The evaluation of crop production that influences surface and groundwater quality is of growing importance in the context of agricultural sustainability in Europe. The primary aim of this study was to understand the relationship between gross nitrogen surplus in land and nitrate concentrations in surface and groundwater. The analysis was based on datasets collected from 2010 to 2021. Nitrate levels were categorized into three distinct quality classes based on the percentage of monitoring points, reflecting a spectrum from high quality, defined as nitrate levels below 25 mg/dm3, to poor quality, characterized by levels exceeding 50 mg/dm3. Redundancy analysis indicated that Gross Nitrogen Balance, a fertilizer use predictor, partially influences water quality, potentially due to long-term effects. Model selection for Gross Nitrogen Balance based on the AICc information criterion identified catch crops (or green cover), high-intensity agriculture, Natura 2000 sites, nitrogen-fixing plants, organic farming, fast-growing tree plantations, and EU27 states as predictors in the group of supported models. The best-fit model revealed differences between EU27 states for Gross Nitrogen Balance. Catch crops and Natura 2000 sites were also significant predictors, the former associated with a positive and the latter with a negative effect on nitrogen balance. In turn, WEI+ increased with nitrogen balance input but decreased with organic farming, indicating that promoting organic practices could help save water resources. Poland emerged as a country with relatively good water quality compared to several European counterparts, such as Denmark, Belgium, Malta, Czechia, Germany, and Lithuania. The implications of this research extend significantly to evaluation of the effects of the Common Agricultural Policy within the European Union.
Halecki et al. (Thu,) studied this question.
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