chapter 14 soil resources. current events to share
TRANSCRIPT
Chapter 14Chapter 14Soil ResourcesSoil Resources
Current events to shareCurrent events to share
Question of the day:Question of the day:
o What ecosystem services does soil What ecosystem services does soil provide for us?provide for us?
o Soil or dirt? What is the scientific term?Soil or dirt? What is the scientific term?
o What is the study of soil? What is the study of soil?
Overview of Chapter 14Overview of Chapter 14
o What is soil?What is soil?o Soil PropertiesSoil Propertieso Major Soil OrdersMajor Soil Orderso Soil ProblemsSoil Problemso Soil Conservation Soil Conservation o Soil ReclamationSoil Reclamation
SoilSoil
o Uppermost layer of earth’s crust that Uppermost layer of earth’s crust that supports plants, animals and microbessupports plants, animals and microbes
o Soil Forming FactorsSoil Forming Factors• Parent MaterialParent Material• TimeTime• ClimateClimate• OrganismsOrganisms• TopographyTopography
o Soil formation- 1 m = 100-100,000 yearsSoil formation- 1 m = 100-100,000 years
Soil formationSoil formation
o Physical weathering- rock weathered by Physical weathering- rock weathered by wind, water, ice, temperature changewind, water, ice, temperature change
o Chemical weathering- Plant roots Chemical weathering- Plant roots produce carbonic acid that dissolves produce carbonic acid that dissolves nutrients and air and water react with nutrients and air and water react with minerals in the exposed cracks. Organic minerals in the exposed cracks. Organic matter (humus) is partially decomposed matter (humus) is partially decomposed dead organic matter and their waste.dead organic matter and their waste.
Soil CompositionSoil Composition
o Mineral Particles (45%)Mineral Particles (45%)• Weathered rockWeathered rock• Provides essential nutrients for plantsProvides essential nutrients for plants
o Organic Material (5%)Organic Material (5%)• Litter, animal dung, dead remains of plants Litter, animal dung, dead remains of plants
and animals, humus (picture)and animals, humus (picture)
o Water (25%)Water (25%)o Air (25%)Air (25%)
Soil CompositionSoil Composition
o Pore space Pore space • 50% of soil50% of soil• Soil air- good for Soil air- good for
aerationaeration• Soil water- Soil water-
provides water to provides water to rootsroots
Soil Horizons- Soil Horizons- Soil coresSoil cores
o O-horizonO-horizon• Rich in organic Rich in organic
materialmaterial
o A-horizonA-horizon• TopsoilTopsoil
o B-horizonB-horizon• Lighter colored Lighter colored
subsoilsubsoil
o C-horizonC-horizon• Weathered parent Weathered parent
materialmaterial
Soil OrganismsSoil Organismso There are millions of microorganisms in There are millions of microorganisms in
1 tsp of fertile agricultural soil1 tsp of fertile agricultural soil
Soil OrganismsSoil Organisms
o Soil organisms provide Soil organisms provide ecosystem ecosystem servicesservices• Def: Important environmental benefits that Def: Important environmental benefits that
ecosystems provide ecosystems provide
o ExamplesExamples• Decaying and cycling organic materialDecaying and cycling organic material• Breaking down toxic materialsBreaking down toxic materials• Cleansing waterCleansing water• Soil aeration (especially done by Soil aeration (especially done by
earthworms)earthworms)
Nutrient Nutrient CyclingCycling
o Nutrients are cycled Nutrients are cycled between plants, between plants, organisms and soilorganisms and soil
o ExampleExample• Bacteria and fungi Bacteria and fungi
decompose plant decompose plant and animal wastesand animal wastes
• They are They are transformed into transformed into COCO22, soil nutrients , soil nutrients and waterand water
Soil PropertiesSoil Propertieso Soil TextureSoil Texture
• Relative proportion of sand, silt and clayRelative proportion of sand, silt and clay• Sand: 2mm-0.05mmSand: 2mm-0.05mm• Silt: 0.05mm-0.002mmSilt: 0.05mm-0.002mm• Clay: >0.002mmClay: >0.002mm
Soil PropertiesSoil Properties
o Soil texture affects soil propertiesSoil texture affects soil propertieso Coarse textured soil (sandy)Coarse textured soil (sandy)
• Will not hold water well- flows through Will not hold water well- flows through easilyeasily
o Fine textured soil (high in clay)Fine textured soil (high in clay)• Poor drainagePoor drainage• Low oxygen levels in soilLow oxygen levels in soil• Due to negatively charged surface, able to Due to negatively charged surface, able to
hold onto important plant nutrients (Khold onto important plant nutrients (K++, , CaCa2+2+, NO, NO22
--))
Soil PropertiesSoil Properties
Soil PropertiesSoil Propertieso Soil TextureSoil Texture
• Relative proportion of sand, silt and clayRelative proportion of sand, silt and clay• Sand: 2mm-0.05mmSand: 2mm-0.05mm• Silt: 0.05mm-0.002mmSilt: 0.05mm-0.002mm• Clay: >0.002mmClay: >0.002mm
Soil PropertiesSoil Properties
o Soil texture affects soil propertiesSoil texture affects soil propertieso Coarse textured soil (sandy)Coarse textured soil (sandy)
• Will not hold water well- flows through Will not hold water well- flows through easilyeasily
o Fine textured soil (high in clay)Fine textured soil (high in clay)• Poor drainagePoor drainage• Low oxygen levels in soilLow oxygen levels in soil• Due to negatively charged surface, able to Due to negatively charged surface, able to
hold onto important plant nutrients (Khold onto important plant nutrients (K++, , CaCa2+2+, NO, NO22
--))
Questions of the day:Questions of the day:
o What event occurred yesterday that What event occurred yesterday that relates to class?relates to class?
