HORTICULTURAL SCIENCE U.S.9769 V3
ASSESSMENT SCHEDULE
Describe management practice(s) used to optimise
the soil water/air ratio for plant processes.
Question
ONE(a)
2.1
2.2
Evidence
Description
of factor
Area X, eg:
Sandy soil
type
Topograph
y is gently
sloping
Explanation of how factor affects
soil water/air ratio
Achievement
For 2 of the 3 areas – 2
factors correctly
described.
Sand increases
macropore/micropore ratio leading
to excessive drainage of water and
higher air content.
Gentle slope allows drainage down
slope, less soil water retention –
lower water/higher air content.
Sandy soil will have lower organic
matter – less water retention,
therefore lower soil water/air ratio.
Organic
matter
Area Y, eg:
Loam soil
type
Topograph
y is steeper
slope
Loam (sand, silt and clay in even
proportions) has a balanced
macropore/ micropore ratio giving
water retention and drainage with
even soil water/air ratio.
Steeper slope gives rapid water
run-off, less time for water
penetration and retention – lower
soil water/air ratio results (after
rain) compared with loam soil on
flat land.
Loam soil will contain average
organic matter levels – higher water
retention, therefore increased soil
water/air ratio.
Organic
matter
Agricultural and Horticultural Science Assessment Schedule U.S. 9769 V3
2
Question
ONE
(a) cont’d
Evidence
Area Z, eg:
Soil type
Topograph
y, relatively
flat
(b)
3.1
Achievement
Clay (clay proportion greater)
decreases macropore/micropore
ratio, leading to excessive water
and lower air content. Clay soil
holds more water.
Bottom of slope – run-off water may
accumulate, leading to
waterlogging.
Decreases soil air to little or no soil
air after rain.
A Value of
Effect on plant growth
r soil water/
e air ratio
a
X 1.5–2.0
Plant growth will slow – reduced
available water to plants.
Y 2.0–2.5
Plant growth will continue – no
noticeable change – available water
in good supply.
Values approximate –
within limits given.
Describes effect
correctly for 2 or 3
areas.
Plant growth may stop – no soil air
for essential plant processes.
Z 4.0–5.0
(c)
3.2
Example:
Area Z will have high water/low air ratio after the
rain – it will also be colder. This will decrease
plant growth as:
 lack of air will decrease root hair respiration
due to oxygen limitation
 lack of oxygen will also reduce the uptake of
minerals by active transport due to lack of
respiration
 colder soil will reduce bacterial activity in
nutrient cycling and reduce the role of
mycorrhizal fungi in mineral uptake.
Describes 1 effect of
high soil water/air ratio
on 2 of the processes.
Agricultural and Horticultural Science Assessment Schedule U.S. 9769 V3
3
Question
(d)
4.1
Evidence
Describes
managemen
t practice,
examples:
Explanation of effect on grape
growth
Install tile
drainage in
Area Z.
Gives a better balanced soil
water/air ratio, improves plant
growth through increased mineral
uptake.
Achievement
Describes 2
management practices
that would optimise
soil water/air ratio.
Increases organic matter in soils
Apply mulch to improve water retention – this
or compost to will improve soil water/air ratio and
Area X.
improve plant growth.
Increases soil water/air ratio and
improves plant growth through
more water being available for
Irrigate Areas growth in each area.
X, Y and Z
using different
methods, eg
using
sprinklers at
X, microjets at
Y at different
frequencies
and
application
rates (use
solenoids to
regulate
frequency and Flocculates clay particles,
length of
increasing the
application),
macropore/micropore ratio – giving
and monitor
better soil air – improves plant
soil water
growth.
levels using
tensiometer.
Area Z
irrigated when
needed (least
often) in dry
weather.
Lime the soil
at
Area Z.
Agricultural and Horticultural Science Assessment Schedule U.S. 9769 V3
4
(e)
Examples:
4.2
Mulching or green manuring or composting to
increase organic matter thus retaining more water
and improving the soil water/air ratio. Also
increases nutrient level of soil and improves plant
growth.
4.3
Irrigation will leach minerals and nutrients from
soil and cause problems at Area Z unless
drainage is installed.
OR
Irrigation using scheduling techniques to avoid
excess water run-off.
Explain soil formation in terms of weathering:
(f)
1.1
Physical factors include: wind, water, erosion.
Describes at least 2
factors.
Chemical factors include: carbonization,
hydration, oxidation.
Biological factors include: effect of living
organisms.
(g)
1.2
Needs to have completed appropriate profile and
explained the top 2 layers in terms of forming
through time, topography, climate, parent rock
and vegetation (humus).
Soil profile sketched
and at least 2 areas
described in the
description.
Agricultural and Horticultural Science Assessment Schedule U.S. 9769 V3