What impact do fertilizers have on land?

Fertilizers have a significant impact on soil quality and acid levels, which is why the choice that states they affect these factors is correct. When fertilizers are applied to land, they introduce various nutrients that can alter the balance of elements in the soil. For example, nitrogen, phosphorus, and potassium are common components of fertilizers that can enhance plant growth. However, an excessive application of these fertilizers can lead to nutrient runoff and changes in soil pH, sometimes resulting in increased acidity.

This increase in acidity can inhibit the availability of certain nutrients to plants and affect microbial activity in the soil, ultimately influencing the overall health of the ecosystem. Additionally, changes in soil quality, such as organic matter levels, can impact water retention and soil structure.

The other options do not accurately capture the primary effects of fertilizers. While it's true that fertilizers might have some indirect effects on soil temperature, promote certain pests in specific contexts, or even relate to soil erosion in certain situations, these are not the main direct impacts observed from the use of fertilizers on land. Thus, the focus on soil quality and acid levels provides a better understanding of the significant implications of fertilizer use.