The Nature Of Soil Ms. Scerra Section I The Nature Of Soil Ms. Scerra

Formation of soil can take thousands of years

Soil is a mixture of weathered rock, decayed organic matter, mineral fragments, water, and air

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

Composition of soil The ingredients that make up soil

1. Clay, silt, and sand are small particles of sediment 2. Decaying, dark-colored plant and animal material is called humus 3. Small spaces between soil particles may be filled with air or water

Soil profile Made up of different layers of soil

Horizon O Top layer of vegetation and organic matter

1. Horizon A – Top layer of soil May be covered with organic litter that may turn into humus Fertile layer with more humus and less rock and mineral particles than other soil horizons

2. Horizon B – middle soil layer Contains less humus and is lighter in color than A horizon

Minerals travel from horizon A to B horizon in a process called leaching

Horizon C – bottom soil layer Has very little organic matter and is not strongly affected by leaching

Contains rock – the parent material from the soil Glaciers can deposit soil that did not form from the bedrock beneath it

Soil types differ in different places

Different regions have different climates that affect soil development

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

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

Soil on steep slopes develops poorly

Section II : Soil Erosion By: Ms. Scerra

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

Causes and Effects of Soil Erosion: Many human activities disturb the natural balance between soil production and soil erosion.

Agricultural Cultivation Increased farming removes the plant cover, leaving soils open to wind and water erosion.

Forest Harvesting Removes forest vegetation which increases erosion and particularly damages tropical rain forest soil

1984 2004

Overgrazing Results when animals graze until almost all ground cover disappears

Excess Sediment Can damage the environment when soil erosion is severe

Preventing Soil Erosion Soil must be protected / conserved

Manage Crops Farmers plant shelter belts of trees to break the force of the wind

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

Farmers can graze animals on vegetation instead of plowing it under

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

Reduce Erosion On Slopes Contour farming reduces soil erosion by planting along the contours of slopes

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

Reduce erosion of exposed soil Water sprayed onto bare soil to reduce wind erosion

Topsoil is replaced and trees are planted

Water flow can be controlled in strip mines

After mining, the land can be reclaimed