Leaf area and yield: Achieving vine balance


Managing vine balance is a key challenge for winegrowers in variable weather conditions. How do we balance vine productive capacity and fruit weight to achieve the desirable yield and fruit characteristics?

According to Bates et al. (2011), too much leaf area relative to fruit weight may result in reduced fruit quality while insufficient leaf area relative to fruit weight may delay ripening. Such observations suggest there may be an optimal leaf area to fruit weight ratio to maximize desirable wine characteristics.   

A 2014 study by Auzmendi and Holzapfel sheds light on the relationship between leaf area, a key indicator of vine capacity, and fruit weight. Obviously, this relationship is of a great interest to the wine industry not only for its consequences on yield but also regarding the maintenance of vineyard productivity level, hence vineyard economic sustainability.

In this study, the authors investigated the impact of four different defoliation treatments on Merlot in Australia. While previous studies only looked at data at harvest, Auzmendi and Holzapfel collected weekly leaf and fruit samples from veraison to harvest. From there, they analyzed correlations between leaf area to fruit weight ratio and other fruit characteristics like berry weight, sugar concentration and anthocyanins.

The results enabled the authors to identify optimal ratios to maximize each of the quantities of interest. Interestingly, the authors found that the optimal ratio to achieve maximum anthocyanins was greater than that to achieve maximum sugar. However, same maximum berry weight could be achieved while imposing a wide range of ratio values.

Implications for this year

As we discuss in a previous blog post,  the 2017 conditions in northern California indicate the possibility of high amounts of nitrogen available with a strong foliar development rate. We do not know yet the full range of implications this will have on vine water needs and yield.  However, greater leaf area size and higher leaf concentration in Nitrogen should:

  • affect crop coefficient, potentially increasing vine water needs for a same climatic demand and,
  • boost plant photosynthetic activity.

To connect the dots between what happens early season with its impact on yield and fruit composition at the end of the season, it is important to monitor different plant and fruit indexes continuously. Benefits from season-long monitoring techniques will result in improved vineyard management practices that can be modulated according to site-specific responses.

As an example, vineyard management decisions can be improved by linking early stages of canopy development (typically the first 100 days post bud break) with their consequences on vine fruit production (typically yeast assimilable nitrogen in pulp content, berry susceptibility to dehydration or maximum berry size). Then, the analysis of plant and fruit indexes variations will pave the way to improved fertilization and irrigation techniques.

This continuous vineyard monitoring enables vineyard managers and winemakers to catch problems earlier and come up with relevant, site specific and timely strategies affecting canopy or water management. Until recently, vineyard managers and winemakers had to use labor-intensive and destructive methods to collect samples. Now, Fruition Sciences provides a suite of non-destructive and cost-effective solutions to help understand vineyard performances throughout the season and even from one season to the next.

Fruition Sciences offers a full suite of products addressing a variety of vine health monitoring needs to enhance fruit and wine quality.

Our DualexⓇ Signature product provides detailed nitrogen accumulation profile so that vineyards can apply fertilizer where and when it’s needed. Another benefits is to get insight of the potential adverse effect of saline irrigation on nutrient uptake.

Our Physiocap product helps growers identify where wood biomass accumulates in your vineyard to improve pruning decisions and track vineyard response to increased crop load.

Our Bacchimeter Ⓡ Map helps vineyards optimize harvesting decisions based on areas of uniform fruit coloration.

Posted by Vintage Report

The Vintage Report is a unique forum that aims to gather the industry’s most prominent vintners and scientists to discuss the previous vintage, present the latest innovative research and share technical advances in viticulture and enology.

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