Best practice sites were selected from each of the crop specific benchmarking exercises. The managers of these sites were interviewed, and common best management practices were identified, as detailed below.

Rate irrigation highly within the management system

All of the case study irrigators cited irrigation as either one of the most important factors in their production system, or the single most important factor. An example is given by this quote from one of the case study interviews, "Irrigation is always number one".

Of course this needs to translate into action in order to have any impact on management input and production output. Two further quotes illustrate this point, "There's no point in doing second best, it's a waste of money", and "It's worth the money we put into it, it's worth the effort we put into it every day...".

When irrigation is seen as a low priority, it is no wonder if management input is minor, and if irrigation performance is poor. Likewise, it is not surprising that the best irrigators all place irrigation as a high priority in their growing system, and that their management input into irrigation is of a high level.

It is also very significant that most of the case study growers exhibit a high level of management input across the whole enterprise. It is not a case of concentrating on irrigation alone. Successful fruit growers tend to practice intensive management in all areas of the total growing system.

Get to know the soils on the property

Efficient irrigation is very difficult without good information about the capacity of the soil that is being irrigated to retain water and make it available to the roots of the crop, and in what layers of the soil profile the roots of the crop are growing.

Soil surveys are mandatory before approval to transfer a water allocation from the Murray-Darling system onto vacant land, and are extremely useful for appropriate crop selection, irrigation system layout, and irrigation management once the crop is planted. Guidelines for irrigation development in South Australia will soon be published {Primary Industries and Resources SA In Press #1270}, and are already available for Sunraysia {Sunraysia Rural Water Authority 1993 #1280}).

Even on existing plantings, irrigation management can be greatly improved by an understanding of the soils. After augering holes across the property to look at rootzone depth, one case study grower said, "You feel a bit more comfortable, ... the top might be drying out a bit, but you know that (the roots are) down there, getting the water from down below".

It is recommended that a professional be employed to undertake the soil survey, as they can provide much valuable information beyond the simple classification of the soil textures in the soil profile.

On small properties it may be possible to join with a group of close neighbours, and have a larger total area surveyed at once. This shares some of the fixed costs amongst more participants, and makes use of the economies of scale available by conducting a large survey.

Design and maintain irrigation systems correctly

Poor irrigation system operation can make good irrigation management almost impossible. A number of the case study growers cited irrigation system setup, age and maintenance as limiting factors in their ability to manage irrigation as well as they would like.

The irrigation industry in Australia operates according to a set of standard practices for irrigation system design and operation, as follows:

• variation in emitter discharge rate between any two emitters within a valve unit should not exceed ±5%.
• for non-pressure compensating emitters, this can be approximated by restricting the variation in emitter pressure between any two emitters within a valve unit within ±10%.
• emitter pressure at all emitters should lie within the range of pressures recommended by the manufacturer.
• distribution uniformity for a full cover irrigation system should aim to exceed 75%, and less than 67% is unacceptable.

All of these standard practices should be strictly adhered to in the design stage. The use of Certified Irrigation Designers under the Irrigation Association of Australia's (IAA) Certified Irrigation Designer (CID) program is highly recommended. All designs should take account of soil survey results and contours.

As irrigation systems age, overall pressure decreases and flow rate increases as nozzles wear, and variation in both increases. Distribution uniformity usually decreases. Existing irrigation systems should undergo a general check annually, preferably during the non-irrigation season to allow major faults to be remedied. Drip/micro and undertree sprinkler systems require regular flushing, at least annually, and possibly chemical treatment, especially drip/micro irrigation systems.

Drip/micro and undertree sprinkler systems should undergo a more thorough test every 2 to 4 years, while overhead sprinkler systems require a detailed test every 5 to 10 years. Replacement or overhaul of components should be conducted as required to return the system operation to the standard practices outlined above.

The selection and maintenance of the pumping plant for an irrigation enterprise can have a dramatic impact on the financial efficiency of the enterprise. Selection should not be based entirely on capital cost, as running costs are a very significant component of the total cost of pumping. Consultants can conduct pump performance tests, but regular overhauling (every 3 to 5 years) is the best means of maintaining the performance of an irrigation pumping plant.

Monitor all aspects of each irrigation event

Monitoring is vital to efficient irrigation management, but monitoring is not confined simply to the decision of when to irrigate. All aspects of the irrigation event should be monitored, to allow adjustments to be made to refine irrigation management.

This is best described by a quote from one of the case studies, "Monitoring is split into many things,....before the irrigation, ....during the irrigation, ....and after the irrigation...."

