Soil Science Test One
Describe the A horizon
"Topsoil" containing an accumulation of humus (highly broken down organic matter) and eluviation. Humus gives this layer its dark color.
What are some grand soil science challenges for 2050?
-Food -- how do we feed the growing population without harming soils? -Nutrients -- how do we preserve end enhance the fertility of soils -Fresh water -- how can we manage soil in a way that will allow us to use groundwater wisely and not pollute it? -Energy -Climate change -Biodiversity -Recycling "wastes" -Global perspective
Chemical Weathering examples
-Hydrolysis -Dissolution -Hydration
Describe the B horizon
-Illuviation is the dominant process -Iron, Aluminum, Calcium, and Clay build up -"Bright redish colors"
Describe the C horizon
-Not much going on -Minimal soil forming activity
What are some characteristics of the rhizosphere?
-Root exudates -Microorganism activity -Higher CO2
What happened to soil in Mesopotamia?
-Siltation (sediments from erosion settling in low gradient canals) -Erosion
About what percent of the soil is air?
20-30%
About what percent of the soil is water?
20-30%
About what percent of the soil is mineral material?
45%
About what percent of the soil is organic material?
5%
Define Polypedon
A group of closely associated pedons in the field
A lowercase "p" designates a soil that has been plowed or otherwise disturbed. Which master horizon is the most likely to be described with a "p?"
A horizon The A horizon consists of our traditional "topsoil," and it is the most likely to be directly disturbed by plowing. Therefore, "Ap" is the most likely scenario for p.
An "h" might be added to further describe a soil found in which master horizon?
A or B. "h" describes an illuvial accumulation of organic matter, which will likely happen in the A or B horizon.
What is a pedon?
About a square meter of soil; a natural body of soil large enough to allow classification of the soil
Name some types of physical weathering
Abrasion by water, abrasion by sand, heat and cooling expansion, wind abrasion, glacier movement, exfloiation, plant roots
What is Illuviation?
Accumulation
t
Accumulation of silicate clays
Four basic processes in soil formation
Additions, losses, translocations, and transformations
Generally speaking, what is soil made of?
Air, water, rocks, and life
Where did soil degradation NOT take place, allowing people to remain there and practice agriculture for long periods of time? Why?
Along the Nile River. The Nile renews the banks yearly with new nutrients and water. -Fertile soil -Dependable water supply -Irrigation and removing salts -Relatively level land -Scant rainfall
Terra preta
Amazonian dark earth -"Created soils" -Dumped organic material
Describe the E horizon
An "acid washed" horizon in which leaching is the primary process. Very little color
Describe the O horizon
An organic layer containing very little mineral matter. Technically speaking, this horizon does not have "texture" because it does not have sand, silt, or clay.
While horizons can be described broadly (for example, an O horizon will be high in organic matter) certain types of soil show different characteristics within those horizons, and the horizons themselves are divided into epipedons (surface horizons) and endopedons (subsurface horizons). List some types of A horizons you might find.
Anthropic Melanic Mollic Ochric Plaggen Umbric
"w" describes a soil with distinctive color or structure without clays, especially within which master horizon?
B
Where might an "s" subhorizon be found (which Master horizon might you expect it to be in)
B because there is often an accumulation of iron and aluminum?
This horizons make up the endopedon:
B horizon C horizon
What does R stand for when describing a soil profile/horizons?
Bedrock R=Bedrock
Who was Curtis F. Marbut?
Championed the use of observable, measurable soil properties to classify soils
Define Soil Series
Class of soils world-wide which share a common suite of soil profile properties. The most specific you can get in taxonomy.
Examples of secondary minerals
Clay
Name the factors of soil formation
Climate, Organisms, Relief, Parent material, Time
Soil formation is a function of what?
Climate, organisms, parent materials, relief, and time
Physical weathering
Disintegration, a mechanical process -Heating & cooling -Freezing and thawing -Abrasion -Exfoliation e.x.
w
Distinctive color or structure without clay accumulation
What is eluviation, and which layers is it especially prominent in?
Eluviation is the movement of material by water, described also as "washing out" or "leaching." It happens a lot in the A and E horizons as water and nutrients move out of them. Another common definition of eluviation is "the leaching of soluble products of weathering."
