soil science exam 1 Flashcards
(42 cards)
1
Q
what is an ideal soil composition?
A
25% water, 25% air, 45% mineral, 5% OM
2
Q
Non-Mineral Essential Elements
A
carbon, hydrogen, oxygen
3
Q
primary macronutrients
A
nitrogen, phosphorus, potassium
4
Q
secondary macronutrients
A
calcium, magnesium, sulfur
5
Q
Micronutrients
A
Iron, Manganese, Boron, Zinc, Copper, Molybdenum, Chlorine, Nickel
6
Q
soil-
A
is a material composed of minerals, gases, water, organic substances, and micro organisms
7
Q
regolith
A
the unconsolidated mantle of weathered rock and soil material on the earth’s surface, loose earth above solid rock, includes Horizons O, A, B, and C
8
Q
Solum -
A
the upper and most weathered part of the soil profile, includes Horizons A, E and B
9
Q
Saprolite -
A
soft, friable weathered bedrock that retains the fabric and structure of parent rock but is porous and can be dug with a spade
10
Q
Substratum-
A
any layer lying beneath the soil solum, either conforming or unconforming
11
Q
O horizon
A
the uppermost horizon of soil. It is primarily made up of organic material, including waste from organisms, the bodies of decomposing organisms, and live organisms.
12
Q
A horizon
A
the topsoil layer that is a zone of overlying organic material and underlying mineral material
13
Q
B horizon
A
A soil horizon composed primarily of mineral material with very little organic matter
14
Q
C horizon
A
The least-weathered soil horizon, which always occurs beneath the B horizon and is similar to the parent material.
15
Q
soil consistence
A
behavior of soil when pressure is applied
16
Q
hue
A
redness or yellowness
17
Q
value
A
lightness or darkness
18
Q
chroma
A
intensity or brightness
19
Q
causes of soil color include:
A
organic matter content, water content, and Presence and oxidation states of iron and manganese oxides in minerals
20
Q
red
A
hematite
21
Q
yellow
A
limonite
22
Q
gleyed soil
A
Soil that formed under poor drainage, resulting in the reduction of iron and other elements in the profile and in gray colors.
23
Q
particle size least to greatest
A
clay, silt, sand
24
Q
clods
A
manmade aggregates
25
peds/aggregates
structural units of sand, silt, and clay
26
angular blocky
sharp edges
27
sub angular blocky
Similar to blocky but slightly more rounded
28
Columnar
column shaped
29
prismatic
prism tops, angular and flat
30
mechanical analysis
is used in the lab to identify soil separates
31
stokes law
speed at which particles of sediment drops based on radius and density; bigger particles drop faster
32
bulk density
The mass of dry soil per unit volume, including the air space
33
porosity
The percentage of the total volume of a rock or sediment that consists of open spaces.
34
when bulk density is high, porosity is ___________
low
35
Macropores
Allow movement of air and drainage of water, Accommodate plant roots, Inhabited by tiny animals, Between peds
36
micropores
Usually filled with water, Too small for air movement, Within peds, Water movement slow, Water not plant available
37
Drop in Bulk Density is caused by _________
soil compaction/poor management (Heavy equipment, Worked when soil is wet, Lose organic matter)
38
Cohesion
attraction of water molecules for each other
39
Adhesion
attraction of water molecules for other solid surfaces(adsorption)
40
capillary is influenced by:
Attraction of water for the solid(adhesion), Surface tension of water (cohesion)
41
infiltration
Process by which water enters the soil pore spaces and becomes soil water
42
percolation
The downward movement of water through soil and rock due to gravity.
unsaturated flow movement of water insoil that is not filled to capacity with water
matric potential tendency of water to adhere to surfaces
Maximum Retentive Capacity - pores are filled with water, water readily percolates or drains out of root zone by gravity
Gravitational Water - moves into,through, out of soil due to gravity
Field Capacity- amount of water that remains after all excess water at saturation has been drained out (1-3 days)
Permanent Wilting Point - plants take up all available water, soil cannot supply any water to keep plants from dying
available water holding capacity Maximum amount of water that soil can store to be extracted by plants, Water held between field capacity and permanent wilting point
Evapotranspiration The combined amount of evaporation and transpiration
transpiration Evaporation of water from the leaves of a plant
aquifers space between soil and rockparticles is filled with water
surface runoff Water flowing off the land into bodies of surface water.
gravimetric water content Mass of water per unit mass of oven dry soil particles
volumetric water content volume of water per unit volume of soil
Soil water storage equivalent depth of soil water contained in a soil layer of specified thickness
Equalibrium is reached when thewater potential is equal throughoutthe area of soil
gravitational potential(Ψg) potential energy which is due to the position of a substance/object in a gravitational field
Osmotic potential (Ψo) Decrease in the water potential which is due to the presence of solutes
pressure potential (ΨP) Soil water potential attributed to any other factors besides gravity and solutes
Matric Potential (Ψm) Subcategory of pressure potential, Decrease in the water potential due to the interaction of water within the soil's solid matrix
tensiometer instrument used to measure soil moisture
Illinois Biomes savanna and grasslands
mass flow Pressure differences between atmosphere and soil air, Changes in soil moisture content, Affected by temperature, wind and barometric pressure
Diffusion Bulk of gaseous exchange, Each gas move in a direction determined by its own partial pressure, Allows extensive movement of air from one area to another even though there is no overall pressure gradient
redox reduced state of an element is changed to the oxidized state
Recrystallization The process by which bonds between atoms in minerals break and re-form in new ways during metamorphism.
