Simulation of Nitrate Ion Leaching in a Sandy Loam Soil Treated with Zeolite Using Hydrus-1D Model

In recent years, nitrogen fertilizer consumption in agriculture, accumulation and movement of salts in soils and modeling their movement have received extensive attention, But in using these substances, there should be a balance between the production increase and the quality of agricultural products, otherwise, undesirable effects, such as environmental pollution and soil and ground water contamination will occur. The objectives of this study were to investigate the effect of potassium zeolite on nitrate ion sorption and retention in a saturated sandy loam soil under laboratory condition with four treatments of 0, 2, 4 and 8 g zeolite per kg soil and to simulate nitrate ion leaching using Hydrus-1D model. The study was conducted as a completely randomized block design. Ammonium nitrate fertilizer with concentration of 10g per liter was added to soil columns and then leaching was performed. Results of the study showed that by increasing the amount of potassium zeolite to soil, the mobility of nitrate ion reduced and the nitrate retention in soil increased. Also, the Convection- Dispersion (CDE) and Mobile- Immobile (MIM) models were used to simulate the nitrate ion mobility in soil. Absorption isotherms and diffusion and dispersion coefficients were determined through the inverse modeling. Because the soil was disturbed, CDE model estimation was closer to observed values in all four treatments. Both the CDE and MIM models showed that as the amount of zeolite applied to the soil increases, the diffusion coefficient and dispersion coefficient of nitrate ion in the soil decreases and increases, respectively.