Soil Quiz 2

Which soils structures (or non-structures) have rapid permeability? Moderate permeability? Poor/slow permeability?

Granular, single - rapid columnal, blocky, prismatic - moderate Platy massive - slow

If a soil sample occupies 53.2 cm3 and weighs 49.3 g, what is the bulk density?

0.93 g/cm3

Humus

-decomposed OM -Musilaginous gel (from plant roots) -granular

Particle size of silt

0.002 - 0.05mm

Particle size for sand

0.05 - 2mm

If a soil sample occupies 367.23 cm3 and weighs 400.23 g, what is the bulk density?

1.09 g/cm3

% of for a rock modifier?

15%

What is the approximate volume composition (not texture percentages) of a loam surface soil with good conditions for plant growth? (inorganic, organic, air, water)

25% H20 25% AIR 5% OM 45% INORGANIC

Which color has the highest value? 2.5YR 5/6 5YR 6/6 7.5YR 4/3

5YR 6/6

Particle size for clay

<0.002mm

What is the size of a micropore?

<0.08mm

What is a puddled soil? How does it form?

A puddled soil is dense, artificially massive soils that are usually done to tillage when the soil is too wet.

Chroma

Amount of pigment mixed with gray value

What kind of soil structure has moderate permeability to water? Massive, Angular Blocky, platy, granular, single grain

Angular blocky

Atterberg limits - briefly explain what Atterberg limits are useful for predicting.

Atterberg limits determines suitability/ susceptibility of soils H20 Contents of fine grained soils at different states of consistency. -Shrinkage limit: filled pore space - Plastic limit to slightly increase the volume of soil -liquid limit

What are some of the benefits of tillage? What are some of the disadvantage of tillage?

Benefits: break up clods, incorporates organic matter, kill weeds, allow wet soil to dry, decrease bulk density Disadvantages: increase oridation, decrease organic matter, lower aggregation, loses macropores, higher chance of erosion, increase of long term bulk density

Influences of Soil Color

Carbonates and PM, and Humus

How does soil color change with age, pm, climate, content of OM, carbonates, etc

Carbonates give high values PM - darkened by humus Fe and MG can increase chroma and appear red waterlogged - chroma colors (gley) older soils can appear redder

Which component of color changes as colors become duller?

Chroma

As organic matter accumulates in the soil, the chroma becomes higher or lower and the value becomes higher or lower.

Chroma lower Value higher

Which soil structure appearance is altered by Na+ content in the soil?

Columnal

-What value is the darkest/lightest in soils?

Darkest = 0 lightest = 10 High numbers closer to white, lower numbers closer to dark

Hue

Dominant spectral color

What number is used as the assumed particle density when calculating pore space?

Dp= 2.65g/cm3

Soil consistence does not change with changes in soil moisture content.... T or F

False

Soils derived from basalt would have a higher or lower value when compared to one derived from granite.

False

What does "friable" mean?

Friable is the ability of the soil to be reduced to smaller pieces with little effort.

Bg soils and color components

Gley... Low chroma Gley Hue

What type of soil structure has the most rapid permeability to water....

Granular

What type of structure is typically found in the A horizon under grasses?

Granular

6 soil structures...

Granular blocky prismatic columnal platy single grane

Which component of color changes as a soil becomes more yellow?

Hue

Which component of soil color is most likely to change as a tropical soil becomes highly weathered?

Hue

Munsel notation... 10YR 5/3

Hue = 10YR Value = 5 Chroma = 3 Munsell notation puts these three attributes together: 10YR 5/3

The Munsell color system includes what three components

Hue, Chroma, Value Hue Dominant spectral color Value Relative blackness or whiteness Chroma Amount of pigment mixed with gray value

Major soil influences

Humus, Ferrous oxide, ferric oxide, hydrated ferric iron

What are the two agents that are responsible for stabilizing soil into semi-permanent peds....

Humus, and sesquioxides

In agriculture, cultivation temporaily loosens the soil, but long-term will ....

Increase bulk density

Micro/Macropores - size and function

MACRO - > 0.08mm (drain water) -creeks, roots, animals Micro - < 0.08mm (retains water)

How do macropores and micropores differ in both in size and function?

Macropores: >0.08mm, drains well, course texture, cracks between peds, root channels, earthworm burrows. Micropores: <0.08mm, retains water, fine texture, space between soil particles

Name two wats that soil compaction affects plant growth?

Makes it harder on plants to break through and limits pore space for water and air

What is a cation? What are some examples of the most prevalent cations found in soil?

Positively charged ions, Mg2+, Ca2+

What type(s) of structure are vertically elongated?

Prismatic and columnal

What is the difference between a puddled soil and a soil crust?

Puddled soils are artificially compacted from being tilled while soil crust is natural

-Major factors affecting consistence

Related to its cohesive abilities... so water infilitration, compaction, Ca+ can bridge together (flocculation), humus, and sequisoxides

Value

Relative blackness or whiteness

What are the two types of non-structure (e.g. absence of structure)?

Single Grain and Massive

What are the two main steps in soil structure formation?

Soil breaks down into ped sized units / channels (faunal, floral, temperature) Stabilization of structural units from Humus, and Sesquioxides

Explain how soil crust forms.

Soil crust forms from the compaction of topsoil and surface rain causing smaller (FINE) particles to float to the surface thus creating artificial plating.

