Soil Science

What are the 6 reasons soil is important?

1. Support plant growth

2. Regulate water supplies

3. Recycle raw materials

4. Modify environment- atmospheric gas exchange

5. Habitat

6. Engineering medium

What gases do soils absorb and release?

Absorb: O2 & CH4

Release: CO2 & N2O

What are the 6 roles for plant growth?

1. Support

2. Aeration

3. Moisture

4. Temperature

5. Phytotoxins

6. Essential nutrients

Soil

Unconsolidated mineral or organic matter on the surface of the Earth that has been subjected to & shows effects of genetic & environmental factors

CLORPT

Climate
Organisms
Conditioned by relief: topography
Parent material
Time

Regolith

Zone on top of bedrock to soil surface

Complex habitat for microbial growth

Pedology

scientific study of soils & their weathering profiles

Edaphology

science that deals w/ influence of soils on living things

The critical zone

outer layers of planet that lie between tops of tallest trees & bottom of the groundwater aquifers that feed our rivers

Name horizons in order

O, A, E, B, C, M

O Horizon & three layers

Dead organic matter, dark colored, low density
Litter layer: fibris Oi
Fermentation zone: hemis Oe

Humification zone: sapric Oa

A horizon

Mineral soil materials w/ accumulation of OM, dark colored
Topsoil

E horizon & zones

Mineral soil, light in color, leaching of clay
Zone of elluviation: zone of maximal leaching
Illuviation: transport of dissolved materials

B horizon

Subsurface horizon, change in material (clay, metals, salt)
Infiltration

C horizon

Rocky layer, unconsolidated material

M horizon

Root limiting, human manufactured layer

Difference between ORGANIC and MINERAL soil

Organic: derived from plants or organisms
80-90% pore space
Mineral soil: derived from rocks or mineral
35-55% pore space

Role of water in soils

Purify water
Store water

Can displace organisms
Contaminate water: runoff

3 Criteria of essentiality

1. Plant cannot complete life cycle in absence of element

2. No other element can substitute it

3. Must be required for the activity of an essential enzyme

Soil contains ___ elements for plant growth C Hopkins Cafe managed by my couzin Monicl

18
Primary: P, K, N
Secondary: S, Ca, Mg
Micro: Cl, Fe, B, Mn, Zn, Cu, Mo, Ni, Co

What is the pedosphere composed of?

Soil air, soil particles, soil water, soil OM, biomass

Constructive vs. Destructive properties

Constructive: forces that change features on earth’s surface
Destructive: force that changes earth’s surface

3 Characteristics of OM

1. Contains carbon

2. Made up of living organisms

3. Increases water holding capacity

Humus

Collection of organic compounds that accumulate in soil when partially broken down
Contains components to make micronutrients more easily used by plants

Kilometers scale

1. Soils channel water from rain to rivers

2. Influence global balance of atmospheric gases

Meters scale

1. Hold water & air for plant

2. Recycle OM

Millimeters scale

1. Channels water & nutrients to plant roots

2. Microhabitats for organisms

Micrometers scale

1. Provides surface for chemical reactions

2. Soil mineral particles form micro-zones of electromagnetic charge

Alfisol (ALF) CLIMATICALLY CONTROLLED

Has argillic or natric horizon

Moderately leached

Strongly weathered soils clay has accumulated in B horizon by illuviation

Forest

Andisol (AND) PARENT MATERIAL INFLUENCE

Volcanic ash soil

Deposited in recent geological times, not highly weathered

Poorly crystalized silicate materials

Melanic epipedon

Light, fluffy- high OM

High water-holding capacity, resistant to water erosion

High fertility

High P fixation capacity

Aridisol (IDI) CLIMATICALLY CONTROLLED

Dry

May have layer rich in carbonate in B horizon

Soil moisture can support plant life for <90 consecutive days

Can be fertile if irrigated

Accumulation of salts in upper profile

Entisol (ENT)

Least weathered soil

No B or very little B horizon development

Soils w/ little to no morphological development- too much soil erosion, not enough time

Gelisol (ELI) CLIMATICALLY CONTROLLED

Permafrost & frost churning

Young soils w/ little profile development

Building structures on gelisols may sink into ground

Histosol (IST) PARENT MATERIAL INFLUENCE

Organic soils w/o permafrost

OM in more than half of upper 80cm

Little profile development due to anaerobic environment

Inceptisol (EPT)

