Soil Science Flashcards
Father of Modern Soil Science
V.V. Dokuchaev
He discussed the factors of soil formation and he introduced the ABC horizon nomenclature system.
V.V. Dokuchaev
In 1941, he published the book “Factors of Soil Formation”.
Hans Jenny
A systematic examination, description, classification, and mapping of the soils in a given area.
Soil Survey and Classification
The vertical section from the soil surface down to the bedrock or water table below.
Soil Profile
It is the horizontal layer of the soil.
Soil Horizon
This master horizon is composed of organic material.
O Horizon
This O subhorizon is where the organic material is well decomposed.
Oa subhorizon
This generally shows show horizons which may differ from one another in terms of various properties.
Soil Profile
The O horizon can be further classified into 3:
Oi, Oe, Oa
The subhorizon where the slightly decomposed organic materials are found within the O horizon.
Oi
This master horizon is generally characterized by being composed of mineral soil particles but strongly darkened by humus or organic matter mixed with the mineral fraction.
A horizon
The two subhorizons of the A horizon are:
Ap (Plowed), Ah (Humus)
Horizons from which clay, iron, aluminum, or some combination of these have been eluviated leaving a light-colored horizon.
E horizon
This master horizon occurs between the A and B horizons.
E horizon
The master horizon that formed below A, E, or O horizon, that is characterized by
- concentration of clay, iron, aluminum, silica
- evidence of removal of carbonates
- blocky structure
B Horizon
The most common B horizons in the country are Bt and Bw. Bt is structure formation and Bw is clay accumulation. Is this statement true or false?
False
This master horizon is relatively unaffected by soil-forming processes.
C Horizon
It is the weathered rock beneath the solum.
A horizon
This master horizon is characterized by a solid bedrock, which is not practically diggable by spade.
R Horizon
The color of the soil is determined by using a ________.
Munsell Color Chart
The three combinations of elements that is used by the Munsell Color Chart to determine the soil’s color classification.
Hue, Value, Chroma
This refers to the dominant wavelength or color of light.
Hue
This refers to the relative lightness and darkness of the color which is a measure of the total quantity of light, sometimes called the brilliance.
Value
The relative purity of the dominant color.
Chroma
This is referred to as the fineness or coarseness of the soil.
Soil Texture
What soil aggregate is abundant if, using the Field Method, will be smooth like baking flour.
Silt
The texture of the soil if the soil will be gritty when rubbed between fingers.
Sandy
The soil aggregate that, if abundant, makes the soil feel somewhat sticky, and the sample can be molded into different shapes like a molding clay.
Clay
The soil texture if there are equal amounts of sand, silt, and clay.
Loam
This is the arrangement of primary soil aggregates into secondary aggregates called peds.
Soil Structure
E: Eluviated.
B: Illuviated.
True or False?
True
It is the most obvious and easily determined soil physical property.
Soil Color
A standardized system used by soil scientists and geologists to determine the color of the soil.
Munsell Color System
“Calcium carbonates and salts” is not one of the factors that influence soil color. True or False?
False.
The factors that influence soil color are:
- Organic Matter
- Fe oxides
- Mn oxides
- Soil Moisture Content
- Calcium carbonates and salts
This provides the dark brown or black color of the soil and is usually found on surface layers.
Organic matter.
This provides the red, yellow, orange, and light brown colors of the soil.
Fe oxides
This is the primary coloring agent of the subsoil.
Fe oxides
This is responsible for black concretions in the soil.
Mn oxides
The soil will darken if it has a high moisture content. True or False?
True.
The drainage of the soil if the color is blue-gray.
Poorly-drained
The drainage of the soil if the has a high chroma.
Well-drained.
This is responsible for the white colors in soils.
Calcium carbonates and salts
The abundance of this soil color factor indicates that the soil has a basic or high pH.
Calcium carbonates and salts.
In the color notation:
10 YR 5/2.
Identify the value, the chroma, and the hue.
The value is 5. The chroma is 2. The hue is 10 YR.
The soil separates that make 100% of the soil’s relative proportion.
Sand, Silt, and Clay.
The maximum effective diameter of the sand, according to the USDA Classification.
2.0 millimeters.
The effective diameter of the sand is 2.0 - 0.05 mm.
The diameter of silt, according to USDA.
0.05 - 0.002 mm
This soil separate has a diameter that is less than 0.002 millimeters.
