Vineyard & Winery Management

November/December 2012

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VINEYARD SOIL & CELLAR Solutions for Struggling Vineyards Adjustments in irrigation, soil nutrition and pest control can bolster weak blocks truggling blocks, or weak areas within a block, are not uncom- mon in vineyards. Fortunately, there are ways to ameliorate these sections to achieve the uniformity and quality of fruit desired. The first step is to delineate the area that is struggling. Is it con- fined to a section within a block, or is the entire block suffering from low vigor, variability, poor produc- tion or poor quality? If it is an area within a block, map out the weak section by using either GPS tech- nology or traditional techniques (pen, paper, Excel) to get an idea of the location, quantity and sever- ity of the vines affected. Aerial imagery can be particularly useful for this as well, and many growers hire the services of companies that provide aerial imagery via custom- ized flights that generate an NDVI (normalized difference vegetation index), which provides a visual indi- cation of plant vigor using ratios of the wavelengths of visible and near-infrared sunlight reflected by plants. Once the area is delineated, the next step is to begin the diagnos- tics. Often, the variability within a block can be attributable to differ- ences in the soil. A good start to assessing the cause of the issues would be to look at any soil studies done prior to replant, or to take soil samples within the constraints of the vineyard layout. Many sites are planted wide enough that a mini- excavator can be used to dig soil pits. Pits can show you the depth of the soil layers, if there is any compaction, and samples can be WWW.VWM-ONLINE.COM taken throughout the soil horizons and sent to a lab for analysis of soil composition including pH, organic matter and nutrient content. REMI COHEN Remi Cohen is the director of winemaking & viticulture for Cliff Lede Vineyards in Napa Valley. Her primary areas of expertise include viticulture, sustainable vineyard manage- ment, winemaking, grower and winery rela- tions, and strategic business development. She also writes a wine industry blog, which can be found at blog.vinestowine.com. EXAMINE SOIL DEPTH The variability may simply be caused by a difference in the soil depth, which can be seen with soil pits. For example, the low-vigor section may have a very shallow effective rooting depth, especially in comparison to the remainder of the block. The low-vigor section may be caused by a relatively shal- low hardpan, which could be an impenetrable clay layer or bedrock. Pre-plant ripping of the soil helps reduce the affects of this variability in soil depth. If this was not done prior to planting, in-row ripping and other remedial efforts may need to be employed. Often soil at the top of a hillside block can be shallower than at the bottom of the hill from years of ero- sion and deposit at the bottom. Vine variability may be further compound- ed by irrigation water running off the top of the slope and collecting at the SHORT COURSE Soil pits can help show the cause of variability. Photo: Paul Anamosa, Vine- yard Soil Technologies Digging pits in both the affected areas as well as the healthy ones in the vineyard may show a sig- nificant difference in one or more parameters that could be caus- ing the variability. If it is not pos- sible to dig soil pits, soil cores can be taken to send soil samples and get an idea of soil composition and texture. Identify the struggling area through NDVI or GPS mapping. Diagnose the cause of the prob- lems with soil pits, soil laboratory analysis and pest/disease testing. Modifications to the irrigation sys- tem may be useful. Compost can provide nutrients and increase organic matter. Specific nutrient deficiencies or toxicities can be addressed with lime, gypsum and/or fertilizers. NOV - DEC 2012 VINEYARD & WINERY MANAGEMENT 39

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