Abstract: The aim of this study was to provide the modeling research of the nitrogen distribution in onion root zone and leaching the N below the root zone from sandy loam soil. Experiments were conducted with the Research Farm of Bastam Agricultural Center, Shahrood, Iran to investigate the nitrogen distribution pattern under sandy loam soil. The study involved field experiment and modeling of nitrogen leaching. Field data were used to calibrate and validate the solute transport model hydrus-2D. The results of the study can be a great help to onion cultivators in selecting appropriate irrigation and fertigation strategies to minimize the nitrogen leaching and obtain a higher yield. To simulation of nitrogen leaching in soil three fertigation strategies were considered. Results of study revealed that in sandy loam soil, fertigation strategy is effecting the nitrogen leaching. With 2 L h-1 emitter discharge, the N leaching was highest in case of alternate day irrigation-weekly fertigation (strategy B) given 10 min before irrigation cut off. However, at 4 L h-1, N leaching was highest in case of alternate day irrigation-weekly fertigation (strategy A) given 10 min after beginning of the irrigation. This implies that in case of permeable soils like sandy loam, fertigation strategies play role in N leaching. Therefore, while designing drip fertigation system in this soil.