Simulation of Nitrogen Cycle under Different Management of Remaining Duration of Fertilizer in Paddy Fields Using HYDRUS_1D

Nitrogen fertilizers used in agriculture are a source of environmental and water resources pollution and using simulation model to recognize its cycle could be important role to control and reduce environmental pollution. In paddy fields¡ nitrogen has complex cycle due to irrigation management and submerged condition. In this study¡ HYDRUS model was used to simulate and study nitrogen cycle under different fertilizer management treatments including 24¡ 48 and 72 hours remaining duration of fertilizer and releasing it by runoff. Micro lysimeters were used for simulating the nitrogen cycle in paddy field. The soil texture of this experiment soil was silty clay loam and after applying the urea fertilizer and treatments of the research¡ ammonium¡ nitrate and nitrite concentrations were measured for 4 months (June to September) at depths of 15 and 30 cm. Changes rate of ammonium to nitrite¡ nitrification and denitrification was obtained more at depth of 15 cm than depth of 30. Model could be simulated ammonium and nitrate more accurately than nitrite so that correlation coefficient of simulation were 0.79¡ 0.70 and 0.60¡ respectively. At a depth of 30 cm changes rate of ammonium to nitrite did not affect by fertilizer management treatment.