Functions of a Greenhouse

1. Functions of a Greenhouse Competencies 7.00-9.00

2. 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

3. Temperature

4. 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.

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

6. Controlling Temperatures • There are two ways to control temperatures in a greenhouse: • Thermostats • Air or ventilation

7. 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

8. Temperature Control Equipment • Heaters • Fans • Cooling pads • Mechanical air conditioners • Ventilators • Shade cloths and materials • Fogging and misting

9. Moisture

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

11. 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.

12. Moisture Control Equipment • Watering system • Shade cloth • Foggers • Mist system • Humidifiers

13. Pest Control

14. Pest Control • Greenhouses must be kept free of: • Insects • Diseases • Weeds • Rodents

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

16. Nutrition

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

18. Light

19. 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

20. Light Control Equipment • Lights • Shade cloths • Shade materials • Black cloth

21. Greenhouse Maintenance

22. 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

23. 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

24. 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

25. 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

26. General Maintenance Practices • Inspect and make repairs for controls and equipment • Heaters • Fans • Pumps • Thermostats • Humidistats • Photocells • Timers • sprayers

27. General Maintenance Practices • Inspect and make repairs for utilities • Water • Electricity • Gas or fuel oil • Waste and trash disposal