How is phosphorus most likely lost from crop fields, contributing to environmental harm?

Phosphorus is most likely lost from crop fields through runoff into surface water. This process occurs when excess phosphorus, often from fertilizers or organic matter, is carried away during rainfall or irrigation events. When it rains, water can wash over the soil surface and transport phosphorus particles into nearby streams, rivers, and lakes. This runoff can lead to nutrient pollution, which stimulates the excessive growth of algae in water bodies, resulting in eutrophication. Eutrophication depletes oxygen in the water and can harm aquatic ecosystems, leading to fish kills and loss of biodiversity.

While other processes such as leaching into groundwater or volatilization into the atmosphere do occur, they are not the primary pathways through which phosphorus is lost and contributes to environmental harm. Leaching typically involves soluble nutrients moving downward through the soil profile, which is less common for phosphorus due to its tendency to bind tightly to soil particles. Volatilization primarily affects nitrogen rather than phosphorus. Thus, runoff into surface water is the most significant mechanism in the context of phosphorus loss from agricultural fields.