Consistent production of good yields of high quality grapes is complicated by the highly variable nature of vineyards. Many factors influence grapevine management, many of them beyond the control of the grower.
Seasonal variation is primarily driven by climate and variation in weather. For example, cold periods at flowering or fruitset can reduce yield while warm temperatures at bud initiation will tend to increase next year’s yield (assuming there are no subsequent perturbations such as frost in the following season). As a consequence, seasonal variation in yield and quality is difficult to predict.
Meanwhile, land is variable and therefore its productivity is too. For this reason, there is no such thing as a uniform vineyard and many vineyard attributes (soils, topography, vine vigour, yield, fruit composition) can be seen to be variable even when the vineyard is under conventional uniform management.
The recent availability of Precision Viticulture tools (remote sensing, the global positioning system, geographical information systems, yield monitoring and mapping, and high resolution soil survey) now make it possible to better understand and manage this variability, whether the objective is to try to reduce it through the targeting of management inputs, or taking advantage of it through strategies such as selective harvesting and product streaming.
Wine Australia has been an active partner in research into spatial variability in vineyards and is currently supporting projects that seek to better enable growers and their advisers to measure, map and understand their variability, and understand the interaction between grape yield and quality. Wine Australia also invests in improved methods for yield estimation and fruit quality assessment.