What is the significance of the Great What is the significance of the Great Green Wall?Green Wall?

Do Now: Do Now:

Soil ResourcesSoil Resources

Chapter 15Chapter 15

Soils and their PreservationSoils and their Preservation

What is Soil?What is Soil?

How Soils are Formed?– From parent material– Formation of 2.5 cm of topsoil requires time

varies 200 – 1000 years– Depth varies (thin film, Poles, to 10 ft, forests )

What is Soil?What is Soil?

• The thin surface layer of the Earth’s crust The thin surface layer of the Earth’s crust consisting of:consisting of:

• minerals minerals • organic matter organic matter

that has been modified by:that has been modified by:• WeatherWeather• WindWind• WaterWater• OrganismsOrganisms

How Soils Are FormedHow Soils Are Formed

• What three Weathering processes What three Weathering processes break parent material into smaller & break parent material into smaller & smaller particles.smaller particles.

How are Soils formedHow are Soils formed

• Weathering processes break parent Weathering processes break parent material into smaller & smaller material into smaller & smaller particles.particles.– biological, chemical, & physicalbiological, chemical, & physical

• Respiring organisms give off CORespiring organisms give off CO22 reacts in reacts in

soil forming Carbonic Acid, Hsoil forming Carbonic Acid, H22COCO33

Soil TopographySoil Topography• Topography affects soil Topography affects soil

deposition . deposition . – Steep slopes have little Steep slopes have little

or no soil. or no soil. – Weathering, Erosion, Weathering, Erosion,

gravity, & runoff.gravity, & runoff.– Slopes and valleys aid in Slopes and valleys aid in

soil formation & give soil formation & give rise to pioneer rise to pioneer organisms.organisms.

Ecological Succession Ecological Succession

Climax Climax CommunityCommunity

Pioneer Pioneer OrganismsOrganisms

Do Now:Do Now:• What are some of the factors attributed to What are some of the factors attributed to

the everglades soil disappearing? the everglades soil disappearing?

Everglades DisappearingEverglades Disappearing• Everglade soil contains 15% or less of mineral Everglade soil contains 15% or less of mineral

particles and large amounts of organic matter.particles and large amounts of organic matter.

• Organic material covered in water never really Organic material covered in water never really decomposed.decomposed.

• When organic material is exposed to oxygen it When organic material is exposed to oxygen it quickly decomposes… quickly decomposes…

• As the ground is drained, soil exposed to air and As the ground is drained, soil exposed to air and decomposition is accelerated.decomposition is accelerated.

Soil Composition• Humus: a mixture of organic material Humus: a mixture of organic material

that binds nutrient mineral ions and that binds nutrient mineral ions and holds water.holds water.

Humus

Mineral matter

Organic matter

Water

Air

What is Soil?• Soil Composition

25%25%

45%45%

5%5%

25%25%

Soil CompositionSoil Composition• Litter: dead leaves/sticks, dung, dead remains of Litter: dead leaves/sticks, dung, dead remains of

plants and animals. plants and animals. – Detritivores like Earthworms, termites, and ants help Detritivores like Earthworms, termites, and ants help

to breakdown humus.to breakdown humus.

• Humus: a mixture of organic material that binds Humus: a mixture of organic material that binds nutrient mineral ions and holds water.nutrient mineral ions and holds water.– Humus persists in agricultural soil for about 20 years. Humus persists in agricultural soil for about 20 years.

– Humus Humus CO CO22 + H + H22O + nutrient minerals O + nutrient minerals

Soil• Pore spaces: Occupy about 50% of a soils Pore spaces: Occupy about 50% of a soils

volume and can be filled with Hvolume and can be filled with H22O O

(soil H(soil H22O) or air (soil air).O) or air (soil air).

• Soil air is found in larger pores.Soil air is found in larger pores.

• Soil HSoil H22O is found in smaller pores O is found in smaller pores

(0.05mm).(0.05mm).

What is Soil?

• Soil Composition

• Other components:

Pore space (wet soil)Pore space (wet soil) Pore space (dry soil)Pore space (dry soil)

Soil Water

• LeachingLeaching: the removal of : the removal of dissolved materials from dissolved materials from soil by the percolating of soil by the percolating of water downward.water downward.

• IlluviationIlluviation: The deposition : The deposition of leached material into of leached material into lower layers of soil.lower layers of soil.

• IlluvialIlluvial materials include: materials include: Fe, & Al compounds, Fe, & Al compounds, humus, and clay.humus, and clay.

Soil Air• Contains less OContains less O22 and more CO and more CO22 compared to compared to

atmospheric air. (due to cellular respiration).atmospheric air. (due to cellular respiration).

What is Soil?

• Soil Horizons

Soil Horizons

• Horizontal layers Horizontal layers of organized soil. of organized soil.

• A soil profile is a A soil profile is a vertical section vertical section from surface to from surface to parent material.parent material.

E-horizon develops if leaching is severe.

Soil Organisms• Castings are produced ad digested soil passes Castings are produced ad digested soil passes

through the intestine of an Earthworm.through the intestine of an Earthworm.

