Garden Irrigation Course. Design irrigation systems, understand the different methods of irrigating for turf and gardens.

Course Code: BHT210
Fee Code: S2
Duration (approx) Duration (approx) 100 hours
Qualification Statement of Attainment
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  • Learn to irrigate plants in gardens
  • Learn from highly qualified and experienced professional horticulturists
  • A course for nurserymen, gardeners, garden managers, park managers, turf managers and others


The main objective of irrigation schemes or systems is to produce a particular desired pattern of plant growth.
Maximum vegetative growth does not necessarily correspond to maximum yield of the part of the plant desired e.g. fruit, nuts, or roots. In addition, achieving maximum yield may require inefficient use of available resources, whether it is land, water, equipment, or labour. 'Optimum yield' is usually the desired objective. This has been defined as the yield at which the benefit/cost ratio is at maximum, although even this may be hard to achieve if any of the resources required for the irrigation system e.g. land, water, or equipment is limited. Therefore, it is important to clearly define the purpose or desired outcome of an irrigation system



Well watered plants are healthier, look better, resist disease, live longer, and in the case of crops, produce more.

Irrigation schemes may also have other outcomes. Large-scale schemes may have an impact on human settlement patterns, causing local migrations of labour to or from irrigated areas with subsequent changes in the availability and cost of housing and services.

Land prices may also be severely affected as land use patterns change. Impoundment of rivers and streams into dams and lakes can result in major environmental changes (such as changes to river characteristics and to flora and fauna populations) in areas both adjacent and far removed from those features. Small scale, even down to individual garden size systems, can still cause far-reaching changes. For example, the base flow component (year-round flow) of many urban streams derives almost entirely from home irrigation of gardens. If this was to stop these streams would cease flowing for much of the year. In addition, much of the excess water from irrigation systems that flow to streams, rivers and lakes is high in chemicals leached out of gardens or other crop areas. These chemicals, particularly nitrogen and phosphorous from fertilisers and pesticides, can cause major changes in vegetation and animal populations in and adjacent to water bodies.


Water for irrigation is generally obtained from one or more of the following sources:

  • On-site storage such as dams or tanks where runoff is collected and stored for later use
  • Bore water or underground wells
  • Irrigation channels where water is distributed from storage facilities often large distances away
  • ­From streams, lakes or rivers From mains or town water systems (usually carried by pipes and/or aqueducts or channels).



Before undertaking or designing a large-scale irrigation project, a feasibility study should be undertaken to show whether it is desirable to commit resources such as capital, labour, time, land, etc. to such a project. Specialist irrigation consultants are used for large projects, as many complex and far-reaching factors such as topographic features, national and international agricultural and financial markets, transport and communications networks, state and federal policies need to be considered.  

The economics of small irrigation systems, including systems for nurseries, farms and even home gardens, also need to be evaluated. Factors to consider include the availability of materials, the expertise and cost required to install and operate the system, and the outcomes and profitability of the system.


