Soil Flashcards

Organic matter
Terms Definitions
residual soil
forms on bedrock
-forms in temperate areas
-receive greater than 63cm of rain a year
-found in forested areas
-found in the eastern part of the U.S.
-reddish brown soil
Soil colors
Brown/black - organic matter
Red/orange/yellow - iron oxides/hydroxides
White - carbonates
Grey - either bare mineral grains, or anerobic conditions


To slowly to break down
the loose, weathered material on Earth's surface in which plants can grow
large igneous rocks are exposed because of uplift and erosion, as pressure is decreased slabs of rock break loose - process of ___________________.
To slowly break down, or rot
40% Sand, 40% Silt, 20% Clay
pore soil
the space between soil particles
the unconsolidated mantle of weathered rocks and soil material on the earth's surface (O through C horizons)
to dissolve out soluble constituents from ashes and soil by percolation
The soil of the A-horizon. Generally gray to black in color. Made up of humus
-found in drier areas of the U.S.
-found in areas with grasses and brush vegetation
-chemical weathering slower in dry climates = less clay
-contains calcite = light gray-brown in color
Dust Bowl
1930's after long drought, strong winds removed soil from Great Plains
Naturally occurring plant and animal resources. Organic matter is a part of compost.
Metamorphic rock
Igneous or sedimentary rocks changed under pressure or heat
B Horizon
Mineral horizon with either or both:
1. An illuvial accumulation of Fe, Al, O.M., clay - orange, yellow, light brown, or
2. Substantial alteration of original mineral material - shows pedagenic process - eliminated some rock structure, aggregated particles together, changed color to orange, yellow,grey, light brown
The process by which soils are depleted of bases and become acidic.
nutrient elements
elements or substances that contribute an organism's growth and health. Some nutrients are essential to completion of the life cycle.
Used in relatively large amounts - greater than .1% of dry plant tissue
slow movement of water through the pores in soil or permeable rock
Soil profile
a vertical thought all the soil horizontal
Soil horizions
Three distinct zones in mature soils. Include A, B, C, E, R, D, O
Soil map
A map showing the distribution of various soil types in an area or region.
Pedalfer soil
red-brown, large amount of iron oxide & aluminum must of eastern US
Loose soil with large grains. Most plants do not grow well here because the sand does not hold water and it has a few nutrients.
Meaning of "clay"
Clay sized particles - <.002 mm
Clay minerals - platey secondary minerals
Spodic diagnostic horizon
B horizon with illuvial accumulation of Fe+3, Al+3 and humas. Bhs or Bs.
a layer of soil differing from the layers above and below it
Chemicals that can be added to soil when it does not have enough nutrients to grow plants
pores, voids
The space not occupied by solid particles in the bulk volume of soil. Sometimes referred to as 'pore space.'
natural resources
the natural wealth of a country, consisting of land, forests, mineral deposits, water, etc.
the falling to earth of any form of water (rain or snow or hail or sleet or mist)
Field work
Test done in a "real world" setting, not in an indoor labratory.
Methods of nutrient movement through the soil.
Mass flow and diffusion
Pieces of soil that are sop small they cannot be seen without a microscope
soil texture
the soil quality that is based on the proportions of soil particles.
Particle density
Density of solids in a soil - nothing to do with pores. Although changes with mineral type, small enough that we can use 2.65 g/cm3 as average density of mineral soils. Organic soils are probably less then 1 g/cm3
Describe some ways that land management can effect soil organisms
Tillage reduces OM, earthworms, mychoriza, etc.
Compaction reduces organisms because reduced aeration,etc.
Biological crusts sensitive to disturbance.
Pesticides reduce soil organisms.
Describe how climate effects soil formation
Mostly from temperature and moisture influencing the rates of formation.

