5.1 introduction to soil systems

Question 1

soil is dynamic

Answer 1

• rocks weather, soil increases
• wind blows, soil decreases
• water washes away nutrients, DOM puts them back
• plants take nutrients then die and decompose, returning nutrients
• plants absorb carbon dioxide and emit oxygen, animals reverse

Question 2

soil is a mixture of

Answer 2

• minerals
• organic matter
• air
• water

Question 3

functions of soil

Answer 3

• medium for plant growth, nutrients, water, place to anchor
• water storage and purification system
• habitat, bacteria, insects and mammals
• modifies the atmosphere, respiration of soil organisms and plant roots

Question 4

pedosphere

Answer 4

• soil

Question 5

lithosphere

Answer 5

• rocks

Question 6

hydrosphere

Answer 6

• water

Question 7

atmosphere

Answer 7

• ari

Question 8

biosphere

Answer 8

• living

Question 9

factors impacting soil characteristics
climate

Answer 9

• precipitation/evaporation balance

Question 10

factors impacting soil characteristics
organisms

Answer 10

• break down DOM and mix it into the upper layers of soil

Question 11

factors impacting soil characteristics
relief

Answer 11

• elevation of the land, aspect and angle of the slope

Question 12

factors impacting soil characteristics
parent material

Answer 12

• original material soil developed from
• bedrock, drift deposit

Question 13

factors impacting soil characteristics
time

Answer 13

• development of soil, non renewable natural capital

Question 14

biotic component of soil

Answer 14

• organic debris broken down by decomposers in the top layer of soil, bacteria, small insects
• earthwords breakdown DOM into humus
• nitrogen fixing bacteria, symbiotic relationship with legume plants

Question 15

soil
inputs

Answer 15

• minerals
  weathering of parent material from physical, chemical and biological processes
• organic matter
  from living organisms on and in the soil
  succession, early plants dying adding organic material
• gases
  nitrogen fixation, atmospheric nitrogen into nitrates and ammonia
  respiration
• water
  direct precipitation, flow

Question 16

soil
stores

Answer 16

• organic matter
  biotic elements, anything that lived
• organisms
  add nutrients when they deposit waste, break down DOM
• minerals
  parent material
• air
  gases in the soil, different soil types different air spaces
• water
• nutrients
  stored in organic matter or free in the soil

Question 17

soil
outputs

Answer 17

• wind, physically removes soil
• water, washes away minerals
• plants harvested or removed from the area, nutrients lost

Question 18

soil
processes, transfers and transformations

Answer 18

gas exchange
- respiration, photosynthesis, nitrogen fixation, evaporation

Question 19

P/E balance determines

Answer 19

• the dominant direction of water movement in soil
• precipitation down
• evaporation up
• hot and dry = high evaporation rates
• brings mineral salts to the surface, water evaporates salts are left, salinization
• wet and cold = high precipitation rates
• water washes soluble minerales out of soil, leeching

Question 20

decomposition

Answer 20

• break down DOM to release plant nutrients
• gradually increases soil fertility

Question 21

weathering

Answer 21

• breakdown of parent material
• adds minerals to the soil

Question 22

soil horizons

Answer 22

o
- organic horizon
- on top of the soil, includes DOM

a
- top soil/ mineral layer
- high proportion of organic matter
- highest biological activity

b
- sub soil
- zone of illuviation/accumulation
- minerals and particles washed in from ones above
- plant roots

c
- decomposed parent material, larger clumps`

Question 23

soil types
sand

Answer 23

• large particles
• well drained, rarely water logged
• subject to drought
• warms up quickly due to high air content

Question 24

soil types
clay

Answer 24

• smallest particles
• poorly drained, prone to waterlogging
• long time to dry after rainfall
• warm up slowly due to high water content

Question 25

soil types
silt

Answer 25

• in between sand and clay