Lecture 2: Soil habitat

Question 1

Soil formation (Dokuchaev equation)

Answer 1

soil=f(cl,o,r,p,t,…)tr
climate, organisms, parent material, relief, relative time

Question 2

What is pedogenesis

Answer 2

exposed rock formes soil

Question 3

what is weathering

Answer 3

degradation of material by chemical/physical processes accelerated by orgniams

Question 4

newly developed soil layer

Answer 4

lithosol/entisol/rudisol

Question 5

Over time formation of forst soil

Answer 5

colonisation of thin litter layer by lichens, mosses, liverworts
lithosol formed with shrubs increasing litter layer and weathering
deciduous forests alter parent material

Question 6

rock cycle

Answer 6

magma forms igneous rock through crystallisation
exposed to weathering
form sedimentary rocks via erosion
heat and pressure make metamorphic rocks

Question 7

igenous rocks

Answer 7

granite, basalt, gabbro

Question 8

sedimentary rocks

Answer 8

limestone, sandstone, shale

Question 9

metamorphic rocks

Answer 9

marble, slate, quartzite

Question 10

weathering rind

Answer 10

biological processes occurring here with mycorrhizae helping

Question 11

Soil horizons

Answer 11

litter
organic (O)
surface (A)
subsoil (B)
substratum (C)
bedrock (R)

Question 12

what is O horizon

Answer 12

organic material with lots of humus

Question 13

what is A horizon

Answer 13

OM accumulates and leaches

Question 14

what is B horizon

Answer 14

deposited minerals and metal salts with less OM

Question 15

what is C horizon

Answer 15

partly weathered parent material

Question 16

what is R horizon

Answer 16

un-weathered parent material

Question 17

soil composition

Answer 17

mostly mineral matter
water
air
less than 5% OM

Question 18

mineral basis of soils

Answer 18

clay (smallest particles)
silt
sand
gravel (largest particles)

Question 19

soil textural classes

Answer 19

form a triangle of clay, silt, sand %

Question 20

why is soil texture important

Answer 20

helps define suitability for agriculture

Question 21

what is clay-rich soil good for

Answer 21

water and nutrient retention

Question 22

what are sandy soils good for

Answer 22

drainage

Question 23

what are heavy soils

Answer 23

how hard to get plough through
insulators

Question 24

minerals

Answer 24

solid chemical compounds

Question 25

primary rock minerals

Answer 25

silicates

Question 26

valency

Answer 26

fill up from outside shells
2,8,8 shells

Question 27

hydrogen bonds

Answer 27

covalent hydrogen atoms bind to electronegative atoms
quite strong

Question 28

silicates

Answer 28

silicon tetrahedrons

Question 29

what type of silicates do soils have

Answer 29

phyllosilicates

Question 30

what are phyllosilicates

Answer 30

2D mineral sheets of tetrahedrons/octrahedrons
3D covalently bonded combos of layers

Question 31

sheet

Answer 31

combinations of planes of atoms (silica in tetrahedral sheet)

Question 32

layer

Answer 32

combinations of sheets (MICA, two silica sheets and alumina sheet)

Question 33

crystal

Answer 33

stacks of layers

Question 34

interlayer space importance

Answer 34

fillied with ions, water, etc. and determines soil properties

Question 35

kaolinite crystal

Answer 35

little interlayer space so little water in

Question 36

muscovite crystal

Answer 36

covalent sandwich bonds
potassium ions weak bonds
can split sandwiches easily

Question 37

chlorite crystal

Answer 37

strong bonds
low interlayer space