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

Desorption of Zinc from soil is one of the important factors that control Zn bioavailability. To investigate the effects of salinity and organic matter on the kinetic release of Zn in a calcareous soil under maize cultivation, an experiment was carried out in greenhouse condition as a 3×4 factorial arranged as completely random design with 3 replications. Factors included three salinity levels (0, 15 and 30 Meq kg^-1 salt supplied as NaCl, CaCl2 and MgCl2 with 3:2:1 proportion, respectively) and four organic matter treatments [without organic matter, cow manure (2 % w/w), wheat straw (2 % w/w) and cow manure + wheat straw (1:1 ratio)]. Soil samples were extracted using DTPA extractant for periods of 0.5, 1, 2, 6, 12 and 24 hours. The organic matter treatments increased the magnitude of released Zn compared to control (without organic matter). The most and the least increase observed in CW (2.3 folds) and WS (19.7 %) treatments respectively. Zinc release rate increased compared to control and the highest increase observed in CM+WS (2.7 folds) treatment. Zinc release rate was decreased and the magnitude of released Zn was increased by increasing of salinity levels. Simple Elovich equation was determined as the best kinetic model for describing released Zn. The possible mechanism that controls the Zn release from calcareous soil could be through diffusion.