Executive Summary:

The DPI Dried Vine Fruit Irrigation Benchmarking Project was initiated during the season 2001/02. It was established primarily as a tool for identifying "best irrigation management practices" with the goal of improving irrigators' performance and efficiency.

This annual report contains nine years of growers' data, from Victoria and New South Wales, covering seasons 2002/03 to 2010/11. Examples of the main information gathered for each site were the amount of water used, the variety, the irrigation system and scheduling method, the pumping and water costs, and the crop yields and gross returns per site.

The study continued to attract growers' interest, with an increasing number of participants and field sites since season 2002/03. In season 2010/11, the number of growers and sites reached 31 and 82 respectively. The total area for the sites studied covered 183 ha, which is almost twice the total area in season 2002/03. The grape varieties planted at the different sites were Carina, Gordo, Sultana, Sunmuscat, Waltham Cross and Zante Currant. It should be noted that this may not be a representative sample of growers and care must be adopted when attempting to extrapolate the results to the broader irrigation community.

Season 2010/11 was a bad year in terms of yield for many growers, e. g. 84% of sites had an average yield reduction of 52% compared to 2010. This was mostly as a result of the favourable conditions for diseases and loss in fruit quality associated with the above normal rainfall events during summer 2010/11. The maximum yield in 2011 was only 6.5 t/ha, while 75% of sites had yields lower than 3.8 t/ha. The median yield in 2011 (2.8 t/ha) was furthermore the lowest result over the nine-year period studied.

In terms of average yield per irrigation system type, the averages for drip (3.3 t/ha), furrow (2.2 t/ha), low level (2.4 t/ha) and overhead (3.5 t/ha) irrigated sites in season 2010/11 were respectively 58%, 49%, 42% and 61% of their corresponding individual nine-year average.

The higher effective rainfall during summer 2010/11 considerably reduced the need for supplementary irrigation. As expected, the irrigation water applied at most sites in 2011 was much lower than in the previous years. Compared to the previous irrigation season, the sites used on average between 3.0 ML/ha (drip) and 5.5 ML/ha (overhead) less water. The average water applied at drip irrigated sites in 2010/11 also continued to be lower than the averages at sites with other irrigation systems.

Throughout the nine-year period, sites using the tensiometer method applied on average the least amount of water, i. e. 5.3 ML/ha, while an average of 6.2 ML/ha was used at sites using capacitance probes.

The irrigation application efficiency results showed there were a higher percentage of sites deemed under-irrigating in 2010/11, i.e. with application efficiency above 90%. That could either be a result of the overestimation of effective rainfall following rainfall events, or else due to the deliberate irrigation reduction at sites that were expecting low yields after diseases and crop damage.

It is important to note that irrigation application efficiency is a useful performance indicator only when it is used in conjunction with other performance indicators such as yield and water applied. The results in 2011 illustrated that point when some sites had high application efficiencies but with zero yields and low water applications.

Over the nine-year period, drip irrigation was the most reliable system to achieve application efficiencies within the recommended 85-90% range.

The results of crop production per water applied at most sites were generally higher in 2011 compared to 2010. In most cases, the higher values were the result of the yields obtained with much less applied irrigation.

A variety comparison showed Gordo had once again the highest seasonal average gross return per megalitre of water applied ($3590/ML in 2010/11). Conversely, Currant ($860/ML) continued to be the lowest performing variety.

In terms of gross return per dollar water input, the low irrigation applied and low water usage costs in 2011 resulted in higher returns at sites not significantly affected by diseases and yield reductions.

The gross return and cost performance indicators should be treated only as technical information, as they are determined using a partial system approach. A sound economic analysis is beyond the scope of the present study, since it would involve a whole system approach and more complex analysis, e.g. to perform marginal analysis.

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