Intro Soil Geo Ch. 3

Question 1

Where can the biggest changes in soil properties be seen?

Answer 1

top 30 to 1000cm
more than 75% of roots are located here.

Question 2

how does soil differ from its parent material?

Answer 2

phase distribution, texture, colour, strucutre, mineralogical composition and presence of organic matter.

Question 3

three soilphases

Answer 3

solid liquid, gas

Question 4

mineral soil

Answer 4

less than 15-20% organic matter

Question 5

organic soils

Answer 5

more than 15-20% organic matter.

Question 6

examples of soil life

Answer 6

bacteria, fungi, protozoa, arthopods, earthworms.

Question 7

calculation to find pore space.

Answer 7

100% - volume of solid%poros

Question 8

why is porosity usually 50% instead of 25%?

Answer 8

aggregates - naturally occurring clusters of soil particles wiht relatively much space between them.
voids and channels created by roots and animals.

Question 9

soilstruture

Answer 9

arrangement of soil particles.

Question 10

primary minerals

Answer 10

quartz and silicates. usually present as sand and gravel.

Question 11

secondary minerals

Answer 11

formed from primary minerals, those in sedimentary soils have arried in material eroded from upstream residual soils

Question 12

residual soils

Answer 12

originate locally from in situ weathering of rock.

Question 13

soil morphology

Answer 13

the soil’s visible and tactile properties including its architecture. It is determined by CLORPT.

Question 14

soil horizon

Answer 14

layers parallel to the soil surfacethat have morphological, chemical, and usually physical and biological characteristics that differ from over and underlying layers. The vertical succession of soil horizons makes up a soil profile.

Question 15

pedogenesis

Answer 15

soil formation

Question 16

include in a soil profile

Answer 16

date, location, altitude, position in horizonization

Question 17

include in each horizon description

Answer 17

depth of top and bottom ofhorizon, colou, texture,organic matter content, presence of calcium, mottles, presence of water table or other notable features.

Question 18

soil texture

Answer 18

the relative proportions of differently sized particles in the soil. We divide into a fine and coarse earth fraction.

Question 19

USDA

Answer 19

United States Department of Agriculture

Question 20

What are the 4 soil textures?

Answer 20

gravel (everything over 2mm)
sand (0.05 to 2 mm)
silt( 2 to 50 micrometres)
clay (less than 2 micrometres)

Question 21

textural class

Answer 21

dependent on the mass ratio between sand, silt and clay, shown on a triangle graph

Question 22

particle size frequency curve

Answer 22

a graph with a logarithmic x axis depicting particle size against percentage of particles.

Question 23

which 3 main factors influence soil colour

Answer 23

organic matter content
water content
presence of iron and manganese.

Question 24

when do you get darker soils?

Answer 24

organic matter coatings, wet soil by both moisture and oxidation.

Question 25

pigments occur where?

Answer 25

coatings on larger grains and as small independent particles between larger grains.

Question 26

mottles

Answer 26

spots of colour in a matrix of another colour. Used to interpret natural drainagecondition of the soils. Found at the depth at which excess water accumulates as it cannot drain any deeper.

Question 27

munsell colour charts

Answer 27

used to determine the colour of the soil. This is standardised.