quiz answers from last thursdayquiz answers from last ... · nrem 301 99--2222--0909 day 9day 9 •...
Post on 04-Jun-2020
4 Views
Preview:
TRANSCRIPT
NREM 301NREM 30199--2222--0909Day 9Day 9Day 9Day 9
•• Quiz Answers from last ThursdayQuiz Answers from last Thursday –– up laterup laterQuiz Answers from last Thursday Quiz Answers from last Thursday up laterup later•• Wrap up discussion on soil texture and Wrap up discussion on soil texture and
porosity.porosity.•• Discuss weathering and soil chemistry/fertilityDiscuss weathering and soil chemistry/fertility•• Lab today Lab today –– “Identifying Soil Bio“Identifying Soil Bio-- and and TT ”” NOTE I di id l fNOTE I di id l fToposequencesToposequences.” .” NOTE: Individual paper from NOTE: Individual paper from today’s lab due in two weeks (October 6)today’s lab due in two weeks (October 6)
Individual 1Individual 1AA BB CC
a)a) Match the letters with numbersMatch the letters with numbers –– A3 B1 C2A3 B1 C211 22 33a)a) Match the letters with numbers Match the letters with numbers –– A3, B1, C2A3, B1, C2
For the following rank letters from high to low & give brief For the following rank letters from high to low & give brief WhyWhyb)b) Organic matter contentOrganic matter content –– A C B (prairie grasses have deeperA C B (prairie grasses have deeperb)b) Organic matter content Organic matter content –– A, C, B (prairie grasses have deeper A, C, B (prairie grasses have deeper
roots and put more organic matter into the soil)roots and put more organic matter into the soil)c)c) Amount of erosion occurring Amount of erosion occurring –– B, C, A (little structure, B, C, A (little structure,
surface litter or root matter in the crop field soil)surface litter or root matter in the crop field soil)surface litter, or root matter in the crop field soil)surface litter, or root matter in the crop field soil)d)d) Degree of structure development in the surface horizon Degree of structure development in the surface horizon –– A, A,
C, B (More roots and organic matter lead to better structure)C, B (More roots and organic matter lead to better structure)
1. What are these two soil features?1. What are these two soil features?2 What causes them?2 What causes them?
Individual 2Individual 2
2. What causes them?2. What causes them?
A BMottles, caused by oxdiation and Mottles, caused by oxdiation and reduction of iron due to a fluctuationreduction of iron due to a fluctuation
Clay coatings, Clay coatings, caused bycaused byreduction of iron due to a fluctuation reduction of iron due to a fluctuation
water tablewater tablecaused by caused by illuviation of clayilluviation of clay
Note: Feature B is waxy in appearance (not evident in the photo).
Individual 3Individual 3
Name the five soil forming factorsName the five soil forming factorsgg
Soils = f(CliPROT)Soils = f(CliPROT)
CliClimatemate
PParent Materialarent Material
RRelief (or Topography)elief (or Topography)
OOrganismsrganisms
TTimeime
Individual 4Individual 4
D fiD fi
Last Individual QuestionLast Individual Question
Define:Define:a)a) Aspect Aspect –– The cardinal direction that the slope faces.The cardinal direction that the slope faces.b)b) Bt horizon Bt horizon –– A subsurface horizon that has received A subsurface horizon that has received
ill i t d t i l f h i ti l lill i t d t i l f h i ti l lilluviated materials from upper horizons, particularly illuviated materials from upper horizons, particularly clays.clays.
c)c) Colluvium Colluvium –– Parent material deposited by gravity.Parent material deposited by gravity.d)d) Eluviation Eluviation –– Leaching or washing out of one horizon to Leaching or washing out of one horizon to
the next. Commonly happens in E horizons.the next. Commonly happens in E horizons.
Your classmates sampled soils last year in Your classmates sampled soils last year in MontanaMontana
Group 1Group 1
1.1. What slope position are they on? What slope position are they on? -- BackslopeBackslope
2.2. Because of the slope position, describe briefly what Because of the slope position, describe briefly what they might see in terms of soil development and why? they might see in terms of soil development and why? –– Very little soil development; high slopes do not allow Very little soil development; high slopes do not allow materials to rest in place long enough to undergomaterials to rest in place long enough to undergomaterials to rest in place long enough to undergo materials to rest in place long enough to undergo pedogenesis.pedogenesis.
