Homeowners apply fertilizers to their lawns in hopes of achieving lush, uniformly green grass. Unfortunately, among many, the misconception prevails that if a little does good, then a lot must do better. However, overfertilized lawns suffer from damage ranging from burned grass to excessive weed growth, making it imperative that fertilizer be correctly applied in order to achieve good results.
Although all inorganic fertilizers present some burn potential, according to the Clemson Cooperative Extension, nitrogen is the primary culprit in lawn damage from fertilizer. Excessive nitrogen forms salts in the soil, extracting water from neighboring plants and causing the plants to appear burned. Overuse of fertilizers also promotes shallow root growth, which makes plants more susceptible to disease and encourages weeds.
There are two types of fertilizer: fast-release and slow-release. All organic fertilizers act as slow-release fertilizers. Because fast-release fertilizers release a large amount of nitrogen at once, their potential for burn tends to be high. Slow-release fertilizers burn less, are available longer and pose a decreased risk of runoff or leaching into the groundwater. For these reasons, slow-release fertilizers are safer and preferred for many lawns and soil types, according to the University of Minnesota Extension.
To prevent damage to your lawn, have your soil tested before applying fertilizers. Soil tests determine the needs of your lawn and prescribe a safe fertilization program. Always follow the instructions on the fertilizer packaging with respect to rates and timing. Applying more does not create a healthier lawn. Use slow-release formulations whenever possible. The Clemson Cooperative Extension further recommends applying fertilizers during cool, dry weather and watering the fertilizer into the lawn afterward.
Unfortunately, once a lawn is burned, the only way to repair the damage is to replace the grass. Landscaper Roger Cook of This Old House recommends cutting out the damaged area, removing and replacing an inch of soil and adding seed or sod.
Fertilizer damage to your lawn indicates improper application of chemical fertilizers, which can have profound implications for your local environment as well. Misapplied fertilizers run off of grass or leach into groundwater, causing pollution problems and human health hazards. Following fertilizer recommendations and instructions precisely not only keeps your lawn lush and green but protects your local waterways as well.