What do you do when it doesn’t rain in winter?

Whatever the weather is like in the Barossa Valley today, Marcos Bonada will be compensating for a lack of rain – and in a number of different ways.

With colleagues from the South Australian Research and Development Institute* (SARDI) and other researchers from CSIRO, Dr Bonada is trialling different irrigation approaches and combinations to try to find the best way to respond to the lower winter rainfall that is becoming a reality in many parts of Australia. The project has been funded by Wine Australia.

‘In most of our cooler regions the vines rely on the moisture stored in the soil for most of their spring and a good part of their summer growth’, he said. ‘Irrigation is only a supplement to maintain the canopy later in the season in most seasons. If we get a dry winter, we go into spring with quite an empty soil profile and the question is how best to manage this.’

The first point to be clear about is that it is best to manage the dry conditions as they arise. Previous research, backed up by early findings from this new trial, shows that if you ignore the problem or just try to compensate by irrigating more heavily in spring, yields suffer. ‘All we got were great big canopies with not many grapes’, Dr Bonada said.

Working in the vineyard at SARDI’s research station near Nuriootpa, the researchers erect a series of rain shelters in autumn and take them down again in spring. Under each one, they try different combinations of sprinklers and dripper irrigation during winter then compare the results with a control site left open to the elements.

‘We’ve done two proper seasons and have just begun our third’, Dr Bonada said.

‘In the first season the vines that were under the covers, whether they had drippers or sprinklers, didn’t perform as well as the ones that were exposed. In the next season, the vines that had the sprinklers did as well as the ones that were exposed, but the drippers still didn’t perform well.’

That’s probably not surprising; a sprinkler should be a better substitute for rain than a dripper because it covers a greater area of soil. And that’s important in cooler regions, where the vine roots are spread right across the row.

However, many vineyards use drippers and it would be a big decision for owners and managers to invest in a new system. So, if the current study continues to show that traditional drippers used to apply water during winter don’t quite cut it, then the next phase of research is to try to develop better regimes for dripper management.

‘Do you put more water on into spring, for example, or look at different ways of applying irrigation? At the moment, we just do fortnightly applications but maybe we are better to apply smaller amounts more regularly or larger amounts less frequently’, Dr Bonada said.

‘Or do we look at installing drippers in different configurations; for example, burying of the dripper line down the mid row so you can water a wider area of soil surface.’

* SARDI is a division of Primary Industries and Regions SA (PIRSA).