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Access Practical Winery & Vineyard's article archive online: practicalwinerylibrary.com TECHNICAL RESOURCE FOR GROWERS & WINERIES 56 Ecological diversity of yeasts to modify wine fermentations By Dr. Kate Howell 60 How green is Willamette Valley? By Neal D. Hulkower 64 Water balance of grape berries By Yun Zhang and Markus Keller, Washington State University 68 Cool-climate solutions for high-vigor vines By Dr. Richard Smart grapegrowing Is there a need for improved vineyard assessment for fruit grading? BY Dr. Peter Dry, Dr. Mardi Longbottom and Marcel Essling, The Australian Wine Research Institute, Glen Osmond, Australia A ssessment schemes are used by wine companies to allocate batches of fruit to particular grades (matched to market requirements). There are many different types of assessment schemes, and they differ in their degree of complexity. At one extreme is a pre-harvest assessment by a viticulturist (a winemaker might or might not participate); up to 10 attributes may be potentially scored, and each attribute classified as "good," "average" or "less than average" (this will be strongly benchmarked within that region). The end result is an allocation to one of four to five grades. At the other extreme is the type of scheme that might comprise multiple inspections: The pre-harvest assessment will be conducted by both viticulturist and winemaker; there are 15 or more vine attributes and seven or more berry attributes, some with up to five categories. The data are collected on a portable computer or similar device and integrated to generate an overall score for grading. The benefit of multi-attribute score sheets is that they provide an opportu52 p r acti c al w i ne ry & v i n e yard J U LY 20 13 nity to integrate many vine characteristics. This is desirable because use of one attribute alone is unlikely to be adequate for the purpose of fruit grading.12 The vine characteristics used for fruit grading can be allocated into one of the following for convenience: •Vine balance, •Canopy microclimate, •Disease, •Berry, or •Yield Some characteristics may fit just as readily into one as another: For example, the extent of lateral shoot development may fit into either "vine balance" or "canopy microclimate." The impact of diseases and other problems such as MOG and sunburn on fruit grade will be discussed in a later article. Vine balance The vine characteristics in this category include: •Leaf area relative to fruit weight, •Percentage growing shoot tips, •Main shoot length, •Extent of lateral shoot development, •Shoot lignifications, and •Time of ripening An overall vine balance "score" is often used in assessment schemes. This is a visual integration of all characteristics, strongly benchmarked within a region. There is no standard method. The leaf area to fruit weight (LA/FW) relationship to wine composition and score is well documented.8,12 However, leaf area and fruit weight per vine are rarely measured in practice because it is considered to be too time-consuming and costly. LA/FW is mainly assessed visually. Percentage active shoot tips (PAS) at véraison, shoot length and extent of lateral shoot growth are all indicators of shoot vigor. PAS is used in many schemes, but it is generally an estimate rather than a precise count. This characteristic is easy to quantify. There is good evidence that cessation of shoot growth by véraison is positively associated with wine quality. This comes from terroir studies19,24 and benchmarking studies with Pinot Noir and Shiraz.26,27 Extent of lateral shoot growth is an indicator of shoot vigor. It is negatively correlated with end-use rating17 and related to canopy density—a high degree of "leafiness" (presumably a consequence of lateral shoot growth) correlated with low wine score for Shiraz. 26 Shoot lignification (SL) is often used in assessment schemes, but there have been relatively few published studies. Wine