What are some words that describe negative impacts on soil?
Erosion Degredation Exhaustion
We began to see human-caused soil disruption with the rise of agriculture about 10,000 years ago. Where was the first agriculture practiced?
Fertile Crescent (basically Mesopotamia)
An Oi horizon is only slightly decomposed. It can be decided as: a) sapric b) hemic c) fibric
Fibric Fibric - least decomposed, recognizable fibers
Describe a histic epipedon
Found as A horizon Very high in organic content Wet during parts of the year
Describe an Anthropic epipedon
Found as an A horizon, an Anthropic epipedon has human transported or modified materials, with artifacts, or high phosphorus or puddled condition (rice paddies)
x
Fragipan (high bulk density, brittle)
What is permanent agriculture?
Growing same thing at same place over and over. Leads to soil degradation. Collapse of civilizations linked to soil degradation (exception along Nile)
Examples of primary minerals
Gypsum Calcite Quartz
An earthworm lives in the soil, acting as a decomposer of organic materials. The earthworm's relationship with the soil fits with soil's role as a what?
Habitat for organisms. The earthworm lives in the soil. One of the soil's 6 primary purposes is to be a habitat for organisms.
a
Highly decomposed organic matter
h
Illuvial accumulation of organic matter
s
Illuvial organic matter and iron, aluminum oxides
What process dominates the B horizon?
Illuviation dominates the B horizon. Here, things like Iron, Aluminum, Calcium, and Clay accumulate, often creating the distinct "redish" color.
e
Intermediately decomposed organic matter
What is the state soil of Michigan?
Kalkasa
What was different about land use in the east (think Lebanon)
Lebanon had more rainfall, which supported forests. More hilly. When forest plants are replaced with crops on hills, erosion will take place. Attempts of permanent agriculture encountered severe soil erosion. Deforestation and overgrazing resulted in more accelerated erosion and siltation in downstream irrigation channels
Amazon
Lots of erosion due to high heat and water. BUT when people dump things like fish, human and animals wastes, etc. a fertile soil can form (farmable soils)
Name the 5 master horizons
O A E B C R=bedrock
Which horizons together make up the epipedon?
O horizon A Horizon
Feasible examples of horizon classification
Oa, Oe, Oi, Bt, Bg, Btg, Bw, Ap, etc.
Because of Marbut, we largely classify soils by what?
Observable traits -Diagnostic horizons -Soil moisture -Soil temperature
In this function, what does "O" stand for? S = f(Cl, O, P, R, & T)
Organisms Organisms influence soil formation
How might the degradation of soil have lead to the downfall of ancient civilizations?
Overworked soil, drained of its nutrients, was no longer able to support crops. People had to move or starve.
In biology, we have many "spheres," including the atmosphere, lithosphere, hydrosphere, and biosphere. The soil is seen as the overlapping site for all of these spheres. What is this "sphere" called?
Pedosphere
Describe agriculture along the Nile
Permanent agriculture resulted in very little erosion, siltation, or saltinization. Soil productivity was maintained
p
Plowed/disturbed
What is soil texture?
Ratio of sand, silt, and clay
The book says that, if soil did not perform this function, "The world would be covered with a layer, possibly hundreds of meters high, of plant and animal wastes and corpses." Which "role of soil" is this referring to?
Recycling system for nutrients and organic wastes One of soil's roles is to act as a recycling system for nutrients and organic wastes. It does this through a collaboration of microorganisms, weathering, and other processes.
What is base saturation?
Refers to type of soil cations on exchange complex. Compex has a net negative charge, so cations are attracted to it
Heavy irrigation in a hot, dry climate leads to a gradual accumulation of ___________ in the soil.
Salt Heavy irrigation in a hot, dry climate leads to a gradual accumulation of salt in the soil.
What does sapric mean?
Sapric -most decomposed, low plant fiber, low water
i
Slightly decomposed organic matter
How might soil mitigate global climate change?
Soil accumulates and stores large amounts of carbon as soil organic matter, reducing the concentration of atmospheric carbon dioxide.