Monitoring of soil moisture before an irrigation is important in scheduling the timing of irrigations, so as to avoid prolonged periods of stress due to inadequate soil moisture, without applying unnecessary irrigations which lead to excessive drainage, and possibly to waterlogging.

Monitoring of system performance and uniformity of application during the irrigation allows adjustments to the system configuration as required, in order to apply the water more evenly over the area being irrigated. This is not necessary at every irrigation, but is an aspect of system maintenance as discussed above.

Monitoring of soil moisture after an irrigation event can provide valuable information about the fate of the water applied, especially if information is available at a number of depths within the soil profile. Inadequate depth of irrigation can lead to salinity problems within the rootzone, whilst over-irrigation leads to excessive drainage. Monitoring can identify problems with the depth of irrigation applied, and allows irrigation depth to be adjusted in the future.

Use objective monitoring tools to schedule irrigation

Monitoring for irrigation scheduling can take many forms, and there is a vast array of tools available. Whilst there is no one "correct" tool or approach, it is vitally important that scheduling is based on quantitative measurements.

All of the case study irrigators used at least one objective monitoring tool, usually a soil based device, in determining the timing of irrigations, although the tools used varied widely. The important thing, however, is that they measured something, rather than relying on intuition, the calender, or when the neighbours watered.

This is related to IBMP 4, regarding monitoring, and has an impact on the quality of the information on which decisions are based. If subjective or qualitative methods of scheduling are used, it is very difficult to be consistent from one irrigation event to another. Good quantitative information provides consistency and confidence in management decisions.

Use more than one tool for scheduling irrigation

Whilst it is important to use an objective monitoring tool to schedule irrigations, it is dangerous to rely exclusively on a single information source, and to ignore other evidence which may suggest that there are problems with the irrigation regime.

There are many ways to assess the water status of the crop, some rather less precise but no less useful as indicators of irrigation success.

All of the case study irrigators used a range of information sources in making decisions on when to irrigate, and how much to apply. Typically, much of the decision relied on a particular tool, but in all cases other factors were taken into account.

The use of additional sources of information improves the quality and reliability of the information on which management decisions are based, and thus ultimately improves the quality of the decisions themselves.

Some of the alternative sources of information that case study irrigators made use of included:

• Regularly walking through the orchard, monitoring the appearance of the trees/vines for evidence of stress.
• Periodically digging holes to check soil moisture visually or by feel.
• Checking drains and testwells after each irrigation to assess the level of drainage produced by the irrigation.
• Monitoring weather patterns and the weather forecast, to aid in predicting irrigations.
• Knowledge of the crop cycle, and especially of the critical periods during which stress should be avoided.

Retain control of irrigation scheduling

With modern technology, it is possible to set up irrigation systems to operate entirely automatically, based on the readings from a probe or a set of probes. This is tempting, as it leaves one less thing for the irrigator to worry about.

Similarly, it is easy to allow a consultant to dictate the irrigation schedule, based on his or her measurements, or to blindly irrigate because the scheduling tool being used indicates that it is time to.

The case study irrigators all firmly held onto control of irrigation scheduling, that is, they took into account the data from the scheduling tool or the recommendation of the consultant, but retained the power to vary the schedule using their own judgement, and the use of other tools.

Ultimately, it is the management skill of the individual manager which determines how well the site performs, and good managers back their own judgement, based on their knowledge of their property, rather than blindly following the advice of a machine or an outsider.

Remain open to new information

Openness to new ideas, and actively seeking out information are important attributes in successful farmers of any crop. In a list of "Best Practices of Top Managers", from an analysis of case studies of Canadian farm managers (Anonymous, 1995), one of the seven best practices cited is; "Top managers have extensive personal networks, which they actively maintain and nurture. These networks provide timely information on a multitude of subjects and issues."

The Riverland/Sunraysia case study irrigators cited a range of different ways in which they obtained access to information about irrigation. All of them saw this process as important, and were willing to talk to anyone with something to offer, even if they later discarded the particular information as not applicable to their situation.

In the case of larger, corporate operations, employee education was seen as important, as was encouraging the employees to make a meaningful contribution toward management decisions.

One extremely interesting observation was that the second top performing irrigator in this citrus sample, and the top performing irrigator in a similar winegrape sample have both been in the horticultural industry for only a short time (around 5 years). Both came into the industry with no prior knowledge, and learnt by asking others and seeking out information from any source available.

There is a lesson for those who have had long experience in the industry and may feel that they know all there is to know about irrigation.

There is always more to learn. There are always better ways to do things..

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