Factors of Soil Formation

Question 1

What are PM weathering rates determined by?

Answer 1

Mineralogy, hardness, porosity, surface area(faster) or finer grains(water retention)

Question 2

Solum

Answer 2

These are the surface and subsoil layers that have undergone same soil-forming conditions

Question 3

Example of soil created by PM…

Answer 3

Quartz sand doesn’t create clay soils due to no Al

Question 4

PM soil formation with igneous rocks…

Answer 4

Form abundant clay minerals with high fertility due to cations and building block

Question 5

Example of materials determining weathering rates…

Answer 5

Granite contains mostly quartz and K feldspars, less quartz and more Na and Ca feldspars are mafic

Question 6

What do sedimentary rocks depend on?

Answer 6

Formation fpressure, composiion of original deposit, sandstone orignates from sand-size sediment

Question 7

Why are transported soils more productive?

Answer 7

Higher porosity

Question 8

How does wind sort particles?

Answer 8

Drops largest particles newar source, carrying smaller larger distances

Question 9

Loess

Answer 9

Terrestrial clastic sediment composed predominantly of silt-size particles formed by accumulation of wind-blown dust

Question 10

Ice/Water particle distribution…

Answer 10

Glacial till and glaciations

Question 11

Colluvium

Answer 11

This is soil and debris that accumulate at the base of a slope by mass wasting or sheet erosion

Question 12

Climate variability in soil formation….

Answer 12

Precipitation/temperature most important, varying depending on elevation/latitude, yearly also

Question 13

Cool humid climate soil characteristicis…

Answer 13

High OM accumulation, weathering products removal and dominant acidification

Question 14

Arid-semiarid climate soil characteristics…

Answer 14

Evapotranspiration exceeds precipitation, OM accumulates more slowly, with rapid soluble salt and carbonate accumulation

Question 15

What is regional climate characterised by?

Answer 15

Mean annual temperature and precipitation

Question 16

Results of poor drainage or high water table?

Answer 16

Dominant redox reactions and gleying

Question 17

Temperature influence on sois…

Answer 17

Increases clay formation, clay type then influenced by climate: smectite found in drier climates than kaolinite

Question 18

Example of topgoraphy improtance?

Answer 18

Slope length and angle determine effective precipitation

Question 19

How slope influences soil?

Answer 19

Soil development(pedon thickness and horizon differentation) decreases with slope with increasing erosion

Question 20

How do slopes differ per hemisphere?

Answer 20

NH north faceing slopes colder due to less incident solar radiation

Question 21

How do plants add OM?

Answer 21

Root exudates, ell death with root growth and death/degradation

Question 22

How does OM influence soil formation?

Answer 22

Produce compounds that chelate cations and humus production

Question 23

How does canopy interception influence soils?

Answer 23

Rainfall assimialtes dissolved ions in crown drip, reacting with soil solid phase differently than pure water

Question 24

Hans Jenny equation?

Answer 24

S = f(Pm, C, R, B, T)

Question 25

Example of climate and time syngerism...

Answer 25

Calcaerous rock with moderate rainfall may have increased OM early, approaching equilibrium in few decades, whilst calcite and lcay take longer for steady levels for vegeatation

Question 26

Hydrolysis

Answer 26

H+ in H2O replacement, like clay mineral feldspar releasing K and adding H, accelearting weathering

Question 27

What can released K ion replaced by H+ do?

Answer 27

Form new complexes, cationic exhcnage, plant use, soil leeching

Question 28

What does hyrdolysis increase with?

Answer 28

OM decomposition, nutrient uptake, nitrification and S oxidation, as pH lowers with increasing H+

Question 29

How does hydration differ from hyrdolysis?

Answer 29

Water does not dissociate, expanding minerals and increasing weathering susceptibility

Question 30

Where are redox reactions most important?

Answer 30

Fe2 oxidation to Fe3 which strains crystals and accelerates weathering rate

Question 31

How do redox reactions influence solubility?

Answer 31

Some cations more mobile when reduced than when oxidised

Question 32

What are the two horizon groups?

Answer 32

Master Horizons - AOEBCR Transitional Horizons

Question 33

A Horizon

Answer 33

Surface layer with high bio-activity thus high humus accumulation, mineral weathering, soluble product leaching and eluviation

Question 34

Eluviation

Answer 34

This is the sideways or downards movement of dissolved or suspended material within soil caused by rainfall

Question 35

O Horizon

Answer 35

Predominanntly organic matter

Question 36

E Horizons

Answer 36

Eluviation influenced by organic acid from A/O horizons combination with leaching waters that weather/translocate silicate clays, fe and al, leaving residual material