Protected Plant Production

Course CodeBHT223
Fee CodeS2
Duration (approx)100 hours
QualificationStatement of Attainment

Learn to Grow Plants in a Greenhouse

  • Learn to grow crops or other plants in a greenhouse, shade house or other protected environment
  • Discover ways to grow plants in places they might not normally be grown
  • Learn techniques to grow plants faster and out of season, for the nursery trade or fruit, vegetable and flower markets

Lesson Structure

There are 7 lessons in this course:

  1. Structures for Protected Cropping
  2. Environmental Control
  3. Cladding Materials and their Properties
  4. Irrigation and Nutrition
  5. Relationship between Production techniques and Horticultural practices
  6. Harvest and Post Harvest Technology
  7. Risk Assessment

Each lesson culminates in an assignment which is submitted to the school, marked by the school's tutors and returned to you with any relevant suggestions, comments, and if necessary, extra reading.

Aims

  • Describe and Evaluate the type and shape of modern growing structures
  • Describe and evaluate environmental controls in protected cropping
  • Explain the nature of solar radiation, transmission properties of glass and its substitutes
  • Determine the water requirements of a crop; and methods of irrigation.
  • Relate horticultural principles to the production and harvesting of a range of crops.
  • Evaluate the factors involved in marketing protected crops
  • Evaluate the factors involved in marketing protected crops
  • Undertake risk assessment.

What You Will Do

  • Identify the main types of growing structure
  • Relate use of structures to shape and type of construction
  • Identify the range of environmental factors controlled within a growing structure
  • Describe the use of the equipment used to measure and monitor these factors
  • Name and describe a range of types of environmental controls
  • Evaluate the use of IT facilities for environmental control
  • Describe the meaning of daylight and explain the role of sunlight and diffused light
  • Relate time of year to the quantity and quality of available light
  • Evaluate how the shape and orientation of a structure will affect light transmission
  • Assess the effectiveness of glass and cladding alternatives for light transmission
  • Describe the durability and insulation properties of glass and alternative materials
  • Select and describe appropriate systems of irrigation for plants grown in situ
  • Select and describe appropriate systems of irrigation for container grown plants
  • Specify and evaluate systems for incorporating plant nutrients into the irrigation water
  • Explain the effects of environmental control on a range of plants
  • Relate the essential features necessary for successful plant establishment and development to their underlying scientific principles.
  • Describe the production of a range of crops
  • State the optimum stage of growth for harvesting a range of crops
  • Describe the harvesting systems for protected crops
  • Explain how shelf life can be affected by pre and post harvesting treatment of the crop
  • State the factors to be considered when marketing crops
  • Evaluate alternative marketing outlets
  • Relate packaging & presentation to marketing
  • Assess benefits to the grower and customer, of grading a crop before marketing
  • Determine elements of risk in the practical operations associated with protected plant production.
  • Identify safe working practices

 
 
What are the Options for Covering a Greenhouse
 
Through constant research new covering materials (or new ways of using old materials) are improved and released onto the market. Materials are developed to suit regional climatic conditions or even microclimates. Manufacturers for example have addressed issues such as excessive dripping, UV breakdown of the cladding and heat retention in poly-houses. This now makes the Poly-house an attractive proposition for a lot of growers as it is also a very cost effective and easily dismantled alternative to houses that have rigid cladding.
 
When choosing covering materials for a growing structure it is important to consider:
  • Insulation (the materials ability to hold heat in).
  • Light transmission (how much of the light reaching the greenhouse will travel through the covering). Some materials will become increasingly opaque over time reducing the amount of light being transmitted.
  • Cost (some materials are far more expensive initially to buy).
  • Durability (how much wear and tear they can withstand).
 
Glass 
Glass is very rigid so it has low flexibility and can't be used on tunnel type structures. It is one of the best materials for insulation, light transmission and durability (will last 50 to 100 years), but the most expensive. It is generally more resistant to storms than most other materials, however they are often damaged during hail storm and can be dangerous, and difficult, to clean up if it is broken. It is more readily cleaned than most other covering materials (this is normally only required for some of the longer lasting materials). Glass for greenhouses is usually double strength, triple strength and tempered triple strength is also available. Low iron glass is sometimes also used and has the best ability for light transmission. 
 
 
Coreflute/Polyflute
This is semi-rigid, with two layers of plastic joined together by a corrugated ribbing in between. Insulation qualities are good, light transmission is good but less than glass or PVC film, cost is reasonably inexpensive given that it will normally last for at least ten years. It has good resistance to inclement weather, and won't shatter like glass. Small puncture holes can be readily patched. It comes in large sheets or rolls and is easy to work with or handle. The large size of the sheeting also reduces heating losses because of gaps between sheets, which can occur with other materials used in smaller sizes (e.g. glass sheets). It is flexible enough to be used on tunnel and arch type greenhouses. Algae can sometimes be a problem on and between the sheets. It also tends to collect dust. 
 
Corrugated PVC Sheet
A semi rigid material, of moderate to high cost, average durability, with good insulation qualities, but light transmission is lower than most of the alternatives.
 
 
Polycarbonate
Long lasting, very strong, expensive. Available in clear or smoky grey sheets, corrugated or 'Grecca'. Excellent light transmission, flexible and easy to work with. Collects dust. Looks good. They tend to yellow over a period of time.
 
 
Corrugated Fibreglass Sheet
Semi rigid, similar to acrylic coated PVC sheet but more expensive. Light transmission not as good as alternatives (i.e.: glass, coreflute, PVC Film). Becomes yellow and brittle with age. Not as widely used today.
 
 
PVC Film  
A very flexible material that is cheap to buy. It has a short lifespan (a few years normally), and is susceptible to damage from hail, winds, storms, etc. There are many different types of films  some have reasonable insulation and good light transmission properties, others are poor. Some have inhibitors that reduce the effect of Ultraviolet light, which is the major contributor to the breakdown of most of these films. Condensation forming on the inside can result in dripping (on plants and you), and can lead to heat loss. In areas where damage from weather is not a major problem then PVC film can be the most cost efficient covering material. It is sometimes used as a double cover to improve insulation, but some light transmission is lost. These films can flap noisily in the wind, particularly if poorly erected. Polyhouses are better sealed than glasshouses and tend to get hotter than glasshouses, and more humid.
 
 
Reinforced PVC Film
Same as PVC film, but with woven thread embedded in the plastic to provide reinforcement  this improves its strength and durability. 
 
There is slightly less light transmission, which at times can be an advantage, depending on the type of plants being grown.  It is more expensive than standard PVC film.
Thin-skin plastics covers are also available and are manufactured using the latest technology. They are usually 200 micron on the outside and 150 micron inside and feature UV stabilised polymers, EVA infra-red heat retention and anti condensation drip protection
 
 

More from ACS