Soils Test Two Study Guide

Clod

a tightly compressed clump of soil

Andisols*

comes from volcanic ejecta; has high AL and humic content

Mollisols*

darker color and quality farming ground with upwards of 6 percent organic matter

Bulk Density

density of the soil as a whole

Forces that allow water to move through soils

gravity and capillary pressure

Soil order for organic soil

histisols

benefits of clay

holds onto water very well

Benefits of Sand

it is well drained

Ideal soil textural class for farming

loam

Most common soil textural class in Western Kentucky

Alford Silt Loam

Best soil order for farming

Mollisols

Difference between mollisols and alfisols

Mollisols are commonly darker in color and contain more organic matter than alfisols, which are older and lighter in color

Oxisols*

Oldest soils usually found in the tropics; highly weathered, red color, high iron content

Soil order common in forest

Oxisols

Gelisols*

Permafrost; cryoturbation occurs which is when freezing ad thawing turns the soils; this is sometimes called frost churning

Gravametric Water Content

the mass of the water in the soil measured in grams

Specific surface area of 1 gram of silt

1500 mm squared

Specific surface area of 1 gram of sand

30 mm squared

Specific surface area of 1 gram of clay

300000 mm squared

How much total water is on earth

400 billion billion gallons

What percent of water is used by agriculture

80%

Who much of the Earth's water is i the oceans?

97%

Alfisols*

Agrillic, natric, or kandic horizons with a high to medium base saturation

Twelve Soil Orders

Alfisols, Andisols, Aridisols, Entisols, Gelisols, Histols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols, and Vertisols

Size of soil aggregates

Anything from 2 millimeters to 0.05 millimeters is sand. Things from 0.05 to 0.02 millimeters is silt. Anything below 0.02 millimeters is clay.

Ultisols

Argillic or kandic horizons with low base saturation

Bulk Density Calculation

Bulk density equals the weight of the soil in grams divided by the volume of the soil in centimeters cubed

Soil forming factor causing differences between aridisols and gelisols

Climate

Particle Densisty

Density of individual particles of of soil

Aridisols

Dry soil and common in desert conditions

Determining Available Water Content (AWC)

Field capacity minus wilting point

Water movement in loam soil over clay soil

The water would quickly fill all the pore space in the loam then slowly fill up the pore space in the clay

Vertisols

High swelliing in clay and deep cracks

Differences between Entisols, Inceptisols, and andisols

Inceptisols are the youngest with hardly any profile development. As they begin to develop horizons and organize, they become Entisols. Andisols are soils with volcanic material.

Mature Soils

Many layers and higher organic matter content. These soils are common around Kentucky

Soil Water Content at Field Capacity

Maximum amount of water that can be stored in a field

Porosity

Measure of how much of the soil is pore space and how much is soil particles

Spodosols

Spodic soils with high Fe, Al, and humus content

Components to Water Budget

Storage = Irrigation + Precipitation + Capillary Rise - runoff - evapotranspiration - deep percolation

Soil Texture's affect on bulk density and porosity

The larger the particles, the lower the bulk density and porosity. The vice versa is also true

Soil Structure

The manner in which soil particles are put together. In other words, it is how the different sand, silt, and clay particles are out together to form the soil structure.

Relationship between textural classes and available water content (AWC)

The sandier the soil the less the AWC and the more clay the soil has the higher the AWC

Water movement in loam soil over sandy soil

The water will completely fill the loam before it begins to drain through the sand. It will then quickly drain through the sand.

Soil forming factor responsible for difference between Inceptisol and Entisol

Time

Young Soils

Typically have less layers and low organic matter content with little plant life

Old Soils

Typically less layers than mature soil with a red color due to accumulation of iron oxide

Difference between alfisols and ultisols

Ultisols shrink and swell much more than aflisols due to a higher clay content; ultisols crack deeply when dry and swell up when wet much more than alfisols

Transpiration

Water loss from leaves into the atmosphere

Gravametric Water Content Calculations

Wet soil minus dry soil divided by dry soil times 100 and your answer is a percent

Histosols*

peat or bog wih over 20 percent organic matter

permanent wilting point

point at which plants are so short of water that they cannot recover

benefits of silt

ready holds onto and releases water

Entisols

second youngest soils with little profile development

Most important soil property affecting water movement in soil

size of soil pores

Ped

smallest coherent structure of soil

Soil Order with high sand content

spodosols

Adhesion of soil water

tendency of soil water to be attracted to itself

Cohesion of soil water

tendency of soil water to stay together and resist being torn apart

Volumetric Water Content

the space the water in the soil takes up measured in

Inceptisols*

the youngest soils with hardly any horizons or other characteristics

maximum retentative capactiy

total water that can be held in soil

hygroscopic water content

water contained in pores

Capillary Water

water in between pores

available water for plants

water levels between field capacity and wilting point