8.Protected environments Flashcards
1
Q
Name key types of protected environments
A
- Greenhouse (Glasshouse) - Freestanding, made of glass
- Conservatory = Made of glass, attached to building
- Cold frame = Mini greenhouse with openable lid
- Polyethylene tunnel = plastic stretched over metal hoops
- Cloche = Small and portable, can be glass or plastic
2
Q
Uses for a protected environment
A
- Plants from warm climates can be grown in colder ones
- Plans can be grown earlier or later in the season
- Crops can be produced out of season
- Propagation is in a controlled environment
- Overwinter tender plants
- Plants grown for education/study/conservation
- Commercially to grow decorative plants for sale
3
Q
Pro’s/con’s of Protected environments
A
- Higher temperature day and night = faster growth for longer
- Gas composition can be controlled (in certain structures)
- Higher humidity than outdoors
- Light levels may be controlled
- Protection from wind/wind chill
- Irrigation needed as no rain - dryer on hot days
- Air movement reduced
- Light levels may be reduced
- Pest and disease which may not occur externally can easily spread - humidity/space
- Optimum growth req different for different plants
4
Q
Pro’s/con’s of using a Greenhouse
A
- Physically robust
- Effectively permanent structure
- Ease of access
- Glass can be broken
- Expensive to build /maintain older units
5
Q
Pro’s/con’s of using a Polytunnel
A
- Can be moved easily
- Cheap
- Ideal for crops which need minimal protection
- Easily damaged
- Access can be hard if low to ground
- Low insulating properties
- Hard to ventilate
6
Q
Lycopersicon esculentum
Why grow in a Greenhouse
A
- Plants may be started early from seed whilst protected from frost
- Warmer night temp encourages faster growth
- Warmer temp enabled faster ripening
- Plant protected from rain
- Can continue to grow/fruit later into the autumn
- Biological control of pests can be used
- Co2 can be controlled to boost growth (commercial)
7
Q
Key materials for use on Protected environment
A
Supporting framework to hold structure
- Aluminum (metal conducts electricity)
- Softwood (High maintenance)
- Cedarwood (Hardwearing/long-lasting)
Cladding material - lets in light and retains heat
- Glass
- Polycarbonate
- PVC
- Polyethylene
- Acrylic (flexi/perspex)
8
Q
Pro’s/con’s of using a Glass cladding
A
- Good light transmition (up to 97%)
- Heavy - requires specialist handling
- Poor thermal efficiency
9
Q
Pro’s/con’s of using a Polyethylene cladding
A
- Very light - easy to use
- Cheap
- Flexible
- Will eventually degrade in sunlight
- Very poor thermal efficiency
10
Q
Pro’s/con’s of using a PVC cladding
A
- Very light - easy to use
- Cheap
- Flexible
- Stronger/longer lasting than Polyethylene
- Will eventually degrade in sunlight
- Very poor thermal efficiency
11
Q
Pro’s/con’s of using a Acrylic cladding
A
- Easy to cut to shape
- Cheap
- Scratches easily
- Gets dirty with age
12
Q
Pro’s/con’s of using a Polycarbonate cladding
A
- Lightweight and strong
- Easily cut to shape
- Twin walled has high insulating properties
- Expensive
13
Q
Natural Light levels within protected environment will depend on:
A
- Aspect - facing sun or not
- Shading from tree’s/buildings
- Orientation
- Cladding material
- Shape of structure - light able to enter or reflect
14
Q
How are protected environments Heated
A
- Passive heating - Structure traps solar radiation
- Oil or gas fired central boiler with wet piped system
- Portable heaters with bottled gas
- Electric heaters
- Costs vary greatly
15
Q
How is ventilation controlled in protected environments
A
- Manual windows - asides and roof (apex) - Warm air rises through roof and cold air sucked in through side windows
- Motored windows
- Electric fans - produce air movement
- Netted sides
