According to Dr. Charles Mitchell of the Alabama Cooperative Extension, homeowners and gardeners are among the worst abusers of fertilizers, mistakenly believing that if a small application of fertilizer is beneficial, then a larger application will yield even better results. However, fertilizers contain chemicals that can be harmful in high doses, not only damaging your lawn or garden but also causing a negative impact on the local environment.
Surface Water Pollution
Fertilizers include nitrogen and phosphorus as primary ingredients, and both contribute to pollution of lakes, rivers and estuaries. When fertilizers are overused, some of the excess runs off from the land when it rains and, eventually, ends up in surface water, where it exerts the expected effects on aquatic plants and algae: it makes them grow. The overgrowth of aquatic plants and algae not only interferes with water recreation but also causes a loss of oxygen, which kills other aquatic organisms such as fish and crabs. According to the College of Agriculture and Life Sciences at North Carolina State University, these "dead zones" can exceed thousands of square miles in size. In 1999, a dead zone roughly the size of New Jersey occurred at the mouth of the Mississippi River. Furthermore, some of the algae and microorganisms that flourish due to fertilizer runoff are toxic to humans, pets, livestock and wild animals.
Pollution of Drinking Water
When algae blooms occur in reservoirs, more chlorination is required to control it in drinking water. Chlorination byproducts have been linked with higher rates of cancer. Furthermore, excessive fertilizer also leaches into groundwater, raising nitrogen levels and causing an illness in infants known as blue-baby syndrome that can be fatal. Cases of nitrate poisoning from drinking water have been reported to poison control centers.
The overuse of fertilizer often begins with the intent of promoting plant growth or health but, in fact, may have the opposite effect. Excessive application of fertilizers may actually damage plants. Nitrogen, one of the essential ingredients in fertilizers, draws out water from your plants, creating what is called "burn" because the plants become brown and dry. Overuse of fertilizer can also cause plants to develop shallow root systems, which reduces their stability and ability to obtain water during dry conditions.
Even organic fertilizer should be used with care and never in amounts that exceed manufacturer recommendations. In a study conducted by researchers at the Autonomous University of Barcelona, overuse of organic fertilizers reduced the number of helpful organisms found in the soil, such as earthworms and microorganisms that protect against disease. Because organic fertilizers break down quickly, they can release substances like ammonia into the soil that can be harmful to plants, animals and helpful microorganisms. When using organic fertilizers like manure in a home garden, always be sure that you know what chemicals and how much of each are being added to your soil.
Proper Use of Fertilizer
The University of Michigan's Department of Occupational Safety and Environmental Health recommends having your soil tested before beginning any fertilizer program. This will allow you to determine the precise needs of the soil and will help you to ensure that you do not over-apply a particular chemical. Your local extension office can help you learn more about soil testing and selecting the right fertilizer for your needs. Always follow the instructions on the package and apply it only at the recommended time. For example, most grass fertilizers are best applied in the autumn, not the summer. Keep fertilizer off of driveways and sidewalks, where it easily runs off into storm drains and pollutes surface water. Finally, the university points out that plants such as trees and shrubs don't require regular fertilizer applications. Apply fertilizer to trees and shrubs only when other possible causes of poor growth have been eliminated.