Agricultural Impact on Groundwater Vulnerability to Nitrate in Northern Croatia

Th ere is noticeable negative impact on soil and water quality caused by nutrient leaching, especially nitrate. Five regions in Croatia are preliminary delineated as nitrate vulnerable zones, including potentially vulnerable zones (PVZ) and vulnerable zones (VZ), one of them being Varaždin County. Agricultural land spreads on 59% of its total area. Th e survey was carried out to analyze two available land use databases, ARKOD and CLC 2006, to determine relation between land use and vulnerability to nitrate. Results of on-going groundwater, soil and percolate research (nitrate concentrations) in the same area are used for more precise nitrate vulnerability determination. Database analysis revealed no signifi cant diff erence in land use within VZ and PVZ. Groundwater monitoring shows no consistency between nitrate concentrations and PVZ/VZ designation. Furthermore, the diff erence in the amount of residual soil nitrogen in two years of research was determined. Results of lysimeter study show that up to 32% of applied nitrogen is percolated to deeper soil layers indicating high agricultural impact on groundwater vulnerability to nitrate.