Soils

Question 1

Why is soil important?

Answer 1

agriculture
supports biodiversity
habitat for some organisms
site of chemical reaction
supports plants for climate regulation

Question 2

What does soil fertility mean?

Answer 2

the ability of soil to sustain plant growth

Question 3

Components of soil: minerals - sand

Answer 3

mixture of small pieces of different rocks or minerals

particles = round

Question 4

Components of soil: minerals - silt

Answer 4

fine sand/clay carried by running water and deposited as a sediment

larger than clay, smaller than sand

Question 5

Components of soil: minerals - clay

Answer 5

grained earth

flat and platey

Question 6

Components of soil: DOM

Answer 6

decomposition - cycling of nutrients

Question 7

Components of soil: soil biota

Answer 7

micro-organisms, spiders, insects, earthworms

Question 8

Components of soil: missing two

Answer 8

water and air

Question 9

Features of soil which affect soil fertility and productivity: water content

Answer 9

essential for all organisms
good soils allow good drainage, but retain enough for soil biota
dissolves nutrients

Question 10

Features of soil which affect soil fertility and productivity: soluble materials (micro/macro nutrients and metal ions)

Answer 10

macro - phosphorus, nitrogen, potassium
micro - boron, cobalt, copper, iron, manganese, magnesium

shortage of nutrients limits plant growth

harmful metals adsorb onto surface of clay particles

Question 11

Features of soil which affect soil fertility and productivity: air content

Answer 11

most processes = aerobic
well aerated = more fertile
aerobic = faster decomposition

Question 12

Features of soil which affect soil fertility and productivity: DOM

Answer 12

more DOM = fertile soils
binds soils
increases nutrients, water retention and food for soil biota

Question 13

Features of soil which affect soil fertility and productivity: pH

Answer 13

fertile soils = 5.5-7
acidic soils = increased leaching and damage to root cell membranes
alkaline soils = phosphates are insoluble

Question 14

Features of soil which affect soil fertility and productivity: soil biota

Answer 14

detritivores break down DOM and release nutrients
decomposers break down DOM and secrete digestive enzymes
nitrogen fixing bacteria
nitrifying bacteria
mycorrhizal fungi

Question 15

Features of soil which affect soil fertility and productivity: soil texture

Answer 15

controlled by different mineral particles
clay = small
silt = medium
sand = small

Question 16

Features of soil which affect soil fertility and productivity: soil structure

Answer 16

soil particles from aggregates (peds)

crumb peds = small and round = good drainage/aeration/root penetration

platy peds = large and flat = decreases drainage/aeration/root penetration

Question 17

Features of soil which affect soil fertility and productivity: soil depth

Answer 17

deeper soil s= dry out rapidly

root anchorage

Question 18

How particle size affects soil properties: drainage

Answer 18

large and spherical = better drainage

quicker in sand than clay soils

Question 19

How particle size affects soil properties: water content and capillary action

Answer 19

more water drawn up in clay soils as water content is higher

Question 20

How particle size affects soil properties: aeration

Answer 20

higher in sandy soils as more porous

Question 21

How particle size affects soil properties: nutrient levels

Answer 21

higher in clay as more water available so more nutrients dissolved

some able to adsorb to clay particles

Question 22

How particle size affects soil properties: thermal capacity

Answer 22

higher water content = higher thermal capacity

Question 23

How particle size affects soil properties: root penetration

Answer 23

higher in sandy soils

Question 24

How particle size affects soil properties: ease of cultivation

Answer 24

higher in sandy soils

Question 25

Soil Analysis: soil texture - sedimentation method

Answer 25

handful of soil in tray rub sample through fingers to separate remove obvious pieces of organic particles and any large chunks half fill cylinder with soil fill rest of cylinder with water invert repeatedly to mix and suspend leave for at least a week use graduations to determine % of sand, silt, clay use soil triangle to determine soil type

Question 26

Soil Analysis: soil texture - soil sieve method

Answer 26

stack of sieves = different sizes 1st = stones, sticks, gravel 2nd = sand 3rd = silt 4th = clay collect total mass of each to work out percentage only works if soil is dry and separated

Question 27

Soil Analysis: water content

Answer 27

weigh crucible add soil and reweight place in oven at 100 degrees for 24hrs weigh crucible and dry soil determine mass of water lost work out % mass of water in original sample

Question 28

how do you know if all the water has evaporated?

Answer 28

heat until constant mass

Question 29

Soil Analysis: soil air

Answer 29

add 250ml of soil to 500ml beaker add 250ml of water and stir record new vol work out % air = loss of expected volume/ original vol of soil

Question 30

Soil Analysis: organic matter

Answer 30

weigh empty crucible add dry soil and reweigh determine mass of soil place in oven at 450 degrees and leave overnight weight soil and crucible again determine loss of mass work out %

Question 31

When determining organic matter content, why should the oven temp be kept below 550 degrees?

Answer 31

to not break down sand, silt, clay difficult to distinguish between mass lost due to DOM and mass lost due to minerals

Question 32

Soil Analysis: soil pH - universal indicator

Answer 32

add 2.5cm3 of soil to test tube add 1cm3 of BaSO4 (speeds up settling) add 3.5cm3 distilled water add 10 drops universal indicator bung test tube and shake leave for 15 minutes use colour card to determine pH

Question 33

Soil Analysis: soil pH - universal indicator paper

Answer 33

same test tube set up as universal indicator dip paper into settled solution

Question 34

Soil Analysis: soil pH - pH probe

Answer 34

calibrate using buffer solution take readings at equal depths

Question 35

Soil Analysis: soil organisms - random sampling

Answer 35

suitable for large areas uses a quadrat - place using randomly selected co-ordinates

Question 36

Soil Analysis: soil organisms - soil flooding (using irritant)

Answer 36

suitable for extracting worms flood area of soil in a quadrat, often using irritant (e.g. mustard powder) worms come to surface and are counted

Question 37

Limitations of soil flooding

Answer 37

worms may die worms may move sideways irritant may not percolate deep enough

Question 38

Soil Analysis: soil organisms - soil pit extraction

Answer 38

dig out area of quadrat to an agreed depth hand sort worms out of soil

Question 39

Limitations of soil pit extraction

Answer 39

worms may move sideways small worms may be missed

Question 40

Human activities affecting soil fertility: aeration by ploughing and drainage

Answer 40

makes soils more aerobic increases rate of nitrogen fixation, nitrification and decomposition of DOM

Question 41

Human activities affecting soil fertility: increasing and decreasing soil nutrient levels

Answer 41

increasing = inorganic fertilisers, organic matter, support natural processes (e.g. nitrogen fixation) decreasing = erosion, biomass removal, increased leaching

Question 42

Human activities affecting soil fertility: irrigation

Answer 42

increases soil fertility where water is the limiting factor - allows plants to keep stomata open dissolves nutrients that can be absorbed as ions

Question 43

Human activities affecting soil fertility: soil compaction

Answer 43

caused by excessive use of heavy machinery reduces aeration and increases chance of waterlogging

Question 44

Human activities affecting soil fertility: controlling pH

Answer 44

ensures nutrients are soluble but not too easily leached crushed limestone increases pH digging in sulphur decreases pH

Question 45

Types of soil erosion: wind

Answer 45

picks up soil particles and moves them most likely to happen to dry/sandy soils

Question 46

Types of soil erosion: water

Answer 46

rain splash erosion surface runoff erosion slumping and landslides

Question 47

Ways in which vegetation reduces soil erosion

Answer 47

root binding