soil - human

Question 1

what is the soil profile?

Answer 1

layers of the soil
humus - thin layer of rotting vegetation, contains nutrients
topsoil - rich in minerals and nutrients, good for growing crops
subsoil - rich in minerals
rock that is being weathered
bedrock - solid rock not yet weathered

Question 2

what are zonal soils?

Answer 2

made of a mixture of solids (minerals & organic matter), liquids and gases that occur on the land surface
characterised by:
- horizons / layers
and / or
- the ability to support rooted plants in a natural environment

Question 3

what are ferralsols?

Answer 3

found in tropical regions
often red / yellow in colour

Question 4

what are podsols?

Answer 4

mature soils found where precipitation levels are high and temp levels are cool

Question 5

what are problems that soils face?

Answer 5

repeated erosion
reduces fertility of soil by removal of topsoil
reduction of the depth of soil available for rooting & water storage for crop growth
= loss of nutrients, increased erosion & runoff
leads to loss of seeds, nitrates and pesticides in the soil
erosion can damage environment:
increased runoff (greater flood hazard), sediment in rivers damages fish spawning grounds, damage to local water sources

Question 6

what is rill erosion?

Answer 6

when rainfall does not soak into the soil it can gather on the surface and run downhill forming small channels of water called rills

Question 7

what is gully erosion?

Answer 7

rills that are unattended grow into larger gullies
affected land is not able to be used for growing crops and creates a hazard for farm machinery

Question 8

what is sheet erosion?

Answer 8

raindrops loosen soil
the overflow land can transport topsoil in a uniform fashion (bedsheet sliding off a bed)

Question 9

what is riverbank erosion?

Answer 9

soil is washed away by unmanaged rivers as they meander across floodplains

Question 10

what is wind erosion?

Answer 10

forces exerted by wind overcome the gravitational and cohesive forces of soil particles on the surface of the ground

Question 11

what is saltation?

Answer 11

suspended particles (0.1 - 0.5 mm diameter) are lifted by wind & fall back to the ground (hop / bounce across the surface)

Question 12

what is suspension?

Answer 12

small particles (<0.1 mm diameter) that have been lifted into the air remain suspended as dust & are transported away from the erosion site
majority of particles (>0.2 mm) will settle back to the ground within 100km of the erosion site
this sediment is called loess

Question 13

what is creep?

Answer 13

particles (>0.5 mm diameter) usually too heavy to be lifted by wind are rolled or moved along the surface by being hit by other moving particles

Question 14

what is abrasion and attrition?

Answer 14

suspended particles cause abrasion of the soil surface when they fall back to the ground
can also hit other particles and break them into smaller particles (attrition)

Question 15

what are causes of soil erosion?

Answer 15

large areas of trees cleared so their roots can’t hold the soil together, so it is washed away by rain loss of arable land
soil blown away by wind on flat cropland
palm trees make the soil unusable so new land is cleared

Question 16

what are solutions of soil erosion?

Answer 16

plant fast growing trees among crops
build dams to hold soil in place
new machinery that keeps soil destruction to a minimum
trees planted around edges of flat farmland - acts as a barrier
planting other crops between palm trees to conserve soil use, so less is eroded

Question 17

how can water erosion be controlled?

Answer 17

installing & maintaining field drains and ditches
reduce water running off roads into fields
protect soil in winter using cover crops
use lots of manure to stabilise topsoil

Question 18

how can wind erosion be controlled?

Answer 18

increase soil cohesion by applying manure to soil to improve its structure
increase plant cover so surface windspeed can be cut
increase roughness of soil surface - leave crop residues & don’t plough them into the soil

Question 19

what is waterlogging?

Answer 19

too many pore spaces in soil occupied by water rather than air
causes insufficient oxygen for plants to respire
causes plant growth and development to be stalled or death

Question 20

what are causes of waterlogging?

Answer 20

surface-fed waterlogging
precipitation, irrigation water / river flood water exceeds the combination of evapotranspiration and percolation, so water stays in and on the soil
groundwater-fed waterlogging
rate of rising groundwater is not matched by rate of evapotranspiration
could be a natural rise or caused by irrigation canals

Question 21

what is salinisation?

Answer 21

A buildup of salts in soil which can become toxic for plants

Question 22

what are causes of salinisation?

Answer 22

excessive water application
irrigation water leaves salt behind when it evaporates
poorly drained farmland

Question 23

what are impacts of salinisation?

Answer 23

land is abandoned as it is too salty to farm = decrease in yields
rivers and groundwater become salinised from water used trying to flush the salt out of the soil salt can become too thick causing a crust, so water runs off it causing flooding

Question 24

what are granular and crumb structures of soil?

Answer 24

individual particles of sand, silt & clay grouped together in small grains
water circulates very easily
found in the top A-horizon of the soil profile