Soil

Question 1

What is soil fertility?

Answer 1

Soils ability to sustain plant growth

Question 2

How does water content make soil fertile?

Answer 2

• good drainage so it doesn’t become waterlogged
• retains enough water for the survival of soil biota
• plant nutrients are also absorbed in ionic form dissolved in water

Question 3

How do soluble materials make soil fertile?

Answer 3

Fertile soils contain micro nutrients such as nitrogen, phosphorus and potassium
They also contain micronutrients like boron, cobalt and iron

Question 4

How does air content make soil fertile?

Answer 4

Aerobic processes are increase with more aerated soils

Question 5

How does dead organic matter increase soil fertility?

Answer 5

Releases plant nutrients as it decomposes
- increases water retention and provides food for soil biota

Question 6

How does pH increase soil fertility?

Answer 6

Fertile soil = 5.5-7.0pH which is the range of tolerance for most plants and other soil biota
Acidic conditions can increase the leaching of plant nutrients and damage root cell membranes
Alkaline conditions can cause phosphates to be insoluble

Question 7

How does soil biota increase soil fertility?

Answer 7

• detritivores = break up dead organic matter and release nutrients into the soil, increase soil drainage and aeration by making tunnels
• decomposers = bacteria and fungi which break down down dead organic matter
• nitrogen fixing bacteria = convert gaseous nitrogen into ammonium ions
• nitrifying bacteria oxides ammonium ions to nitrite ions then to nitrate ions
• mycorrhizal fungi form symbiotic relationships with plant roots and aid phosphate uptake by the plants

Question 8

How does soil texture increase the soil fertility?

Answer 8

Clay soils:
- poorly drained
- tiny pore space = good capillary action
- more likely to be water logged
- nutrients adsorb easily onto clay
- high thermal capacity
- hard for root penetration
- hard to cultivate
Sandy spoil = opposite

Question 9

How does soil structure increase soil fertility?

Answer 9

Soil particles form aggregates called peds
- bound together by polysaccharide gums produced by decomposition
- crumb peds are small and round = good drainage, aeration and easy root penetration = improve soil fertility
- plate peds are large and flat which reduces drainage, aeration and root penetration = reduce soil fertility

Question 10

How does soil depth increase soil fertility?

Answer 10

Deeper solid are less likely to become waterlogged or to dry out rapidly
Aid goof root anchorage

Question 11

How does aeration by ploughing and drainage affect soil fertility?

Answer 11

Ploughing and drainage makes soils more aerobic, increasing the rates of nitrogen fixation, nitrification and the decomposition of dead organisms matter

Question 12

How does soil nutrient levels affect soil fertility?

Answer 12

Farmers add inorganic fertilisers, organic matter to increase nutrient levels such as bacterial nitrogen
Farming can deplete natural soil nutrient levels

Question 13

How does irrigation affect soil fertility?

Answer 13

Stops water being a limiting factor for growth
Sufficient water allows plants to keep their stomata open and continue photosynthesis
Water also dissolves nutrients into ionic forms to be absorbed

Question 14

How does soil compaction affect soil fertility?

Answer 14

Excessive use of heavy machinery or lots of livestock can cause soil compaction
- reducing aeration and makes water-logging more likely, especially when the soil is wet

Question 15

How does pH control affect soil fertility?

Answer 15

Ensure nutrients are soluble but no too easily leached

Question 16

What is wind erosion?

Answer 16

Dry soils, low clay content, loose, little cohesion
- easily swept away in the wind

Question 17

What is rain splash water erosion?

Answer 17

When soil particles are dislodged by the splash of a raindrop, soil particles are dispersed in all directions, overtime large amounts of soil can be shifted

Question 18

What is surface runoff water erosion?

Answer 18

Infiltration capacity of the soil has been exceeded,this can occur when the rainfall is heavy or prolonged, or if soil is impermeable so more water flows over ground surface

Question 19

What is slumping and landslide water erosion?

Answer 19

Soil on slopes becomes very wet the increase mass and lubricant ,ales the downward movement of large amounts of soil more likely, made worse by deforestation

Question 20

How can vegetation reduce the rates of soil erosion?

