You have always heard that you can get too much of a good thing, and that is true with fertilizer. Fertilizing lawns and gardens can increase their growth and beauty with no harmful effects; however, if excessive amounts of fertilizer are applied, it can lead to pollution of groundwater and streams. This is true of both chemical and organic fertilizers.
If you use more nitrogen than plants can use, it can get into groundwater and streams. Too much nitrogen in drinking water is especially harmful to newborns and expectant mothers.
Phosphorus does not leach into groundwater, but it can wash into streams. Excess phosphorus in streams and lakes will increase algae growth. This can reduce the supply of oxygen in the water, resulting in a fish kill.
The best way to prevent fertilizers from contaminating our groundwater and streams is to soil test. Following a soil test recommendation will assure that you are applying the necessary nutrients in the proper amounts. This not only protects the environment, but it saves you money by only applying the proper amount of what your lawn or garden needs.
Another way to prevent pollution with fertilizers would be to sweep up any fertilizer that is accidentally scattered on sidewalks or driveways during application.