Sketch the types of horizons and relative thicknesses Sketch the types of horizons and relative thicknesses Group 2Group 2 Last Group QuestionLast Group Question
ypypyou would find as time increases (assume temperate you would find as time increases (assume temperate forest veg. & all other soil forming factors are equal)forest veg. & all other soil forming factors are equal)
A A
B
A O
E
C CBw
Bt
E
C
CC
Time (years)Time (years)0 1,000’s
Soil TextureSoil TextureSandSand SiltSilt ClayClay
Holding Holding LowLow MediumMedium HighHighwaterwaterAerationAeration GoodGood MediumMedium PoorPoorOM levelOM level LowLow MediumMedium HighHighSpring Spring FastFast MediumMedium SlowSlowwarmwarm--upupCompactCompact LowLow MediumMedium HighHighErosionErosion LowLow HighHigh LowLowFertilityFertility LowLow MediumMedium HighHighGroup Group pH pH changechange
HighHigh MediumMedium LowLowExerciseExercise
Soil StructureSoil StructureAggregation ofAggregation of
Granular PedGranular Ped
Aggregation of Aggregation of Sand, Silt, Sand, Silt, Clay & OMClay & OMaa bb Clay & OMClay & OM
‘Glued’ ‘Glued’ together intotogether into
Peds or Peds or AggregatesAggregates
cc dd
ee ff
Strength of structure has a role in water movementStrength of structure has a role in water movement
Porosity and Bulk DensityPorosity and Bulk DensityPorosity and Bulk DensityPorosity and Bulk Density
Bulk Density = Bulk Density =
Weight of oven Weight of oven dry soil / dry soil / yy
Volume of whole Volume of whole soil (solids + airsoil (solids + airsoil (solids + air soil (solids + air
space)space)Nikki D’Adamo
Doolittle Praririe Soil (right) vs. Adjacent Crop Field (left)
Strength of structure also has a Strength of structure also has a l i il il i il irole in soil erosionrole in soil erosion
Jim Richardson/National Geographic Image Collection
Loss of Porosity and Structure by Loss of Porosity and Structure by Compaction by large equipmentCompaction by large equipmentCompaction by large equipmentCompaction by large equipment
Agricultural ActivitiesAgricultural Activities
Logging ActivitiesLogging Activities
What Happens to Soil Structure When What Happens to Soil Structure When --Forest (or Prairie) is replaced by corn & soybeans?Forest (or Prairie) is replaced by corn & soybeans?( ) p y y( ) p y y
Results of CultivationResults of Cultivation
S D dS D d
Infiltration rates drop fromInfiltration rates drop from
Structure DestroyedStructure Destroyed
Infiltration rates drop fromInfiltration rates drop from33--6 in/hr to 0.56 in/hr to 0.5--1.5 in/hr1.5 in/hr
R ff i 20R ff i 20 60%60%Runoff increases 20Runoff increases 20--60%60%Streams carry more waterStreams carry more water
Poor Soil Structure and TreesPoor Soil Structure and Trees
Porosity reducedPorosity reducedAeration reducedAeration reducedMoisture increasedMoisture increasedMicrobial activity reducedMicrobial activity reduced
Weathering in Weathering in SoilSoil
WeatheringWeathering refers refers to the alteration of to the alteration of
rocks and rocks and minerals at or minerals at or
near the Earth’snear the Earth’snear the Earth s near the Earth s surface.surface.
Two types:Two types:
PhysicalPhysicalPhysicalPhysical
& Chemical& Chemical
Physical WeatheringPhysical WeatheringDefinition: disintegration of rock material into smaller-sized
fragments. The general mechanism for physical weathering is the establishment of sufficient stress for theweathering is the establishment of sufficient stress for the rock material to break.
