Techniques to increase plant production

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Techniques to increase plant production

• AS 90451
• Describe physical factors of the environment and
  techniques used to modify them for plant
  production

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Contents

• In the previous PPT we covered
• PLANT PROCESSES
• ENVIRONMENTAL FACTORS
• AND PLANT GROWTH
• TECHNIQUES
• In This presentation we focus on TECHNIQUES
  including
• Hothouse Production
• CO2 enrichment,
• artificial shelter,
• sprinkler irrigation,
• tile drainage,
• hail cannon,
• wind machines,
• reflective mulch,
• training systems.

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Hot Houses
For example, young capsicum plants require
optimum day and night-time temperatures of 25C
and 1823ºC respectively.

• 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.

Warmer temperatures in a hothouse increases
insect activity, thus increasing pollination
(fruit set).
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Tomato hothouse
Increased air temperature in the glasshouse
increases the rate of photosynthesis, which
produces more carbohydrates and speeds up the
ripening process.
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.
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?
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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

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CO2 Enrichment
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Plate 1. Carbon dioxide generator.
Plates 6b. Liquid CO2 tanks.

• CO2 Enrichment

Liquid Carbon dioxide tank supplying a greenhouse.
Carbon dioxide generator for a large greenhouse
(burns fossil fuels to generate CO2
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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

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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.

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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.

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Natural Shelter Belts

• 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)

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Benefits of shelterFruit 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.

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Benefits of shelterPollination

• 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.

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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.

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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.

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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.

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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 5C 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.

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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.

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Reflective mulch

• 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.

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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.

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Fruit development

• All fruit requires the following process.
• Flower bud set
• Flower burst
• Pollination
• Fertilisation
• Fruit development
• Fruit ripening

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Fruit development
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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 20C respectively, would
  generate 15 heat units (20 10) / 2 15.

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Effect of Light and Water on Plant Production
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Kiwifruit Data Exercise
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Pests and Diseases

• Pests and diseases can influence the crop that
  can be grown in a certain region, ie apples
  arent 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.

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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.

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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.

Explain how increasing carbon dioxide levels
increases crop yield. In your explanation
describe, by giving figures, the carbon dioxide
levels before and after enrichment explain how
plant growth is improved, leading to increased
crop yield.
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