o What role does soil texture play in soil What role does soil texture play in soil nutrients amount?nutrients amount?
o What is What is terra preta? terra preta? Why is it so Why is it so valuable?valuable?
Soil PropertiesSoil Properties
o Soil AciditySoil Acidity• Measured using pH scaleMeasured using pH scale
• 0-7 = acidic0-7 = acidic• 7 = neutral7 = neutral• 7-14 = basic7-14 = basic
• pH of most soils range from 4-8pH of most soils range from 4-8• Affects solubility of certain plant nutrientsAffects solubility of certain plant nutrients• Optimum soil pH is 6-7Optimum soil pH is 6-7
• This is the pH where plant nutrients are most This is the pH where plant nutrients are most available to plantsavailable to plants
• Soil amendments (ex: lime) can be used to Soil amendments (ex: lime) can be used to achieve this pHachieve this pH
Major Soil GroupsMajor Soil Groups
o Variations in soil forming factors cause Variations in soil forming factors cause variation in soils around globevariation in soils around globe
o Soil TaxonomySoil Taxonomy• Separates soils into 12 ordersSeparates soils into 12 orders• Subdivided into more than 19,000 soil series Subdivided into more than 19,000 soil series
that vary by localitythat vary by locality
o Five common soil orders (just briefly Five common soil orders (just briefly going over)going over)• Spodosols, alfisols, mollisols, aridosols, Spodosols, alfisols, mollisols, aridosols,
oxisolsoxisols
Major Soil GroupsMajor Soil Groups
o SpodosolsSpodosols• Form under Form under
coniferous forestsconiferous forests• O-horizon composed O-horizon composed
of needlesof needles• E-horizon is ash-gray E-horizon is ash-gray
under A-horizonunder A-horizon• Not good farmland- Not good farmland-
too acidictoo acidic
Major Soil GroupsMajor Soil Groups
o AlfisolsAlfisols• Brown to gray-brown Brown to gray-brown
A-horizonA-horizon• Precipitation high Precipitation high
enough to leach enough to leach most organics and most organics and nutrients out of O-, nutrients out of O-, A- and B-horizonsA- and B-horizons
• Soil fertility Soil fertility maintained by leaf maintained by leaf litterlitter
Major Soil GroupsMajor Soil Groups
o MollisolsMollisols• Found in temperate, Found in temperate,
semi-arid grasslandsemi-arid grassland• Very fertile soilVery fertile soil• Thick, dark brown/ Thick, dark brown/
black A-horizonblack A-horizon• Soluble nutrients Soluble nutrients
stay in A-horizon stay in A-horizon due to low leachingdue to low leaching
Major Soil GroupsMajor Soil Groups
o AridosolsAridosols• Found in arid regions Found in arid regions
of all continentsof all continents• Low precipitation Low precipitation
preclude leaching preclude leaching and growth of lush and growth of lush vegetationvegetation
• Development of salic Development of salic horizon possiblehorizon possible
Major Soil GroupsMajor Soil Groups
o OxisolsOxisols• Found in tropical and Found in tropical and
subtropical areas with subtropical areas with high precipitationhigh precipitation
• Very little organic Very little organic material accumulation material accumulation due to fast decay ratedue to fast decay rate
• B-horizon is highly B-horizon is highly leached and nutrient leached and nutrient poorpoor
Soil ProblemsSoil Problems
o Soil ErosionSoil Erosion• Def: wearing away or removal of soil from Def: wearing away or removal of soil from
the land the land • Caused primarily by water and windCaused primarily by water and wind
o Why a problem?Why a problem?• Causes a loss in soil fertility as organic Causes a loss in soil fertility as organic
material and nutrients are erodedmaterial and nutrients are eroded• More fertilizers must be used to replace More fertilizers must be used to replace
nutrients lost to erosionnutrients lost to erosiono Accelerated by poor soil management Accelerated by poor soil management
practicespractices
Case in Point: American Case in Point: American Dust BowlDust Bowl
o Great Plains have low Great Plains have low precipitation and subject precipitation and subject to droughtto drought• 1930-1937 severe drought1930-1937 severe drought• No natural vegetation No natural vegetation
roots to hold soil in placeroots to hold soil in place• Replaced by annual cropsReplaced by annual crops
• Winds blew soil as far east Winds blew soil as far east as NYC and DC.as NYC and DC.
