Cutting Post Harvest Irrigation: Can it save you money?

Rebecca Bruce DPI Tatura

Reduced water allocations and increasing water costs are likely to remain long term issues for Goulburn Valley fruit growers. What if you could significantly reduce irrigation with no negative effects on the following seasons’ fruit yield or quality? Many growers are using the post harvest period to reduce their total irrigation. It is unknown whether some of these practices may be negatively affecting yield and labour costs due to a potential increase in thinning requirements due to an increase in fruit defects. A Department of Primary Industries (DPI) field day in May at the sites of a research trial on a T204 peach orchard in Toolamba and a WBC pear orchard in Shepparton East was held for local growers to come and see tree response to irrigation cut-backs. Some growers attending the peach demonstration commented that their trees appeared more stressed than those in the trial block, and that their trees defoliated earlier than normal as a result of reduced irrigation applications.

Rebecca Bruce counting flower numbers in a peach block

Deficit irrigation treatments were imposed in the research trials on peach and pear from harvest in February 2008. Irrigation volume applied after harvest ranged from 0% to 200% of normal grower post harvest irrigation, which was around 2.5 megalitres per hectare for the peaches. DPI found that trees receiving less than normal grower irrigation were more stressed than those receiving higher irrigation levels.

To see how the reduction in irrigation post harvest may have affected the following seasons’ crop, and the impact on the length of harvest, DPI measured the number and weight of fruiting and vegetative buds, the duration of flowering and flower numbers.

This season the trees will receive the same amount of irrigation up to harvest. Fruit set and the impact of the deficit treatments on yield and fruit quality will be measured. Restricted levels of irrigation will again be imposed after harvest, and tree stress measurements recorded.

Another field day will be held in early December so that local fruit growers can come along to talk about what DPI has found and what it might mean for their irrigation strategies after harvest 2009. Further information about the field day will be made available closer to December.

For up-to-date information on the trials throughout the season, visit the DPI Fruitcheque website www.dpi.vic.gov.au/fruitcheque and click on the link ‘Introduction to the G.V. Post Harvest Deficit Irrigation Trial’. For more information contact Henry Schneider, DPI Cobram (03) 5871 0615.