Temp increases the rate of biochemical reactions, while both temp and moisture effect soil organisms.
Soil nutrients that are typically available as negative anions.
PO4 -3, S04 -2, N03 -
Graph quantity of soil organic matter as move in latitude from the artic to tropics
Low productivity and low decomposition (low water for orgs, cold) in artic so little soil organic matter. High productivity but high decomposition in tropics), so low soil organic matter. Temperate zones high soil organic matter.
What does high soil PH lead to?
Phosphorus and boron insoluble and unavailable to plants. Concentrations of micronutrients becoming very low and so plant growth is restrained.
Describe the basic trophic levels in the soil food web.
The primary producers are the plants and soil organic matter. There are several levels of consumers beginning with bacteria, mycorrhiza, mites, and other fungi as primary consumers. Highest levels of consumers include earthworms and small mammals that feed from the soil. (Ref Soil Org PPT slide 2 and pg 319 of Soil Elements)
What are the physical properties of soil?
Soil colour, soil texture, and soil structure.
organic material in soil
flat slopes
little erosion, poor drainage
Components of the hydrologic cycle
Three Nutrients
Nitrogen, Phosphorus and potassium
not allowing fluid to pass through
Elements or compounds. The smallest part of an element that retains its characteristics is an atom
Inclusion of water into a mineral
What enhances water availability?
Horizon types
Soil depth
Percipitation and other water supply
Organic matter eventually breaks down into basic chemicals that can dissolve in water and becomes food for plants
a loose material consisting of grains of rock or coral
As moving sand, pebbles, and larger rocks grind and scrape against one another, these rock materials are worn away
The outermost layer of the Earth, composed of rock, representing less than 0.1% of the Earth's total volume
clay soil
drains slowly, plant roots have trougle penetrating soil
A mixture of plant parts (leaves, stems, flowers) and soil that has been piled up, soaked with water, and allowed to rot.
Soil formation when all other factors are held constant (O,R,P,T)
Small particles, not visible to the eye
Slightly moldable
Smaller pores than sand
Some water retention and less aeration than sand.
Low nutrition


Rock that is rich in useful materials. Ores may have the minerals lead, silver and copper. They can be found in deep tunnels or on earth's surface.
a material made of organic or inorganic particles with diameter from 0.001 to .1 u.m.
Molecular movement along a gradient. Water diffusion occurs from wet areas to dry ones. Gas and solute diffusion occur from wet areas to dry ones. Gas and solute diffusion occur from zones of high concentration to zones of low concentration.
light colored surface horizon, low in organic matter, common in desert soils
central portion of the earth believed to be composed mainly of iron and nickel in a molten state
George Washington Carver
An early proponent of crop rotation
occurs when agents of erosion lay down sediment
can change the shape of land
Rock cycle
A sequence of events involving the formation, alteration, destruction, and reformation of rocks as the result of such processes as erosion, transportation, deposition, lithification, and metamorphism.
The part of the Earth System that includes the crust, mantle, and inner core
Describe physical weathering
Mechanical breakdown of rocks without any chemical alteration.
Describe nitrogen fixers
Bacteria and actinomycetes that take atmospheric N2 which is strongly bonded together and convert it ammonium for plant uptake in exchange fore organic carbon from the plant. Symbiotic. Rhizobium is very common nitrogen fixer in legumes. Does not provide all the N a plant needs. Also lichens fix nitrogen.
List profiles
Has a Bt Horizon. Moderate base saturation (35-50%). Lower fertility than Mollisols but still excellent soil. Common under deciduous forests and grasslands.
A E Bt1 Bt2 C, or A Bt1 Bt2 BC
Soil is made up of large-sized pieces and feels gritty like sand
parent material
the unconsolidated and more of less chemically weathered mineral or organic matter from which the soil solum develops.
process where the surface of the earth is worn away by the action of water, glaciers, winds, waves
No Till farming
Provides cover to help prevent water runoff and does not disturb the soil, which helps prevent erosion
direction of slope
south facing slopes - more sunlight, soil warmer & drier (Northern Hemispherea0
Influences of parent material on a soil
Water movement
Whethering rate
Nutrient cycling
Depth of soil
Change in soil storage
Equals inputs minus outputs. Usually done on a watershed basis.
Factors - precipitation, leaching to creek or aquifer, overland flow, transpiration, evaportation
Soil is made of small pieces and feels gummy, like wet clay
Watershed map
A map showing the route taken by water draining from land.
Surface and subsurface run-off
Surface run off happens to the fraction that doesn't infiltrate
Subsurface run off is water that infiltrates but drains by gravity (such as down a hill), through capiliarity or because it hit a pan layer to a stream or body of water.
Define and explain gleization
Occurs in water logged, poorly drained soils. Causes mottles of orange and grey creating either a Bg or Cg horizon.

