1 Introduction
1.1 BACKGROUND
Within its responsibility of providing policy advice to government, MAF Policy has identified the need to:
"Promote sustainable farm and orchard management planning including collaborative development of best management practice guidelines, and to provide environmental indicators or reporting systems for monitoring soil quality, water quality, air quality, biodiversity and energy use."
Within the objective of facilitating resource management, sustainable irrigation needs to be encouraged and promoted, and an Operational Research Programme was formulated to meet this need. The programme aimed to develop procedures that would lead to more sustainable irrigation through having the procedures accepted and adopted by the New Zealand farming industry.
A study to develop a set of indicators that farmers could use to monitor the sustainability of their irrigation practices was funded by MAF Policy (MAF Technical Paper 00/03). This was followed by the development of Best Management Guidelines for Sustainable Irrigated Agriculture. (MAF Technical Paper 00/05).
1.2 SUMMARY OF INDICATORS AND GUIDELINES REPORTS
The main concept behind the Indicators of Sustainable Irrigated Agriculture Report (MAF Technical Paper 00/03), and Best Management Guidelines Report (MAF Technical Paper 00/05), is that the fundamental goal of irrigation is to maximise net profit over the long term. If that is not achieved, irrigation will not be sustainable. In doing this, environmental and social goals must also be met because they have a direct effect on the long-term profitability of farming.
Maximising long-term profit requires farmers to make the best daily, seasonal and long-term decisions that they can. Making the right decisions is best achieved if clear objectives with measurable performance criteria are specified. The Indicators Report defines the objectives of irrigation and recommends indicators that can be determined and used as performance measures. Feedback from the indicators can be used to continually improve the sustainability of farming practices.
The Best Management Guidelines Report explains how the basic information required to calculate the recommended indicators can be obtained and used to assess performance. The report provides extensive information on how irrigation systems can be designed and operated to maximise performance.
How the system is designed, operated and managed is also vital to the success of irrigation. Daily decisions, such as where to irrigate and how much water to apply must be made. Irrigation strategies, crop choices, and crop priorities for allocating water have to be determined, and the irrigation system must be maintained. In the longer-term, decisions such as applying for changes or reapplying for resource consents and replacement or upgrading of irrigation equipment must also be made.
1.3 TESTING THE CONCEPT AND GUIDELINES
Following the development of Indicators of Sustainable Irrigated Agriculture and Best Management Guidelines for Sustainable Irrigated Agriculture, two projects, the first to test the measurement and use of the indicators (Wells et al., 1998), and the second to test the use of the Guidelines on three farms (McIndoe et al, 1998), were implemented.
A fundamental requirement of using the Best Management Guidelines and Indicators is that depths of water applied and soil moisture status must be measured. Without being able to realistically measure both of these components, the Guidelines are of limited use.
The Best Management Guidelines were only partially field-tested in the 1997/98 irrigation season, for three main reasons. These were difficulties in obtaining and installing suitable flow measuring equipment, difficulties in providing regular soil moisture data to the farmers, and an extreme summer of very high temperatures and little rainfall.
Because of these difficulties, limited testing of the Guidelines was carried out only on the two dairy farms. The project objective for the cropping farm was changed to carry out a case study to demonstrate the benefits of improving the irrigation design on the farm financial and environmental performance (Borrie et al, 1998).
To ensure that the full value of the Indicators and Best Management Guidelines were achievable, MAF Policy decided to continue the programme for a further irrigation season.
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