Clay
The feel method provides a quick, highly accurate, and reliable estimates of soil texture in the field. True or False?
False.
The field/feel method is not highly accurate, but reliable nonetheless.
Methods used in the laboratory in conducting Particle Size Analysis.
Hydrometer Method and Pipette Method
It is used to describe the soil texture based on the relative proportions of sand, silt, and clay in various types of soil.
Soil Texture Triangle
It is used to compare the compositions of soil aggregates within the soil to determine its overall classification.
Soil Texture Triangle
The soil has a strong soil structure if the peds are clearly observable and there is prominent arrangement of natural surfaces. True or False?
True
These are aggregates of soil particles formed as a result of pedogenic processes.
Peds
The peds are observable in place and there is a distinct arrangement of surfaces of weakness. This means that the soil structure of the soi is weak.
True or False?
False. Having peds that are observable and has a distinct arrangement makes it have a moderate soil structure.
The soil structure is weak if the peds are hardly observable in place. True or False?
True.
This refers to the degree of plasticity and stickiness of the soil.
Soil Consistence.
Which is referred to when these are provided?
- Soil Color
- Soil Texture
- Soil Structure
- Soil Consistence
- Soil pH
- Reaction to H2O2
- Abundance of Roots
Soil Properties
This soil property is affected by the type and amount of clay that is in the soil.
Soil Consistence.
The soil consistency is _______ is the wet soil adheres when pressed between thumb and finger.
Sticky
The soil consistence if ______ if the wet soil does not adhere to the fingers.
Non-sticky
This is the measure of acidity and alkalinity of soils.
Soil pH
The optimal pH range for most plants.
5.5 - 7
pH levels range from 0-14. What is the soil pH if the pH levels are equal to 7?
Neutral
What is the soil pH if the levels are equal to 9?
Alkaline
What is the soil pH if the level is equal to 5?
Acidic
This is a qualitative test for the organic matter content of the soil.
Reaction to H2O2
This refers to the formation of gas bubbles in a liquid by a chemical reaction.
Effervescence
Calcite exhibits effervescence when exposed to hydrochloric acid. True or False?
True.
Quartz exhibits effervescence when exposed to hydrochloric acid. True or False?
False
The distribution of roots in the soil profile indicates how well the soil supports the development of root system. True or False?
True
What is the abundance of roots if the percentage is 5-15%?
Few.
It is a naturally occurring inorganic substance which has a fairly definite chemical composition and physical properties.
Mineral.
What is the size of the roots if its diameter is more than 5.0 mm?
Coarse
These are minerals that are formed by the cooling and solidification of molten rocks or magma.
Primary minerals
These minerals originate from the chemical weathering of primary minerals.
Secondary minerals.
This is a combination of two or more minerals.
Rocks
The three major groups of rocks.
Igneous, Sedimentary, Metamorphic.
The group of rocks that are formed from the cooling and solidification of magma.
Igneous rocks
They are considered as the mother of all rocks
Igneous rocks
They are the most abundant rocks in the Earth’s crust.
Igneous
These rocks are formed from the fragmentation of existing rocks.
Sedimentary rocks.
These are the most abundant rocks in the Earth’s surface.
Sedimentary rocks.
These are derived by partial melting and alteration of igneous and sedimentary rocks due to pressure, heat, or chemical action.
Metamorphic rocks
Give at least 3 physical properties of minerals.
The physical properties of minerals are:
1. Luster
2. Cleavage or Fracture
3. Hardness
4. Color
5. Streak
_________ refers to the color of the mineral in reflected light.
Luster refers to the color of the mineral in reflected light.
Three kinds of luster.
- Metallic luster
- Submetallic luster
- Nonmetallic
________ is the property of breaking along one or more smooth, parallel planes.
Cleavage is the physical property of breaking along one or more smooth, parallel planes.
Some minerals break in directions other than those along cleavage planes and form irregular patterns. This property is called ________.
Fracture.
Minerals that fracture weather faster than those that cleave. True or False?
False. Minerals that fracture weather more slowly than those that cleave.
This refers to the resistance which a mineral offers to scratching or abrasion.
Hardness refers to the resistance which a mineral offers to scratching or abrasion.
Softer minerals will weather more slowly than harder minerals. Is this statement true or false?
False. Harder minerals will weather more slowly than softer minerals.
