Presentation on theme: "Earth’s Surface: Chapter 4 Section 3 Human Activities Affect Soil"— Presentation transcript:
1 Earth’s Surface: Chapter 4 Section 3 Human Activities Affect Soil Learning Targets:1) I can explain why soil is a necessary resource2) I can describe how soil is affected by people3) I can demonstrate how to conserve soil
2 Soil is a Necessary Resource Soil helps to sustain life on EarthSoil supports the growth of plants which in turn supply food for animals.Therefore, soil provides nearly all the food you eatPlants provide us with cotton for clothing, medicines, lumber, and the oxygen we breatheSoil helps purify water as it drains through the groundSoil 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 lossThere are 3 main activities that affect soil resources1) Farming2) Construction and Development3) Mining
4 FarmingFarming 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 nutrientsFertilizers 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 cropsThe 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 produceIn 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 coverOvergrazing 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 desertificationDesertification 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 upSome 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 reservoirsIt can make the rivers and lakes muddy and harm the organisms that live thereIt can raise the level of water and cause flooding
12 MiningStrip mining and open pit mining involves the removal of plants and soil which causes soil lossBy exposing the rocks and minerals to the air and to rainwater, it speeds up the rate of chemical weatheringWhich can cause a type of pollution known as acid drainageAbandoned mines can fill with rainwaterSulfide minerals react with air and water to produce sulfuric acidThe acid water drains from the mines, polluting the nearby areas.
14 Soil ConservationSoil conservation is important, because it can be difficult or impossible to replaceA soil with well developed horizons can take hundreds to thousands of years to formThe following are soil conservation methods1) Crop Rotation2) Conservation Tillage3) Terraces4) Contour Plowing5) Windbreaks
15 Crop RotationCrop 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 nitrogenBean crops, such as soybeans restore nitrogen to the soilBy rotating these crops, farmers can help maintain soil fertility.
18 Conservation TillageConservation 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 allThis is called no till farming.
24 Contour PlowingContour plowing is the practice of plowing along the curves or contours of a slopeIt 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.