• Mycorrhizae: root fungus that lives in symbiosis Mycorrhizae: root fungus that lives in symbiosis with vascular plants (Tracheophytes).with vascular plants (Tracheophytes).

• Mycelium: threadlike body of the fungus that Mycelium: threadlike body of the fungus that brings nutrients and water to the roots of the plant. brings nutrients and water to the roots of the plant. In turn the fungus receives glucose from the plant In turn the fungus receives glucose from the plant via photosynthesis.via photosynthesis.

Earthworm Castings

?

???????

Earthworm Dissection

Nutrient Cycling

• The pathways of various nutrient minerals or The pathways of various nutrient minerals or elements from the environment. Decomposition, elements from the environment. Decomposition, assimilation, absorptionassimilation, absorption

?

What is Soil?

• Nutrient Cycling

(alternate slide)

Organic matter in soil

Decomposition

Minerals freed and available to plant

Plant roots absorb minerals from soil

Elements incorporated into organic matter in

plants

Elements in organic matter in

animals

Soil Texture

• The texture of a soil is determined by The texture of a soil is determined by the percentages of particles like sand, the percentages of particles like sand, silt, & clay that it contains.silt, & clay that it contains.

In soil, small particles (less than 0.002mm) are called?

In soil, small particles (less than 0.002mm) are called?

Clay

Soil Properties and Major Soil Types

• Soil Texture: Sand, Silt, and Clay

Soil Ions

• Soil minerals are often present in Soil minerals are often present in charged versions called ions. charged versions called ions.

• LoamLoam: an ideal agricultural soil that : an ideal agricultural soil that has an optimum combination of soil has an optimum combination of soil particle sizes.particle sizes.

Soil Properties and Major Soil Types

• Availability of nutrient minerals in clay

Results of Negatively Charged Clay

Home work:• This is “Black dirt”

from Pine Island NY.– Yes that is it’s natural

color!

• What can account for this significant difference in the physical and chemical nature of their soil?

Soil Properties and Major Soil Types

• Soil Properties Affected by Soil Texture

Soil Properties and Major Soil Types

• Soil Acidity

pH scale0

7

14

Most soils (pH = 4-8)

Pygmy Forest

Death Valley

Major Soil Types

Soil Groups

• SpodosolsSpodosols: have : have distinct layers distinct layers (usually caused by (usually caused by colder climate, colder climate, ample precipitation, ample precipitation, & good drainage. & good drainage.

Soil Groups

• AlfisolsAlfisols: temperate deciduous : temperate deciduous forests produce this soil forests produce this soil group. Brown to gray A-group. Brown to gray A-horizon, enough precipitation horizon, enough precipitation to wash clay and to wash clay and soluble soluble nutrients into the B-horizonnutrients into the B-horizon..

• Maintained by detritus (leaf Maintained by detritus (leaf litter, twigs, acorn shells.litter, twigs, acorn shells.

• Fertile soilFertile soil

AridosolsAridosolsAridosolsAridosols: desert : desert and arid regions , and arid regions , hot and dry hot and dry climates.climates.Poor quality soil Poor quality soil with specially with specially adapted plant adapted plant species.species.

OxisolsOxisols

OxisolsOxisols: tropical : tropical rainforests, hot rainforests, hot and wet climates.and wet climates.Poor quality soil Poor quality soil due to mineral due to mineral and nutrient and nutrient storage within the storage within the rainforest rainforest organisms.organisms.

Dust Bowl

???????

Soil Problems

Sustainable Soil Use:

• Wise use of soil resources, without a reduction in the amount or fertility of soil,

• So that it is productive for future generation

Soil Problems

Soil Erosion• Caused whean rainfall loosens particles

water, wind, and ice transport away soil.• Reduces the amount of soil which reduces

soil fertility• Sediment, flows into streams, rivers,and

lakes affecting water quility and biotic habitats

Soil Problems• Case-in-Point: The American Dust Bowl

Soil Problems

• Nutrient Mineral Depletion

Soil Problems, Dust Bowl

• Soil Problems in the United States

• Cultivated soils in southern Iowa, northern Missouri, western and

southern Texas, & eastern Tennessee have greatest erosion

• 25% of agricultural lands lose more topsoil than formed

Soil Problems

• World Soil Problems

• Mineral depletion in tropical rainforest soils

• Degradation in the African Sahel

Soil Conservation and Regeneration

• Conservation Tillage

Soil Conservation and Regeneration

• Crop Rotation

CORN

1st Year

SOYBEANS

2nd Year

OATS

3rd Year

ALFALFA

4th Year

Soil Conservation and Regeneration

• Contour Plowing, Strip Cropping, and Terracing

Strip cropping & contour plowing

Terracing

Soil Conservation and Regeneration

• Preserving Soil Fertility• Organic fertilizers• e.g., manure, compost• slow release, but nutrient content

varies• Commercial inorganic fertilizers• e.g., typical bagged fertilizer• exact nutrient content known, but

prone to leaching

Soil Conservation and Regeneration

• Soil Reclamation

• increasing productivity on eroded landShelterbelts