Inception of B horizon

Often found at fairly steep slopes

Found in mountain regions where steep slopes retard profile

Change in color & structure but no illuvial accumulation of clay

Mollisol (OLL) CLIMATICALLY CONTROLLED

Soft, dark soils of grasslands

Calcium-rich OM

Surface horizon has granular or crumb structures due to high OM, fine roots & swelling-type clays

Oxisol (OX)

Most weathered soil

Spodosol OD

Climatically controlled

Ultisol (ULT)

Climatically controlled

Vertisol (ERT)

Develop from limestone, basalt or other Ca & Mg rich parent materials

Dark from parent material, not much OM present
High content of dark, sticky, swelling, shrinkinh & cracking clay types

What do family names indicate?

Soil texture

Mineral composition

Soil temperature

What do soil series indicate?

Location where they were first classified

Order

Soil forming processes & contrasting climates

Suborder

Soil moisture & temperature

Great group

Differentiating horizons & features

Pedon

Smallest volume that can be called a soil

Polypedon

Group of similar pedons on the landscape

What 3 things are soil taxonomy based on?

Diagnostic surface horizons
Diagnostic subsurface horizons
Soil moisture regimes

Aquic

Saturated often

Can occur anywhere

Gleying & mottling

Regime characteristic of poorly drained soils

Udic

Humid

Soil moisture high enough to meet plant needs but not so wet you have redoximorphic features
Dry <90 days in most years

CT

Ustic

Semiarid
Some moisture available for plants but significant periods of drought occur

Aridic

Arid & semiarid, requires irrigation

Moist for <90 consecutive days

Unsuitable for cultivation w/o irrigation

Drier than Xeric

Xeric

Summer drought, Mediterranean

Cool moist winters & warm dry summers w/ long periods of drought in the summer

Moist for 50% of growing season

Soil temperature regimes

Hyperthermic

Thermic

Mesic

Fridgid

Cyric

Anthropic

Human transported or modified materials w/ artifacts or high phosphorus or puddled conditions

Epipedon

Folistic

Organic horizon saturated for less than 30 days per normal year

Epipedon

Histic*

Thick layer of OM overlying mineral soil

Formed in wet areas

Black to brown color

Naturally occurring over wide areas

Epipedon

Melanic*

Volcanic ash soils

Thick, black, high in OM

Naturally occurring over wide areas

Epipedon

Mollic*

Thick, dark colore, high base saturation

Well-developed structure

Grassland soils

Naturally occurring over wide areas

Epipedon

Ochric*

Lighter in color

Lower in OM, thinner than mollic

May be hard & massive when dry

Naturally occurring over wide areas

Epipedon

Plaggen

Human made sod-like horizon created by years of manuring, often w/ artifacts & spade marks

Epipedon

Umbric*

Similar to mollic except low base saturation

Naturally occurring over wide areas

Epipedon

Solumn

Biochemically weathered materials

Limnic

Deposited in water by precipitation or aquatic organisms

Traditional horizons

Dominated by the properties of one horizon but having subordinate properties of another

Subordinate distinction

Further divides master horizons (lowercase letter)

p (subordinate)

tillage or other mechanical disturbance

b (subordinate)

Buried horizons

Major genetic features developed before burial

h (subordinate)

Illuvial accumulation of OM

s (subordinate)

Illuvial accumulation of sesquioxides & OM

t (subordinate)

Illuvial accumulation of silicate clay

k (subordinate) kk

Accumulation of secondary carbonates

kk: engulfment of horizon by secondary carbonates

w (subordinate)

Color/structure development w/ little illuvial accumulation

x (subordinate)

Fragipan

Firm but brittle, root restrictive

f (subordinate) ff

Permanent ice

ff: dry permafrost

g (subordinate)

Gleying, water saturation likely

Albic horizon

White

Eluvial loss of clay: losing clay pigments

Mostly contains sand & silt

Aquic conditions

Spodic horizon

Red or brown

Illuvial material containing OM & aluminum w/ or w/o iron

Argillic, natric

Less weathered

High CEC

Climate arg: water for translocation, weathering (evidence of past humid climates)

Kandic, oxic

Weathered

Low CEC