SoilsSoils

CharacteristicsCharacteristics

TextureTexture

Soil ProfileSoil Profile

Soil TypesSoil Types

Threats to SoilThreats to Soil

Soil CharacteristicsSoil Characteristics

3 characteristics of soil that affect its value for 3 characteristics of soil that affect its value for farming and growing vegetation afarming and growing vegetation are:re:

   

1.1. Organic ContentOrganic Content

2.2. Mineral ContentMineral Content

3.3. Soil TextureSoil Texture

Soil CharacteristicsSoil Characteristics

1.1. Organic ContentOrganic Content - A soil's fertility is determined as a ratio - A soil's fertility is determined as a ratio

of the organic content to the content of of the organic content to the content of ground bed rock. Amount of dead and ground bed rock. Amount of dead and decomposing material.decomposing material.

Soil CharacteristicsSoil Characteristics

  

2.2. Mineral ContentMineral Content

- Varies with precipitation because heavy rains tend to leech soils removing minerals from the root region of soil.

Soil CharacteristicsSoil Characteristics

3. Soil Texture (pg. 138)3. Soil Texture (pg. 138)- - refers to the mixture of fine particles refers to the mixture of fine particles (sand),(sand), very fine particles very fine particles (silt)(silt) and and

extra fine particles extra fine particles (clay).(clay).  The best   The best texture for agriculture is an even texture for agriculture is an even mixture of each mixture of each (loam)(loam)..

Triangular graph of Triangular graph of Soil Soil TextureTexture

Pg. 139

Soil ProfileSoil Profile (pg. 135-136)(pg. 135-136)

O Horizon – “Organic”O Horizon – “Organic” HUMUS:HUMUS: dead or dead or

decaying plant matter, decaying plant matter, leaf litter and other leaf litter and other organic material organic material lying lying on the surfaceon the surface..

darkdark because of the because of the decomposition.decomposition.

decompose into decompose into nutrientsnutrients that enrich the that enrich the soils.soils.

Soil ProfileSoil Profile

A Horizon – “Topsoil”A Horizon – “Topsoil” darker than the lower darker than the lower

layers.layers. looseloose and and crumblycrumbly with with

varying amounts or varying amounts or organic matter.organic matter.

most most productiveproductive layer of layer of soil.soil.

Soil ProfileSoil Profile

B Horizon – “Subsoil”B Horizon – “Subsoil” Light coloredLight colored, dense, , dense,

and and low in organiclow in organic mattermatter..

materials materials leached from leached from the topsoilthe topsoil accumulate accumulate here.here.

Soil ProfileSoil Profile

C Horizon – C Horizon – “Weathered Parent “Weathered Parent Material”Material”

transition areatransition area between between soil and parent material.soil and parent material.

Partially disintegratedPartially disintegrated parent material.parent material.

mineralmineral particles.particles. less organic/living matterless organic/living matter..

Soil Soil Formation/AdvancementFormation/Advancement

: the process by which rocks are gradually broken down into smaller particles and mixed with decaying organic material.

Differentiate among the terms Differentiate among the terms humushumus, , leachingleaching, , eluviationeluviation and and capillary actioncapillary action..

HumusHumus is the accumulation of dead and decayed plant and animal is the accumulation of dead and decayed plant and animal matter that makes up the matter that makes up the organic nature of soilorganic nature of soil. Occurs where . Occurs where there is substantial there is substantial plant and animalplant and animal growth. growth.

LeachingLeaching is the process where nutrients are washed down through is the process where nutrients are washed down through the soil with the the soil with the movement of water downmovement of water down the soil profile. Occurs the soil profile. Occurs where there is substantial rainfall.where there is substantial rainfall.

EluviationEluviation is the lateral or is the lateral or downward movement of clay and downward movement of clay and other fine materialsother fine materials in suspension. Occurs where there is in suspension. Occurs where there is substantial rainfallsubstantial rainfall..

Capillary actionCapillary action results when water molecules are attracted to clay results when water molecules are attracted to clay particles and particles and drawn upwarddrawn upward through the soil profile. Occurs where through the soil profile. Occurs where it is it is substantially drysubstantially dry. .

(Pg. 135)

Using the triangular graph of soil texture, which combination would make the poorest soil?A) 20% sand, 70% clay, 10% silt B) 60% sand, 30% clay, 10% siltC) 40% sand, 30% clay, 30% silt D) 50% sand, 10% clay, 40% silt

*

Using the triangular graph of soil texture, which condition would make Using the triangular graph of soil texture, which condition would make the least favourable soil for farming?the least favourable soil for farming?

(A) 40% sand, 20% clay, 40% silt(A) 40% sand, 20% clay, 40% silt (B) 30% sand, 10% clay, 60% silt(B) 30% sand, 10% clay, 60% silt(C) 25% sand, 60% clay, 15% silt(C) 25% sand, 60% clay, 15% silt (D) 50% sand, 10% clay, 40% silt(D) 50% sand, 10% clay, 40% silt*

Using the triangular graph of soil texture, a soil texture Using the triangular graph of soil texture, a soil texture combination of 20% sand, 10% clay and 70% silt would constitute combination of 20% sand, 10% clay and 70% silt would constitute which soil type?which soil type?

