Techniques to increase plant
production
AS 90451
Describe physical factors of the environment and techniques
used to modify them for plant production
Contents
In the previous PPT we covered
• PLANT PROCESSES
• ENVIRONMENTAL FACTORS
• AND PLANT GROWTH
• TECHNIQUES
• In This presentation we focus on TECHNIQUES including:
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Hothouse Production
CO2 enrichment,
artificial shelter,
sprinkler irrigation,
tile drainage,
hail cannon,
wind machines,
reflective mulch,
training systems.
Hot Houses
• The ultimate method of manipulating the
environment is to build a hothouse.
• The primary reason for having a hot
house is to increase air temperature.
• Most glasshouse grown plants generally
require high temperatures during the day,
and lower temperatures during the night.
For example, young
capsicum plants
require optimum
day and night-time
temperatures of
25°C and 18–23ºC
respectively.
Warmer temperatures in a hothouse increases insect
activity, thus increasing pollination (fruit set).
Tomato hothouse
Ventilation reduces the
chances of plant diseases,
as it increases air
movement, and reduces
temperature and humidity.
This ensures that fungal
spores do not settle on
leaves.
Increased air temperature
in the glasshouse increases
the rate of photosynthesis,
which produces more
carbohydrates and speeds
up the ripening process.
Bit of a tradeoff – do you open the
vents to decrease humidity and
decrease the temp. Or keep them
closed to increase temp but risk too
much humidity?
CO2 Enrichment
• ‘Normal’ air contains about 380 - 390 ppm (0.3%) of
CO2.
• All plants grow well at this level but as CO2 levels are
raised, photosynthesis increases proportionately
resulting in more sugars and carbohydrates available
for plant growth.
• Any actively growing crop in a tightly clad greenhouse
with little or no ventilation can readily reduce the CO2
level during the day to as low as 200 ppm. This
decrease in photosynthesis decreases plant growth –
so growers need to ventilate hothouses to avoid this.
• A CO2 generator increases levels fro 380 to 1000 1,300 ppm. Resulting in increased production
CO2 Enrichment
• CO2 Enrichment
Liquid Carbon dioxide tank
supplying a greenhouse.
Carbon dioxide generator for a large
greenhouse (burns fossil fuels to generate
CO2
CO2 Enrichment
Practice Question
• If a backyard gardener places a portable gas heater into her
greenhouse. Describe the effect will it have on plant
production and explain how this is more effective than an
electric heater.
• Hint:
Artificial Shelter
Could be in the form of:
• Fences, wind belts, shade cloth barriers, walls, etc.
• Shelter reduces wind (air movement) and can provide extra shading. As a
result:
• Sunlight is reduced in the southern area of land adjacent to the shelter.
• Humidity is increased on the inside of the shelter belt.
• Temperature is increased on the inside of the shelter belt.
• The frequency of frost is increased on the inside of the shelter belt.
Artificial Shelter
• There are no roots associated with artificial shelter, so vines close to the
shelter have no competition for nutrients, water and some light. Therefore
there is minimal drop-off in yields from these rows, unlike the drop in yields
associated with natural shelter. The incidence of bird damage is reduced,
due to there being no nesting or resting sites for birds.
Natural Shelter Belts
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Natural = plants.
Porosity of shelter should be about 50%.
Shelter should be a continuous length, with no gaps.
Are slow to develop
Have a maintenance cost (need to be pruned each year at
around $100/hr)
Benefits of shelter
Fruit damage
• Strong winds result in fruit such as apples “banging” each
other, resulting in bruising and therefore a lowering of quality.
• Strong winds may cause fruit such as kiwifruit, that are grown
on a support system, to come in contact with wires or wood,
causing marking and bruising, thereby reducing crop quality.
Benefits of shelter
Pollination
• Insects such as bees require
calm conditions for flight
between hives and target fruit
crops. Shelter maintains these
conditions, allowing bees to
move from flower to flower,
and in doing so, pollinate
crops, resulting in optimum
fruit set and the potential for
high yield.
Sprinkler irrigation
• We already know of the importance of
water in photosynthesis, nutrient uptake
and fruit development.
• Sprinkler irrigation (any irrigation) simply
gives more control over the timing and
amount of water delivery.
• Advantages in relation to fruit production
are particularly important as increased fruit
size can be achieved.
Tile Drainage
• Tile Drainage (any drainage system)
primary function is to get rid of excess
soil water and therefore increase
oxygen availability to the roots.
• Drainage will therefore increase
respiration and nutrient uptake.
• Nutrient uptake will increase because it
requires energy for nutrient uptake
(increased respiration ) and because
there will be more root growth and
hence increased access to soil
nutrients.
Hail Cannons
• Hail canons are used to shatter ice
particles inside hail clouds.
• They use repeated sonic booms to
achieve this.
