Because fertilizers are relatively inexpensive, many people are tempted to add more and more nitrogen to their home landscape, often without regard to whether plants need it at that particular time. Fertilizers high in nitrogen discourage flowering and favor leafy growth, so vegetable production and your flower garden may pay the price. Heavy fertilization of lawns can produce excessive growth, which makes for difficult or frequent mowing. Extra nitrogen not used by plants may be leached into the groundwater in the form of nitrate, a common pollutant. Your groundwater is at higher risk of contamination from excess nitrogen fertilizer if you have soils that drain quickly, such as river loam, coastal sand, or volcanic deposits.
Water contaminated with high levels of nitrate is considered unsafe to drink.
Pregnant women and infants are especially at risk because high nitrate levels can cause a type of blue-baby syndrome. In some areas, the cost of nitrate-contaminated groundwater is great. Public water suppliers cannot use water from a contaminated source because of the health risk, and locating a safe source of water may be very expensive. Households on private wells may need to install treatment systems. The wise use of nitrogen fertilizer by each home can greatly reduce the risk of groundwater contamination.