I just read a study published in the latest edition of the American Journal of Enology and Viticulture by Justin Morris and Gary Main, both from the University of Arkansas.  In their study they found that a 60+10 balanced pruning scheme increased the yield and clusters per vine when compared to a 30+10, but did not affect fruit composition.  So, better yield with the same quality.  When they left spurs to 3 nodes or 6 nodes they found no difference in yield; however, 3 node spurs were found to produce better soluble solids in the fruit and better vine vigor.  Resulting shoots should also be positioned (sometimes called combing) downward  to reduce vine vigor and lower fruit pH.  Vines were grown on either a GDC or SC (single curtain, aka high curtain) training system.

You can read the abstract here: http://ajevonline.org/cgi/content/abstract/61/4/445 or the entire article if you are a member of the society.

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