~ Stephen Tebb, Winemaker
I recently gave a talk at the UC Davis Tahoe Environmental Research Center titled “The Science of Wine”. It was a great evening with a very enthusiastic and engaged audience.
In putting the talk together, I realized how important scientific research and our subsequent understanding of viticulture and fermentation science has allowed us to dramatically improve the “craft” or “art” of winemaking. Science impacts how we think about everything we do in the vineyard and the cellar.
As vintners, we gather scientific data constantly to help inform the many decisions we make. Consider just the vineyard for a moment, where we use a number of scientific advances and tools.
Right now during bloom time or flowering, we are measuring the nutrient status of the vines. We take samples of leaf stem (petioles) and run plant tissue analysis, which lets us know if the vines are deficient or in excess of important nutrients or minerals such as nitrogen, potassium, calcium, boron and zinc to name a few. As result, we are able to act in a specific and targeted way to bring the vines into balance for the duration of the growing season.
Also at this time of the year we pay attention to the vines’ water needs. We want just enough water to maintain the health of the vines, yet not too much to encourage excessive vegetative growth.
We monitor the vineyard with infrared aerial imaging, or more accurately an NDVI image (Normalized Difference Vegetation Index), which is basically an aerial photograph with the vineyard displayed in various colors that clearly maps out the differences in vegetation vigor or stress due to variations in chlorophyll content.
Not only does this scientific tool help in our irrigation strategy, but it also allows us to “see” potential problem areas that we might otherwise overlook on the ground, providing information we can use to target where additional water or nutrients might be applied.
We employ another scientific tool in irrigation management to measure the leaf water potential. Using a small portable pressure chamber, we can measure how much pressure it takes for sap to flow through a leaf stem. The amount of pressure indicates the stress level of the vine and lets us know if we need to irrigate more or less. As this procedure is quick and easy, we can use the scientific data in real time for accurate water application decisions on the spot.
In my UC Davis presentation, I also talked about how scientific observation and documentation assist in the development of American Viticultural Areas (AVA’s). Many factors such as elevation, topography, climate, and soil type are all carefully analyzed, researched and recorded in order to define the characteristics of an appellation such as Howell Mountain, for example.
It is through the systematic analysis of this scientific documentation that we are able to prove what we believe to be true. The same grape varietal produces different and distinctive wine when grown in different locations. I was able to underscore that point with samples of our Robert Craig 2007 Spring Mountain Cabernet Sauvignon and 2007 Mount Veeder Cabernet Sauvignon. Each wine exhibited a unique reflection of where it was grown.
Next installment: The science behind the production process…stay tuned!
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