Functions of a Greenhouse Competencies

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

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.

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

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

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

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

Moisture

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

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.

Moisture Control Equipment Watering system Shade cloth Foggers Mist system Humidifiers

Pest Control

Greenhouses must be kept free of: Insects Diseases Weeds Rodents

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

Nutrition

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

Light

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

Light Control Equipment Lights Shade cloths Shade materials Black cloth

Greenhouse Maintenance

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

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

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

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

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

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