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