhizosphere is limited. A greenhouse experiment was performed to determine Zn-release characteristics in the bulk and the rhizosphere soils using a rhizobox. The kinetics of Zn release was determined by successive extraction with diethylenetriaminepentaacetic acid (DTPA)– triethanolamine (TEA) in a period of 1 to 504 h at 25 ± 1 °C in the bulk and the rhizosphere soils. Moreover, Zn extracted by using three extractants DTPA-TEA, ammonium bicarbonate (AB)-DTPA, and Mehlich 3] in the bulk and the rhizosphere soils. The results showed that Zn extracted in the rhizosphere soils were significantly (P < 0.01) lower than the bulk soils. The mean of Zn release in the bulk and the rhizosphere soils were 5.31 and 4.91 mg kg?1, respectively. Release kinetics of Zn conformed fairly well to power function, first order, parabolic diffusion, and simplified Elovich equations. The results of kinetics study indicated that release-rate coefficients decreased in the rhizosphere soils compare to the bulk soils. The correlation studies showed that Zn release after 504 h was significantly correlated (P < 0.05) with Zn extracted by using DTPA-TEA, AB-DTPA, and Mehlich 3 in the bulk and the rhizosphere soils. The results of this research showed that Zn-release characteristics in the bean rhizosphere soils were different from the bulk soils. |