humus material formed from decaying leaves and other organic matter
Allophane and Imogolite Not well known, Volcanic origin, some formed from igneous rocks, Imogolite more advanced weathering than allophane
Crystalline Silicate Clays the dominant clay type in most soils that has the highest net negative charge and comes in either 2:1 or 1:1 ratios
Noncrystalline Silicate Clays Tightly bonded silicon,aluminum and oxygen, Lacks well defined structure, Allophane, Imogolite, Volcanic ash, Characteristic of Andisols, High positive and negative charge, High water holding capacity
Iron and Aluminum Oxides Highly weathered soils in warm, humid areas (Oxisols, Ultisols)
Organic (Humus) Non crystalline colloids dominated by long carbon chain molecules
tetrahedral sheets composed of 4 oxygen atoms in a tetrahedron with a silicon atom in the center
tetrahedron four-sided
octahedral sheets composed of 6 oxygen atoms in an octahedron with an aluminum atom in the center
octahedron 8 sided polyhedron
Isomorphous Substitution process by which one element fills a position usually filled by another of similar size
1:1 silicate clay kaolinite
2:1 silicate clays expanding smectite
2:1 silicate clays limited expanding vermiculite
2:1 silicate clays non expanding mica and chlorites
Cation Echange Capacity (CEC) the total amount of cations that a soil can retain (parking spots)
biomass living bacteria and fungi
non-biomass cellulose, starch, and lignin in dead plants
Carbohydrates most plentiful
fats, oils, and waxes seeds and leaf coatings, decompose slowly
Lignins - plant cell walls, decompose slowly
Polyphenols - tannins in leaves, root, bark
Proteins - nitrogen and other essential elements (S, Mn, Cu,Fe), simple break down easily, complex more resistant
Biochemical recalcitrance - complexity of the OM composition (carbohydrates, lignin)
Chemical stabilization - attaching of OM to soil clay particles
Physical protection - held within soil aggregates and unavailable to most microbes
Glacial activity - younger soil, not as much exposure to weathering
Native vegetation - particularly deep perennial roots
Climate - short growing season, cold weather prevents decomposition
active organic matter serves as a primary food for microbes to feed on
Stable Organic Matter soil organisms digest and decompose material, accumulates over long period of time
water retention and drainage Increases ability to hold water, Similar to a sponge - swell and retain water
soil structure active OM, better aeration, increased friability
nutrient cycling and retention Active OM full of accessible nutrients, Nutrients consumed by soil organisms and released into soil solution
Microbial Diversity and Resiliency Main food source for soil organisms, Microbes drive nutrient cycles and availability of nutrients, Maintains microbial habitats
Igneous rocks form by The crystallization of molten magma or lava
Sedimentary rocks form from weathering and erosion
metamorphic rocks form from other rocks
weathering The breaking down of rocks and other materials on the Earth's surface.
physical weathering the mechanical breakdown of rocks and minerals
glacial weathering Glaciers and avalanches can cause weathering as ice and rock interact.
biogeochemical weathering dissolution or chemical alteration of original material (usually most important)
Hydration - water molecules bind to a mineral
Hydrolysis - water molecules split into hydrogen and hydroxyl, hydrogen replace a cation in mineral structure
Dissolution - water dissolves minerals by hydrating cations and anions until they are dissociated, surrounded by water
Acid reactions - weathering accelerated by presence of acid, increase hydrogen ions in the water
Oxydation-Reduction - Minerals with Iron, manganese or sulfur affected
Complexation - biological soil processes produce acids, causing disintegration
Colluvium unconsolidated sediment that accumulates at the base of a slope
Alluvium the sorted material deposited by a stream
fluvial of or found in a river
lacustrine lake deposits
floodplains the flat area around a river that is covered with sediment as a result of frequent flooding
alluvial fans Fan-shaped deposits of sediments dropped by streams flowing out of mountains
delta deposits Created when sediments deposited by a river overload the river and it clogs itself.
eolian deposited by wind
marine related to the sea; existing in or produced by the sea
Drift - material of glacial origin, deposited by ice or waters
Glacial till - materials deposited directly by ice, heterogenous mixture of debris, bolder to clay size
Glacial Outwash - material washed away from glacier by meltwater, glaciofluvial material, Sandy and coarse, layered
Moraines - irregular ridges of deposited glacial till
Valley fills - sand and gravels sorted by flowing water (from outwash plain)
Lacustrine deposits - formed in glacial lakes, coarser near shore, finer towards middle lake, flat areas that were fertile after lakes dried
bioturbation the disturbance of sedimentary deposits by living organisms