S = f(Cl, O, P, R, & T)
Soil formation is a function of Climate, Organisms, Parent materials, Relief, and Time
List the 6 primary "purposes" of soil
Soil is a: 1) Medium for plant growth 2) Recycling system for nutrients and organic wastes 3)System for water supply and purification 4)Engineering medium 5)Modifier of the atmosphere 6) Habitat for organisms
Why can soil be described as an "ecological entity?"
Soil is intimately connected to air, water, rocks, and life. As a crucial piece of the environment, it plays a role in many ecosystem services, rather it be provisioning, regulating, cultural, or supportive. The main roles of soil involve being a medium for plant growth, a recycling center for nutrients and wastes, a modifier of the atmosphere, a habitat for organisms, an engineering medium, and a system for water supply and purification. These roles are not completely independent; rather, they work together.
Why is Nathaniel Shaler's comment that "all soil may be regarded as rock matter on its way to the sea" not entirely true?
Soil is more than just rock. It is also made of air, water, and life.
g
Strong greyling/mottling
Define Edaphology
Study of soils as a habitat and medium for plant growth
Define Pedology
Study of soils in their natural environment
What is an endopedon?
Subsurface horizons (e.g., B)
What is an epipedon?
Surface horizons (O & A)
Describe the three subhorizons that may be found in the O horizon. What do they mean? What do they describe?
The a, e, and i subhorizons denote the degree of organic matter decomposition in the O horizon. Oa - highly decomposed (sapric) Oe - moderately decomposed (hemic) Oi - slightly decomposed (fibric) Sapric -most decomposed, low plant fiber, low water content Hemic - intermediate decompostion Fibric - least decomposed, recognizable fibers
What is the rhizosphere?
The root-influenced zone; the soil layer that surrounds actively growing roots
Describe a soil classified as Oa
This soil is made of up highly decomposed organic material on the earth's surface. It is sapric, meaning that it is the most decomposed of the three possible subhorizons within the O horizon. It is low in plant fiber and low in water.
Examples of land use
Tilling, clearing, fertilization, agriculture, etc. Taking other plant material away from the soil and replacing it
True or false: Different materials weather at different rates
True
Consider a prairie ecosystem in which rich soil is held together by prairie grasses. How might degredation caused by overgrazing, overuse, or development impact the local atmosphere of the altered prairie?
Without the native prairie grasses holding the soil together, and without the shade and nutrients contributed by the plants, surface soils will dry out. In places where the soil is dry, poorly structured, and unvegetated, soil particles can be picked up by winds and contribute great quantities of dust to the atmosphere, reducing visability, contributing to human heath problems, and even altering the temperature of the air and earth.
This suffix is used with the O horizon, and describes highly decomposed organic matter:
a
These three lowercase letters, describing subhorizons, are used to describe how decomposed organic material is within the O horizon
a, e, and i a describes highly decomposed material e describes intermediately decomposed organic material i describes slightly decomposed organic matter All of these describe soil within the O horizon
There are many subhorizon distinctions within master horizons, designated by lowercase letters. Name some subhorizons.
a, e, g, h, i, p, s, t, x, p, o, and w
An Oe horizon would be described as: a) sapric b) hemic c)fibric
b) hemic "e" descibes a hemic soil, a soil that is moderately decomposed
This suffix describes organic soil that is intermediately decomposed. It is used with the O horizon:
e
Describe the "h" subhorizon
h stands for "humic," an illuvial accumulation of organic matter. It is used with the B horizon (Bh)
This suffix describes slightly decomposed organic matter and is used with the O horizon
i
Which subhorizon: Low activity clays Few weatherable materials Little rock structure Fe and Al oxides
o (oxic horizon)
Which subhorizon letter: Illuvial accumulation of both sesquioxides and organic matter. Both the organic matter and sesquioxide components of humus-sesquioxide complexes are important.
s
Heavy irrigation leads to ____________________.
saltinization
Which subhorizon letter is used to describe an accumulation of clays, especially in the B horizon?
t
Which subhorizon: Accumulation of silicate clays
t
Which subhorizon: Distinctive color or structure without clay accumulation
w
Which subhorizon describes a layer that is firm, brittle, and may have high bulk densities from natural processes?
x
