NRES 251 Exam 2

Isomorphic Substitution

the replacement of one atom by another of similar size in a crystal lattice without disrupting or changing the crystal structure of the mineral

CEC

How many cations can be retained on soil particle surfaces. Positive

AEC

How many anions can be retained on soil particle surfaces. Negative

recharge area

a location where water enters the ground and infiltrates down to the water table

discharge area

the location where groundwater flows back up to the surface

field capacity

ability of a soil to hold water against the downward pull of gravity

permanent wilting point

The point at which a plant can no longer recover from a lack of water

hydraulic gradient

The slope of the water table. It is determined by finding the height difference between two points on the water table and dividing by the horizontal distance between the two points.

confined aquifer

an aquifer surrounded by a layer of impermeable rock or clay that impedes water flow

unconfined aquifer

an aquifer made of porous rock covered by soil out of which water can easily flow

artesian well

A well in which water rises because of pressure within the aquifer

Infiltration

Flow of water from the land surface into the subsurface.

Percolation

The downward movement of water through soil and rock due to gravity.

hydrologic cycle

The cycle through which water in the hydrosphere moves; includes such processes as evaporation, precipitation, and surface and groundwater runoff

Adhesion

An attraction between molecules of different substances

vapor movement

occurs as vapor pressure differences develop in relatively dry soils

Soil thermal properties

pH dependent charge

The portion of the cation or anion exchange capacity which varies with pH. Excess protons (H+) are attracted to hydroxyl (-OH) and carboxyl groups (-CO2H) at broken edges of minerals and in organic matter. They adda positive charge to the exposed edge, making it less negative. The opposite happens at higher pH's. This phenomenon is more common with Fe and Al oxides, non crystalline silicate clays and organic matter.

soil acidity

affects and is affected by plants-low pH increases leaching

perched aquifer

Localized zone of saturation above the main water table created by an underlying layer of impermeable material.

Unsaturated conditions

Soil containing little water

Saturated Conditions

Soil containing a decent amount of water

potentiometric surface

an imaginary surface that defines the level to which water in a confined aquifer would rise were it completely pierced with wells

water potential

the potential energy of a volume of water, expressed as a pressure

hydraulic conductivity

A factor relating to groundwater flow; it is a coefficient that takes into account the permeability of the aquifer and the viscosity of the fluid.

plant available water

volume of water in soil between field capacity and permanent wilting point

soil temperature

how warm or cold a soil is; another important characteristic that affects what types of plants can grow in an area

Capillarity

the attraction between molecules that results in the rise of a liquid in small tubes

Cohesion

Attraction between molecules of the same substance

Aquifer

An underground formation that contains groundwater

water table

the level below which the ground is saturated with water.

Charge

Acidity or Basicness of a soil

surface area

Combined surface area of all the particles in a sample m^2 g^-1

Functions of colloids

Nutrient transfer

Mineral Structure, 2:1 1:1

Chlorites 2:1 two tetrahedral sheets, Kaolinite 1:1 one tetrahedral and one Octahedral sheet

How to Control soil temperature

Mulch, Compaction, Moisture, Shade, and Exposure

What affects soil composition

CLORPT

Saturated calculation

Ratio of water volume to the volume of voids in soil depicted by S

total water potential

Made up mainly of solute potential and pressure potential combined

What can soil color tell us?

Parent Material, mineral in the soil

value

light/dark

chroma

color intensity

hue

Specific Color

surface seal

a thin layer of fine particles deposited on the surface of a soil that greatly reduces the permeability of the soil surface to water