Lesson Structure:  Irrigation Management (Horticulture) BHT305

There are 8 lessons:

1  Waste water and recycling:

• Introduction
• Humans and Water
• Water and Plant Growth
• Minimising Plant Requirements
• Xeriscaping
• Waste Water
• Types of Water Wastage: Evaporation, Seepage, Runoff, Overspray, Scheduling
• Recycling Waste Water
• Waste Water Treatment (Reed-Beds)
• Suitable Plants

2  Measuring water usage

• Climate
• The Hydrological Cycle: Direct Fall onto the Land Surface, Intercepted Rainfall, Water Falling Directly into Water-Bodies
• Infiltration
• Rainfall: Distribution, Variability, Frequency, Intensity, Evaporation, Effective Rainfall, Calculating Effective Rainfall
• Temperature
• Wind
• Microclimates
• Special Applications:  Irrigation of Vines, Efficient Orchard Irrigation, Scheduling, Regulated Deficit Irrigation
• Measuring Soil Moisture
• Water Monitoring Equipment: Gypsum Blocks, Neutron Probe Meters, Tensiometers, Ceramic Block Sensors, Heat Sensor System, Dielectric Scanning Device, Applications
• Measuring Water Usage: Soil Characteristics, Unique Crop Requirements, Local Evapotranspiration Levels

3  Drainage

• Introduction
• Drainage: Rainfall
• Improving Permeability During Construction: Cultivation, Adding Soil Ameliorants, Chemical Treatments
• Improving Surface Drainage After Construction: Sand Slitting, Aerating, Sub Soiling
• Layout of Drains: Outlet, Gradients, Distance Between Drainage Pipes, Depth Of Drains
• Types of Drains
• Laying the Drain
• Contingencies to Deal With Flood

4  Irrigation controllers

• Irrigation Controllers
• Controllers: Automatic Controllers, Time Clocks, Computerised Tap Controllers, Manual Controllers, Battery Powered Solenoid Valves
• Water Volumes and Duration
• Technical Data Sheet Mechanical Tap Timer
• Technical Data Sheet Electronic Tap Timer
• Pumps and Pressure Systems
• Types of Pumps: Table: Comparison Of Pump Types, Shallow Well Pumps, Deep Well Pumps
• Pumping Mechanisms: Piston Pumps, Centrifugal Pumps, Turbine Pumps
• When a Centrifugal Pump Fails to Operate

5  System maintenance

• Maintenance of Watering Systems: System Maintenance
• Maintenance Procedures and Scheduling: Periodic Inspections, Routine Upkeep, Contingency Work, Scheduling Work
• Maintaining Trickle Irrigation Systems: Cleaning Filters, Flushing the System, Use of Chlorine, Chlorination in Doses, Continuous Chlorination
• Maintaining Water Quality
• How to Improve the Quality of Water From Any Source
• Problems of Water Quality and Their Remedies – Physical Impurities: Sediment, Turbidity, Colour
• Problems of Water Quality and Their Remedies – Chemical Impurities: Hardness, Alkalinity, Corrosion, Iron, Salinity, Tastes and Odours
• Problems of Water Quality and Their Remedies – Biological Impurities: Algae, Micro organisms
• Problems of Water Quality and Their Remedies – Bacteriological Impurities

6  Fertigation

• Introduction
• Advantages of Fertigation
• Disadvantages of Fertigation
• Fertigation Types: Proportional Application, Quantitative Application, Continuous Application, Three Stage Application
• Fertiliser Injectors: Pump Injectors, Pressure Differential Injectors, Suction Injectors, Fertiliser Applications
• Plant Nursery Fertiliser Injection Techniques

7  Design evaluation

• Design Considerations: Water availability, Source and quality of water, Regulations, Site details, Finances and labour requirements
• Importance of Design
• Surface/Flood Irrigation: Border Check System, Hillside Flooding, Furrow Irrigation
• Sprinkler Irrigation: Wind Velocity and Wetting Pattern, Droplet Size, Rotational Speed, Evaporation
• Trickle Irrigation: Evaporation, Saves Labour, Does Not Get Water Where It’s Not Wanted, Reduces Weeds, Reduces Disease
• Microjet Irrigation
• Do it Yourself Micro Irrigation Systems
• Time Length of Watering
• Automatic Systems
• Water Management in Turf

8  System design

• Pre-Planning Information: What is the soil like? dimensions and other measurements, Relevant by laws, Environment of the locality, Available resources, Client/owner preferencies and priorities, photos of site
• Type of System
• Underground Pipes
• Drainage

Learning Goals: Irrigation Management (Horticulture) BHT305

• Devise ways to optimise water efficiency (ie. minimise wastage), during irrigation of plants
• Schedule irrigation for a large scale situation such as a large nursery, crop, turf, garden or pasture
• Analyse the design of different drainage systems
• Understand the operation of irrigation controllers and pumps for appropriate tasks
• Manage the maintenance of irrigation systems, both small and large scale
• Manage the fertigation of plants through an irrigation system
• Evaluate the design of large scale irrigation systems
• Design an irrigation system, including its drainage

Practicals:

• Contact your regional or local water authority. Ask them for information on their water restriction policy. When are water restrictions enforced and how do they affect water users? Focus mainly on the problems experienced by agricultural users. Consider ways that users can minimise their dependence on water access? Write a brief report on your findings and submit with your assignment.
• Visit a property that uses irrigation. Discuss with the manager the methods that are used to decide when to water and how much water to use. Is irrigation an important element in the success or otherwise of the property?
• Choose a drainage system to which you can get access. Remember a drainage system is designed to cope with most situations. They are many examples in your local everyday environment. Some examples might include the guttering on your house or even on your car. Discuss how the system operates and include sketches to show design features.
• Contact a number of companies that offer computerised and technology solutions to irrigation. Obtain prices and information if possible on appropriate working installations of their product. If possible try a follow up visit at least one (1) operation and discuss the product with a user as well as a retailer. If distance or transport is a problem then you could try writing for this information, which would be suitable for the purpose of this set task.
• Visit a property that uses large irrigation systems. Enquire about the maintenance of their systems. Consider how is water quality monitored and maintained?
• Investigate at least two irrigation supply companies.
• Observe how they service customers. Consider: are there any other services they provide?