YouTube- How a hail cannon works
• Hail is only a problem in fruit
production when the fruit is on the
vine and there is a cold spell. Ie at
the end of the growing season going
into autumn.
Wind machines
• Wind machines are used to provide frost
protection for orchards and vineyards.
When an inversion layer forms above the
plants, the temperature may be up to 5°C
warmer 10 to 16 metres above the plants.
Under these conditions, colder air becomes
trapped below the inversion layer
increasing the risk of frost damage at
ground level. Wind machines can move
warmer air from the inversion layer
downward to prevent or minimise frost
damage caused by colder air.
Frost damage
• Frost damage happens
early in the growing season
shortly after budbreak. If
the developing flowers area
damaged it can greatly
reduce or even completely
destroy the entire years
crop before it has started.
Reflective mulch
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Exactly what it sounds like – a much layer that:
Suppresses weeds
Retains soil moisture
And reflects the light back up towards the plant.
And repel some insect pests (the shiney light scares them
away)
• Therefore it increases water availability, nutrient availability,
and light availability.
Training systems
• Training systems are designed to shape the
tree/ vine to achieve one or more of:
• Improved aeration around branches
• Reduce competition for light between trees
• Improve the ability of a tree to harvest light
• Support branches/ vines laden with heavy
fruit
• Improve workability of the plant in relation to
spraying and harvesting.
Fruit development
• All fruit requires the
following process.
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Flower bud set
Flower burst
Pollination
Fertilisation
Fruit development
Fruit ripening
Fruit development
Process
Environmental factors to consider
Bud set
Some flower buds require a chill factor to set the
bud (eg apples)
Bud burst (blossom) Usually occurs in spring – prone to frost damage
Pollination
Usually requires insect activity = warm air temp!
Fertilisation
Pollen grain grows pollen tube – respiration =
warm air temp and healthy flower needed.
Fruit development
Most fruit is sugar and water – lots of sugar + lots
of sunlight + plenty of water availability
Fruit Ripening
Requires heat! And often direct light!
Heat units
• Crop growth and development is often described in terms of
time, e.g., it takes 60 frost free days for barley to mature
• However, a consideration of temperature is also important
because temperature determines the rate of growth. The
time/temperature relationship that governs plant growth and
development is measured in heat units. or growing-degree
days.
• Heat units are calculated by adding the minimum and
maximum daily temperatures together and dividing by two
• For example, a day with minimum and maximum
temperatures of 10 and 20°C respectively, would generate 15
heat units [(20 + 10) / 2 = 15].
Effect of Light and Water on Plant
Production
Kiwifruit Data Exercise
Canopy
lighter
denser
Kiwifruit Data
Crop Load
Fruit / m2
Fruit weight (g)
low crop load
26
113
high crop load
36
107
low crop load
35
91
high crop load
48
84
Overall, canopy density had a greater effect on fruit weight than crop load.
Exercise 2
Graph the above data to show the relationship between canopy density and
crop loading
Explain the effect of canopy density on fruit size.
Exercise 3
Explain the effect of crop load on fruit size.
Exercise 4
Justify the manipulation in terms of quantity and quality of kiwifruit.
Exercise 1
Pests and Diseases
• Pests and diseases can influence the crop that can be
grown in a certain region, ie apples aren’t grown in
the Waikato and grapes are no longer commercially
grown in West Auckland due to dampness of the
climates (botrytis).
• New growth of all plants are very susceptible to pests
and diseases.
• Pests chew the tender tasty tips of plants restricting
the development of the plants and their ability to carry
out plant processes.
• Fungi such as mildew destroy apical buds.
• Pests chew the plants providing an entry point for
diseases which restricts the ability of the plant to grow
at an optimum rate.
Crop quality and quantity are affected
by physical factors in a glasshouse.
This photo is of an orchid glasshouse
that is being used modify physical
factors.
• List the environmental factors that could be altered with a
glasshouse.
2009 exam Q1
• Many commercial glasshouse growers increase
the carbon dioxide levels in glasshouses in
order to increase crop yields. Artificially raising
carbon dioxide levels is called enrichment.
Achievement with
Explain
how increasing
carbon dioxide
levelswith
increases
Q
Achievement
Achievement
Merit crop yield.
Excellence
In your explanation:
ONE
• describe, by giving figures, the carbon dioxide levels before and after
(a)
Describes how the carbon
Explains how plant growth
enrichment dioxide levels change
is improved, leading to
before
andgrowth
after grower
increased
crop yield.
• explain
how
plant
is
improved,
leading
to increased crop yield.
A1
or
M1
intervention.
Example:
Example:
The computer increases
the levels of carbon dioxide
from 330 ppm to over 800
ppm.
By increasing the volume of
carbon dioxide, the rate of
photosynthesis is
increased, which increases
growth. This leads to higher
and earlier yields, and
ensures better fruit setting,
etc.