What is the primary environmental concern associated with excessive nitrogen fertilizer use?

Excessive nitrogen fertilizer use primarily leads to water contamination, specifically nitrate pollution in water bodies. When nitrogen is applied in surplus to crops, it can leach into the groundwater or run off into nearby rivers, lakes, and streams. This can result in various environmental issues such as eutrophication, where nutrients in the water lead to algal blooms that deplete oxygen levels, harming aquatic life.

The impact of nitrogen fertilizers on water quality is significant because it can affect drinking water sources, leading to health concerns for both humans and animals. In particular, high concentrations of nitrates in drinking water have been linked to adverse health effects, especially in infants who can develop methemoglobinemia, a condition that affects the blood's ability to carry oxygen.

While soil erosion, greenhouse gas emissions, and loss of biodiversity are important environmental issues, the direct and immediate risk posed by excessive nitrogen fertilizer is most clearly reflected in its ability to contaminate water resources.