What can be a consequence of excessive nitrogen application to soil?

• A. Enhanced soil fertility and plant growth
• B. Increased organic matter content
• C. Nutrient runoff and water pollution
• D. Reduction in soil pH levels only

Answer: (C)

Excessive nitrogen application to soil can lead to nutrient runoff and water pollution. When nitrogen is applied in larger quantities than plants can absorb, it can leach into waterways through rainwater runoff. This runoff can lead to eutrophication, a process where excess nutrients, particularly nitrogen and phosphorus, enter water bodies and stimulate excessive growth of algae. This algal bloom can deplete oxygen in the water, harming aquatic life and disrupting ecosystems.

In contrast, while nitrogen does promote soil fertility and can enhance plant growth when applied correctly, too much can lead to negative outcomes. Increased organic matter content is generally a benefit of appropriate nitrogen use, not a direct consequence of excessive nitrogen. Additionally, while nitrogen can influence soil pH, the reduction in soil pH levels is not the sole or primary consequence of excessive application; the broader environmental impact through nutrient runoff is a more immediate concern.