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How does soil erosion lower crop yields and harm water quality?

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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.

Soil erosion significantly impacts agricultural productivity and environmental health by degrading the land and polluting water systems.

Impact on Crop Yields

Soil erosion lowers crop yields primarily by stripping away the topsoil, which contains essential humus, plant nutrients, and beneficial organisms necessary for plant growth. As these vital components are washed away, the soil's ability to support healthy crops diminishes. Furthermore, erosion reduces the soil's capacity to retain water, leaving plants with less moisture during critical growth periods. Conversely, effective soil management practices—such as contour farming—help retain water and nutrients, which directly correlates to increased production.123

Harm to Water Quality

When eroded soil enters waterways as sediment, it acts as a pollutant that impairs water quality. This sediment fills stream channels, irrigation canals, and reservoirs, increasing maintenance costs and water clarification expenses. Additionally, soil erosion often carries agricultural fertilizer runoff into aquatic ecosystems. This excess loading of nutrients, such as nitrogen and phosphorus, triggers cultural eutrophication, leading to harmful algal blooms that deplete dissolved oxygen, damage fisheries, and degrade the overall health of freshwater and coastal marine systems.456