The number of hardness of talc, which is characterized by its ability to be scratched by the fingernails.
1
Which is harder? Calcite or Flourite? What is their number in the scale?
Flourite is harder than Calcite.
Calcite - 3
Flourite - 4
Orthoclase is softer than Gypsum. True or False?
False. Orthoclase is much harder than Gypsum.
Orthoclase - 6
Gypsum - 2
The hardest mineral, according to the Moh’s Scale of Hardness.
Diamond
Is quartz harder than corundum?
No. Corundum is harder than Quartz.
Corundum - 9
Quartz - 7
Hardness of Apatite.
5
Hardness of Topaz.
8
Hardness of Orthoclase
6
Hardness of Corundum
9
Hardness of Calcite
3
Hardness of Talc
1
Hardness of Gypsum
2
The mineral that can scratch corundum
Diamond
Hardness scale of mineral that can scratch topaz
9
Hardness scale of mineral that can scratch quartz.
8
Hardness scale of a mineral that can be scratched slightly by a thumbnail.
2
Hardness scale of a mineral that can be scratched by a copper coin.
3
Hardness scale of a mineral that can be scratched by a knifeblade.
5
Color is more reliable than streak. True or False?
False.
It is the color of the finely powdered mineral and is relatively constant.
Streak.
Color is not a good means of distinguishing minerals because it is extremely variable. True or False?
True
Give at least 2 characteristics of minerals.
These are the characteristics of minerals:
1. Naturally occurring
2. Inorganic
3. Homogenous substance
4. Have definite chemical composition
5. Ordered atomic arrangement
6. Crystalline
The scientist that developed the Mohs’ Scale of Hardness.
Friedrich Mohs
He is the father of mineralogy
Georgius Agricola
The luster of a mineral that is opaque and dull, dark colored.
Submetallic
The luster of a mineral that does not reflect light.
Nonmetallic
The luster of a mineral that is opaque and reflects light as a metal would.
Metallic
Not all minerals have cleavages. True or False?
True
The number of lines that are created when a mineral is split will be the number of cleavage lines. True or False?
True
This is the true color of the mineral.
Streak.
To determine streak, the mineral is placed against a surface of a streak plate, a small slab or glazed porcelain. True or False?
False.
To determine streak, the mineral is rubbed against a surface of streak plate, a small slab of unglazed porcelain.
Gold makes a yellowish-gold color when run across a streak plate. True or False?
True.
When pyrite is run across a streak plate, it has a yellowish-gold color. True or False?
False.
Pyrite has a black or dark-green streak despite its gold appearance.
The mineral is often called by miners as “fool’s gold.”
Pyrite.
The mineral that has a grey color but has a red streak.
Hematite.
Hema means blood. T/F
True.
The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate. T/F?
True.
It is the mineral property that we will not use because of its unreliability.
Color.
The outside color of the mineral tells you a lot about its important characteristics. T/F?
False.
The outside color does not tell you much about the important characteristics.
The most common primary mineral in soils.
Quartz.
Which of the following are not primary minerals?
a. Quartz
b. Feldspar
c. Iron Oxides
d. Gypsum.
Iron Oxides and Gypsum.
Primary Minerals include:
Quartz
Feldspar
Amphibole
Micas
Carbonates
Apatite.
Secondary Minerals include:
Gypsum
Iron Oxides
Clay Minerals
It is the original source of practically all soil phosphorus.
Apatite
Apatite and Calcite are soluble. True or False?
True.
These are the parent material of mineral soils.
Rocks
Aggregate of minerals.
Rocks
Igneous Rocks are classified based on their basis of their chemical composition and mode of occurrence, especially with their calcium content.
True or False?
False. Igneous rocks are classified particularly based on their SiO2 content.
Two modes of occurrence of igneous rocks.
- Plutonic/Intrusive Igneous Rocks.
- Volcanic/Extrusive Igneous Rocks.
Refers to the location of igneous rocks at the time of formation.
Mode of occurrence.
These are igneous rocks that that found within the Earth’s crush and were formed by a relatively slow cooling process.
Plutonic Rocks.
Plutonic Rocks have fine, glassy texture. T/F?
False
Volcanic Rocks are usually found at or near the Earth’s surface, and they were developed by a rapid, or very rapid cooling process.
True or False?
True.
Igneous rocks that are coarsely textured.
Plutonic rocks.
