1. Soil Conservation

2. Arable Land Land that can be used to grow crops
Can become degraded which decreases the amount of arable land
As the human population continues to grow, the amount of arable land decreases

3. Soil Layers
Plant roots grow in topsoil or the surface layer of soil. It is richer in organic matter than subsoil
Several layers lie under the topsoil
The bottom layer is bedrock, which is the solid rock from which most soil originally forms

4. Formation of Soil – Where Does It Come From?
Most soil forms when rock is broken down into smaller fragments by wind, water, and weathering – can take hundreds or thousands of years to form a small amount of soil
Decomposers, such as fungi and bacteria, decompose detritus, or dead stuff such as leaves, to add nutrients to the soil

5. Soil Erosion
Definition: the wearing away of rock or soil by wind and water
In the U.S., about half of the original topsoil has been lost to erosion in the past 200 years
Without topsoil, crops cannot be grown

6. Desertification
Definition: the process by which land in arid or semiarid areas becomes more desertlike
Can be caused by human activity or climatic changes

7. Soil Conservation
Soil usually erodes downhill. Many methods of conservation are designed to prevent downhill erosion. They include:
Contour plowing – plowing across the slope of a hill instead of up and down the slope
No-till farming – a crop is harvested without turning over the soil

9. Soil Conservation Quiz
____________ land is land that can be used to grow crops.
Most plant roots grow in which layer of soil?
What decomposes dead stuff, or detritus, to form soil?
Describe contour plowing.
Describe no-till farming.