16. QQuueessttiioonn:: [[AAPPRRIILL,, 22001100]]
PPaappeerr 22BB
List TWO properties of soil that
are affected by soil texture. (4)
The distance between soil particles
The amount of air between soil
crumbs/drainage
The rise of water in the soil
(capillarity)
Any TWO
17. CCllaayy SSooiill iiss mmaaddee lliigghhtteerr bbyy
aaddddiinngg::--
i) humus
How do these work?
ii) lime
23. 0-45cm
45-90cm
Bedrock
Upper topsoil layer is
dark. Why?
Lower soil layer is rich
Lower soil layer is rich
in salts. Why?
in salts. Why?
24. QQuueessttiioonn:: [[AAPPRRIILL,, 22001100]] PPaappeerr 22BB
Explain how humus:
i) Increases the soil’s water
content. (2)
Absorbing large amounts of water
or reducing evaporation from the
soil.
25. QQuueessttiioonn:: [[AAPPRRIILL,, 22001100]] PPaappeerr 22BB
b. Explain how humus:
ii) Improves the texture of a clay
soil. (2)
Humus helps soil particles
stick together into larger crumbs.
26.
27. SSaannddyy SSooiill::
light soil
water drains quickly
As water drains
quickly TWO
disadvantages
result:
28. 11.. SSooiill ddrriieess uupp qquuiicckkllyy
Why is this a disadvantage for the
farmer?
Water is expensive!!
32. HHuummuuss
a jam-like substance made up of
decayed plants and animals
is found in the topsoil
– blackish in colour
33. HHuummuuss
if there is not enough oxygen,
materials accumulate to form
half decayed materials called
peat
peat decays into humus if placed
in well aerated soil
35. HHuummuuss iimmpprroovveess ssooiill bbyy::--
providing mineral salts from
decay by bacteria and fungi
providing air spaces
retaining water
improves crumb structure
(prevents soil from being blown
away)
42. percentage of organic matter =
loss in weight ´
weight of original dry sample
100
Original weight: 105 g
Final weight: 100 g
Loss in weight: 5 g
5 ´100 = 4.8%
105
43. SSOOIILL
rock particles
humus
mineral salts
water
air
organisms
44. WWaatteerr
is found as thin films around soil
particles
water moves
upwards towards
the surface by
capillarity
49. PPeerrcceennttaaggee ooff wwaatteerr iinn ssooiill::
loss in weight ´
original wet sample
100
Original wet weight: 200 g
Final weight: 185 g
Loss in weight: 15 g
15 ´100 = 7.5%
200
50. SSOOIILL
rock particles
humus
mineral salts
water
air
organisms
52. SSaalliinniissaattiioonn iiss aa SSooiill PPrroobblleemm
gradual accumulation of salt in the soil, usually due to
improper irrigation techniques
often in arid and semi-arid
areas (natural mineral salt
conc. high)
– The little precipitation that
falls is quickly evaporated
– Leaves behind salts
salt concentrations get to
levels toxic to plants
60. EExxppeerriimmeenntt
percentage of air = volume of air in soil
volume of soil sample
´ 100
Conclusion:
Air is important in soil for roots to respire
and for decomposers to remain alive.
61. rock particles
humus
mineral salts
water
air
organisms
SSOOIILL
64. EEaarrtthhwwoorrmmss iimmpprroovvee ssooiill bbyy::
1. their burrows they mix and loosen the soil
and so help to drain and aerate it
2. providing salts due to their wastes and by
pulling leaves into the soil
66. EEaarrtthhwwoorrmmss iimmpprroovvee ssooiill bbyy::
4. binding soil particles together by the
secretions from the intestines
5. making the soil finer – young roots can
emerge easier
83. QQuueessttiioonn:: [[MMAAYY,, 22001111]] PPaappeerr 11
Give the biological explanation of the
message in the following poster. (3)
Decomposers, consisting of
bacteria and fungi, bring
about the decay of the dead
plant material. The decaying
material is called compost
and is vital for the growth of
plants as mineral ions are
released into the soil. Plants
use nitrates, phosphates and
other mineral salts to keep
healthy.
85. CCrroopp rroottaattiioonn
means the planned order of specific
crops planted on the same field
rotation may vary from 2 or 3 year or
longer period
e.g.
- wheat in autumn
- root crop in summer
- barley or oats in spring
- leguminous plants (clover, peas)
86. if the same crop is planted:
certain salts are depleted
87. BBeenneeffiittss ooff CCrroopp
rroottaattiioonn
1. maintains crumb structure
2. supplies nitrates
3. reduces infection to plants as a
pest cannot continue its life cycle if
a different crop is planted