1. Earth’s Surface: Chapter 4 Section 3 Human Activities Affect Soil
Learning Targets:
1) I can explain why soil is a necessary resource
2) I can describe how soil is affected by people
3) I can demonstrate how to conserve soil

2. Soil is a Necessary Resource
Soil helps to sustain life on Earth
Soil supports the growth of plants which in turn supply food for animals.
Therefore, soil provides nearly all the food you eat
Plants provide us with cotton for clothing, medicines, lumber, and the oxygen we breathe
Soil helps purify water as it drains through the ground
Soil provides a home for a variety of living things

3. Land-Use Practices Can Harm Soil
Any activity that exposes soil to wind and rain can lead to soil loss
There are 3 main activities that affect soil resources
1) Farming
2) Construction and Development
3) Mining

4. Farming
Farming is very important to society, however it can have some harmful effects and lead to soil loss.
Some fertilizers can make it difficult for microorganisms in the soil to produce nutrients
Fertilizers also add to water pollution when rainwater drains from the fields and carries the excess nutrients to river, lakes and oceans

5. Farming Some farming practices can also lead to soil loss
Farmers clear trees and other plants and plow up the soil to plant crops
The soil is more exposed to rain and wind and is more likely to get washed or blown away.
American farmers lose about 5 metric tons of soil for each metric ton of grain they produce
In other parts of the world, the losses are higher

6. Farming - Overgrazing Overgrazing can be another problem
Overgrazing occurs when farm animals eat large amounts of land cover
Overgrazing destroys natural vegetation and can cause the soil to be washed or blown away more easily.
Overgrazing and the clearing of land in some parts of the world (dry) for farming has led to desertification
Desertification is the expansion of desert conditions in areas where the natural plant cover has been destroyed

10. Construction and Development
As people build, roads, houses, malls, and other buildings plants the ___________ are dug up
Some of it washes or blows away because its protective cover has been removed.
The soil can end up in low lying areas, rivers, streams, lakes or reservoirs
It can make the rivers and lakes muddy and harm the organisms that live there
It can raise the level of water and cause flooding

12. Mining
Strip mining and open pit mining involves the removal of plants and soil which causes soil loss
By exposing the rocks and minerals to the air and to rainwater, it speeds up the rate of chemical weathering
Which can cause a type of pollution known as acid drainage
Abandoned mines can fill with rainwater
Sulfide minerals react with air and water to produce sulfuric acid
The acid water drains from the mines, polluting the nearby areas.

14. Soil Conservation
Soil conservation is important, because it can be difficult or impossible to replace
A soil with well developed horizons can take hundreds to thousands of years to form
The following are soil conservation methods
1) Crop Rotation
2) Conservation Tillage
3) Terraces
4) Contour Plowing
5) Windbreaks

15. Crop Rotation
Crop rotation is a process of growing different crops on the same field in different years.
Grain crops, such as wheat, use up a lot of nitrogen
Bean crops, such as soybeans restore nitrogen to the soil
By rotating these crops, farmers can help maintain soil fertility.

16. CROP ROTATION

17. CROP ROTATION

18. Conservation Tillage
Conservation tillage is a method that reduces the number of times fields are plowed in a year.
The less soil is disturbed by plowing, the less likely it is to be washed or blown away.
In one method of conservation tillage, fields are not plowed at all
This is called no till farming.

20. NO TILL FARMING

21. NO TILL FARMING

22. Terraces
Terraces are flat, steplike areas built on a hillside to hold rainwater and prevent it from running downhill
Crops are planted on the flat tops of the terraces.

23. TERRACING

24. Contour Plowing
Contour plowing is the practice of plowing along the curves or contours of a slope
It helps channel rainwater so that it does not run straight downhill, carrying away soil with it.
Strip cropping is often combined with contour plowing.
Strips of grasses, shrubs or other plants are planted between bands of a grain crop along the curve of a slope.
These strips of plants also help slow the runoff of water.

25. CONTOUR PLOWING

26. Windbreaks
Windbreaks are rows of trees planted between fields to “break,” or reduce, the force of winds that carry off soil

27. WINDBREAKS