Investigation of Zinc Desorption Kinetic in an Agricultural Calcareous Soil as Influenced by Applied Organic Materials and Salinity Using Mathematical Models

Desorption of Zinc (Zn) from soil is one of the important factors that control Zn bioavailability. To investigate the effect of salinity and organic matter on release kinetic of Zn in a calcareous soil under maze cultivation, a factorial experiment as a completely randomized design with three replications was conducted in greenhouse conditions. The first factor consisted of salinity levels (0, 15 and 30 Meq kg-1 salt) and the second factor was organic matter (cattle manure (CM) and wheat straw (WS)) at two levels (0 and 2 % w/w). Soil samples were extracted using DTPA extractant for periods of 0.5, 1, 2, 6, 12 and 24 hours. Overall patterns of Zn extracted were characterized by a fast release reaction during the first two hours followed by a slower reaction. The organic matter treatments increased the magnitude of released Zn compared to control. The most and the least amount of released Zn observed in CW and WS treatments respectively. By application of all organic treatments, Zn release rate increased compared to control and the highest increase observed in CM+WS treatment. The results showed that Zn desorption rate was decreased and the magnitude of released Zn was increased by increasing of salinity levels. Based on the highest correlation coefficient and the lowest mean standard error of the estimate, simple Elovich equation determined as the best kinetic model for describing Zn desorption, so, it seems that the main mechanism controlling the Zn release in the tested soil is diffusion phenomena.