Functions of a Greenhouse

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Functions of a Greenhouse

• Competencies 7.00-9.00

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Functions of a Greenhouse

• The basic function of a greenhouse is to provide
  a protective environment for crop production.
• Several factors must be monitored
• Temperature
• Moisture
• Pest control
• Nutrition
• Light

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Temperature
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Temperature

• Temperature ranges must be conducive to crop
  production
• The cost of heat is the second highest expense of
  greenhouse plant production. (labor is the
  greatest expense)
• Greenhouses lose heat through the plastic, glass,
  etc. and additional heat has to be provided
  especially in winter.

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Greenhouse Effect

• The greenhouse effect is the way greenhouses
  collect and store heat from the sun.
• Radiant energy warms the greenhouse and its
  contents

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Controlling Temperatures

• There are two ways to control temperatures in a
  greenhouse
• Thermostats
• Air or ventilation

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Thermostats

• Thermostats should be at plant level for most
  accurate control.
• There are two kinds of thermostats
• Aspirated thermostat-small fan blows air
  continuously over the temperature sensing unit to
  help maintain a more uniform temperature
• Thermistor-uses solid state electronics that
  enable growers to use computers to monitor the
  greenhouse environment

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Temperature Control Equipment

• Heaters
• Fans
• Cooling pads
• Mechanical air conditioners
• Ventilators
• Shade cloths and materials
• Fogging and misting

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Moisture
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Moisture

• Moisture must also be conducive to plant
  production
• Moisture is monitored by
• Watering
• Humidity levels

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Controlling Moisture Levels

• Humidistat is used to control fogging or misting
  systems to regulate relative humidity (moisture)
  in the air.
• Heat dries moisture from the air and moisture
  must be added by both watering and through
  misting and fogging for most plants.

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Moisture Control Equipment

• Watering system
• Shade cloth
• Foggers
• Mist system
• Humidifiers

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Pest Control
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Pest Control

• Greenhouses must be kept free of
• Insects
• Diseases
• Weeds
• Rodents

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Pest Control

• Use proper sanitation practices
• Control weeds around greenhouse
• Prevent weeds, insects, rodents, and diseases
  inside the greenhouse

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Nutrition
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Nutrition

• Nutrition must be monitored in
• Soil
• Water
• Air (ventilation is necessary to supply carbon
  dioxide)

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Light
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Controlling Light Levels

• Photocell measures light intensity and relays
  signal to computer that turns on lights or
  activates the shade cloth to control light
• Timer is used to turn lights on or off at a
  certain time

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Light Control Equipment

• Lights
• Shade cloths
• Shade materials
• Black cloth

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Greenhouse Maintenance
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Maintaining Temperature Equipment

• Inspect heaters
• Use adequate clean fuel
• Ensure that thermostats are working properly
• Inspect fans, fan motors, belts, etc.
• Check water levels in cooling pads and are clean
• Shade cloths should be attached and applied or
  removed depending on need

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Maintaining Light Equipment

• Determine need for shade cloths to be attached or
  removed
• Replace light bulbs as needed
• Ensure that timers and photocells are working
  correctly

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Maintaining Moisture Equipment

• Inspect humidistats and fogging or mist systems
• Ensure that water lines and faucets are not
  leaking
• Determine if there is an adequate source of high
  quality and clean water

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General Maintenance Practices

• Inspect and make structural repairs
• Loose, torn or cut plastic covers
• Broken glass or fiberglass
• Door locks and fasteners
• Air leaks
• Damaged framework and foundation

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General Maintenance Practices

• Inspect and make repairs for controls and
  equipment
• Heaters
• Fans
• Pumps
• Thermostats
• Humidistats
• Photocells
• Timers
• sprayers

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General Maintenance Practices

• Inspect and make repairs for utilities
• Water
• Electricity
• Gas or fuel oil
• Waste and trash disposal