Optimising vine balance in Australian vineyards: developing a toolbox for industry to ensure best practice, sustainability and profitability

Abstract

Canopy management trials conducted in commercial vineyards and at the Waite campus, University of Adelaide, demonstrated that a new tool, VitiCanopy, was effective at capturing canopy architecture differences that resulted in fruit and wine compositional changes and berry and wine sensory differences. Vine balance is more easily measured with VitiCanopy than other traditional measures that are labour intensive. VitiCanopy measurements of leaf area index, canopy porosity and growth rate were also highly correlated with vine performance and quality and can be measured early in the growing season, allowing within season management decisions to be made. These outcomes provide new information and tools that will lead to more informed vineyard management in Australian vineyards.

Summary

Australian vineyards need to produce high quality fruit to remain competitive in the global market. Vineyard practitioners use a variety of management practices to control canopy size and to achieve vine balance. To help assist management decisions, researchers have developed indices to assess vine performance but they are often subjective and/or difficult for growers to apply, hence adoption by industry is low. Also, the link between canopy management, vine balance indices and wine quality has not been clearly understood.

The main objectives of the project were:

• to determine canopy parameters that indicate optimal vine performance and wine quality and evaluate how effectively these can be manipulated using management techniques.
• to develop an accurate, inexpensive, labour saving toolbox for assessing vine balance in the field and deploy this toolbox to the industry.

Experimental field trials on Shiraz (in collaboration with Treasury Wine Estate) and Semillon were carried out across a number of regions (Coonawarra, McLaren Vale, Barossa, Padthaway and Adelaide-Waite Campus). At these sites, canopy manipulation treatments were performed over three seasons and focused on altering vine vigour and yield. Vine performance was assessed using measures of yield and yield components, canopy architecture, berry and wine chemistry and berry and wine sensory.

The project has met the primary objectives and has provided:

• Valuable information on the outcomes of common industry canopy management practices. It was found that the outcome of the same management practice is season and region dependent. This finding is not surprising as a site’s potential is largely due to the environment in which it is grown. Moreover, industry standard practices such as shoot thinning, leaf plucking and bunch thinning, proved ineffective in modifying vine performance in most cases. Practices that were effective are summarised below.
• A better understanding of the effect of cover cropping as a tool to suppress excessive vigour. In all cases, canopy size and yield were effectively reduced with the use of cover crops, however, the effect on berry and wine chemistry was very limited. Wine obtained from cover crop treatments was characterised by riper aromas and a richer mouthfeel.

Information on the use of sacrificial canes as a technique to control vine vigour. The results showed that leaving four sacrificial canes (‘kickers’) successfully suppressed vigour but also dramatically decreased yield with strong carryover effects after two seasons of continuous application. The effects were greater when kickers were removed at veraison compared to flowering. The results also suggest that kickers tend to create high variability in canopy architecture and yield between vines that could complicate vineyard management.

New understanding on the effect of delayed winter pruning. Pruning was carried out after budburst, at EL 9-11, and appeared to be ineffective in delaying ripening and also showed very large yield reductions. Similarly to sacrificial canes, late pruning reduced shoot vigour and also created high vine variability.
Important correlations between canopy parameters, vine balance indices and vine performance. The canopy architecture measures of LAI and porosity correlated better than yield with berry and wine chemistry and sensory measures. The vine balance indicators Y/P and Y/LAI produced very similar correlations with berry and wine chemistry especially when the flowering LAI measure was used. It was also observed that the early season canopy architecture measures are better indicators of grape and wine quality than the veraison measures. Moreover, the canopy growth rate showed interesting links to grape and wine quality. A greater growth rate early in the season correlated positively with grape and wine chemistry measures. Conversely, a greater late season growth rate, from veraison to harvest, was detrimental to quality.

A toolbox in the form of two smartphone Apps, VitiCanopy and VitiSense, was created. VitiCanopy measures canopy architecture as Leaf Area Index (LAI) and canopy porosity. VitiCanopy was tested against traditional destructive methods and dedicated instrumentation with results found to be comparable to those of more established methods. The App is intended as an alternative to other destructive or non-destructive methods to estimate LAI with the advantages of being free, highly portable and providing immediate results. Since the results are geo-referenced, data can be used for GIS applications and mapping. VitiSense, was developed to make sensory assessments more accessible and able to be carried out in-field. Grape growers and winemakers taste grapes before harvest and they rely on the information from this assessment to make decisions on harvest date and grading and allocation of grapes for a specific wine style. VitiSense provides users with an easy tool to perform a structured and geo-referenced berry tasting assessment in the vineyard, and has the potential to be used for other assessments such as wine. The combination of VitiCanopy and VitiSense can provide easy indications of the links between canopy architecture and grape sensory attributes in a vineyard.

VitiCanopy has proved to be a useful tool to assist vineyard management decision making. It can be used to assess the outcome of a management intervention and to calculate canopy growth rate. For example, when VitiCanopy was unable to show a change in canopy architecture after a treatment, the treatment proved ineffective on vine performance. Vine balance can be effectively measured using new indices that calculate LAI and canopy porosity using VitiCanopy with the advantage of being easy and quick to take compared to a measure of pruning weight or destructive measures of leaf area.