Protected Plant Production BHT223

Learn to Grow Crops in a Greenhouse

Extend crop production throughout the year. Study structures for protected cropping, learn how to manage environmental controls, and develop strong practices for growing vegetables, cut flowers, and herbs. Suitable for beginners.

Course Duration: 100 hours

Course Structure

This course consists of 10 lessons.

  1. Structures For Protected Cropping
    • Greenhouses as a business
    • Greenhouse system
    • Components of a greenhouse facility
    • Deciding on what you need
    • Siting greenhouses
    • Suitability of different structures for specific cropping, depending on natural light transmission
    • Cleanliness in the glasshouse
    • Types of greenhouses
    • Greenhouse checklist
    • Framing materials
    • Covering materials
    • Components
    • Commonly used greenhouse designs
    • Shade houses
    • Greenhouse or Conservatory
    • Shade-house Designs
    • Cold frames
  2. Environmental Control
    • Control of the Environment
    • Measurement of environmental factors
    • Moisture
    • Problems with greenhouses
    • Heating & ventilation systems
    • Thermal screens
    • Insulation
    • Lighting equipment
    • Types of lights
    • Artificial light
    • Photosynthesis
    • Environmental factors which effect photosynthesis
    • The meaning of C3 & C4
    • Day-length manipulation
    • Heated propagators
    • Irrigation & nutrition control
    • Optimum growth requirements for certain plants
  3. Cladding Materials And Their Properties
    • Factors affecting light transmission: shape and orientation
    • Covering Materials
    • Rigid & Film plastics
    • Heat Insulation and Cost Effectiveness
    • Light transmission properties
  4. Irrigation
    • The Nursery irrigation program
    • Irrigation practices
    • Irrigation systems
    • Plants and Water
    • Equipment and Methods
    • Automatic systems
    • Sprinklers
    • Overhead spray lines
    • Flood benches
    • Capillary benches
    • Capillary watering
    • Trickle irrigation
    • Watering container plants
    • Precision application techniques
    • Water supply and quality
    • Liquid feed systems
    • Water treatment
    • Water Sources
    • Scheduling Irrigation
    • Maintenance of watering systems
  5. Nursery Nutrition
    • Fertilisers in the greenhouse
    • Plant Nutrients
    • The Nutrient Elements
    • Major Elements
    • Minor Elements
    • Total Salts
    • Diagnoses of nutritional problems
    • Nutrition Management
    • Soils, media and nutrition
    • Pore space in soils and growing media
    • Percolation rates
    • Buffering capacity
    • Cation exchange capacity
    • Soil temperature
    • Soil pH
    • Laboratory testing of soils
    • Soil sampling
    • Nutrient availability & pH
    • Measuring Salinity
    • Methods of Measuring pH
    • Types of Fertilizers
    • Applying Fertilizers
    • Applying nutrients at the propagation stage
    • Fertilizing problems
    • Factors affecting fertilizer application
    • Application of liquid fertilisers
    • Carbon dioxide enrichment in the greenhouse
  6. Relationship Between Production Techniques And Horticultural Practices
    • Which crops are grown under cover?
    • Potting mixes
    • Propagation media
    • Mixes/substrates for starting cuttings/seeds
    • Pots and containers
    • Containers for propagation
    • Potting up plants
    • Shrubs and trees
    • Transplanting Between Pots
    • Tomato production notes
    • Lettuce production notes (Lactuca sativa)
    • Notes for the production of potted Begonias
    • General environmental requirements
    • Growing on areas for container plants
    • Hydroponics
    • The variables of a system
    • Why practice hydroponics?
    • Growth control: chemical and cultural
    • Hormone forms
    • Other chemical treatments
    • Other treatments to improve cutting success
    • Producing VAM inoculum
    • Improving strike rate
    • Sexual propagation
    • Storing seed
    • Difficult seeds
    • Dormancy factors affecting seeds
    • How to sow seeds in containers
    • Germination
    • Planting and crop establishment
  7. Horticultural Management In A Greenhouse: Pests And Diseases
    • Fungi
    • Common fungal problems
    • Pest, disease and disorder control (chemical and cultural)
    • Cultural Controls
    • Current Legislation
    • Biological Control and Integrated Pest Management
    • Beneficial agents
    • Economic thresholds
    • Methods of introduction
    • Major pests, diseases and disorders of crops identified
    • Pests
    • Diseases
    • Diagnosis of problems
    • Finding out what the problem is
    • Tell-tale symptoms
    • Conducting an Inspection
    • IPM (Integrated Pest Management)
    • Non-chemical pest control methods
    • Diagnosis of plant disorders
  8. Harvest & Post Harvest Technology
    • Crop Harvesting
    • Post-harvest Treatments
    • Grading Standards
    • Conditioning for Market
    • Marketing to the Wholesale Market
    • Culture and Management Requirements of Some Greenhouse Crops
    • Harvest and Post-harvest of Selected Orchids
    • Post-harvest Requirements of Mushrooms
    • Grading Systems
    • Fruit grading in the USA
    • Equipment that may be needed in a grading shed
  9. Greenhouse Plants
    • What is a greenhouse plant?
    • What is suited to greenhouse growing?
    • How to grow specific crops
    • Examples of crops
    • Lilium (Lilies, Fam. Liliaceae)
    • The most commonly grown lilies
    • Most commonly grown species
    • Lily cultivation
    • Rosa spp. (Roses, Fam. Rosaceae)
    • Growing conditions and culture: General requirements
    • Greenhouse roses
    • Tomato
  10. Risk Assessment
    • Identifying risk in the workplace
    • Identification of safe working practices
    • Risk Control Methods
    • Risk assessment of protected crop production
    • Using machines to do the heavy work
    • Earthworks
    • Cleaning and Sharpening Tools

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Course Aim   

Learn to Manage Humidity and Other Factors Inside a Greenhouse

Growing in a greenhouse opens up a lot of possibilities for controlling aspects of the crop production; but it can also create an unnatural environment that may have detrimental aspects unless you exercise control properly over the environment.

