Soil

Question 1

name the 5 components of soil

Answer 1

mineral skeleton 
water 
air 
biota 
DOM

Question 2

what is meant by mineral skeleton?

Answer 2

particles broken down by weathering of rocks. Proportions of different sized particles = soil texture

Question 3

why is air important in soil?

Answer 3

provides gases for aerobic processes for organisms i.e. decomposition, N2 fixation and nitrification

Question 4

why is water important in soil?

Answer 4

plants need it for various processes i.e. photosynthesis and nutrients can only be absorbed if dissolved in it

Question 5

why is biota important in soil?

Answer 5

responsible for decomposition and aid aeration/draining and nutrient recycling

Question 6

why is DOM important in soil?

Answer 6

• source of food for some organisms
• produces humus and releases nutrients
• humus helps to bind soil together = soil stability

Question 7

definition of soil fertility

Answer 7

the ability of soil to sustain plant growth

Question 8

Name the 6 factors that influence soil fertility

Answer 8

drainage 
aeration 
thermal capacity 
nutrient levels 
root penetration 
capillary action

Question 9

name the 3 types of soil particles from largest to smallest

Answer 9

sand, silt, clay

Question 10

what does it mean by soil texture?

Answer 10

how big the particles are

Question 11

Drainage: the _____ the particle, the larger the ____space so drainage is ______. For example _____. This is the opposite for _____ particles like _____.

Answer 11

1. larger
2. pore
3. easier
4. sand
5. smaller
6. clay

Question 12

Thermal capacity: H2O has a ______ thermal capacity (warm/cool ______). ______ retains more H2O so takes _____ to warm/cool. So the ____ H2O the more temp. _____>

Answer 12

1. high
2. slowly
3. clay
4. longer
5. more
6. stable

Question 13

How do soil texture influence aeration?

Answer 13

the larger the particle, the larger the pore space = increase aeration/air

Question 14

which soil texture is the WORST when conserving nutrients and why

Answer 14

sand as it has increased drainage due to large particle size so increase leaching

Question 15

Is clay good at absorbing nutrients?

Answer 15

Clay absorbs more nutrients/minerals

- Clay have negative charges = positive charged nutrient ions attach

Question 16

which soil texture is root penetration easiest in?

Answer 16

sandy soils

Question 17

which soil texture is root penetration hardest in and why?

Answer 17

clay - particles held together by capillary H2O on particle surfaces = harder for roots to penetrate between particles

Question 18

which texture is best at capillary action and why?

Answer 18

clay - tiny pores = H2O can rise towards surface

no capillary rise in sandy soils

Question 19

How does soil biota increase soil fertility? and explain

Answer 19

• detritivores break up DOM (i.e. worms) decomposers break down DOM (i.e. fungi secrete enzymes) = releases nutrients
• N2 nitrifying bact. = atmospheric N2 to ammonia
• Nitrifying bact. = oxidise ammonia - nitrite - nitrate
• mycorrhizal fungi (symbiotic relationship with roots) = increase phosphate uptake

Question 20

difference between micronutrients and macronutrients with examples

Answer 20

micro = plants need in small amounts i.e. magnesium, cobalt, boron 
macro = need in large amounts i.e. N2, phosphorus, potassium

Question 21

in fertile soil: _____ ions (i.e. aluminium and _____ metals) are _____ onto surface of particles (usually ___) so does not ______ in ____ where they could harm ____

Answer 21

1. toxic
2. heavy
3. absorbed
4. clay
5. dissolve
6. H2O
7. biota

Question 22

name the 3 reasons why DOM is important

Answer 22

1. food for biota
2. releases nutrients i.e. humus
3. increases H2O retention

Question 23

definition of a ped

Answer 23

when soil particles aggregates (clump together) - held together by polysaccharide gum

Question 24

Which is ped is more fertile and why: crumb or platy?

Answer 24

crumb: small round particles = good aeration/drainage/easy root penetration
platy: large/flat so decreases those factors

Question 25

for soil fertility which is better: deeper or shallow soils?

Answer 25

deeper = less likely to be waterlogged/dry out. Good root drainage.

Question 26

why do soils need high water content but also good drainage?

Answer 26

- ions are dissolved in H2O | - drainage; avoid anaerobic conditions

Question 27

How does the pH influence soil fertility?

Answer 27

optimum pH = 5-7 too acidic = cell membrane damage/rapid leaching too alkali = inhibit nutrient uptake i.e. phosphate becomes insoluble

Question 28

name the 5 human activities that affect soil fertility and briefly explain

Answer 28

irrigation: increase fertility = allows stomata to be open + continue gas exchange + H2O dissolves nutrients use of fertilisers: increase nutrients + support processes like N2 cycle pH control: ensures nutrients soluble not easily leached compaction: more compact = less aeration/decrease drainage/harder roots to penetrate ploughing and drainage: increase aeration = more aerobic processes (i.e. more fixation/nitrification/decomp.)

Question 29

state at least 5 out of the 8 factors that could affect infiltration rate

Answer 29

soil moisture, soil texture, soil structure, organic matter content, vegetation cover, soil depth, gradient, intensity of precipitation

Question 30

in soils not been affected by _____ activities the rate of erosion is likely to be the same or ____ that rate of soil ______. Erosion is a problem when it occurs _____ rapidly than soil _______

Answer 30

1. human 2. less 3. formation 4. more 5. formation

Question 31

all forms of ____ erosion are increased by ______ gradients

Answer 31

1. water | 2. steeper

Question 32

Name the 2 types of water erosion

Answer 32

rain splash erosion: particles dislodged, move into pore spaces = reducing infiltration surface runoff erosion: caused by surface runoff (infiltration capacity of soil exceeded), particles dislodged can cause landslides. loss of roots binding from deforestation affect this.