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Igneous Rocks:
1. Granite - intrusive
2. Obsidian - extrusive
3. Basalt - intrusive
4. Pumice - extrusive
5. Rhyolite - extrusive
6. Gabbro - intrusive
7. Andesite - extrusive
These sedimentary rocks are formed from sediments or fragments, resulting from the weathering of any type of rock.
Clastic Sedimentary rocks
The sediments may be clay, silt, sand, gravels, and others.
These sedimentary rocks are produced by chemical or biochemical precipitation of ions from solution.
Precipitate or Non-clastic Sedimentary Rocks.
Biochemical precipitates usually involve marine animals and may be fossiliferous.
The term for the true soil.
Solum.
The conglomerate is a sedimentary rock that is non-clastic. True or False?
False. The conglomerate is a clastic sedimentary rock.
Sandstone is a clastic sedimentary rock. True or False?
True. The sandstone is a clastic sedimentary rock composed of sand-sized minerals.
Shale is a fine-grained, non-clastic sedimentary rock. True or False?
False. Shale is a clastic sedimentary rock and is composed of mud that is mixed with flakes of clay minerals.
Limestone is a non-clastic sedimentary rock. True or False?
True. It is usually composed of skeletal fragments of marine organisms such as corals.
Metamorphic rocks are rocks that are formed from igneous and sedimentary rocks. True or False?
True.
Metamorphic rocks are foliated if they have parallel layers of different minerals.
True
Non-banded metamorphic rocks have a uniform pattern of mineral crystals. T/F?
False. Non-banded or non-foliated metamorphic rocks have random pattern of mineral crystals.
The pattern of mineral crystals in banded or foliated metamorphic are uniform in some, and alternating in others. T/F
True.
REVIEW CARD!!!
Metamorphic rocks.
1. Gneiss - foliated
2. Slate - foliated
3. Marble - nonfoliated
4. Quartzite - nonfoliated
It is the physical, chemical, and biological alteration of rocks or minerals at or near the Earth’s surface.
Weathering
It involves specific processes acting on rock materials.
Weathering
It is the rock altered by weathering, either broken into smaller pieces or some of its constituent minerals altered or dissolved.
Parent material
Weathering is involved in the formation of landforms and soils. True or False?
True.
Two types of weathering.
Physical and Chemical weathering.
A type of weathering where it breaks down rocks without changing the composition.
Physical Weathering
This type of weathering changes the shape and size of the parent material but not in chemical composition.
Physical weathering.
REVIEW CARD!
Physical Weathering
1. Pressure release
2. Freeze and Thaw
3. Salt Weathering
4. Temperature Change
5. Wetting and Drying.
It is the propagation of fractures near the surface of solid rock due to expansion related to release of confining pressure when deeply buried rock is unroofed.
Pressure Release Weathering
Weathering that involves the repeated free and thaw of water in the cracks and pores of rocks.
Free and Thaw
A very effective process for widening and extending cracks and thereby breaking rocks into smaller pieces, in freeze and thaw weathering.
Frost Wedging
It is a process of rock disintegration by salts that have accumulated at and near the rock surface.
Salt Weathering
It is the repeated swelling and shrinking of minerals with different expansion rates due to the extreme range of temperatures that can shatter rocks.
Thermal Expansion
It is also known as Onion-skin weathering.
Wetting and drying
This weathering involves exfoliation or the peeling away of sheets of rock millimeters to meters in thickness from a rock’s surface due to a range of physical and chemical processes during weathering.
Wetting and Drying.
This refers to the processes that decompose rocks and minerals are chemically altered such that new minerals are formed.
Chemical Weathering
REVIEW CARD!!!
Chemical Weathering
1. Hydration
2. Hydrolysis
3. Oxidation
4. Carbonation
5. Chelation
It is the dissolution of easily soluble salts in water, without a chemical reaction.
Hydration
Examples of this chemical weathering are the dissolution of NaCl and KCl.
Hydration.
The chemical weathering that involves the chemical reaction of minerals with water.
Hydrolysis.
This causes more chemical weathering than any other type of chemical weathering.
Hydrolysis.
An igneous rock that can be weathered by hydrolysis.
Granite.
The chemical weathering that refers to the reaction of certain metals with oxygen in the air to form compounds called oxides.
Oxidation.
Metals that are affected by oxidation include iron, copper, and silver. True or False?
