Britannica Sources used in this answer

How can fertilizer use increase crop yields while also polluting waterways?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A row of cattle with brown and black coats eat feed from a long trough in a South African feedlot, separated by wooden fencing. — Feed Feedlot cattle eating grain in an intensive animal farm in South Africa.

Fertilizers increase crop yields by providing essential inorganic nutrients—primarily nitrogen, phosphorus, and potassium—that plants absorb from the soil to synthesize tissues and support growth. By supplementing these nutrients, farmers can improve production efficiency and increase profit margins.12

However, when these nutrients are applied in excess or at the wrong time, they become "resources out of place," leading to significant environmental harm. This runoff acts as a negative externality, as the chemicals migrate from fields into groundwater and surface water systems.23

Once in waterways, these nutrients trigger eutrophication, a process where nitrates and phosphates stimulate the rapid growth of algae and aquatic plants. This overgrowth eventually depletes oxygen levels in the water, which can kill fish and other aquatic life, creating "dead zones" where ecosystems struggle to survive. Furthermore, high concentrations of nitrates in groundwater can pose direct health risks to humans and livestock. Minimizing this pollution is an ethical imperative, as the impact of agricultural runoff extends far beyond the individual farm, affecting broader ecological health and public safety.432