Section ISection IThe Nature Of SoilThe Nature Of Soil

Ms. ScerraMs. Scerra

Formation of soilFormation of soil

can take thousands of yearscan take thousands of years

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

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

Composition of soilComposition of soil

The ingredients that make up soilThe ingredients that make up soil

1. Clay, silt, and sand are small 1. Clay, silt, and sand are small particles particles of sedimentof 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 particles may be filled with air or may be filled with air or waterwater

Soil profileSoil profile Made up of different layers of soilMade up of different layers of soil

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

mattermatter

1. Horizon A – Top layer of soil1. Horizon A – Top layer of soil

May be covered with May be covered with organic litter that may organic litter that may turn into humusturn into humus

Fertile layer with more Fertile layer with more humus and less rock humus and less rock and mineral particles and mineral particles than other soil horizonsthan other soil horizons

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

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

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

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

Soil types Soil types differdiffer in different places in different places

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

developmentdevelopment

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

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

Soil on steep slopes develops poorlySoil on steep slopes develops poorly

Section II : Soil ErosionSection II : Soil Erosion

By: Ms. Scerra

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.

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.

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.

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

1984 2004

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

Excess SedimentExcess Sediment Can damage the Can damage the

environment environment when soil erosion when soil erosion is severeis severe

Preventing Soil ErosionPreventing Soil Erosion

Soil must be protected / conservedSoil must be protected / conserved

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

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

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

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

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

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

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

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

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

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