True
It is the reaction between calcite and weak acids in rain water and acids in groundwater.
Carbonation
Rocks that are weathered mainly by carbonation are ____ and _____.
Marble and limestone
Sinkholes, Karst topography, and stalactites are results of carbonation. True or False?
True
The process in which organic acids hasten the weathering reaction by combining with some weathering products.
Chelation.
It reflects the composition, size, and arrangement of the solid particles of the soil.
Soil Physical Property
Two types of soil physical properties
Static and Dynamic
Soil physical properties that do not change on short time scales under natural conditions.
Static
Properties that are readily changed on short time scales under natural conditions.
Dynamic
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Importance and uses of Soil Texture Determination
1. To describe the soil profile and soil horizons.
2. Key determinants of the appropriate land use.
3. Soil health indicator.
It is the relative proportion of the various size groups of individual soil grains in a mass of soils.
Soil Texture
REVIEW CARD!
Albert Atterberg, a Swedish agricultural scientist, proposed the size limits of soil particles which was accepted by the IUSS during the Berlin Conference in 1913.
Albert Atterberg proposed the size limits of soil particles which was accepted by the USDA during the Berlin Conference in 1913.
True or False?
False
This refers to the amount of particle surface area exposed and available as a site for chemical and physical processes per unit mass or volume soil.
Specific surface area
REVIEW CARD!!!
Surface area
1. Sand - 50 cm2/g
2. Silt - 500 cm2/g
3. Clay - 5,000,000 cm2/g
Charge
1. Sand - None
2. Silt - None
3. Clay - Negative
The finer the texture, the less permeable it is to air and water.
TRUE
REVIEW CARD!!!
The Specific Surface Area involves
1. Adsorption / retention of water
2. Adsorption of chemicals
3. Area for chemical reactions
4. Aggregation
5. Microbial colonization
The coarser the texture, the more permeable the soil is to air and water.
True or False?
True
If the soil texture is fine, the higher its capacity in holding water.
TRUE OR FALSE
True
The coarser the texture, the lesser its water holding capacity.
TRUE OR FALSE
True
Two methods of Soil Texture Determination.
Field Method and Laboratory Method
The other term for Field method
Feel method
It is used to provide “quick” reliable estimates of soil texture in the field.
Field/Feel Method
It enables immediate interpretation of soil texture down the soil profile.
Field / Feel Method
The field method is more accurate than the laboratory method.
True or False?
False. The field / feel method is less accurate than the laboratory method.
He developed the Stokes’ Law.
George Gabriel Stokes
Stokes’ Law states that the settling of spherical particles in a viscous medium is directly proportional to the size of the particle.
True or False?
True
The dispersing agent that is used in hydrometer analysis / method.
Calgon solution / Sodium hexametaphosphate
There are 12 soil textures in the Soil Texture Triangle. True or False?
True
The arrangement of primary sand, silt, and clay particles into secondary aggregates called peds or structural units which have distinct shapes.
Soil Structure
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Importance of Good Soil Structure
- Increases infiltration of water
- Improves seedling emergence, root growth, and rooting depth
- Large continuous pores increase permeability.
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Soil structures
- Granular
- Platy
- Wedge
- Blocky
- Prismatic
- Columnar
Review Card!
Infiltration rate of soil structures
1. Single Grain: Rapid
2. Blocky: Moderate-Slow
3. Platy: Slow-Very Slow
4. Granular: Rapid-Moderate
5. Prismatic: Moderate-Slow
6. Massive: Very Slow
sabot?
Formula for Particle Density
Dp = Ms/Vp
What is Dp?
Particle Density
What is Ms?
Mass of soil solid (ODW)(g)
Symbol for particle volume
Vp
Density of the bulk soil.
Bulk Density
Formula of Bulk Density
Db = Ms/Vt
In bulk density, what does Vt represent?
Total volume of the soil.
The use of core sampler driven into the soil when determining bulk density.
Core method
Determining the bulk density by digging a hole and filling it with measured volume of water.
Excavation method
The higher the bulk density, the more compact is the soil.
True
Review Card!
As soil bulk density increases.
1. Soils become more compact
2. Soil strength increases
3. Pore spaces decreases
Soil Compaction results in a decrease of the size or number of macropores.
Soil physical property which indicates how much of the bulk volume is compacted by pores.
Porosity
Normal range of porosity values
0.35 - 0.65