MANAGE THE FERTIGATION OF PLANTS THROUGH AN IRRIGATION SYSTEM

Fertigation involves the controlled injection of liquid fertiliser to irrigation water. Fertigation is distinguished from chemigation which involves the application of other chemicals such as insecticides and fungicides to irrigation systems and which is therefore, more tightly regulated due to the implications for human health in agricultural irrigation.

Fertigation is only suited to irrigation systems that have been well designed to meet the needs of the plants they are intended to water. A good design means even distribution of water and fertiliser.

There are four main requirements of a fertigation. It should be able to regulate:
• The amount of fertiliser required.
• The proportion of fertiliser in the solution.
• The start and finish time for fertiliser application.
• The duration of the fertiliser application.

Advantages of Fertigation
There are a number of advantages of fertigation if appropriate equipment and fertilisers are chosen and the system is well maintained.

• If used in conjunction with an efficient irrigation system, both water and nutrients supplied through fertigation can be delivered at rates to achieve the optimum yield from a given crop.
• Fertiliser applications can easily be adjusted throughout the growing season and in accordance with specific crop requirements.
• The delivery of solid fertilisers is often labour intensive, whereas fertigation is not.
• Other fertilisers may be washed away in run-off or leached into the subsoil beyond the root systems of plants if rain follows soon after application and therefore may have to be re-applied.
• Fertigation offers a more measured approach to fertilisation by delivering a continuous
  application of uniform, small amounts of fertiliser directly around plant roots.

With fertigation, compaction around plants caused by foot traffic is reduced thereby improving the rate of uptake of nutrients by plants.

Disadvantages of Fertigation
Fertigation is applicable to some systems and not others.

• it works well with trickle irrigation but can cause problems if used with sprinklers that do not evenly distribute the fertiliser.
• Corrosion to fittings and nozzles is another side effect to be aware of when deciding whether or not to use fertigation. As such, those parts of an irrigation system which come into contact with nutrients should be made of non-corrosive materials such as stainless steel and plastics.
• Irrigation maintenance costs could increase. If so, then fertigation may not be a viable option.
• Plants in pots which are usually given slow release fertilisers tend to develop high salinity levels during fertigation.
• The inclusion of fertiliser in mists such as in a shade house or greenhouse can produce algal problems. The nutrients in the irrigation system might also cause the presence of bacteria and slime moulds.

In order to overcome these issues, the irrigation system should be regularly cleaned by running acid or chlorine through it – but not when fertiliser is being applied. Therefore, good hygiene practices must be observed.

FERTIGATION TYPES
The main types of fertigation system are as follows:

Proportional Application
With this system, the fertiliser application rate is proportional to the rate of discharge of water. For example, one litre of solution in 200 litres of water. The proportion can be easily increased when plants are using more water and decreased when they are not.

Quantitative Application
This method allows for a given concentration of nutrients to be injected for a particular group of plants. A different concentration may be applied to another group of plants. it is well suited to automatic systems.

Continuous Application
With this method, a constant amount of nutrients is injected throughout the irrigation no matter what the water discharge rate is.

Three Stage Application
This method involves irrigation until the soil is wetted, followed by a period of nutrient injection, and then a further period of irrigation. The latter irrigation is intended to flush out the nutrients from the system.

FERTILISER INJECTORS
Injectors are used in fertigation to provide nutrients to the irrigation water. The correct choice of injector is important. Three main types of injector are as follows:…

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Excerpt From The Course

WATER VOLUMES AND DURATION

The exact procedure to determine the optimum flow rate and number of control stations for any irrigation system is impractical to define.

A general procedure to be followed is:

1) Divide the area to be irrigated into sections having similar water requirements according to plant and soil types and degree of enclosure and shading.

2) Select and design the sprinkler or other irrigation water distribution systems for all sections of the area to be irrigated, selecting tentative water application rates in ranges suitable for each section.

3) Further divide the sections decided upon in step 1 into smaller areas where necessary each requiring approximately the same water flow rate.

4) Calculate the peak daily irrigation water requirements for all sections of the irrigation area from peak monthly evaporation figures or other data where applicable.

5) Calculate the time required to apply the peak daily irrigation water requirements of each section calculated in step 4 using the tentative water application rates selected in step 2.

6) Calculate the total time required to apply the peak daily irrigation water requirements to all the sections selected in step 3.

7) Revise and refine the calculations and tentative decisions made in steps 2, 3, 5, 6 dependent on how the total daily irrigation time calculated in step 6 compares to the time available to carry out the irrigation each day.

Note: when designating your irrigation zones, bear in mind that mature plants require less water than young or establishing plants.

Also, consider that in terms of water usage efficiency, unless there are rain or other sensors built in to the system, a good system is only as good as the programmes which are set in the controller. If you do not set up your watering zones and times accurately, you may end up using more water than watering by hand.