Final answer:
Extra fertilizer leaves the farm through runoff and leaching, contributing to eutrophication and environmental pollution. Fertilizers are used to improve crop yields, but their overuse can have significant ecological consequences.
Step-by-step explanation:
Extra fertilizer leaves the farm primarily through the process of runoff. When there is high rainfall or excessive irrigation, fertilizers can be washed from the agricultural fields into nearby waterways. This runoff can contribute significantly to eutrophication of freshwater bodies, leading to excessive growth of algae and cyanobacteria, which can create dead zones and affect the ecosystem's health. Farmers use fertilizers that contain nitrogen because nitrogen is a critical nutrient for plant growth and it can significantly increase crop yields. However, the added nitrogen can also lead to environmental issues if not managed correctly. Preventive measures include reducing fertilizer use and preserving wetlands, which can act as natural filters for runoff. Additionally, surface runoff isn't the only way extra fertilizer can leave a farm. It can also leach into the groundwater, contributing to pollution and the eutrophication of water bodies. Responsible regulation and use of these fertilizers are important to minimize their environmental impact.