Answer 20

• acts as a natural windbreak reducing wind, velocity
• vegetation and leaf litter cover reduces impact of rainsplash
• soil organic matter including colloidal material humus binds the soil
• plant roots hold soil together
• plants increase infiltration of water into the soil, reducing the rates of runoff which reduces water erosion

Question 21

How does vegetation removal increase the rates of soil erosion?

Answer 21

Removes protection form wind and rain

Question 22

How does ploughing vulnerable soils increase the rates of soil erosion?

Answer 22

Breaks up the soil structure, exposing soil particles to erosion by water or wind

Question 23

How does overgrazing increase rate of soil erosion?

Answer 23

If livestock density is too high then vegetation will be eaten aster, increasing exposure of the soil

Question 24

How does reduced soil biota increase the rate of erosion?

Answer 24

Ploughing, reducing soil organic matter and the use of agrochemical cab reduce the number of living organism in the soil
E.g. detritivores, decomposers

Question 25

How does soil compaction increase the rates of soil erosion?

Answer 25

Heavy machinery or lots of livestock increase compaction of the soil Reducing infiltration rate = increase runoff

Question 26

How does cultivating steep slopes increase the rates of soil erosion?

Answer 26

Surface runoff flows more rapidly down steeper slopes so it has more kinetic energy to pick up and carry soil particles

Question 27

How is reduced productivity an effect of accelerated soil erosion?

Answer 27

- mostly the fertile top soil is what’s is eroded - remaining soil may be less fertile so plant growth may be reduced - erosion may leave shallower soils so root penetration is more difficult

Question 28

How is sedimentation in rivers and reservoirs an effect of accelerated soil erosion?

Answer 28

Soil particles flow into rivers and may be deposited if the water slows down and has less kinetic energy - more likely to have floods as it reduces the rivers capacity

Question 29

How is increased atmospheric particulates an effect of soil erosion?

Answer 29

Wind erosion increases the level of atmospheric particulates, can make health problems worse e.g. asthma

Question 30

How is desertification and effect of accelerated soil erosion?

Answer 30

More difficult for vegetation to grow with leads to further soil Edison and reduced rainfall

Question 31

How can zero-tillage cultivation reduce soil erosion?

Answer 31

Cultivation that minimises soil disturbance reduces the risk of soil erosion Direct drilling of sends into the ground causes less disturbance than ploughing and sowing

Question 32

How can long-term crops reduce soil erosion?

Answer 32

Growth of crops that do not require frequent replanting and soil disturbance reduced the erosion rate E.g. tree crops

Question 33

How can contour ploughing reduce soil erosion?

Answer 33

Ploughing along the contorts perpendicular to the slope reduces erosion as the water flow is stopped by the furrows and loses its kinetic energy, slow flow rate = less soil particles are deposited

Question 34

How can tied ridging reduce soil erosion?

Answer 34

Field is divided into a cross-cross of intersecting ridges, these retain water when it rains, increasing infiltration and reducing the runoff that may have caused erosion

Question 35

How can terracing reduce soil erosion?

Answer 35

Series of narrow fields are created with he soil held in place by retaining walls built along the contours, water flowing over the walls so lows down as is flows across the fields

Question 36

How can rows of stones reduce soil erosion?

Answer 36

Stones laid along the contours can slow runoff and reduce the erosion rate Any disturbed soil is deposited behind the stone rows

Question 37

How can wind breaks reduced soil erosion?

Answer 37

Reduces wind velocity

Question 38

How can multi-cropping reduce soil erosion?

Answer 38

Growing more than one crop in a field can reduce exposure to wind of they are harvested at different times

Question 39

How can increasing soil organic matter reduce soil erosion?

Answer 39

Any method that retains or adds organic matter will reduce the risk of erosion Protects against rain splash erosion

Question 40

How can livestock management reduce soil erosion?

Answer 40

Stocking density can be managed to reduce soil damage Can be removed if high risk of compaction

Question 41

What is the universal soil loss equation?

Answer 41

Used to estimate the rate of soil erosion for particular local conditions and cultivation practices