Horticulture Science Chapter 12

Controlled-Environment Horticulture

Horticulture Science Chapter 12

Controlled-Environment Horticulture

Student Learning ObjectivesStudent Learning Objectives•Discuss different designs, construction materials, and locations of greenhouses.•Describe the methods of controlling indor plant growth factors for the benefit of the crops. •Describe how greenhouses are used in the production of horticulture plants. •Compare and contrast greenhouse and field production of crops.

Student Learning ObjectivesStudent Learning Objectives•Compare and contrast types of greenhouses. •Identify and describe greenhouse glazing materials.

•Describe the functions of the headhouse.•Describe greenhouse bench options.

Chapter 12.1

Controlled-Environment Facilities and Their Operation – What is a

greenhouse?

Page #389

What factors are necessary for plant

growth? • 1. • 2. • 3. • 4. • 5.

• Controlled Environment: humans, not nature determine the factors, and the change

What is a greenhouse? • Greenhouse: specially constructed

building for growing plants under controlled conditions. Must allow light transmission!

• Main Factors to consider: – Types– Glazing (covering) material – Location

Chapter 12.2

Greenhouse Design and Construction

Page #390

What are the common greenhouse designs?

1. Even-span greenhouse structures are single houses that have roofs with an even pitch and an even width. - AKA: freestanding or A-Frame – May also use a hoophouse/headhouse: attached

building for storage or office. – Most common type – This is our greenhouse at North Mac!

What are the common greenhouse designs?

2. Uneven-span greenhouses have unequal pitches and widths. – Use of this style is limited to hillsides. – Rare in Illinois

What are the common greenhouse designs?

3. Quonset Greenhouse: or Gothic Arch - usually smaller- arched roof - “old fashion” type, not seen much today

What are the common greenhouse designs?

3. The lean-to greenhouse or coldframe shares a wall with a building and relies on the building structure to provide some support for the greenhouse roof.- possible disadvantages?

What are the common greenhouse designs?

4. Ridge-and-furrow greenhouse structures consist of a number of greenhouses connected along the length of the house. – Ridge-and-furrow greenhouses are

best oriented north and south to reduce permanent shadows on the crops, which are created by the gutters.

– Figure 12-8 page 393– Creates a greenhouse range

What are the common greenhouse designs?

5. Retractable-roof greenhouse designs allow the roof to be opened and closed.

6. Saw-tooth: page 394

What are the common greenhouse designs?

7. Shadehouses are structures used to protect plants from wind, heat, and light intensity. – Synthetic shade cloth is the most widely used

covering material.

Greenhouse Construction

• The greenhouse framework supports the greenhouse covering material.

• Should need Little maintenance• Allow light to pass – no shadow• Light weight material• Withstand humidity

Material For Framework?

• Metal • Wood

What materials are used for greenhouse glazing?

• The covering of the greenhouse is referred to as the glazing.

• Considerations in choosing a glazing material include – durability– light transmission– cost– affects on heating costs

Greenhouse Glazing Materials

• Glass– It has the highest light transmission. – Available in several grades and weights– The fact that it is very long lasting can make it

less costly than other glazing materials in the long run.

– Tempered glass is stronger than regular glass. – Tempered glass may still break during

hailstorms, and it has a high initial cost.

Greenhouse Glazing Materials

• Film Plastic (Flexible Sheets)• Woven polyethylene, polyvinyl fluoride,

polyvinyl chloride, etc. • Polyethylene sheets are stretched over

the greenhouse framework; it is not very durable and must be replaced every one to three years depending on the thickness used.

Greenhouse Glazing Materials

• Structured sheets, including polycarbonate, acrylic, and fiberglass materials, have grown in popularity. – Sheets made with double walls offer good

insulation.

Structured Sheet Glazing Materials1. Polycarbonate structured sheets are most widely used because they have good light transmission, they resist hail damage, and they are easy to work with. – Polycarbonate is much stronger than glass, but it

is lighter in weight. – In addition, polycarbonate has good insulation

properties and is flame retardant.– Our Greenhouse at North Mac!

Structured Sheet Glazing Materials

2. Acrylic structured sheets have high light transmission, but they cost more than polycarbonate sheets, are prone to hail damage, and are less flexible.

Structured Sheet Glazing Materials

3. Fiberglass – It discolors after 7 to 10 years and provides

poor insulation. – Fiberglass loses light transmission as it wears

out, and it becomes extremely flammable as it ages and the fibers become exposed.

Other Greenhouse Considerations

• Greenhouses should be as air tight as possible to keep pests, wind and temperature variation out!

• Consider the ground covering in the greenhouse:– Rock– Bare soil– concrete

Greenhouse Locations p. #400• Considerations when planning:

– Market – Accessibility– Climate conditions– Topography– Utilities – Labor supply– Zoning laws – Future Expansions

Greenhouse Orientation

• One of the most important factors when building!

• No tall structures (buildings/trees) be in the vicinity

• Natural Light availability? • Our region: east – west direction

Greenhouse Bench Options

• The greenhouse bench is the structure that holds the plants above the ground.

• Materials used for benches include expanded galvanized steel, aluminum, plastic, and rot-resistant wood.

• Expanded galvanized steel provides good air circulation and allows water to drain from pots.

Things to consider when selecting benches…

• Flat surface• Air circulation• Drainage• Materials

Greenhouse Bench Options

• Benches should be narrow enough for workers to reach for plants and to provide care.

• Benches are arranged in the greenhouse with aisle space and growing space in mind.

• Bench space vs. floor space

Bench Layout (Arrangement)

– Longitudinal - Typically used for fresh flower production. This type arrangement allows for mechanization, but it is difficult for employees to move across the greenhouse.

– Cross benching - Provides for easy accessibility to all benches but does not maximize growing space.

– Peninsular - Provides accessibility by employees, while maximizing the growing area.

Greenhouse Bench Options

1. Movable benches 2. Pyramid benches 2. Rolling benches or a type of movable

bench maximize growing space by limiting space for aisles.

• The benches are placed on pipes.• With little effort, the entire bench can be

moved from side to side.

Chapter 12.3

Internal Environmental Controls

Page #405