SSC 200 Exam #3

Runoff

Precipitation that reaches the surface of the Earth and ponds or flows over the surface (if the surface is full of water)

Infiltration

Portion of the precipitation that reaches the Earth’s surface and seeps into the ground

Evaporation

Radiant energy from the sun heats water, causing it to form vapor when water molecules become “excited” and transform from liquid phase to a gas phase

Transpiration

Plants take in water through the roots and release it through the leaves (evaporation through the leaves)

Detention ponds

The temporary storage of stormwater runoff in a designated area, allowing for gradual release and treatment before discharge.

Cohesion

The attraction of water molecules for each other primarily due to hydrogen bonding

Adhesion

The attraction of water molecules for solid surfaces. Water adsorption to the surface of soil via H-bonding

Surface Tension

When water molecules have a greater attraction for each other than the air above, this creates the water-air interference

Water repellency

The adhesive forces at the water-solid interface are less than the cohesive force of water

Hydrophobic

Water resistant. Soils display resistance to wetting and frequently do not hold water to support good plant growth

Hydrophilic

Adhesion and cohesion forces cause the water to “cling” to surfaces

Capillarity 

The movement of water up a wick made of hydrophilic solid materials

Gravitational potential

Force with a positive potential that pulls water down

Matric potential

A force with a negative potential that is a measure of how tightly water is held in the soil by adhesion and capillary forces

Osmotic potential

A force with a negative potential that moves water towards a higher concentration to reach an equilibrium concentration 

Positive potential energy

Energy is stored and can be used for “work” (ex. water held behind a dam)

Negative potential energy

Energy must be expanded to move water (ex. attractive forces)

Leaf Area Index (LAI)

The average density of vegetation above the soil surface

Macropores

Water is draining due to gravity, unavailable to plants

Mesopores

Water available for plants to use

Micropores

Water is tightly held due to capillary forces

Saturation

All voids are filled with water and there is no air in the soil

Gravitational water

Water is between saturation and field field capacity, water that will drain freely

Field capacity

The amount of water a soil can hold against the pull of gravity. Water content of the soil after draining for 24-48 hours

Plant-available water (PAW)

Water between field capacity and permanent wilting point, water that the soil will relinquish to the plant

Hydroscopic coefficient (air dry)

Soil water content air-dried soil, main agents for holding this water are clay colloids.

Oven dry

Soil is dried at a specific temperature (~105-100C) until all moisture has evaporated.

Electrical resistance blocks

Used to estimate soil moisture, includes using a porous bloc with electrodes embedded in it.

Tensiometer

Used to estimate soil moisture, measures the tension of the water due to adhesive forces with soil solids

Time domain reflectometry (TDR)

Non-destructive method for measuring soil moisture by using radar to transmit signals into soils and analyzing the reflected signals

Single vs double ring infiltrometer 

Tools used to measure the rate at which water infiltrates, or soaks, into the soil

Gravimetric water content

Wet Weight (g) - Oven Dry (g) / Oven Dry (g)

Volumetric water content

Wet Weight (g) - Oven Dry (g) / Total Volume (cm³)

Saturated flow

All pores are filled with water and free water movement, gravity being the driving force

Unsaturated flow

Not all pores are filled with water, capillary flow through micropores and can occur in any direction

Hydraulic conductivity (K)

Describes how fast water moves through soil, a measure of the ability of a soil to transmit water

Saturated hydraulic conductivity (Ksat)

Measure of how easily a saturated soil transmits water

Detachment

Individual particles are loosened from the soil mass (rain splash, flowing water, wind)

Transport

Water or wind carries the detached particles downslope or downward

Deposition

Detached particles are deposited in places of a lower elevation

Sedimentation

The process of suspended particles settling out due to gravity

Sheet erosion

Uniform erosion from the entire soil surface following detachment due to raindrops

Rill erosion

The removal of soil by concentrated water running through little streamlets, can be repaired by tillage

Gully erosion

Channels deeper than 18 inches that cannot be erased by cultivation or simple land leveling. Least amount of soil is eroded this way.

T-values (soil-less tolerance)

Soil loss tolerance limits developed for different soils

Revised Universal Soil Loss Equation (RUSLE)

Equation used to determine the amount of soil lost annually by erosion (R x K x LS x C x P)

Revised Wind Erosion Prediction Equation (RWEQ)

Equation used to determine the amount of soil lost by wind = f(I x C x K x L x V)

Contour planting

Permanently vegetated strips located between larger crop strips on sloping land

Terraces

Engineered structures used to manage soil erosion and water runoff.

