Soil Science 1

soil vs dirt

soil is only soil when it is in its natural place/working in the whole system.

once removed from the system, then it’s dirt

soil is the technical term; can also use “earth”

pedosphere

soil layer; outermost layer of the earth, composed of soil and subject to soil formation processes

interacts with hydrosphere, atmosphere, biosphere, and lithosphere.

earthly soil ecosystem services

provisioning

regulating

supporting

non-material

soil provisioning ecosystem services

food production

fiber and fuel

raw materials

soil regulating ecosystem services

water regulation and infiltration

carbon storage and climate regulation

nutrient cycling

pest and disease control

soil supporting ecosystem services

habitat for biodiversity

soil formation

primary production (eg plant growth)

soil non-material ecosystem services

cultural identity and heritage

recreational and aesthetic values

education and scientific values

soil functions

modifying composition and properties of atmosphere (CO2 and NO2-major greenhouse gases; soil is part of their cycles: reservoir/microorganisms)

providing habitat for an enormous diversity of organisms

supporting plant growth

recycling waste products of society and nature

largely controlling flow of water through the hydrologic cycle

functioning in built environments as construction material and support for building foundations

formal definition of soil

layer(s) of generally loose mineral and/or organic matter that are affected by physical, chemical, and/or biological processes at or near the planetary surface and usually holds liquids, gases, and biota and support plants.

physical properties of soil

not completely solid (~50/50 solid/pore space)

solid:

• mineral - 45%

• organic - 5%

porous:

• air - 20-30%

• water - 20-30%

soil acts as support for plant growth

physical support

aeration for roots

moisture supply and storage

moderation of root zone and near-ground air temperature

provide and maintain an environment relatively free of phytotoxins

nutrient resources (soil contains 13 out of 17 essential nutrient elements plants require)

macronutrients plants need (not from soil)

C (carbon)

H (hydrogen)

O (oxygen)

macronutrients plants need (from soil)

Ca (calcium)

Mg (magnesium)

K (potassium)

N (nitrogen)

P (phosphorus)

S (sulfur)

micronutrients plants need (from soil)

Cu (copper)

Co (cobalt)

Fe (iron)

Mn (manganese)

Ni (nickel)

Zn (zinc)

B (boron)

Mo (molybdenum)

soil quality, degradation, and resilience

human population grown more and more from the same/smaller amount of land

soil quality

measure of the ability to carry out ecological functions

soil degredation

results from erosion, salt accumulation, nutrient depletion, and organic matter depletion

soil resilience

measure of recovery from disturbance or demand

despite macro and micronutrients being from soil solids, the elements must be absorbed:

in a dissolved state. they are delivered to plants via the water

macronutrients

needed in relatively large amounts

micronutrients

needed in relatively small amounts

soil takes how long to form?

800-1000 years to form 1 inch of soil

non renewable resource in our lifetimes

soil body

3 dimensional

natural body

exists in the landscape

forms in upper part of the regolith

pedon

minimal unit to study soils

lacks boundaries between neighbors

smallest body of on kind of soil that is large enough to represent the nature and arrangement of horizons and variability in the other properties

unit of observation, sampling, and classification

soil profile

2-d representation

soil pedon

3-d

solum

soil

parent material

not soil

regolith

layer of unconsolidated rocky material covering bedrock

not soil

landscapes

constructed or consist of polypedons (have boundaries)

horizons

pedogenic

O, A, E, and B common master horizon designators

subordinate horizon designators

modify master horizon designators

soil formula

soil = f(climate, organisms, relief, parent material, time)

why would one horizon be darker?

more organic material

more horizons in a pedon means

more developed/more time/older

minimum pedon size

1m x 1m to depth of not soil

maximum pedon size

8m x 8m to depth of not soil

A

mineral horizon (<20% organic C) which forms at the surface, or beneath an O horizon

B

horizon formed beneath A, E, or O horizon and is a zone of accumulation (iluvial horizons)

C

layer of unconsolidated material showing little weathering (alteration) and biological activity (e.g. beach sand, alluvium deposited by rivers, glacial till deposited by glaciers)

E

intensively leached eluvial horizon in which organic matter along with iron and aluminum oxides and clay have been removed. most commonly found in forest soils

L

include both organic and mineral limnic materials that were either deposited in water by precipitation or through the actions of aquatic organisms, such as algae and diatoms, or derived from underwater and floating aquatic plants and subsequently modified by aquatic animals

M

a root limiting nearly continuous, horizontally oriented, human-manufactured materials (e.g. geotextile liners, asphalt, concrete, rubber, and plastic)

O

a surface horizon dominated by organic materials (>20% organic carbon)

R

consolidated rock that can not be dug with a shovel and shows little evidence of weathering (e.g. granite, sandstone)

W

water within or beneath the soil. not used for shallow water, ice, or snow above the soil surface. clay accumulation

a

highly decomposed organic matter

b

buried soil horizon

c

concretions or nodules

co

coprogenous earth

d

dense unconsolidated materials

di

diatomaceous earth

e

intermediately ‘hemic’ decomposed organic matter

f

frozen soil

ff

dry permafrost

g

strong gleying

h

illuvial accumulation of organic matter

i

slightly ‘fibric’ decomposed organic matter

j

jarosite (yellow sulfate material)

jj

cryoturbation (frost churning)

k

accumulation of carbonates

kk

engulfment of carbonates, >50% of soil by mass

m

cementation or induration

n

accumulation of sodium

o

accumulation of iron and aluminum oxides

p

plowing or other disturbance

q

accumulation of silica

r

weathered or soft bedrock

s

illuvial organic matter and iron, aluminum oxides

se

presence of sulfides

ss

slickensides (shines clay typically on wedges)

t

accumulation of silicate clays

u

human-manufactured artifacts

v

plinthite (high iron, red material)

w

distinctive color or structure without clay accumulation

x

fragipan (high bulk density, brittle)

y

accumulation of gypsum

yy

gypsum >50% of soil by mass

z

accumulation of soluble salts

illuvial

recieving material washed down from previous horizons

eluvial

material is washed out of the horizon

loess

windblown materials composed primarily of silt with some very fine sand and coarse clay. cover wide areas in the central united states, argentina, eastern europe, and central china

not a horizon: layer of material that has not undergone soil forming processes

the soil interface (lithosphere, atmosphere, hydrosphere, biosphere) at many different scales

kilometer→meter→millimeter→micrometer & nanometer

soil physical properties

size separates

textural class

particle arrangement

density

porosity

color

engineering

erosion

size separates

coarse fraction

earth-fine fraction

coarse fraction

>2mm

boulder

stone

cobble

gravel

boulder size separate

>600mm

stone size separate

600-250mm

cobble size separate

250-75mm

gravel size separate

75-2mm

earth fine fraction

<2mm

sand

silt

clay

sand size separate

2-0.05mm

silt size separate

0.05-0.002mm

clay size separate

<0.002mm

textural class

soil behavior and management

permanent property of soil

earth fine fraction

influence of surface area

holding water films

retain nutrients and other chemicals

release of mineral nutrients

soil particle to stick together (aggregate)

microorganisms