Results from the reduction of iron (addition of electron) from decomposing organic matter. Occurs when no O2 present. Normally O2 would take up the electrons. Can be mottled because of cycles of wetting/anerobic conditions.
Causes of soil structural development
Don't really know - the following contribute:

Climatic conditions like wet/dry cycles and freeze/thaw

Clay content

Oxides, O.M. and carbonates

Organisms, plant roots, exudates
Spodisols and OM
OM goes down in elluvial E horizon but back up in Bhs horizon. Unusual. Most soils OM decreases at some rate with depth.
Limitations of extremely shallow or deep soil
Shallow soil is poorer at supplying nutrients, water, anchorage

Deep soil course may drain to quickly of water
What are the 5 factors that influence soil formation?
Climate, parent material, relief, organisms, and time.
The three soils orders defined by base saturation and the base saturation %s
Mollisols - greater than 50%
Alfisols - 50-35%
Ultisols - less than 35%
Graph change in depth of soil as move in latitude from artic to tropics (inc temp)
Shallow in artic
Highly variable in temperate
Deep and well formed in tropics
Father of Pedology
reduces pressure on igneous rock
Methods of transporting unconsolidated materials
An argillic diagnostic horizon
Bt horizon
Acid rain
Sulfur dioxide, nitrogen compounds, and carbon dioxide released by industries react with water in the atmosphere to form this
Twelve soil orders
Alfisols, Andisols, Aridisols, Entisols, Gelisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols, Vertisols.
A process of rearranging soil particles to decrease pore space and increase bulk density. It produces a compacted, dense soil layer.
Biological activity
The activity of organism breaks rocks
A drainage basin. The direction in which water draining form land.
One of the numerous features that taken together make up the surface of the Earth, including broad features
Tightly packed soil with tiny grains. Many plants cannot grow here because the grains are so close together.
Forms of Organic Matter
1. Recognizable detritus/litter
2. Humus (not recognizable)- waste from organisms
3. Colloidal material
Changed area just outside of plant roots. Where exudates accumultation, microorganisms feed off of exudates, nutrients are extracted.
Wearing down of rocks bu natural forces; over time, rocks crack,m crumble, and are broken apart by water and wind
master horizons
Major soil horizons identified by capital letters:O, A, E, B, C, R
the emission of water vapor from the leaves of plants
Biological Weathering
The processes of weathering by which living things, including animals, plants, and other organisms, break down rock into smaller pieces or particles, at , or near, the Earth's surface
chemical make up - influences types of plants soil can support
The outer covering of the earth where plants grow. Soil is made up of minerals (sand, silt, clay), air, water, and organic matter.
Munsell color system
Standard system for accurate color description. Compare soil to standard coloer chips and describe hue, chroma, and value with a system of numbers and letters.
Sources of nutrients in soil
Parent material, atmospheric deposition, secondary minerals, soil organic matter, and exchange sites.
Characteristics of Andisols
Developed from volcanic material. A Horizons that are rich in Al-humic materials. Secondary minerals are predominately amporphous. Range from moderate to well developed.
The upper and most weathered part of the soil profile; the A, E, and B horizons.
a gradation or variety of a color; tint:
water held in rocks and soil below the surface
Time's effect on soil
longer forming - soil becomes thicker
Soil productivity is dependant on
Support, water, aeration, nutrients and symbionts.
Orders that are likely to have Bt Horizon
Alfisols, Ultisols
convergent plate boundary
tectonic boundary where two plates are moving toward each other
Functions of soil water
Holds water for roots and animals
Acts as a solvent/medium transfering nutrients from soil particles to roots
Moves material through soil and out of soil - microscopically and macroscopically through layers.
Describe mass flow of nutrients
Nutrients move proportionally to water movement and concentration in water. Fast way to move nutrients. Driven by transpiration.
What are soil colloids?
They are very small particles that stay suspended in water. The most important ones are clay minerals and organic matter.
The law of the minimum
Plant growth is constrained by the essential elment that is most limiting. Barrel stave example.
5 essential functions of soil
1) Medium for plant growth2) Regulator of water supplies3) Recycler of raw materials4) Habitat for soil organisms5) Engineering medium
Describe the sources of nutrients to soils and speed of availability
Readily available in soil solution. Moderately available on exchange sites depends on number of sites and exchangable ions available. Slow availability from organic matter as decomposes - depends on size of matter.
Types of minerals in soil by size
Sand - .05-2 mm
Silt - .002-.05mm
Clay - <.002mm
What does low soil PH lead to?
Reduced number and activities of soil organisms like worms, bacteria, nitrogen fixing bacteria, and organisms that break down organic matter. Increased concentrations of the micronutrients like iron manganese and zince which leads to toxicity. Phosphorus
Elements mostly from solid soils
Ca2 + K+ Mg2 + N from NO3-, NH4+ P from H2PO4-, HPO4 2- S from SO4 2-
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