Filter Stripes

Strips or areas of permanent vegetation used to reduce sediment

Riparian buffers

Areas are trees and/or shrubs along streams, lakes, ponds, or wetlands

Swales

Grassed ditch used to conduct surface water from high to low elevation

Hydro-mulch

Plant based fiber with a tackifier that binds to soil particles and mixed with water to make a slurry

Geotextiles

Woven non-biodegradable polypropylene fabric

Turbidity

The amount of sediment suspended in water

Coagulants

Chemical substances that used in water treatment to decrease turbidity

Flocculants

Bind suspended solids together

Chitosan

Natural biopolymer derived from chitin, found in the exoskeletons of crustaceans and the cell walls of fungi. Used as water treatment.

Polyacrylamide (PAM)

Flocculant used to chemically treat turbid water

Geologic erosion

Erosion that takes place without the influence of humans

Human-accelerated erosion

Erosion caused by disturbance of soi/vegetation by humans

Soil water content

The amount of water in the soil

Soil water potential 

A measure of the energy status of the soil water

Pedon

Soil characterized by a small three-dimensional hypothetical unit 

Polypedon

Contiguous and closely related pedons

Alfisols

Argillic (Bt) subsurface horizon with 35% or MORE base saturation, similar to ultisol. Found in conditions of mild acid weathering

Andisols

Parent material specific, recent volcanic ash deposits

Ultisols

Argillic (Bt) subsurface horizon with LESS than 35% base saturation. Most common soil in NC, highly weathered.

Oxisols

The most highly weathered of all the soils. Subsurface horizons are dominated by oxides of iron and aluminum. Naturally low fertility

Entisols

Little profile development, no B-horizon, the “throw away” soil profile.

Inceptisols 

Process of soil formation being in its early stages. Weak B horizons (Bw), support 20% of world’s population.

Aridisols

Climate specific dry soils, that contain CaCO₃  and exhibit subsurface horizon development

Histosols

Parent material specific organic soils, mainly formed in wetland accumulations of plant residues. Extensive in wet and cold climates.

Mollisols

Dark mineral soils common in grasslands. Best soil to grow plants with, high organic content

Gelisols 

Climate specific, permanently frozen layers found in very cold regions.

Verisols

Parent material specific, characterized by high levels of shrink/swell clays, leads to vertical mixing of the profile

Spodosols

Climate specific, extremely acidic, sandy soils in forested areas with evidence of illuviated organic matter (Bh)

Onchric

Fails to meet the definitions for any other epipedons (too light, too thin, too low in organic matter) 

Umbric

Same characteristics as mollic, but base saturation is LESS than 50%

Mollic

A thick-dark, colored mineral horizon at the surface. Percent base saturation is MORE than 50%

Histic 

A layer of organic soil that is naturally saturated with water (wet, mostly organic)

Folistic

Like histic, but not saturated with water for more than 30 days. (Cold, mostly organic)

Melanic

Soils developed from volcanic ash

Oxic

Highly weathered, very high in Fe and Al oxides

Natric

Like argillic with the addition that sodium has accumulated and where there is >15% exchangeable sodium

Salic

Accumulation of salts

Cambic

In illuvial accumulation of carbonates (mostly CaCO₃) 

Spodic

Illuvial horizon characterized by the accumulation of colloidal organic matter, aluminum oxide and iron

Argilic

The Bt horizon identifies the argillic horizon

Order 

Highest and most general of the soil classification system (ex. argiudolls _______ would be Mollisols)

Suborder

Grouped by similarities in soil formation such as wetter/dryer soil colder/warmer soil, etc. (ex. argiudolls ___________ would be Udolls)

Subgroup

Describes a profile characteristic, wetness, sand, etc. Always second to last word (only one word) (ex. Aquic Argiudolls)

Series

Names from the town or landscape feature near where the soil was first recognized (ex. Norfolk)

Family

Based on soil properties that affect management and root penetration, such as texture, temperature, clay minerals, CEC, and depth. One or more words separated by a comma (ex. Fine-loamy mixed, super active, mesic)

Great Group

Based on differences between soil horizons (ex. Argiudolls)

Ustic

Soil moisture is intermediate between Udic and Aridic regimes — generally winters are relatively dry

Aridic 

Soil is dry for at least half the growing season

Xeric

Found in typically Mediterranean-type climates with cool, moist winters and warm, dry summers

Aquic

Soil is saturated with water, free of gaseous oxygen and has poor aeration

Udic

Soil moisture is sufficiently high year-round to meet the plant needs