Nitrate Concentration in Leachate—Essential Information for Reducing Nitrogen Surplus and Groundwater Pollution from Agricultural Land in Slovakia

Abstract

The aim of the study was to detect nitrate concentrations in leachate within agricultural land in three districts of Slovakia, namely Nitra, Nové Zámky and Dunajská Streda as well as in the DEEPWATER-CE pilot area. Using the average values of leachable nitrogen in the period 2015–2018 and the long-term amount of percolated water, the nitrate concentration values in leachate were detected. In most defined groundwater monitoring sites, the current nitrogen surplus and corresponding nitrate concentration in leachate create preconditions for the gradual reduction of groundwater nitrate pollution. However, in some groundwater monitoring places, especially in the Nitra district, the nitrate concentration in leachate exceeds 50 mg L−1, which is completely unacceptable from the point of groundwater pollution. In detected hot-spots, it is necessary to reduce the nitrogen surplus up to 15 kg ha−1 on average per year. In this sense, the nitrate concentration in leachate is an important indicator for the revision of existing measures in agriculture.