Optimising canopy function to increase yield while maintaining wine aroma, flavour and colour, with decreased inputs

Abstract

Concern existed that extended use of irrigation strategies such as regulated deficit irrigation (RDI) could reduce vine capacity until the vine becomes uneconomic. Using an existing irrigation trial this project has examined the long-term impact of RDI and a prolonged deficit strategy (PD) in comparison with a well-watered control.

Summary

The increasing use of irrigation strategies such as regulated deficit irrigation (RDI) over the last 15 years has led to concern that a progressive decline in vine ‘capacity’ could occur, reducing the economic viability of a given planting. This project utilised an existing irrigation trial in Sunraysia, an area that produces a significant proportion of Australia’s wine grape crop, to examine the long-term impact of such irrigation strategies and the mitigation of any long-term effects.

The trial site consisted of a 12 year old planting of Cabernet Sauvignon vines on own-roots irrigated using an RDI type strategy, with prolonged deficit (PD) and well-watered control treatments imposed in a replicated block design. The PD treatment extended RDI in both duration and severity by suspending irrigation and allowing soil moisture to be drawn down to a low level for two to three weeks after the milder site standard RDI deficit period. RDI had been used at this site since the vines were planted. The PD treatment had been in place from the 2002/3 season and the well-watered control was altered from additional water during the RDI deficit period alone (from 2002/3) to additional water throughout the season in 2005/6. Use of the well-watered control allowed the speed of recovery of RDI vines from any reduction in ‘capacity’ to be examined as well as acting as a non-water limited comparison for the longer-term impacts of RDI and PD.

Both the RDI and PD treatments reduced canopy size and yield relative to the well watered control, but there was no evidence that these reductions were increasing year-on year. In fact the relative differences were remarkably stable, showing little seasonal variation. These results suggest that not only is the current use of RDI sustainable and unlikely to result in a progressive decline in vine productivity, but further, that RDI strategies can be extended without any risk of such a decline.