Perennial Cover Crops to Optimize Vegetative Growth of Cabernet Sauvignon Grapevines.

Perennial cover crops used to reduce vine vigor and improve canopy characteristics have not been substantially investigated under warm, humid field conditions.   Five complete vineyard floor cover crops were investigated with field grown Cabernet Sauvignon  grapevines over six growing seasons at Dobson, NC.  Tall fescue (Festuca arundinacea)  'KY-31', perennial ryegrass (Lolium perenne), and orchardgrass (Dactylis glomerata) were all effective in reducing annual pruning weights.  Rate of shoot growth in vines grown with Fescue ‘KY-31’ or orchardgrass  was reduced 23% compared to control vines managed with an herbicide strip under the trellis.  Fescue ‘KY-31’ produced the greatest amount of  biomass and resulted in 49% more soil moisture loss than that which occurred from herbicide strip plots over a 45-day period (bloom to rapid onset of ripening) in 2006 as measured with lysimeter. Total N concentration in control vines in 2009 (1.04 %) was significantly greater than total N values of cover crop vines (0.86-0.91%), except with KY-31 fescue (0.96%). Root dry weight, at 60 to 100 cm soil depth, was significantly greater for KY-31 fescue vines compared to control vines, suggesting that treatments caused a downward displacement of grapevine roots. Nematode (Dagger, Xiphimena americanum) populations were significantly greater in perennial ryegrass plots compared to other cover crop treatments (2009).  The use of cover crops generally improved vine canopy characteristics via reduced canopy density and increased fruit exposure.