Dr Bruno Holzapfel.

Timing of irrigation and nutrition management on grape vines influences both berry composition and vine growth.

Senior research viticulturist, Dr Bruno Holzapfel, said findings of a large field trial would help growers achieve the right balance between vine vigour and fruit quality.

"Water and nitrogen supply are seen as major contributors to shoot growth and yield, but on the other hand the effect on berry quality can be detrimental," Dr Holzapfel, of the National Wine and Grape Industry Centre, Wagga Wagga, said.

"The requirements and uptake of nitrogen and water vary during growing season, therefore the timing of supply can have a significant effect on canopy and berry size, and grape composition."

The Co-operative Research Centre for Viticulture field trial, operating since 2000, investigated the implications of irrigation and nutrition management.

Impacts of nitrogen and irrigation timing included the shading of grapes affecting colour development, competition between vine shoots and fruit, and increased susceptibility to disease under large canopies.

"Our work showed that the timing of nitrogen application and irrigation management altered juice nitrogen composition," Dr Holzapfel said.

"Other fruit parameters, like berry ripeness, colour or size can be improved by applying less water by using either partial rootzone drying (PRD) or regulated deficit irrigation (RDI).

"The improvement of berry composition by using less water often led often to lower yields and smaller canopies.

'While the application of nitrogen at different periods during the growing season did not produce differences in the canopy, PRD and RDI led to reduction in canopy size at season’s end."

The study showed shoot growth in spring was already reduced by these treatments.

"Some of these changes in shoot length, particularly in early spring, could be explained by lower starch reserves in the wood of the trunk and cordon of the vines accumulated in the previous season," he said.

"In the roots this was even more pronounced, where the implementation of PRD and RDI led to significant lower levels.

"This impact on shoot growth eases until sufficient leaf is established and the growth is less dependent on stored reserves."

"The results so far underline the importance of nitrogen and water supply on canopy development during the current and following season."

Contact Dr Bruno Holzapfel, Wagga Wagga, 02 6933 2113.