What can be a result of applying excessive fertilizers?

Applying excessive fertilizers can lead to nutrient runoff, which occurs when the soil becomes saturated with nutrients beyond what plants can absorb. This excess can be washed away by rain or irrigation, entering nearby waterways. Nutrient runoff can cause various environmental issues, such as algal blooms in lakes and rivers. These blooms lead to oxygen depletion in the water, harming aquatic wildlife and disrupting ecosystems.

In contrast, while some might think that excessive fertilization could improve crop yield, yields may not increase proportionately and could even decline due to nutrient imbalances or plant toxicity. Improved soil structure is generally associated with proper organic matter and nutrient management, rather than excess fertilizer, which can lead to a decline in soil health and structure. Finally, excessive fertilizer doesn't inherently improve pest control; in fact, it could lead to increased pest problems due to the unnatural stimulation of plant growth, making crops more susceptible to disease and pest pressure. Therefore, the most immediate and concerning consequence of applying too much fertilizer is nutrient runoff.