The quantity of nitrate in groundwater is affected by diffuse agricultural pollution and hence, it is strongly linked to the amount of applied nitrogen (in surplus) on agricultural land. In order to determine nitrate-nitrogen leaching in diverse precipitation conditions, lysimetric field experiment was set in 2011 in Varaždin County, Croatia. Leachate from three zero-tension pan lysimeters on agricultural plot (maize) was collected twice a month or after abundant rainfall. Research results show that 25% of total precipitation leached in 2012 and 13% in 2013. ANOVA results confirm there is a statistically significant difference in NO3-N concentrations between hydrological dry and wet years. In dry years NO3-N concentrations vary from 36 to 56 mg/1 and in 2013 from 8 to 40 mg/I.