Common processes:Common processes:1. Expansion
a) Crystallization: freezing water, salt crystal growthb) Th l i / t ti diff ti lb) Thermal expansion/contraction: differential
expansion/contraction of minerals, effects of fire.c) Unloadingd) Plant and animal influences (e.g., roots, lichens)
2. Abrasion of material during transport by water, ice, wind, g p y , , ,and gravity.
Soil Parent Materials Soil Parent Materials –– the raw mineral material the raw mineral material soils are developing in.soils are developing in.
Rocks and Rocks and MineralsMinerals Deposited in oceans Deposited in oceans --marine sedimentmarine sediment
Deposited in lakes Deposited in lakes --------lacustrine sediment lacustrine sediment Deposited in streams Deposited in streams --alluviumalluvium –– floodplain, deltafloodplain, delta
terrace fanterrace fanterrace, fanterrace, fanice ice
transporttransportDeposited by ice Deposited by ice --------glacial till glacial till ------ morainesmoraines
Deposited by water Deposited by water ----outwash outwash –– alluvium, marine alluvium, marine lacustrinelacustrine
ResidualResidualparent materialparent material
lacustrinelacustrine
Deposited by wind Deposited by wind -- eolian eolian ------ loess, eolian sand, loess, eolian sand, sedimentsediment volcanic ashvolcanic ash
Deposited by gravity Deposited by gravity ––colluvium colluvium –– creep, landslidescreep, landslides
parent materialparent material(bedrock weathered (bedrock weathered in place)in place)
types of types of d itd it
examples of examples of
Modified from Brady and Weil. 2002. The nature and properties of soils. 13th edition. Prentice Hall.
depositsdeposits landforms or landforms or depositsdeposits
Chemical WeatheringChemical Weathering
Definition: weathering of rock material that results gin a change in chemical composition.
Common processes:1. Hydration2. Hydrolysis3. Oxidation/Reduction4. Dissolution
A id R i ( b i )5. Acid Reactions (eg. carbonation)6. Complexation/Chelation
1. Hydration: the chemical combination of water with another substance; binding of intact t l l t i lwater molecules to a mineral.
Example: Hydration of iron oxide to hydrous oxidesFe2O3 + H2O 2FeOOH (same as Fe2O3*H2O)(hematite) (goethite)( ) (g )Produces Red colors Produces Yellow and brown colors
2. Hydrolysis: reaction of minerals with split water molecules, leading to cation displacement.
Example: Hydrolysis of feldspar and production of kaolinite clay.2KAlSi3O8 + 2H+ + 9H2O Si2O5Al2(OH)4 + 4H4SiO4 + 2K+
(K-feldspar) (kaolinite) (soluble silica/silicic(K feldspar) (kaolinite) (soluble silica/silicic acid) + (potassium ions)
3. Oxidation/Reduction: process of substance losing (oxidation) or gaining (reduction) electrons (e-).Example: Oxidation and reduction of ironExample: Oxidation and reduction of iron2Fe2+ + 4HCO3 + 0.5 O2 + 2H2O Fe2O3 + 4H2CO3
(iron oxide or hematite, with Fe3+)
4. Dissolution: Water hydrates the cations and anions in a solid until they are dissociatedsolid until they are dissociated from one another and are completely surrounded by water molecules.
