section ii and iii

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Section II Section II The Nature Of Soil The Nature Of Soil

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Page 1: Section ii and iii

Section IISection IIThe Nature Of SoilThe Nature Of Soil

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Formation of soilFormation of soil can take thousands of yearscan take thousands of years

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SoilSoil is a mixture of weathered rock, is a mixture of weathered rock,

decayed organic matter, mineral decayed organic matter, mineral fragments, water, and airfragments, water, and air

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formation is influenced by climate, formation is influenced by climate, slope, type of rock, types of slope, type of rock, types of vegetation, and length of time that vegetation, and length of time that the rock has been weatheringthe rock has been weathering

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Composition of soilComposition of soil the ingredients that make up soilthe ingredients that make up soil

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1. clay, silt, and sand are small 1. clay, silt, and sand are small particles of sedimentparticles of sediment

2. decaying, dark-colored plant and 2. decaying, dark-colored plant and animal material is called humusanimal material is called humus

3. small spaces between soil 3. small spaces between soil particles may be filled with air or particles may be filled with air or waterwater

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Soil profileSoil profile made up of different layers of soilmade up of different layers of soil

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Horizon OHorizon O top layer of vegetation and organic top layer of vegetation and organic

mattermatter

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2. Horizon B – middle soil layer2. Horizon B – middle soil layer contains less humus and is lighter in contains less humus and is lighter in

color than A horizoncolor than A horizon

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minerals travel from horizon A to B minerals travel from horizon A to B horizon in a process called leachinghorizon in a process called leaching

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Horizon C – bottom soil layerHorizon C – bottom soil layer has very little organic matter and is has very little organic matter and is

not strongly affected by leachingnot strongly affected by leaching

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Contains rock – the parent material Contains rock – the parent material from the soilfrom the soil

Glaciers can deposit soil that did not Glaciers can deposit soil that did not form from the bedrock beneath itform from the bedrock beneath it

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Soil types – differ in different placesSoil types – differ in different places

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Different regions have different Different regions have different climates that affect soil climates that affect soil

developmentdevelopment

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Parent rock affects soil formation Parent rock affects soil formation and type of vegetation that grows in and type of vegetation that grows in

a regiona region

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Time affects soil development Time affects soil development because the longer the weathering because the longer the weathering has occurred, the less the soil has occurred, the less the soil resembles parent rockresembles parent rock

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Soil on steep slopes develops poorlySoil on steep slopes develops poorly

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Section IIISection III Soil ErosionSoil Erosion

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Soil erosion or loss is important Soil erosion or loss is important because plants do not grow as well because plants do not grow as well when topsoil is lost.when topsoil is lost.

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Causes and effects of soil erosion – Causes and effects of soil erosion – many human activities disturb the many human activities disturb the natural balance between soil natural balance between soil production and soil erosion.production and soil erosion.

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Agricultural CultivationAgricultural Cultivation increased farming removes the plant increased farming removes the plant

cover, leaving soils open to wind and cover, leaving soils open to wind and water erosion.water erosion.

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Forest HarvestingForest Harvesting Removes forest vegetation which Removes forest vegetation which

increases erosion and particularly increases erosion and particularly damages tropical rain forest soildamages tropical rain forest soil

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1984 2004

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OvergrazingOvergrazing Results when animals graze Results when animals graze until almost all ground cover until almost all ground cover disappearsdisappears

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Excess SedimentExcess Sediment Can damage the Can damage the

environment environment when soil erosion when soil erosion is severeis severe

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Preventing Soil ErosionPreventing Soil Erosion Soil must be protected / conservedSoil must be protected / conserved

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Manage CropsManage Crops Farmers plant shelter belts of trees Farmers plant shelter belts of trees

to break the force of the windto break the force of the wind

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Bare soil can be covered with Bare soil can be covered with decaying plants to hold soil in placedecaying plants to hold soil in place

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Farmers can graze animals on Farmers can graze animals on vegetation instead of plowing it vegetation instead of plowing it underunder

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With no-till farming, plant stalks are left in the field to provide cover for soil

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Reduce Erosion On SlopesReduce Erosion On Slopes Contour farming reduces soil erosion Contour farming reduces soil erosion

by planting along the contours of by planting along the contours of slopesslopes

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Terracing creates steep-sided flat Terracing creates steep-sided flat areas for crops on the sides of hills areas for crops on the sides of hills and mountainsand mountains

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Reduce erosion of exposed soilReduce erosion of exposed soil water sprayed onto bare soil to water sprayed onto bare soil to

reduce wind erosionreduce wind erosion

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Topsoil is replaced and trees are Topsoil is replaced and trees are plantedplanted

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Water flow can be controlled in strip Water flow can be controlled in strip minesmines

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After mining, the land can be After mining, the land can be reclaimedreclaimed