How can physical soil crusting influence plant growth? What are the main causes?

Soil crusting only happens with fine textured soil. Rain, then dryout creates plates on top. Poor seedling emergence in a typical fine crust. main causes: low organic matter %, high silt %, high exchange of sodium %, puddled soil, bare soil.

Explain the following statement: Structure can modify texture.

Structure can modify texture because the structure is the arrangement of soil particles and the texture is the combination of silt, clay, sand, and OM.

Which soil is most affected by compaction, surface soils or subsoils?

Surface soils

-What hue is the most yellow in soils?

Temperate soils

liquid limit

The liquid limit (LL) is conceptually defined as the water content at which the behavior of a clayey soil changes from plastic to liquid.

What is soil tilth?

The physical condition of a soil related to tillage, seedbed and ease with which plants emerge and penetrate soil

Tilth definition....

The physical condition of a soil related to tillage, seedbed and ease with which plants emerge and penetrate soil...

plastic limit

The plastic limit (PL) is determined by rolling out a thread of the fine portion of a soil on a flat, non-porous surface.

shrinkage limit

The shrinkage limit (SL) is the water content where further loss of moisture will not result in any more volume reduction.

Compaction - What are the causes? Which soils and conditions are the most susceptible to compaction? Disadvantages?

Tires, foot, glacial or any other pressure exerting down on loam soils. Conditions... wet soils Disadvantages... decrease water infiltration, reduce root growth, increase runoff

4 soil forming processes and an example

Transformation - OM decomp Translocation - moving within soils Loess - erosion leaching Additions - organic matter / humans

-What hue is the reddest hue in soils?

Tropical soils

Silts are more like sand with respect to fertility but are more like clay with respect to water holding ability.... T or F

True

Which component of color changes as soil becomes darker?

Value

OM soils and color components

Value decreases chroma decreases

Calcium Carbonate soils and color components

Value increases Chroma decreases

What is a hectare furrow slice (hfs)? About how many kilograms does one hfs weigh?

a hectare furrow slice is the assumed mass of a hectare to depth of 15 cm, 2200 Mg. one hfs weighs about 2 million kg.

If a soil sample occupies 40 cm3 and weighs 50.2 g when dry, what is the bulk density? Assume your Dp is 2.65 g/cm3. What would the pore space be in the previous question?

a. 1.26 g/cm3 b. 52.45% pore space

Gypsum in a soil layer dissolves in water that is percolating through the soil. The water flows deeper into groundwater and eventually enters a stream... this is an example of....

addition

Soil structure is....

arrangement of sand, silt and clay (and OM)

How is granular structure formed?

at the surface there is more probability of small organisms, and roots breaking apart. more temp subseptability

what type of soil structure is found in arid regions and forms where sodium has deflocculated clay particles on the top of the structures? prismatic, columnar, platy, massive, granular

columnar

Management options for managers and soil structures

dry soils minimize compaction areas surface soils are most compacted

-What chroma is the dullest/brightest in soils?

duller /neutral to the left lower numbers, brighter to the right, higher numbers

If a soil sample occupies 254.12 cm3 and weighs 365.24 g, what is the bulk density? Assume your Dp is 2.65 g/cm3. What would the pore space be in the previous question?

e. 1.44 g/cm3 f. 45.66% pore space

Bulk Density (Db) is typically measured in what units?

g/CM3

what type of soil structure is the most likely to be found in a prairie A Horizon? prismatic, granular, platy, blocky, single grain

granular

Which of the following surface textures is most likely to have the LOWEST bulk density, all other factors being equal? clay loam, loamy sands, high organic matter soils, sandy clay, silty clay loam

high organic matter soils

Quartzite soils and color components

high values

What soil properties affect soil tilth?

include the formation and stability of aggregated soil particles, moisture content, degree of aeration, rate of water infiltration and drainage.

Assuming they have the same structure, which soil has a higher bulk density, loamy sand or a clayey textured soil? Why?

loamy sand has a higher bulk density because organic matter content generally low and the solid particles are less likely to be aggregated.

Which of the following surface textures is most likely to have the HIGHEST bulk density, all other factors being equal? clay loam, loamy sands, high organic matter soils, sandy clay, silty clay loam

loamy sands

Dark PM soils and color components

lower values

Bulk Density

mass of oven dry soils ----------------------------- volume of oven dry soils

What type of soil pore will retain water against the force of gravity?

micropores

What are some of the major effects of compaction in terms of soil health and plant growth?

more compaction: decrease water infiltration, increased runoff, decreased root growth

Which type of structure is horizontally elongated

platy

What is soil structure?

refers to the arrangement of soil separates into units called soil aggregates. Granular blocky platy prismatic columnal single grain

2 types of absence of structure

single grain massive (no planes of weakness)

What type of soil is prone to forming soil crusts?

soils from alluvial material

Which soils typically have a higher Db, surface or subsurface soils?

soils with low pore space, subsoils

Explain the difference in appearance between angular blocky and subangular blocky structures.

subangular has rounded corners, while angular has sharper edges

How does soil structure relate to soil texture?

texture of a soil determines soil water-holding capacity, permeability, and soil workability. Sand, silt, clay, and organic matter particles in a soil combine with one another to form larger particles. Soil structure is the arrangement of the soil particles into aggregates of various sizes and shapes.

Moist Soils and color components

value decrease, chroma decreases

drier soils and color components

value increases chroma increases