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October 2016 WINES&VINES 79 WINE EAST GRAPEGROWING populations at the research sites— may explain the variable impact of native vegetation on reducing vine size. Growers in Long Island, N.Y., have been experimenting with under-trellis mowing of native vegetation several times through- out the season. Costs of under- trellis mowing compare well to the herbicide regime (approximately $120 per acre). 13 Alice Wise, se- nior viticulture research and ex- tension associate with Cornell Cooperative Extension of Suffolk County, N.Y., pointed out that, while more growers are interested in under-trellis mowing, a deter- rent for its adoption may be the price of suitable mowers, which range "from $3,500 for a single head to more than $15,000 for two mowing heads with a row middle mower" (see top photo on page 80). Wise also noted that "under- vine mowing is a viable option for under-vine management, though it is best suited to mature, laser- planted vineyards because of the risk of trunk damage to young vines and crooked trunks." 13 Impact of under-trellis cover crops on root distribution and size Research on under-trellis cover crops focused more on the mani- festations of cover crop/vine com- petition than on the mechanisms. Understanding how cover crops impact the distribution of grape- vine roots and other morphologi- cal and physiological root traits may help to reduce uncertainty of vine response to cover cropping. We found that vines managed with under-trellis cover crops for a short term (three years) and long term (seven years) had a deeper distribution of fine roots, which are responsible for the ma- jority of water and nutrient up- take, compared to those managed with an under-trellis bare soil strip. 7,14 A decreased proliferation of fine roots in shallow soil layers (0-20 cm) due to cover crop com- petition may reduce vine access to nutrients, often more abun- dant in shallow rather than deep soil strata. 14 We also found that vines man- aged with under-vine creeping red fescue over a seven-year period had a 45% lower absorptive root biomass than those growing with- out under-vine grass. Surprisingly, despite the shift in root distribu- tion toward low-fertility deep soil and smaller root system, vines growing with under-vine grass ac- cessed enough resources to main- tain aboveground vegetative growth, suggesting that grape- vines may be capable of acclimat- ing to cover crop competition. 14 This study, however, was con- ducted during a humid season (rainfall from grapevine bud burst to harvest = 584 mm). A drier year or a less fertile site may result in more reduced canopy growth. Other impacts of under-trellis management strategies Under-trellis management strate- gies can impact leachate composi- tion. 4,13 For example, dissolved organic carbon leaching was re- duced by maintaining a green cover—white clover (Trifolium repens) or native vegetation— under the trellis compared to conventional under-trellis strate- gies such as herbicide (glyphosate) application or soil cultivation. 4 Thus, not only herbicide applica- tion but also soil cultivation can increase carbon loss from the soil, in addition to increasing its erosiv- ity. Also, total nitrogen concentra- tion was higher in leachate samples collected from under-trellis glyphosate and white clover plots compared to those from native vegetation or cultivation plots. 4 In several studies, the use of under-trellis cover crops did not significantly impact, either posi- tively or negatively, juice chemis- try—including total soluble sugar (Brix), pH and titratable acidity (TA), or total phenolics or antho- cyanins. 12 In other cases, an in- crease in juice Brix or reduction in TA (1 g/L) was attributed to the devigorating effect and increased fruit sunlight exposure brought on by the presence of under-trellis cover crops. 12,15 The cost of establishing and maintaining under trellis cover crops A partial budget analysis was de- veloped for one of the studies on under-trellis cover crops using - B E C O PA D - Y E A S T & E N Z Y M E S - C R U S H PA D E Q U I P M E N T - S T E R I L E F I LT R AT I O N - W I N E R Y H O S E - O A K A LT E R N AT I V E S EASTERN WINE LABS Serving the Analytical needs of East Coast Wineries WWW.EASTERNWINELABS.COM Ph 609-859-4302 Cell 609-668-2854 chemist@easternwinelabs.com AOAC Member EasternWineLab_Mar09.qxp 1/22/09 9:47 AM Page 1 Hauser Packaging Quality European Bottles • DIAM Corks Custom Packaging • Finger Lakes Warehouse 888-600-2671 • hauserpack.com