Simulation of Nitrate and Sodium Transport in Soil Treatment with Vermicompost Under Different Irrigation Regimes

The simulation of nitrate and sodium transport was done in native soil and soil treatment by vermicompost under three irrigation flow rates in saturation and unsaturation states. For this purpose, 12 columns with 20 cm length and 5.9 cm diameter chopped of PVC pipes were used that soil layer in column was 10 cm. All of columns saturated at 24 hours, and leaching was immediately done with distilled water at 24 hours, too. Next, the solution consist of 1mMol KNO3 and 25.42 mg in 1 liter distilled water injected to soil columns with three different water flow rates during 570 minutes, and the nitrate and sodium concentrations were measured in effluent solutions at specified time intervals. The Advection-Dispersion model was used for simulating of solute transport, and dispersivity and distribution coefficients of nitrate and sodium were determined by inverse method. Sodium breakthrough in native soil and soil treatment with vermicompost condition occurred at 280 and 160 minutes under saturated condition with flow rate 0.0704 cm/min, 330 and 200 minutes under unsaturated condition with flow rate 0.0477 cm/min, but sodium breakthrough did not occurred in unsaturated condition with flow rate 0.0208 cm/min. Nitrate breakthrough in native soil with flow rates 0.0704, 0.0477 and 0.0208 cm/min occurred in 50, 80 and 120 minutes, and become maximum in 120, 200 and 270 minutes. Nitrate breakthrough in soil treatment with vermicompost in flow rates 0.0704, 0.0477 and 0.0208 cm/min occurred in 30, 40 and 80 minutes, and become maximum in 80, 120 and 240 minutes. The results showed the breakthrough times of nitrate and sodium and time of maximum concentration of nitrate were decreased by application of vermicompost and increasing soil water flow rate. The results of modeling showed dispersivity and distribution coefficients were increased by using of vermicompost and decreasing soil water flow rate.