View
227
Download
0
Category
Preview:
Citation preview
8/3/2019 Greenhouse Functions and Controls
1/22
Greenhouse Functions andControls
Horticulture II
8/3/2019 Greenhouse Functions and Controls
2/22
Greenhouse Basics
Plants grow naturally outside, so why dowe need a structure to grow them in?
What is the purpose/function of agreenhouse?
The basic function is to provide a
protective environment for crop(plant)production.
8/3/2019 Greenhouse Functions and Controls
3/22
Greenhouse Environment
What things make up the greenhouseenvironment?
Temperature
Moisture
Pest Control
Nutrition
8/3/2019 Greenhouse Functions and Controls
4/22
Temperature
Different plants have different temperaturepreferences for optimum growth.
Some plants prefer cool or even cold temps Some plants prefer warm or hot temps
The trick is to provide a temperature rangethat is conducive to plant growth.
Grow plants together that prefer the sametemperature range.
8/3/2019 Greenhouse Functions and Controls
5/22
Moisture
Just as temperature matters, so doesmoisture.
Some plants need dry environments, whileothers need very wet environments.
How are moisture levels controlled?
Watering
Humidity
Level of water vapor in the air.
8/3/2019 Greenhouse Functions and Controls
6/22
Pest Control
One of the biggest problems growersface is pest control.
What types of pests?
Insects (aphids, whiteflies, etc)
Diseases (fungus, bacteria, viral)
Weeds (oxalis, henbit, etc)
Rodents (mice, rats)
8/3/2019 Greenhouse Functions and Controls
7/22
Nutrition
Plants, like animals, need nutrients to survive.
Growers provide plants with the nutrients they
need by supplementing either the water orsoil with added nutrients.
Growers also have to ensure adequateventilation.
Carbon dioxide
8/3/2019 Greenhouse Functions and Controls
8/22
Greenhouse Operating Expenses
In addition to the cost of plants, pots,soil, fertilizer, etc, growers also have to
deal with two other MAJOR expenses. Labor
Heat
Labor is usually the greatest expense.
Heat is usually the second highestexpense.
8/3/2019 Greenhouse Functions and Controls
9/22
What is the greenhouse effect?
Lets try a demonstration to find out.
You will need:
Scissors
Plastic wrap or bag
Popsicle sticks
Glue
Tape
8/3/2019 Greenhouse Functions and Controls
10/22
Building your Greenhouse
Attach your Popsicle sticks together tobuild a small house or box.
Cover the entire structure with plastic,leaving the bottom uncovered.
Tape the plastic to the greenhouse
8/3/2019 Greenhouse Functions and Controls
11/22
The Greenhouse Effect
Place your completed greenhouse onthe window sill.
Note the temperature on thethermometer by the window.
At the end of the period we will put the
thermometer in your greenhouses tosee what happens.
8/3/2019 Greenhouse Functions and Controls
12/22
Environmental Control
In order for a greenhouse to beeffective, the greenhouse environment
has to be closely controlled. What happens if the environment is not
controlled?
How do we ensure that the environmentis kept constant?
8/3/2019 Greenhouse Functions and Controls
13/22
Environmental Controls
In a greenhouse we use environmentalcontrols to manipulate and control the
environment. Thermostats
Temperature
Humidistats
Humidity
Photocells Light
8/3/2019 Greenhouse Functions and Controls
14/22
The Greenhouse Effect
Summarized The greenhouse effect is the way
greenhouses collect and store heat from
the sun. Radiant energy (the heat you feel when
near something hot) warms the
greenhouses (and whatever is inside ofit).
8/3/2019 Greenhouse Functions and Controls
15/22
Heat Loss
Greenhouses, while efficient collectorsof heat, are not good at storing it.
Heat is lost through the greenhousecovering (called glazing) and additionalheat may have to be provided.
Especially in winter.
8/3/2019 Greenhouse Functions and Controls
16/22
Heat Control
Heat, or more specifically temperature,has to be closely monitored and
continually adjusted in a greenhouse. Temperature in a greenhouse is
monitored by a thermostat, which
controls sensors to open vents, operateexhaust fans or intake fans which pullair through a pad cooling system.
8/3/2019 Greenhouse Functions and Controls
17/22
Thermostats
Where should a thermostat be located?
Ideally they should be located at plant level
for the best and most accurate control.
Thermostat types
Aspirated
Thermistor
8/3/2019 Greenhouse Functions and Controls
18/22
Aspirated Thermostats
An aspirated thermostat utilizes a smallfan which blows air continuously over
the temperature sensing unit. This helps to maintain a more uniform
temperature.
8/3/2019 Greenhouse Functions and Controls
19/22
Thermistors
A thermistor is a relatively new control thatutilizes solid-state electronics.
These devices allow the grower to usecomputers to monitor and control thegreenhouse environment.
Growers can set defined temperature ranges
for certain time periods and the computersturn heat and cooling devices on and off asneeded to maintain the desired temperatures.
8/3/2019 Greenhouse Functions and Controls
20/22
Light Control
Light levels have to be monitored ingreenhouses to ensure that plants are
receiving the correct amount. Photocells measure light intensities and may
relay that information to computers that turnson additional lights or activates a shade cloth
to reduce light. Timers may also be used to lights on or off at
certain times.
8/3/2019 Greenhouse Functions and Controls
21/22
Moisture Control
Moisture in the air (humidity) should also beclosely monitored for optimum growingconditions.
A Humidistat measures the relative humidityin the air and controls fogging or mistingsystems to regulate the humidity.
Humidity changes as heat dries the moisturefrom the air.
Moisture must be added by both watering andfogging or misting for most plants.
8/3/2019 Greenhouse Functions and Controls
22/22
Summary
The greenhouse environment has to beclosely monitored so that plants grow in
the best possible conditions. A plantthat grows in an environment wheretemperature, moisture, light, nutrition,
and pest levels are ideal and continuouswill be as strong and healthy as it canpossibly be.
Recommended