Crop control for consistent supply of quality grapes
Abstract
The project aimed to develop and evaluate crop control techniques to stabilise yield from seasonto- season and assess their impact on key wine quality indices; facilitate industry adoption of reliable, robust and objective crop forecasting systems and to continue research into the physiological, environmental and cultural determinants of crop yield components. These issues are addressed in the body of research that was undertaken across a number of sites and varieties in both the warm and cooler regions.
The project has developed techniques, supported by software and manuals, whereby vineyard managers can improve their ability to set and consistently hit yield targets based on ‘informed pruning’, accurate crop forecasting and crop adjustment by shoot thinning or bunch removal, including mechanical thinning. Reponses to imposition of the various crop control techniques on key indices of wine quality varied between seasons and variety. The results indicate that stabilization of wine quality from season to season is much more problematic than achieving yield targets due to the effects of other seasonal factors not related to crop load (eg. temperature during berry development). Adoption of lighter pruning systems, which had high bunch numbers with fewer and smaller berries per bunch enhanced fruit and wine composition provided adequate maturity levels were achieved. In general crop regulation treatments (shoot thinning, bunch removal at veraison, mechanical thinning) advanced maturity, but effects on other indices of fruit quality were small when measured at similar levels of maturity (eg. enhanced berry colour and spectral properties in wine of Shiraz and Cabernet Sauvignon).
Investigations into physiological, environmental and cultural determinants of crop yield components have made significant contributions to enhancement of knowledge in these areas of research. The research has highlighted the importance of both the seasonal and treatment effects on fruitfulness and inflorescence development in spring and subsequent effects on crop development including fruit set and berry development. Seasonal differences in fruit composition (pH, titratable acidity, berry color and phenolics) and wine spectral properties were much larger than effects of pruning or crop thinning when harvested at similar sugar levels. Lighter pruning systems produced higher levels of colour and phenolics in berries and wine, possibly due to differences in canopy structure and fruit exposure as the skin to flesh ratios were similar for all treatments.
Summary
Developed and evaluated crop control techniques to stabilise yield from season-to-season and assessed their impact on key wine quality indices. Facilitated industry adoption of reliable, robust and objective crop forecasting systems. Conducted research into the physiological, environmental and cultural determinants of yield. The research highlighted the importance of seasonal and treatment effects on fruitfulness, inflorescence development in spring and subsequent effects on fruit set and berry development.