Lecture 3: Soil Architecture and Physical Properties

Question 1

How to describe physical properties of soil?

Answer 1

-Color
-Texture
-Structure
-Density

Question 2

What is used to describe the color of a soil?

Answer 2

-Hue
-Value
-Chroma

Question 3

Hue

Answer 3

redness/ yellowness

Question 4

Value

Answer 4

lightness or darkness (0=black)

Question 5

Chroma

Answer 5

intensity/brightness (0=neutral grey)

Question 6

What influences the color of soil?

Answer 6

-soil organic matter (SOM) content
-water content
-oxidation state of iron and manganese

Question 7

What is soil texture?

Answer 7

the particle size of soil

Question 8

Sand size

Answer 8

<2.0mm to > or = to 0.05

Question 9

Silt size

Answer 9

<0.05mm to > or = to 0.02mm (= > or = to 2um)

Question 10

Clay size

Answer 10

<0.002mm (= < 2 um)

Question 11

Sand

Answer 11

-visible to the eye
-gritty
*well aerated and loose, but infertile and prone to drought

Question 12

Silt

Answer 12

-flour like feel
-low plasticity and stickiness
*fertile, but susceptible to wind and water erosion

Question 13

Clay

Answer 13

-tends to remain in suspension
-rich in nutrients
-very high water capacity
*properties vary with type and amount of clay present

Question 14

Feel method clay

Answer 14

flexible, smooth, and shiny

Question 15

Feel method silt loam

Answer 15

crumbly, smooth, and dull

Question 16

Feel method sandy loam

Answer 16

chunky and gritty

Question 17

What is soil structure?

Answer 17

Soil structure is the arrangement of the soil particles

Question 18

What factors contribute to the formation and destruction of aggregates?

Answer 18

-di and trivalent cations (eg. Ca 2+, Fe 3+, Al 3+)
-bacteria because they tend to make biofilms
-iron and aluminum sesquioxides
-tillage (bad for aggregates)