Envirothon: Soil Flashcards
What is soil?
A complex, self-renewing, living system; Soil is a resource that most terrestrial life depends on directly or indirectly for survival
What is soil composed of?
Inorganic minerals, organic humus, living organisms, moisture, and air.
Soils are the product of what?
Interactions between abiotic and biotic processes
What is the study of soils called?
Pedology
What two Greek words make the English word “pedology”?
pedon and logos; Pedon meaning soil and logos meaning logic
In the early years of soil study, how was it thought that soil types were determined?
By the parent material
Who changed how people thought soil types were determined?
V.V. Dokuchaev
What did V.V. Dokuchaev discover?
In the late 1800s, he discovered that different soils develop over identical bedrock exposed to various climates.
Which man in 1920 had the idea that climate plays a large role in soil formation?
C.F. Marbut; Chief of the United States Soil Survey
What are the 5 categories for factors that influence soil development?
- The type of parent(source) material
- The climate under which the soil components have existed since accumulation
- The plant and animal life in and on the soil
- The relief of the land
- The length of time the other factors have interacted
The five categories of factors are what?
Interdependent
How does soil formation begin?
The degradation of parent material
What is parent material?
Unconsolidated, chemically weathered mineral, rock, or organic matter
What are the climate forces that act on parent material to form soil?
Precipitation, temperature, humidity, and
wind
What greatly influences the way wind and water acts on the parent soil?
The relief of the land and the types of plants and animals that inhabit the area
What things furnish organic matter?
Animals, insects, bacteria, fungi, and other plants
Plant and animal actions cause differences in what?
Differences in the amount of organic matter, nutrients, structure, and porosity of soil
What is an important factor in soil formation?
Time
Finish the quote: “The physical and chemical changes
brought about by climate, living organisms, and relief are”
Slow
Why does the length of time needed to convert raw geologic materials into soils vary?
It depends on the nature of the material and the interaction of other factors
How are soils deposited?
In layers
What is the difference between a mature soil and an immature soil?
A mature soil has defined layers, while an immature soil does not
What is a soil profile?
A vertical column of soil
What are the soil layers called?
Soil horizons
O Horizon
The O horizon is dominated by organic material. It contains fresh and decaying plant matter from leaves, needles, twigs, moss, lichens, and other organic accumulations
A Horizon
The A horizon is formed at the surface or below the O horizon. It is an accumulation of organic matter and
minerals. It is generally darker than the lower horizons because of the decaying organic matter. This horizon is where most plant root activity occurs. It may
be referred to as the surface layer in a soil survey.
E Horizon
The main feature of the E horizon is the loss of silicate clay, iron, or aluminum, or some combination of these, leaving a concentration of sand and silt-sized particles.
B Horizon
The B horizon lies directly below an A, E, or O horizon. It is
referred to as the subsoil. It is usually lighter colored, denser, and lower in organic matter than upper horizons. As the recipient of material from upper and lower soil layers, the B horizon is often called the “zone of accumulation.”
Leaching
When water percolates through soil and wash soil particles through A and B Horizons
What is the “zone of leaching” layer?
A Horizon
Fragipan
A dense, nearly impermeable subsurface layer
Hardpan (in Florida)
When a fragipan is made up of extremely compacted soil particles
Caliche
Layers cemented by calcium carbonate
Ironpan
Layers cemented by iron oxide
C Horizon
Also called the substratum; This layer may consist of less clay or other less-weathered sediments than the layers above. Partially disintegrated parent material and mineral particles are in this horizon.
R Horizon
Bedrock; It can be withing several inches of the surface or many feet below.
Master horizons are divided into what?
Specific layers
Suffix Symbol A
Highly decomposed organic materials
Suffix Symbol B
Buried soil horizon
Suffix Symbol C
Concretions — grains, pellets, or nodules of various sizes, shapes, and colors consisting of concentrated compounds or cemented soil grains
Suffix Symbol D
Physical root restriction
Suffix Symbol E
Organic material of intermediate decomposition
Suffix Symbol F
Frozen soil
Suffix Symbol G
Strong gleying — soil that is formed under poor drainage, resulting in the reduction of iron and other elements and in gray colors and mottles
Suffix Symbol H
Alluvial accumulation of organic matter
Suffix Symbol I
Slightly decomposed organic matter
Suffix Symbol K
Accumulation of carbonates
Suffix Symbol M
Cementation
Suffix Symbol N
Accumulation of sodium
Suffix Symbol O
Residual accumulation of sesquioxides
Suffix Symbol P
Tillage or other disturbance
Suffix Symbol Q
Accumulation of silica
Suffix Symbol R
Weathered or soft rock
Suffix Symbol S
Alluvial accumulation of sesquioxides and organic matter
Suffix Symbol T
Accumulation of alluvial clay
Suffix Symbol V
Plinthite: an iron-rich, humus-poor mixture of clay with quartz and other minerals; redoximorphic feature in highly weathered soil.
Suffix Symbol W
Development of color or structure
Suffix Symbol X
Fragipan character
Suffix Symbol Y
Accumulation of gypsum
Suffix Symbol Z
Accumulation of salts more soluble than gypsum
What varies with location?
The thickness of each layer
When will not all horizons be present?
When under disturbed conditions, such as intense agricultural development or where erosion is severe
What is used to define soil types?
Soil characteristics
What are the most common soil characteristics?
Texture, color, porosity, compaction, and permeability
Soil texture only refers to what?
Mineral particles smaller than 2 millimeters (mm)
How is the term “soil texture” used by the USDA?
To designate the percentages of sand, silt, and clay in a sample of soil
Soil Seperate
Each grouping of particle sizes
How many soil seperates are there?
8
What are the soil seperates?
Very coarse sand: 2.00–1.00 mm Coarse sand: 1.00–0.50 mm Medium sand: 0.50–0.25 mm Fine sand: 0.25–0.10 mm Very fine sand: 0.10–0.05 mm Coarse silt: 0.05–0.005 mm Fine: silt 0.005–0.002 mm Clay: less than 0.002 mm
The texture of a soil gives an indication of what?
- The relative water-holding capacity
- Mineralogy
- Susceptibility to being transported by wind or water
- Chemical properties
Mechanical Analysis
The process by which soil separates are obtained
How many major texture class names are there?
12
What are the major texture class names?
Sand Loamy sand Sandy loam Sandy clay loam Sandy clay Clay Clay loam Loam Silt loam Silty clay loam Silty clay Silt
How is the texture of a soil done in the field?
By feel
How is the soil felt, to determine its texture?
The soil is rubbed between the thumb and fingers and an estimate of the amount of the various separates
present is made on the basis of the degree to which the characteristic properties are expressed.
How are silts different from silt loams?
Silts have less sand and clay
How do you read a soil triangle?
Sand, silt, clay
What order do these go in (smallest to largest): sand, clay, silt?
Clay, silt, sand
What are soil colors produced by?
Organic matter, iron compounds, silica, lime, manganese
compounds, aluminum hydroxide, and various salts
How are soil colors measured?
By comparison with a chart known as the Munsell Soil Color charts