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

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

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

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

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

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

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

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.

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

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.

CROP ROTATION

CROP ROTATION

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.

NO TILL FARMING

NO TILL FARMING

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.

TERRACING

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.

CONTOUR PLOWING

Windbreaks Windbreaks are rows of trees planted

between fields to “break,” or reduce, the force of winds that carry off soil

WINDBREAKS