Question 33

describe wind erosion

Answer 33

soils are dry/unprotected, wind can carry it away as little cohesion between particles

Question 34

name the 5 ways how vegetation reduces soil erosion

Answer 34

- decrease wind velocity - more infiltration = less runoff - roots bind the soil - organic matter/humus bind soil - increased interception (vegetation/leaf litter) = impact of raindrops reduced FOR REMOVAL OF VEGETATION IT IS THE OPPOSITE

Question 35

name the 6 activities that can increase soil erosion

Answer 35

1. removal of vegetation: {give general points} 2. ploughing vulnerable soils: breaks up soil structure = particles exposed 3. overgrazing: less vege. = increase soil exposure. Hooves = disturbance/root damage 4. compaction: due to livestock densities/machinery/lack of detritivores. Smaller pores = less infiltration 5. reduced biota: less nutrients for vege., less humus produced = less adhesion between particles. Less worms: less aeration, less infiltration 6. cultivating steep slopes: more kinetic energy (carries more particles), disturbing soil

Question 36

Name the 10 methods of reducing soil erosion

Answer 36

``` long term crops terracing tied ridging rows of stones windbreaks Zero-tillage cultivation contour ploughing multicropping increasing soil organic matter livestock management ```

Question 37

how does long term crops reduce soil erosion

Answer 37

crops used that don't need to be replanted often = reduces soil disturbance i.e. permanent bush/tree crops (coffee, fruit, tea)

Question 38

Which method to reduce soil erosion for which gradient: 1. Used for a steep slope 2. Used for predominantly flat land 3. Used for a gentle gradient 4. Used for a slope And explain briefly what each method does

Answer 38

1. terracing: H2O flows over walls quickly, but slows as it goes down = allows H2O to infiltrate 2. tied ridging: field has criss-cross pattern of intersecting ridges = retains H2O, increases infiltration 3. rows of stones: rows of stones placed in contours, reduces velocity of runoff = soil deposited behind rocks 4. contour ploughing: contours made at 90 degrees to slope, kinetic energy lost = soil particles deposited

Question 39

What is zero tillage cultivation?

Answer 39

not ploughing/sowing but direct drilling of seeds = reduces soil disturbance

Question 40

How do windbreaks reduce erosion and give examples

Answer 40

reduce wind velocity = less soil particles carried away (hedgerows/rows of trees)

Question 41

What is multicropping and how does it reduce erosion

Answer 41

growing more than one crop in a field at the same time and harvesting/re-sown at different times. Reduces erosion as: always be vegetation to reduce wind velocity

Question 42

which uses human labour and which uses machinery: strip cropping and multicropping

Answer 42

``` strip = machinery multi = human ```

Question 43

how does increasing soil organic matter reduce soil erosion

Answer 43

DOM on surface (mulch) = protect from wind/impact from raindrops. DOM decomposes produces humus

Question 44

how does livestock management reduce erosion?

Answer 44

managing stock density = reduces compaction | managing livestock movement = reducing access to vulnerable soil i.e. riverbanks

Question 45

what does the universal soil erosion loss equation work out? and what is it?

Answer 45

rate of erosion (annual soil loss) = RxKxLxSxCxP

Question 46

If you have to rearrange the universal soil erosion loss equation how would you do it?

Answer 46

have erosion rate on the top and all the letters on the bottom

Question 47

when in a question and it gives u the erosion rate and tells you that the farming methods have changed i.e. contour ploughing used instead of ploughing or fruit was grown instead of wheat what do you do?

Answer 47

erosion rate divided by old method then multiply the whole equation by the new method or change = new erosion rate

Question 48

Name all the symbols in the universal soil erosion loss equation: 1. R 2. K 3. L 4. S 5. C 6. P

Answer 48

1. rainfall erosivity 2. soil erodibility 3. slope length factor 4. slope gradient factor 5. crop management factor 6. erosion control factor

Question 49

Name the 5 problems caused by soil erosion

Answer 49

- landslide - sedimentation: turbid H2O = blocks out light for photosynthetic organisms. O2 levels drop. Sediments deposited, river more narrow = H2O overspills/flooding - reduced productivity : soil has no fertility = lower food produced - desertification: when a habitat becomes a desert - atmospheric particles: dust clouds/sandstorms reduce light penetration

Question 50

Method for soil water content: 1. soil sample collected (i.e. _____ sampler or _____) 2. sample placed in sealed bag (reduce water _____ by ___________) 3. organisms/large particles _______ 4. sample placed in pre-weighed __________ basin 5. basin ______ at about 100 for __ hours 6. basin is ________ 7. stages 5-6 repeated until _______ ______ is reached 8. calculate ______ content

Answer 50

1. core, auger 2. loss, evaporation 3. removed 4. evaporating 5. heated, 24 6. reweighed 7. constant mass 8. water

Question 51

what is the equation for % water content?

Answer 51

wet soil mass - dry soil mass / wet soil mass X100

Question 52

Method for soil organic matter content: Steps 1-7 of the soil water content method THEN 8. A ___ soil sample places in ________ crucible which is then _______ 9. crucible _______ in a ____ or a bunsen burner 10. crucible is _______ 11. stages 9-10 repeated until _______ _____ is reached 12. calculate _____ matter content

Answer 52

8. dry, preweighed, reweighed 9. heated, furnace 10. reweighed 11. constant mass 12. organic

Question 53

what is the equation for % organic matter content?

Answer 53

dry soil mass - burnt soil mass / dry soil mass X100