Example: Dissolution of salt
NaCl Na+ + Cl-
5. Acid Reactions: Strong or weak acids react with soil minerals to hasten weathering.
Example: CarbonationCaCO3 + CO2 + H2O Ca2+ + 2HCO3
-CaCO3 CO2 H2O Ca 2HCO3
(Calcium Carbonate + Carbon Dioxide + Water) yields (Calcium + Carbonic Acid)Acid)
6. Complexation/Chelation: Formation of metal organic complexes in which ametal-organic complexes in which a metal cation (e.g., Fe3+ or Al3+) becomes part of an organic ring structure
CH2 COOH
CCOOH
CH2 COOH
CCOO
structure.Example: Chelation of iron
OH + Fe(NO3)3
C
CH2 COOH
O Fe + 3HNO3
C
CH2 COO
citric acid
chelated iron
Physical Physical yyweathering by weathering by
root actionroot actionroot actionroot action
Ph i lPh i lPhysical Physical weathering weathering due todue todue to due to water and water and wind actionwind actionwind actionwind action
Slot Canyon, Slot Canyon, Zion National Zion National Park UtahPark UtahPark, UtahPark, Utah
Physical weathering Physical weathering –– wave abrasion of wave abrasion of limestone pebbles, Lake Michiganlimestone pebbles, Lake Michigan
Source: Sandor
Physical weathering – fire cracked rock Idahocracked rock, Idaho
Source: Jim Gubbels
Weathering till boulder, Sierra Nevada Mountains
Source: Sandor
Physical weathering – Unloading in granite, Sierra Nevada Mountains
Chemical and physical weathering rind in diorite till boulder, Des Moines Lobe
Source: Sandor
Deep biogeoDeep biogeo--Deep biogeoDeep biogeochemical weathering chemical weathering
in bedrockin bedrockin bedrockin bedrock
Ulti l i G iUlti l i G iUltisol in GeorgiaUltisol in Georgia
Source: Sandor
Common Igneous RocksCommon Igneous RocksIgneous rocks are formed from magma (molten rock)Igneous rocks are formed from magma (molten rock)
Common Primary Silicate Minerals
Common Primary Silicate MineralsCommon Primary Silicate MineralsPrimary minerals, the original minerals of the Earth, are formed at high temperature and/or
pressure in igneous and metamorphic rocks. They constitute the majority of sand and silt in soils.
Mineral Composition Si:O
Quartz Si02 1:2
Feldspar 1:2Feldspar K-feldspar (orthoclase)
KAlSi3O8
NaAlSi3O8
1:2(Si or Al:
O)
Plagioclase
3 8
CaAl2Si2O8
Mafic Minerals:
Mica (biotite) Fe, Mg aluminosilicates 2:5 Amphibole (hornblende)
Fe, Mg, Ca aluminosilicates
4:11
Pyroxene (augite) Fe, Mg, Ca aluminosilicates
1:3
Clay minerals have a layer silicate crystal tetrahedron
Clay building blocks:
y
structure consisting of tetrahedral and octahedral sheets tetrahedral sheet
octahedron
octahedral sheet
E l1 layer of1:1 clay
1 tetrahedral sheet bonded with1 octahedral sheet
Example:
1 octahedral sheet
Properties of Common Clay MineralsProperties of Common Clay Minerals
cmol(+)/kg or
Kaolinite mostly in highly-weathered, acidic soils like Ultisols and Oxisols
and exchangeable cations
Smectite mostly in less weathered, base-rich soils lik M lli l d Alfi lcations
and exchangeable
like Mollisols and Alfisols
exchangeable cations(Mg2+)
Cation Exchange Capacity (CEC) Cation Exchange Capacity (CEC) –– a key soil fertility property of a key soil fertility property of some clay minerals and humussome clay minerals and humus
CEC definition: the amount of exchangeable cations a soil can adsorb. Adsorption
Negatively charged clay Cation Exchangeplant root
refers to the holding of these cations near clay surfaces by electrical attraction.
exchange
plant root
exchange
reactions
Cations in the soil water solution
Several plant nutrients occur in soil as cations (positively charged ions),
Exchangeable cationsadsorbed to clay surface
Plant roots mainly take up nutrient ions from the soil solution
for example Ca2+, Mg2+, K+, Fe2+, Cu2+, Zn2+, and others. Negatively-charged clay and humus particles hold cations in soil, prevent leaching loss of these cations, and make them available for uptake by plants.
Origin of Cation Exchange Origin of Cation Exchange C i (CEC) i Cl Mi lC i (CEC) i Cl Mi lCapacity (CEC) in Clay MineralsCapacity (CEC) in Clay Minerals
tetrahedral sheet
Ca2+ K+
Exchangeable cations
• Mainly found in 2:1 clays
Two kinds of CEC:
octahedral sheettetrahedral sheet
Ca2+ K+
Two kinds of CEC:
• Permanent (through isomorphic substitution) at the time of clay mineral formationclay mineral formation
• pH dependant
Permanent CECPermanent CECCEC mainly results from process of isomorphous substitution during clay mineral formation.
Isomorphous substitution involves the replacement of one element for another inside the clay mineral at the time of formation It cannot be undoneformation. It cannot be undone.
