Which aspect is necessary for the understanding of high nitrates and phosphorus levels in lakes?

Understanding high nitrates and phosphorus levels in lakes is greatly influenced by the application of excess fertilizers in agricultural practices. When fertilizers are used in large amounts, they increase the nutrient load in the soil, and when it rains or when snow melts, these excess nutrients can be washed off the land and into nearby water bodies, such as lakes. This process, known as nutrient runoff, can lead to algal blooms, which deplete oxygen levels in the water and harm aquatic life.

While other factors, such as natural filtration systems and crop rotation practices, play a role in nutrient management and environmental stewardship, they do not directly relate to the immediate and significant impact of excess fertilizers in contributing to elevated nitrate and phosphorus levels in aquatic ecosystems. Overwatering crops can result in runoff but is not the primary driver in nutrient levels compared to the direct impact of excess fertilizer application.