Issue link: http://winesandvines.uberflip.com/i/658375
70 WINES&VINES April 2016 GRAPEGROWING the requirements, the more im- pact and validity the designation Alsace Grand cru would have." She continues: "A good property (producing Merlot in St. Emil- lion/Pomerol) may well do an additional summer prune to fur- ther restrict yield to make only, say, 3,000 quarts of wine for every 2.5 acres. A basic Merlot from California's Central Valley, France's Languedoc or Italy's Veneto may have been made to about three or four times this yield, and the taste is obviously stretched accordingly." Halliday and Johnson also note caveats with respect to the HYLQ relationship, including hail and rot. Yet, in general, these phrases "the stricter the require- ments, the more impact and va- lidity" and "stretched accordingly" imply a direct dependence of quality that arises from increased concentrations of good flavors in fruit from lower-yielding grape- vines—like that of Curve 1. Claims that low yield is key to wine quality imply a relationship unlike Curve 2. Some high-end wines in California carry back labels touting their extremely low yield, which implies a relation- ship consistent with Curve 3 or possibly Curve 1. The complexity of yield A l t h o u g h t h e n a t u r e o f t h e yield-quality relationship is fun- damentally important to those in the business, there has been surprisingly little direct effort t o r e s o l v e i t . C r o p y i e l d i n grapevine production depends on many factors over two sea- sons: varieties, weather and cultural practices. The propen- sity to initiate flower clusters and the number of flowers in a cluster varies among wine grape varieties, but also depends on environmental conditions in- cluding but not limited to tem- perature, light on the developing bud and vine water status. Fruit set (the fraction of retained flowers) of any variety is sensi- tive to environmental factors such as untimely rain and low temperatures. Vine row spacing (established at planting) affects yield rather directly. Once a vineyard is established, pruning takes place before the season begins, and shoot and cluster thinning during the season is the main means of regulating yield. Water and nutrient supply are usually regulated with the o b j e c t i v e s o f d e s i r a b l e v i n e growth and fruit quality, and therefore they impact yield as well. Because the sources of yield are so varied, the task of determining the facts about HYLQ is enormous. It is important to note that the HYLQ concept tells us that whether yield is reduced by win- ter pruning to lower shoots per vine, summer pruning (or clus- ter thinning) or poor fruit set, each action is said to have the same positive impact on flavor intensity. Thus, in the popular press, it is the yield per se that determines the fruit quality. If great winegrowing is as simple as getting as far to the left along Curve 1 or 3 as possible, then it is hardly a challenge worth ap- preciating. In the following sec- t i o n s , w e w i l l t u r n t o t h e empirical evidence related to various means of altering yield, keeping in mind that with so many paths to yield, it could turn out that none of the hypo- thetical scenarios for quality response to yield are a reliable generalization. Although the nature of the yield- quality relationship is fundamentally important to those in the business, there has been surprisingly little direct effort to resolve it.