Micro Irrigation

Micro irrigation can use either drippers (creating a slow drip or trickle of water); or micro sprays. These methods can ensure water is delivered to only where it is needed. It needs only low pressure and discharge is slow so that water is able to soak in therefore avoiding puddling or runoff.
Widely used in ornamental gardens, vegetable and container growing, micro irrigation can be a particularly efficient way of irrigating when water resources are limited.
It is quite simple install, but some planning must be done to make it work well.
An important initial step is to measure your water flow or pressure. This can simply done by placing a bucket under your tap and measuring how long it takes for the bucket to fill. You should ensure no other tap is being used at the same time. If the bucket takes 15 seconds to fill, then you have 40 litres per minute. Remember this should be done from several taps as the flow rate can often vary, particularly from front to back. The pressure should influence which nozzles to use. If it is very high pressure you made need to use a pressure regulating valve at the water source.
It is important to prepare a plan of your property, measuring boundaries and areas to be watered, also take into account the different sort of areas to be irrigated, for example, shade house, lawn, perennials. Gather some product leaflets, these usually have much useful information on spray patterns available and connections that are needed.
Several points should be remembered when selecting which equipment to use.
Drippers are more suited:
  • To watering individual plants such as potted plants and isolated trees and shrubs.
  • They work better in heavy clay soils where penetration is slow.
  • The concentrated wetting pattern they provide means they are better on severe slopes (located up the slope from the plant).
  • They are preferable for plants which may suffer mildew, etc, if watered from above.
  • They will still work when water pressure is extremely low.
  • They help keep weeds down by less soil being damp enough for seed germination.
Micro sprays can either be spray jets discharging a course to fine spray or sprays which discharge the water in streams or fingers. Both are suited to:
  • Fitting into any garden shape with a variety of watering patterns and flow rates available.
  • Free draining soils because of vertical draining patterns of such soils (as apposed to a horizontal pattern in heavy clay soils). This also means they better for shallow rooted ornamentals, shrubs and annuals generally.
Micro sprays are better for:
  • exposed areas subject to wind.
  • penetrating dense foliage and compact garden beds.
Spray Jets are suited to:
  • protected areas and shade houses.
  • areas requiring a micro climate, such as a fernery.
Also available are Misters to increase humidity and Rotor sprays for larger areas.
Once all this information is taken in to consideration you should be able to tell what is needed where and how much equipment you will need to buy.
Remember that you will have to install different lines if you want to use drippers and sprays, as they work on different pressures, though they can be connected to the same tap with two shut off valves and a tee piece.
When installing a system it can be either above or below ground, but lay it down first on the surface while you follow your plan. Use connection pieces rather than forcing the hose round sharp bends. Flush out the system before connecting nozzles and incorporate a filter into the system which should be regularly cleaned as blocked filters are the most common cause of failure.
To minimise water wastage watering at the most suitable time and in the proper manner is a must. Firstly you should consider how much watering needs to be done according to the plants and soil present. If you have a garden with native or mediterranean plants frequent watering will not be as necessary as it is for a vegetable garden or annual bed. Observe your plants and see how long they last before they start showing signs that watering is necessary. Plants suffering lack of water may show signs such leaf wilt, leaf yellowing, leaf burning and stunted growth, though it is not recommended to wait for such symptoms. Over watering can result in soft, lush, leggy growth with few flowers or fruit and a susceptibility to disease. Too much watering will leach nutrients from the soil.
Also observe your soil, a free draining sandy soil with delicate ornamentals may need watering up to twice a day in dry weather, while a heavier clay soil which holds a lot of water may require watering once every three days. Do not water on a strictly regular basis, make sure it is needed.
The time and manner of watering should also be considered. It is much better to water heavily, less frequently, as this will encourage deeper roots and make the plant less susceptible to dry periods. Though there are plants which are naturally shallow rooted and require more frequent water. Do not water during the heat of the day, as much of the moisture will be evaporated into the air and top layer of warm soil. It is much better to water in the evening or early morning. If you have an automated system with a timer, watering in the middle of the night is a good idea, particularly with large irrigation systems, as the water pressure is usually better then. Evening and night watering though can produce mildew problems as the leaves stay wet for a long period.
When timing your watering according to the weather, it must be kept in mind that a windy day can be more drying than a hot day, and that long periods of cloud cover do not mean that the soil is not drying out plants still drink up water both in sun and shade.


Lesson Structure

There are 10 lessons in this course:

