NCEA Level 2 Agricultural and Horticultural Science (90451) 2011 — page 1 of 4
Assessment Schedule – 2011
Subject: Describe physical factors of the environment and techniques used to modify
them for plant production (90451)
Evidence Statement
Question
ONE
(a)
Achievement
Achievement with Merit
Achievement with Excellence
Glasshouse Production
Describes the cause of
humidity.
Explains how humidity affects
crop quantity and quality.
Example:
Example:
Humidity is the level of water
content in the air. High humidity
is produced by a combination of
heat and water within the
glasshouse.
Production requires a level of
humidity that leads to retention
of water for photosynthesis, but
not too high a level that would
increase the chances of
disease. If diseases occur on
the leaves, then leaf area for
photosynthesis is reduced,
while diseases in the stem
reduce the transport of water
and photosynthates.
A1
High humidity decreases
transpiration. The plant also
uses energy resources to fight
infection, due to high humidity,
which decreases yield.
High moisture (78% can cause
Botrytis) and temperature levels
encourage bacteria and other
microorganisms to multiply,
which can often cause disease,
and this shows up as rotting
and other imperfections.
Low humidity – under 60%.
Spores dry out, reducing spread
of disease.
M1
(b)
(c)
Describes how a technique
controls humidity.
Example:
When humidity levels become
too high, excess moisture can
be flushed out by raising the
temperature and opening vents.
When humidity levels are too
low, reduce the temperature
and close the vents.
A2
Explains how humidity control
can affect temperature and
carbon dioxide levels.
Justifies the use of automated
ventilation as the better
technique for humidity control.
Example:
Example:
Venting the glasshouse to
reduce humidity means that
heat is also escaping, and at
the same time carbon dioxide
can be drawn in at lower levels.
If humidity is being removed by
flushing in which a burst of heat
drives upwards, taking humidity
with it, then a reduction in
temperature will also occur.
Expensive to set up, but can
control at the same time
mechanisms that regulate
several physical factors
(temperature, humidity, water,
carbon dioxide), and therefore
maintain optimum growing
conditions, resulting in
increased yields. This operates
24 hours per day with a low
human input, and makes best
use of the expensive growth
inputs.
M2
NCEA Level 2 Agricultural and Horticultural Science (90451) 2011 — page 2 of 4
Crop is high-value, due to
higher quality and appearance
because humidity is controlled,
and in conjunction with the
higher yields, the overall returns
will cover higher production and
installation costs. Economies of
scale resulting from a more
precise growing environment
provided by computerisation.
Increased yields give increased
labour costs at harvesting, for
grading and packing work. But
overall returns exceed costs of
production, and therefore
profitability increases.
With a non-automated system,
yields are often low quality, as
levels of humidity, CO2 and
temperature are measured less
accurately. More labour is
needed to measure levels,
increasing labour costs for
lower quality output, resulting in
lower returns.
E
NCEA Level 2 Agricultural and Horticultural Science (90451) 2011 — page 3 of 4
Question
TWO
(a)
Achievement
Achievement with Merit
Achievement with Excellence
Site and Site Selection
Describes how topography
affects the number and severity
of frosts.
Explains how topography
affects differences in frosts.
Example:
Sloping ground encourages a
downward movement of air and
prevents frost from settling. Flat
sites have less sun exposure
and are prone to calm
conditions, both of which favour
frost development. A hillside
location with a sunny aspect has
prolonged sunny exposure and
a warmer microclimate, making
frosts less likely.
Hilly locations are less likely to
suffer from frost damage, due to
fewer frost days and less severe
frosts when they do occur.
A1
Example:
M1
(b)
(c)
Describes a frost protection
technique.
Explains how the technique
improves production.
Example:
Example:
Wind machines are elevated
fans that are able to mix air,
creating a movement of air over
a significant distance in an
orchard or vineyard.
Air movement prevents frost
from settling on developing buds
that have the potential to form
fruit. If frost forms, cellular
material freezes and buds die.
Wind machines keep buds safe
from freezing, meaning that fruit
quantity is maintained, while the
impact of early frosts that could
affect the quality of mature fruit
is avoided.
A2
M2
Justifies the use of a frost
protection technique on a flat
site.
Example:
In an apple orchard on flat land,
the use of overhead sprinklers is
an excellent technique to use,
because it can achieve two
outcomes – frost protection in
early spring, and irrigation in
summer. The latter is
particularly vital for crop quality,
because of its impact on fruit
size. By covering buds with a
film of water that freezes, the
impact of the latent heat of
freezing protects the buds from
damage.
Other techniques such as wind
machines could have a similar
outcome, but at a much greater
expense, and without the added
advantage of supplying irrigation
water from an elevated position.
Wind machines also have an
environmental impact, both
visually and in terms of noise,
whereas overhead sprinklers
have neither of these concerns.
E
NCEA Level 2 Agricultural and Horticultural Science (90451) 2011 — page 4 of 4
Question
Achievement
THREE
Light and Training Systems
(a)
Describes how the amount of
light affects plant production.
Achievement with Merit
Achievement with Excellence
Example:
Exposes the crop to more light,
provides ventilation around the
leaves / fruit, and supports the
crop so that growth is
concentrated on fruit
development rather than
secondary growth.
A1
(b)
Explains how the training
system improves the amount of
light available.
(c)
Example:
The system thins the canopy by
lifting and spreading out the
branches, allowing (typically)
30% more light through the
canopy and reducing the dense
shade on the ground.
This increases the rate of
photosynthesis, which produces
carbohydrates / sugars for
respiration, providing energy for
tree growth and increased
yields. Greater exposure to
sunlight, and the resulting
higher temperature, produces a
better colouration and / or sugar
content that are desired in
further use or processing.
M1
Justifies the training of fruit
crops as the best technique for
improving the amount of
available light.
Training systems allow for
optimum utilisation of available
light received from above the
canopy. Systems can vary,
depending on the growth habit
of the crop, and not only does
the training system affect the
amount of light from above, but
it also influences the distribution
of light within the canopy layers.
The design of the training
system allows for efficiencies
when performing other
management practices, such as
spraying and harvesting. Light
can be influenced by thinning /
pruning practices, but these
form part of the training system
in vines and canes. Reflective
mulch reflects upwards light that
reaches the ground, but the
amount of light reaching the
ground is strongly influenced by
the training system used.
E
Judgement Statement
Achievement
Achievement with Merit
Achievement with Excellence
2 A1
2 M1
2 M1
2 A2
2 M2
2 M2
2E