Short-Term Effects of the EU Nitrate Directive Reintroduction: Reduced N Loads to River from an Alluvial Aquifer in Northern Italy

The Po Plain (northern Italy) is one of the largest aquifers in Europe, and 67% of the utilized agricultural land in this area is classified as a nitrate vulnerable zone (NVZ). However, it hosts intensive agriculture and livestock farming. In a stretch of the Mincio River (a tributary of the Po River), hydraulic heads and physico-chemical parameters of river and groundwater were monitored for a hydrologic year (2020-2021), to evaluate the effects of manure fertilization and flooding irrigation on surface- and groundwater chemistry. From 2020 the Nitrate Directive's fertilization limit was reintroduced and a comparison has been performed comparing surface- and groundwater data from the 2019 fertilization period (before limit reintroduction) and 2020 (after). Results suggest that in 2021 the phreatic aquifer displayed elevated nitrate (NO3-) concentrations, exceeding 50 mg L-1, although average values were lower than those of 2019. Nitrate loads in the Mincio River reached 6670 kg NO3- d(-1) and resulted from the overfertilization in the surrounding area and the quick transfer of nitrogen from groundwater to the river. As compared to 2019, the river loads decreased by 59%, suggesting that the introduction of fertilization limits can produce measurable, short-term responses in alluvial aquifers.

Automated summary

The Po Plain in northern Italy is a large aquifer with a significant percentage of its agricultural land classified as a nitrate vulnerable zone. Intensive agriculture and livestock farming in this area have led to elevated nitrate concentrations in the groundwater and surface water. The study examines the impact of manure fertilization and flooding irrigation on the water chemistry of the Mincio River, a tributary of the Po River, and highlights the effectiveness of fertilizer limits in reducing nitrate loads.