  1. Introduction to Irrigation
    • Objective of irrigation
    • A wider view
    • Water sources
    • Improving water quality
    • Water quality problems
    • Physical impurities -sediment. turbidity, colour
    • Chemical impurities -hardness, alkalinity, corrosion, iron, salinity, tastes and odours
    • Biological impurities - algae, microorganisms
  2. Soil Characteristics
    • Understanding soils - sand, silt, clay, organic material
    • Naming the soil
    • Different soils for different purposes
    • Improving soils
    • Chemical soil properties - pH, sodicity, salinity
    • Physical soil properties - uniformity, available soil water capacity, infiltration, internal drainage
    • Kinds of soil moisture
    • Gravitational water
    • Capillary water
    • Hygroscopic water
    • Transpiration and Wilting Point
    • Feel test for estimating soil moisture
    • Fertigation
  3. Estimating Plant Needs and Irrigation Scheduling
    • When to irrigate
    • Symptoms of water deficiency
    • Symptoms of water excess
    • Checklist for home gardeners
    • Timing of irrigations
    • Measuring water available to plants
    • Calculating field capacity
    • Calculating permanent wilting point
    • Available moisture range
    • Rooting depths of selected plants
    • Water extraction by roots
    • irrigation calculations
    • Irrigation system efficiency
    • Estimating water needs
    • Estimated water loss under different climatic conditions
    • Tensiometers
    • Water requirements of turf grasses
    • Importance of schedules
    • Water volumes and duration
  4. Drainage
    • Reasons for drainage
    • Improving permeability during construction
    • Cultivation
    • Adding soil ameliorants
    • Chemical treatments
    • Improving surface drainage after construction -sand slitting, aerating, sub soiling
    • Drain layout - herringbone, grid
    • Outlet
    • Gradients
    • Distance between pies
    • Drain depth
    • Drain types
    • Laing drains
    • Dams and water storage -site choice, size
    • Soil degradation
    • Erosion - water, wind, control
    • Soil acidification
    • Soil compaction
    • Chemical residues
    • Waste water treatment using reed beds
    • Suitable plants
  5. Types of Irrigation Systems
    • Gravity systems, pressurised systems
    • Sub surface systems, surface systems
    • Flood irrigation -border check, hillside, furrow
    • Pressurised systems - drip, sprinkler
    • Conventional systems - portable, semi permanent, permanent
    • Mechanised systems - travelling irrigators - soft hose, gard hose, boom types
    • Centre pivot irrigation systems
    • System components
    • Electric drive, hydraulic drive, water drive
    • Linear move systems, drive system
    • Fixed sprinkler systems -hand move, hose move, permeant
    • Quick coupling
    • Sprinkler heads - spray, rotating
    • Drive mechanisms - impact drive, gear, ball, cam, hex, cam gear drives
    • Design considerations
  6. Trickle Systems
    • Reasons to choose trickle
    • Do it yourself micro irrigation for amateurs
    • Time duration for watering
    • Automated systems
    • Microjet irrigation
    • Trickle system maintenance
    • Cleaning filters
    • Flushing
    • Using chlorine, doses, continuous chlorination
  7. Design Specifications
    • System components
    • Hydraulics - pressure
    • Measuring pressure - bourdon gauge, head of water
    • Calculating discharge or flow
    • Bernoulli's Equation
    • Velocity
    • Friction loss in systems
    • Water hammer
  8. Pumps and Filters
    • Types of pumps - piston, radial, mixed flow, axial flow
    • Pumps and pressure systems
    • Shallow well pumps, deep well pumps
    • Pumping mechanisms - piston, centrifugal, turbine
    • When a centrifugal pump fails
    • Preventing clogging in trickle irrigation
    • Controllers - automated, manual
  9. Selecting the Right System for a Plant
    • Water saving measures
    • Filtration
    • Flood, sprinkler, trickle irrigation
    • Case studies - putting greens, ornamental gardens, etc
  10. Design and Operation of Systems
    • Cyclic watering
    • Pulse watering
    • Irrigation schedules
    • Sprinkler spacings
    • Considering sprinkler performance in design
    • Electrical factors
    • Electric powered automatic systems
    • Design considerations


  • 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
    • 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.


Some people make a career out of irrigation; while others may use this course to broaden and deepen their understanding of how to grow plants, making them a better horticulturist, gardener, landscaper, nurseryman or farmer.
Anyone who works in the management of gardens, parks, turf or plant nurseries, can benefit greatly from developing a deeper understanding of irrigation, and how to manage the water requirements of  plants -precisely what this course will help you to achieve.
Irrigation companies employ people to both supply and install irrigation equipment. This course can be a very worthwhile training for anyone working in either.
If you want to learn more about irrigation of gardens, this is an excellent place to start.


  • Home gardeners
  • Professional gardeners
  • Those working at an irrigation retailer
  • Garden designers
  • Landscapers
Member of the Future Farmers Network

UK Register of Learning Providers, UK PRN10000112

Alternative Technology Association Member

Accredited ACS Global Partner

Member of the Nursery and Garden Industry Association since 1993

Member of Study Gold Coast

Recognised since 1999 by IARC

Course Contributors

The following academics were involved in the development and/or updating of this course.

Barbara Seguel

Teacher and Researcher, Biologist, Aquaculture expert.
Barbara has a B.Sc. and M.Sc in Aquaculture Engineering.
Over the past decade, Barbara has worked in Hawaii, Mexico, Chile, New Zealand, and is now settled in Australia. She has co authored severa

Rosemary Davies (Horticulturist)

Rosemary trained in Horticulture at Melbourne Universities Burnley campus; studying all aspects of horticulture -vegetable and fruit production, landscaping, amenity, turf, aboriculture and the horticultural sciences.
Initially she worked with the Depart

Dr. Lynette Morgan (Crops)

Lyn has a broad expertise in horticulture and crop production. Her first job was on a mushroom farm, and at university she undertook a major project studying tomatoes. She has studied nursery production and written books on hydroponic production of herbs.

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