Examples of isomorphous substitution: • Aluminum (Al3+) substitution for Silicon (Si4+) in Al3+Si4+Aluminum (Al ) substitution for Silicon (Si ) in tetrahedral sheet. • Magnesium (Mg2+) substitution for Aluminum (Al3+) in octahedral sheet.
Note in both cases a cation with lower valence replaces one of higher valence, resulting in a net negative charge, or layer charge. This negative charge is offset by the exchangeable cations.
pH Dependant CECpH Dependant CECpH Dependant CECpH Dependant CEC• Some variable or pH-dependent charge also occurs at
d l dexposed clay edges. • If pH rises, H+ dissociates from OH- at clay edges,
increasing the CEC. • If pH decreases, H+ can be attached to the clay surface
OH- groups, causing a decrease in CEC. • Under very acidic conditions such as in highly weathered
f ftropical soils, small amounts of positive surface charge can develop (i.e., anion exchange capacity. This variable charge is most important in kaolinite and aluminum and iron oxides which are abundant in highlyaluminum and iron oxides, which are abundant in highly weathered soils.
• The CEC of humus is also pH-dependent.
pH and Nutrient AvailabilitypH and Nutrient Availability
Base saturation Base saturation –– a soil property related to Cation Exchange a soil property related to Cation Exchange Capacity and also essential to soil fertilityCapacity and also essential to soil fertilityBase saturation % refers to the proportion of base forming cations (calciumBase saturation % refers to the proportion of base-forming cations (calcium, magnesium, potassium – all major plant nutrients, and sodium) on cation exchange sites. The remaining cation exchange sites are occupied by exchangeable acids (hydrogen and aluminum ions).
Base Saturation % = Ca2+ + Mg2+ + K+ + Na+ x 100CEC
Base saturation is positively correlated with pH. Acidic, highly weathered soils such as Ultisols and Oxisols have lower base saturation (and lower CEC) than less weathered, less acidic ( )soils such as Mollisols and Alfisols.
)EC
Site
s (%
)C
E
Soil pH Source: Birkeland 1999
Range of Soil pHRange of Soil pH
Relative concentration of H+ or OH -of H or OH
Acid Neutral Alkaline
pH 3 4 5 6 7 8 9 10
acid sulfate soils leached soils many fertile soils calcareous soil sodic soil
lemon juice pure water soap
Source: Jenny. 1980. The Soil Resource
Predict the Effect of Igneous Rock Parent Materials on Soil & Predict the Effect of Igneous Rock Parent Materials on Soil & Ecosystem Properties. Higher or Lower in Which One?Ecosystem Properties. Higher or Lower in Which One?
Igneous Rock Parent MaterialS il/E P G i ( i h i G bb ( i h i i
y p gy p g
Soil/Ecosystem Property Granite (rich in silica)
Gabbro (rich in iron and magnesium)
Clay Content
Sand Content
Available Water Capacity
CEC and Bases
Ecosystem Biomass
S il i ttSoil organic matter, nitrogen,fertility
Predict the Effect of Igneous Rock Parent Materials on Soil & Predict the Effect of Igneous Rock Parent Materials on Soil & Ecosystem Properties. Higher or Lower in Which One?Ecosystem Properties. Higher or Lower in Which One?
Igneous Rock Parent MaterialS il/E P G i ( i h i G bb ( i h i i
y p gy p g
Soil/Ecosystem Property Granite (rich in silica)
Gabbro (rich in iron and magnesium)
Clay Content Lower Higher
Sand Content Higher Lower
Available Water Capacity Medium Medium
CEC and Bases Lower Higherg
Ecosystem Biomass Lower Higher
S il i tt L Hi hSoil organic matter, nitrogen,fertility
Lower Higher
Effect of Parent Material on Soils and Ecosystems Effect of Parent Material on Soils and Ecosystems (A Lithosequence)(A Lithosequence)
Igneous Rock Parent Material
(A Lithosequence)(A Lithosequence)Example from Sierra Nevada Mountains, California (Jenny, 1980)
Soil Properties Silicic Rocks Mafic Rocks
Organic Carbon % 1 74 2 88Organic Carbon % 1.74 2.88
Total Nitrogen % 0.074 0.121
Clay % 12 21
Exchangeable 5 11Bases (cmol+/kg)
Today’s Lab Today’s Lab –– Reactor Woods Reactor Woods ––Identify and describe soil bioIdentify and describe soil bio-- and topoand topo--sequences sequences yy pp qq(logical orders of soils that are different because of (logical orders of soils that are different because of position in the landscape)position in the landscape)
• Wear long pants! (poison ivy)
E h ill h il b d il d i ti• Each group will have a soil probe and a soil description kit. You will describe three cores from different landscape positions (summitt, backslope, footslope)
• We will also walk down the hill to Onion Creek and look at soils along the way.
