Irrigation - Gardens

Course CodeBHT210
Fee CodeS2
Duration (approx)100 hours
QualificationStatement of Attainment

Irrigation Design and Installation

Learn about irrigation technique: estimating plant needs, operations, scheduling, pumps, filters, systems, drainage, and more.

  • Learn about the equipment and techniques used for plant watering
  • Learn to irrigate plants in gardens, plant nurseries, indoors, greenhouses, etc.
  • Become a better gardener, nurseryman or horticulturist

Lesson Structure

There are 10 lessons in this course:

  1. Introduction to Irrigation
  2. Soil Characteristics & Problems
  3. Estimating Plant Needs & Irrigation Scheduling
  4. Drainage
  5. Types of Irrigation Systems
  6. Trickle Systems
  7. Design Specifications
  8. Pumps & Filters
  9. Selecting the Right System for a Plant
  10. Design & Operation of Systems.

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.


  • Explain the significance of soil in irrigation.
  • Explain how to determine when to irrigate in a small scale situation.
  • Manage irrigation in a given situation.
  • Explain the significance of different aspects of moving water including: drainage, pumps, filters, storage and recirculation.
  • Select an appropriate irrigation system for a given situation.
  • Explain the principles of design for a simple irrigation system.
  • Design a simple irrigation system.
  • Oversee the installation of an irrigation system.


Irrigation is the technique of supplying a plant’s needs for water. It is an integral part of successful crop production ranking as highly in terms of importance with fertilising and the control of weeds, pests and diseases. Its interrelationship with these other techniques can determine the outcome of the irrigation, whether beneficial or detrimental, depending on the skill with which it was undertaken. For example, irrigation may provide adequate water for successful crop production or it may provide too much. In the latter case, this could cause overloading of drainage systems or cause water tables to rise to the point whereby salts etc. are brought within reach of the plants’ root zones. Water may also make nutrients readily available or it may leach nutrients if applied excessively.


Water is essential to plant growth and is often the major limitation to productivity.  Irrigation is now playing a more important role in horticulture than ever before.  However, depending on the climate, the value of the plant, the value of the land and its suitability for irrigation, the cost, reliability and quality of the water supply, irrigation may or may not be possible or feasible.
Irrigation is most widely undertaken in arid and semi-arid climates where soils may be quite fertile, but natural rainfall is insufficient for plant requirements. It is also undertaken successfully in areas with other climate characteristics where it can be used to overcome water shortages in dry times, thus extending growing seasons and hence the types of crops that can be grown, or simply increasing the range of crops. It may also act as a safeguard against times of irregular or unreliable rainfall. Irrigation requirements may range from the complete supply of a plant's needs over the entire growing season down to the occasional small supplementary needs of plants in severe dry seasons. The use of irrigation to produce improved yields where plants can be grown with just natural rainfall is termed as supplemental irrigation.
It may supplement the existing rainfall and improve growth rates by extending the growth period of the plant, or by ensuring there is adequate moisture during critical periods when the plant is growing most rapidly.  The value of irrigation can vary greatly from year to year depending on the distribution of rainfall during the growth season. Irrigation at appropriate times may also improve the quality of turf or the general health of garden plants.


Soil  Affects Irrigation Requirements

Soil Uniformity

The more uniform the irrigation block, the easier it will be to manage. Problems of patchiness can arise, for example, in hand forming when a cut is made into subsoil that is more clayey or more sandy than the topsoil. So, it is necessary to level the land and examine the soil to the depth of the maximum cut to determine the likely effect on soil texture.


Available soil water capacity

A high available soil water capacity is desirable for crops because the higher it is, the less likely the plant is to become stressed between irrigations. The best soils are generally loams or clay loams. The soil needs to be examined to the likely maximum rooting depth both to determine the available soil water capacity and to ensure there is no bedrock, hardpan or other root impeding layers.



This refers to process of water entry into the soil. It is influenced by:

a) Soil type and soil texture. Sandy soils generally have higher long term water penetration rates than clayey soils.

b) The condition of the surface soil. Water will enter faster if the soil surface is friable and open or is extensively and deeply cracked. Compacted or crusted soil with few cracks has a low infiltration rate.

c) The stability of the surface soil. Low water stability means that the soil crumbs do not stay together when wetted. Low water stability results in slow water penetration unless the soil is sandy. Also, it often results in the formation of a surface crust as the soil dries which will reduce infiltration at the next irrigation.

d) Depth of soil above an impermeable layer. The soil may consist of a light loam topsoil over a clay subsoil or bedrock. In this case, water up over the impermeable layer reduces water penetration.

Extra Books or Reference Materials

  • The course provides you with everything that you need to complete it successfully.
  • Assignments may ask you to look for extra information (eg. by contacting nurseries, visiting gardens or searching the internet), but our school's resources and tutors are always available as a back up. If you hit a "roadblock", we can quickly send you additional information or provide expert advice over the phone or email; to keep you moving in your studies.
  • Some students choose to buy additional references, to take their learning beyond what is essential for the course. If a student wants to buy books, we operate an online bookshop offering ebooks written by staff at the school. Student discounts are available if you are studying with us. The range of e books available is being expanded rapidly, with at least one new ebook being written and published by our staff every month.
  • See  for ebooks (available in pounds stirling). We also sell books through our Australian bookshop (selling in Australian dollars) at


This course is going to be of value to people working in:

  • Parks & gardens
  • Landscaping
  • Irrigation
  • Garden maintenance
  • Green keeping & turf care
  • Garden centres  




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