Environmental Science / Unit 5: Land and Soil
5.4 Soil Erosion and Conservation
Notes
Erosion is the movement of soil by wind or water. Natural erosion is slow, but human activity can speed it up.
- Causes: removing vegetation, plowing, overgrazing, construction, and deforestation.
- Effects: loss of topsoil and fertility, sediment pollution of streams, reduced crop yields. The Dust Bowl of the 1930s in the US was caused by drought plus plowing of prairie grasses.
- Contour plowing: plow across a slope, not up and down.
- Terracing: build steps on steep hillsides.
- Windbreaks: rows of trees that slow wind.
- No-till farming: plant without plowing, leaving crop residue.
- Cover crops keep soil covered between harvests.
- Example: farmers plant tree rows along the edge of a field to reduce wind erosion. This is a windbreak.
Practice
Which farming method reduces erosion on a sloped field by plowing across the hill?
Furrows across the slope slow runoff and trap water.
The Dust Bowl of the 1930s was caused mainly by:
Without grass roots to hold it, dry topsoil blew away.
How does no-till farming help conserve soil?
Less disturbance keeps soil structure and cover intact.
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