• Farmers went bankruptFarmers went bankrupt
Ken Burns “American Dust Bowl” Ken Burns “American Dust Bowl” documentarydocumentary
Soil ProblemsSoil Problemso Nutrient Mineral DepletionNutrient Mineral Depletion
Soil ProblemsSoil Problemso Soil SalinizationSoil Salinization
• Def: gradual accumulation Def: gradual accumulation of salt in the soil, usually of salt in the soil, usually due to improper irrigation due to improper irrigation techniquestechniques
o Often in arid and semi-Often in arid and semi-arid areasarid areas• The little precipitation The little precipitation
that falls is quickly that falls is quickly evaporatedevaporated
• Leaves behind saltsLeaves behind saltso Salt concentrations get Salt concentrations get
to levels toxic to plantsto levels toxic to plants
Soil ProblemsSoil Problems
o DesertificationDesertification• Def: degradation of once-Def: degradation of once-
fertile rangeland, fertile rangeland, agricultural land, or tropical agricultural land, or tropical dry forest into dry forest into nonproductive desertnonproductive desert
o Typically a human-induced Typically a human-induced conditioncondition
o Change in vegetation Change in vegetation changes climate, further changes climate, further decreasing precipitation decreasing precipitation levelslevels
Soil ConservationSoil Conservation
o Conservation TillageConservation Tillage• Residues from Residues from
previous year’s crops previous year’s crops are left in place to are left in place to prevent soil erosionprevent soil erosion
• Includes no tillageIncludes no tillage
o Crop RotationCrop Rotation• Planting a series of different crops in the Planting a series of different crops in the
same field over a period of yearssame field over a period of years• Lessens pest and insect diseaseLessens pest and insect disease
Soil ConservationSoil Conservation
o Contour PlowingContour Plowing• Plowing around hill Plowing around hill
instead of up-downinstead of up-down• Decreases soil erosionDecreases soil erosion
o Strip CroppingStrip Cropping• Alternating strips of Alternating strips of
different crops along different crops along natural contoursnatural contours
o TerracingTerracing• Creating terraces on Creating terraces on
steep slopes to steep slopes to prevent erosionprevent erosion
Strip Strip CroppingCropping
TerraciTerracingng
Preserving Soil FertilityPreserving Soil Fertility
o Organic fertilizersOrganic fertilizers• Animal manure, crop residue, bone meal and Animal manure, crop residue, bone meal and
compostcompost• Nutrient available to plants only as material Nutrient available to plants only as material
decomposesdecomposes• Slow acting and long lastingSlow acting and long lasting
o Inorganic fertilizersInorganic fertilizers• Manufactured from chemical compoundsManufactured from chemical compounds• SolubleSoluble
• Fast acting, short lastingFast acting, short lasting• Environmentally sound to limit useEnvironmentally sound to limit use
• Mobile- easily leach and pollute groundwaterMobile- easily leach and pollute groundwater
Soil ReclamationSoil Reclamation
o Two stepsTwo steps1.1. Stabilize land to Stabilize land to
prevent further prevent further erosionerosion
2.2. Restoring soil to Restoring soil to former fertilityformer fertility
o Best way to do this is Best way to do this is shelterbeltsshelterbelts
• Row of trees planted Row of trees planted to reduce wind erosion to reduce wind erosion of soilof soil
Soil Conservation Policies in USSoil Conservation Policies in US
o Soil Conservation Act 1935Soil Conservation Act 1935• Authorized formation of Soil Conservation Authorized formation of Soil Conservation
Service, now called Natural Resource Service, now called Natural Resource Conservation Service (NRCS)Conservation Service (NRCS)
• Assess soil damage and develop policies to Assess soil damage and develop policies to improve soilimprove soil
o Food Security Act (Farm Bill) 1985Food Security Act (Farm Bill) 1985• Required farmers with highly erodible soil Required farmers with highly erodible soil
had to change their farming practiceshad to change their farming practices• Instituted Conservation Reserve ProgramInstituted Conservation Reserve Program
• Pays farmers to stop farming highly erodible landPays farmers to stop farming highly erodible land
Soils Pop QuizSoils Pop Quiz
1. What is the study of soil?1. What is the study of soil?
2. What is the study of agriculture?2. What is the study of agriculture?
3. What three components make up soil 3. What three components make up soil texture?texture?
4. What materials makes up soil? In what 4. What materials makes up soil? In what percentages?percentages?
5. Name two elements that we may want to 5. Name two elements that we may want to examine to determine the soil’s health and examine to determine the soil’s health and ability to grow plants.ability to grow plants.
Day 2 Pop QuizDay 2 Pop Quiz
1.What is the study of soil = pedology1.What is the study of soil = pedology
2. Study of agriculture = agronomy2. Study of agriculture = agronomy
3. Soil texture = sand, silt, clay3. Soil texture = sand, silt, clay
4. Minerals 45%(from parent material= 4. Minerals 45%(from parent material= bedrock), humus 5% (organic matter), bedrock), humus 5% (organic matter), water 25%, air 25%water 25%, air 25%
5. N, P, K, (main three) maybe Ca, Mg 5. N, P, K, (main three) maybe Ca, Mg