•• NOTE: Individual paper from today’s lab due in two NOTE: Individual paper from today’s lab due in two weeks (October 6)weeks (October 6)
Depth (cm)
BiBi f tf t20
BioBio--sequence sequence -- forest forest member. member.
40Hayden Hayden -- developed developed under deciduous forest under deciduous forest in Des Moines Lobe tillin Des Moines Lobe till
60in Des Moines Lobe till.in Des Moines Lobe till.
80
100100
120120
Source: Aandahl 1982
ApproximateApproximateDepth (cm)Depth (cm) BioBio--sequence sequence --
S M bS M b2020
Savanna Member Savanna Member
Lester Lester --4040 developed in developed in
deciduous forest deciduous forest –– prairieprairie
6060–– prairie prairie transition transition ecotone ecotone ( )( )
8080(savanna)(savanna)
100100
120120Source: Sandor
BiBiBioBio--sequence sequence ––Prairie Member Prairie Member
Clarion soil Clarion soil -- Shown Shown to 48 into 48 in
Source: Sandor
Landscape of toposequence:Landscape of toposequence: ClarionClarion -- wellwell--drained higher drained higher soils (lighter brown tones);soils (lighter brown tones); WebsterWebster –– dark, poorlydark, poorly--drained drained
t l t d ilt l t d il Ok b jiOk b ji d k i l l dd k i l l dwet elongated soils;wet elongated soils; OkobojiOkoboji –– dark, circular, closed dark, circular, closed depressions;depressions; HarpsHarps –– dark circular above Okoboji, more dark circular above Okoboji, more calcareous;calcareous; StordenStorden –– very light yellow tops of hillsvery light yellow tops of hills;; y g y py g y p
Thi k b tThink about the original
t tivegetation –recall your
i it tvisit to Doolittle P i i
Source: Lee Burras or Jerry Miller
Des Moines Lobe UplandDes Moines Lobe UplandPrairie
Drainage classesDrainage classes
•• Excessively drainedExcessively drained•• Somewhat excessively Somewhat excessively
draineddrainedW llW ll d i dd i d•• WellWell--draineddrained
•• Moderately wellModerately well--draineddrained•• Somewhat poorly drainedSomewhat poorly drainedSomewhat poorly drainedSomewhat poorly drained•• Poorly drainedPoorly drained•• Very poorly drainedVery poorly drainedy p yy p y•• Permanently wetPermanently wet
Compare the Webster to the Nicollet and Clarion.
Upland SoilsUpland Soils –– ClarionClarion--WebsterWebster--Nicollet AssociationNicollet Association
Note: Parent materials Note: Parent materials –– glacial till or local alluviumglacial till or local alluviumUpland depressional soil sequence from center out Upland depressional soil sequence from center out ––
Okoboji 6, Harps 95, Canisteo 507Okoboji 6, Harps 95, Canisteo 507Webster 107Webster 107 - depressional, nondepressional, non--circular soilcircular soil
Best drained soils Best drained soils –– Clarion 138 & Storden 62Clarion 138 & Storden 62 but Storden is erodedbut Storden is erodedNicolletNicollet – somewhat poorly drainedsomewhat poorly drained
Soil Landscape Model for Central IowaSoil Landscape Model for Central Iowa
HaydenHayden--LesterLester--StordenStordenHaydenHayden--LesterLester--StordenStordenAssociationAssociation
ClarionClarion--WebsterWebster--NicolletNicolletAssociationAssociation
ColandColand--SpillvilleSpillville--ZookZookAssociationAssociation
top related