Soil and winegrape quality in biodynamically and organically managed vineyards
By: Reeve, Jennifer R.
Wines produced from biodynamically grown grapes have received increasing attention. Similar to organic agriculture, biodynamics eliminates synthetic chem. fertilizers and pesticides. The primary difference between the 2 farming systems is that biodynamics uses a series of soil and plant amendments, called preparations., said to stimulate the soil and enhance plant health and quality of produce. Whether these preperationns. actually augment soil or winegrape quality is unclear and controversial. A long-term, replicated, 4.9-ha study was initiated in 1996 on a com. Merlot vineyard near Ukiah, California, to investigate the effects of these biodynamic preparations. on soil and winegrape quality. The study consisted of 2 treatments, biodynamic and organic (the control), each replicated 4 times in a randomized, complete block design. All management practices were the same in all plots, except for the addition of the preparations to the biodynamic treatment. No differences were found in soil quality in the first 6 years. Nutrient analyses of leaf tissue, clusters per vine, yield per vine, cluster weight, and berry weight showed no differences. Although average pruning weights. for both treatments in 2001 to 2003 fell within the optimal range of 0.3 to 0.6 kg/m for producing high-quality winegrapes, ratios of yield to pruning weight were significantly different (p < 0.05) and indicated that the biodynamic treatment had ideal vine balance for producing high-quality winegrapes but that the control vines were slightly overcropped. Biodynamically treated winegrapes had significantly higher (p < 0.05) Brix and notably higher (p < 0.1) total phenols and total anthocyanins in 2003. Biodynamic preparations may affect winegrape canopy and chem. but were not shown to affect the soil parameters or tissue nutrients measured in this study.