  • Greenhouse temperatures may not always be optimum for plant growth. They may rise too high or drop too low.
  • Levels of carbon dioxide, oxygen and other gases in the air can become inappropriate for a plant
  • In a sealed off environment humidity can rise beyond what is ideal for crop growth.
  • Light levels may be diminished, or magnified in some greenhouses.

All of these factors are manageable; but managing them requires knowledge and experience.

Relative Humidity and Vapour Pressure Deficit

The amount of moisture held in the air of the growing environment has major effects on many aspects of crop development and disease prevention.  Relative humidity (RH) levels are a measure of the amount of moisture currently held in the greenhouse air and are influenced by factors such as the amount of water vapour given off by the plants during transpiration, any misting, fogging or damping down used for temperature control as well as ambient humidity levels in the air brought into the growing area.  High RH slows the rate of water loss via transpiration from the plants, thus slowing the transport of water and calcium from the roots to developing plant parts.  High humidity also increases the risk of fungal and bacterial pathogen infection, particularly where condensation may wet foliage.  Low RH increases the rate of transpiration and foliage desiccation can occur, plants may also wilt during the warmest part of the day.

Greenhouse sensors often measure both RH and the Vapour pressure deficient (VPD) which is more meaningful from a plant growth perspective than RH.  VPD is the difference between the amount of moisture in the air and how much moisture the air can hold when saturated.  VPD is better than just looking at RH as it takes into account the effect of temperature on the water holding capacity of the air, rather than giving just a relative measure of the water content of the air.  VPD gives an absolute measure of how much more water the air can hold, and how close it is to saturation.  Higher VPD values means that the air has a higher capacity to hold more water and this stimulates plant transpiration from the leaves.  Lower VPD means the air is at or near saturation, so the air cannot take more moisture from the leaf in this high humidity condition.  Higher VPD increases the transpiration demand and assists with prevention of conditions such as blossom end rot, fruit cracking and tip burn.  VPD in crops such as tomatoes are best run below 0.062 psi (0.43 kPa) for good plant growth, however disease infection is most damaging below 0.030 psi, so greenhouse climates are best adjusted to keep above 0.030 to prevent disease outbreaks.

When the air in the greenhouse becomes fully saturated with moisture this is called the `dew point’ or `saturation vapour pressure’ and this is directly related to temperature.  When the dew point is reached, free water forms on the plants and greenhouse structures in the form of condensation which needs to be avoided as it is a major disease risk.  At saturation VPD, plants stop transpiring and physiological disorders start occur.  The size of the vapour pressure deficit tells a grower how close to saturation and condensation the greenhouse environment is.

Controlling Greenhouse Humidity

Controlling the RH or VPD inside a greenhouse is relatively simple – moist air needs to be regularly vented out as the transpiration of a mature crop will bring RH levels up rapidly.  Drier air can be rapidly brought in from outside to lower RH levels on a continual basis.  If the outside air is very humid, lowering RH inside the greenhouse can be more difficult.  Low humidity levels can be rectified with use of techniques such as damping down of the greenhouse floor, evaporation pans or pads (usually installed in front of air inlets which also have a cooling effect on the air), or automatic misting or fogging.

While misting or fogging systems are commonly used for plant propagation from cuttings and other material, in cropping greenhouses they are used to control humidity automatically usually via a number of sensors positioned in the crop canopy and greenhouse which feed data back to a central computer programme.  Misting or fogging is then automatically controlled as required to increase humidity levels to within the optimum range.  Many greenhouses use misting or fogging primarily for temperature reduction during summer, rather than to increase humidity, which in a large, healthy crop tends to run on the high, rather than low side.

Greenhouses Extend the Possibilities for a Farm

Using a greenhouse (or any other protective structure) can make it possible not only to grow things faster; but sometimes grow things that may have otherwise been difficult or impossible to grow.

Greenhouses are used to control the environment which plants grow in. The environment is extremely complex though, and there are many interactions between the different aspects of the environment. The amount of light allowed to get to plants might affect the temperature. If you close the vents or doors of a glasshouse, you may stop the temperature from dropping, but at the same time, you may be changing the balance of gasses in the air. Every time man interferes to alter one thing, he ends up altering a number of things. 

This course shows you how to use a greenhouse, shade house, cloche or other such structure; expanding your understanding and awareness of both what you might grow and how you might best grow a wide range of different crops.

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Fee Information (S2)
Prices in Australian Dollars

PlanAust. PriceOverseas Price
A 1 x $781.66  1 x $710.60
B 2 x $416.96  2 x $379.05

Note: Australian prices include GST. 

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