(A) sandy clay(A) sandy clay (B) sandy loam(B) sandy loam(C) silty clay(C) silty clay (D) silty loam(D) silty loam*

Using the triangular graph of soil texture below, which Using the triangular graph of soil texture below, which combination would make the most favourable soil for farming?combination would make the most favourable soil for farming?(A) 10% sand, 15% clay, 75% silt(A) 10% sand, 15% clay, 75% silt (B) 15% sand, 55% clay, 30% (B) 15% sand, 55% clay, 30% siltsilt(C) 20% sand, 70% clay, 10% silt(C) 20% sand, 70% clay, 10% silt (D) 50% sand, 20% clay, 30% (D) 50% sand, 20% clay, 30% siltsilt

*

Which process transports insoluble inorganic matter downward through the soil?

A) accumulation of humusB) capillary actionC) eluviationD) leaching

Which term refers to the process by which particles of insoluble inorganic matter are transported downward through the soil?

(A) accumulation of humus(B) capillary action(C) eluviation(D) leaching

Which refers to the upward movement of soluble Which refers to the upward movement of soluble material through the soil by water?material through the soil by water?

(A) capillary action(A) capillary action(B) eluviation(B) eluviation(C) erosion(C) erosion(D) leaching(D) leaching

Which term refers to the process by which minerals Which term refers to the process by which minerals and dissolved salts are transported upward and dissolved salts are transported upward through the soil?through the soil?

(A) accumulation of humus(A) accumulation of humus(B) capillary action(B) capillary action(C) eluviation(C) eluviation(D) leaching(D) leaching

3 types of Soil3 types of Soilpg. 136-137pg. 136-137

1.1. LatosolLatosol

2.2. PodzolPodzol

3.3. ChernozemChernozem

LatosolLatosol

Typically in Typically in tropical rainforesttropical rainforest.. Very deep, very well drained, Very deep, very well drained,

homogeneous.homogeneous. InfertileInfertile due to…. due to….

- Highly - Highly weatheredweathered and and leachedleached soils because of high soils because of high amounts of amounts of rainfallrainfall. .

They tend to have medium to They tend to have medium to very high very high clayclay contents. contents.

PodzolPodzol

Typically found in the Typically found in the Boreal Boreal forestforest..

Extends immediately Extends immediately south south of the tundraof the tundra regions of the regions of the Northern Hemisphere. Northern Hemisphere.

Gray in color, ashy appearance.Gray in color, ashy appearance. Often Often severely leachedseverely leached and and

highly acidic.highly acidic. They are They are low in agricultural low in agricultural

value, forestsvalue, forests being their most being their most common and practical coverage.common and practical coverage.

ChernozemChernozem

Rich in organic matter in the Rich in organic matter in the form of form of humushumus. .

True chernozem is True chernozem is black in black in color.color.

They are found in They are found in grasslandsgrasslands which are which are semi-aridsemi-arid……

Resulting in Resulting in less leachingless leaching and a and a mineral rich soilmineral rich soil. .

It is It is very suitable for very suitable for agricultureagriculture. .

Threats to SoilThreats to Soil

EnvironmentalEnvironmental Factors:Factors:

1. Temperature1. Temperature

- affects - affects humus humus (low temps. slow the (low temps. slow the decay decay of organic matter).of organic matter).

2.2. Precipitation Precipitation

- affects - affects mineral contentmineral content (rain causes (rain causes minerals to be eluviated). minerals to be eluviated).

Threats to SoilThreats to Soilpg. 140-143pg. 140-143

• Poor soil managementPoor soil management

- agricultural areas - agricultural areas and grasslands.and grasslands.

• Urban ExpansionUrban Expansion

- settling in rich farmland- settling in rich farmland

Threats to SoilThreats to Soil

• DesertificationDesertification – – the spread of desert-like the spread of desert-like conditions in semi-arid environmentsconditions in semi-arid environments

Threats to SoilThreats to Soil

• FloodingFlooding• OvergrazingOvergrazing• Deforestation Deforestation

• Erosion

Reducing Soil ErosionReducing Soil ErosionPg. 142Pg. 142

Soil Erosion can be reduced Soil Erosion can be reduced by:by:

1. Strip cropping1. Strip cropping• Alternating strips of open-growing crops and close-growing crops.

• If the open-growing crops are eroded by wind or water, the close-growing crops will not be affected.

2. Cover cropping2. Cover cropping

• When soil is ready to use, this crop gets ploughed back into the soil, increasing the humus content.

• Planting close-growing crop in soil while it rebuilds its nutrients.

Reducing Soil ErosionReducing Soil Erosion

3. Contour ploughing3. Contour ploughing

• Respects the natural shape of the land and forms mini-terraces which discourages water run-off.

Reducing Soil ErosionReducing Soil Erosion

4. Terracing4. Terracing

• Constructing steps or shelves in the sides of hills or sloping land to reduce water run-off and retain moisture.