Newsletter Archives > Viticulture

In the Vineyard : Spring 2004

Measuring Vineyard Variability, To Grow More Consistent Grapes

Science without religion is lame, religion without science is blind. -- Albert Einstein.

Here at Chehalem our religion is to grow high-quality grapes and translate them to high-quality wines. In this context we are very happy to be collaborating with Jessica Cortell, a graduate student from Oregon State University, in looking at spatial variability within our oldest vineyard, Ridgecrest.

Laboratory Work at OSU: Mike Eyres, Chehalem Enologist, and Marieta Blasco Perez, Spanish PhD student working 2003 harvest with Chehalem, in the lab with Dr. Jim Kennedy, internationally known wine chemist and tannin researcher, who heads OSU enology programs including Jessica Cortell's thesis work.

Our motivation, in simple terms, is to better understand what makes our 5 acre block consistently our best block, year after year, and what makes the immediately adjacent block slightly, but consistently, less impressive. The two blocks contain predominantly the same clone, Pommard, are planted at the same density and differ in age by just one year (1982 versus 1983).

Jessica, with the help of a large team, collected an enormous amount of data during 2003, as part of a USDA Center for Small Fruits Research project performed at Chehalem and Archery Summit vineyards. This data provides us the opportunity to quantify and qualify some of the variability that exists. The research starts in the vineyard and is being extended right through to the resulting wines.

Jessica incorporated precision viticulture tools such as GIS (Geographic Information System), GPS (Global Positioning System) and aerial infra-red photography. She also partook in a considerable amount of data collection the old fashioned way, walking up and down many many rows with a clip-board, recording physical measurements and making observations at different phenological stages. Some of the key parameters monitored in the vineyard included soil characteristics (type, depth, nutrient levels and pH), water relations, vine growth and crop load. With all this information Jessica could then identify certain areas within each block as being low vigor, moderate vigor and higher vigor. (See graphic)

As harvest 2003 approached, we collected fruit samples from the different parts of the two blocks. From these representative samples we obtained average cluster and berry weights, counted the number of seeds and determined the composition of the juice (sugar levels, pH, TA, amino acid concentration and phenolic profile). Next, we studied the multiple small fermentations for color hue and color density, rate of fermentation and total phenolic levels after fermentative extraction. With the wines yet to complete their malolactic fermentation, full sensory evaluation of the wines has not been completed. However, we anticipate tasting these individual wine lots blind (i.e.: not knowing which lot is from which part of the vineyard) and with a cross-section of winemakers and consumers to achieve an assessment of quality.

With the results of this multi-year study, we hope that we can continue to customize our farming practices across all our vineyards at a smaller and smaller resolution. We would never want to make our vineyards and their resulting wines generic but rather enhance general vineyard health and optimize grape and wine quality.

Vigor Index for Chehalem West (left) and East (right). Plant Vigor Density Diagrams from OSU's Jessica Cortell's studies, showing the two oldest Ridgecrest blocks, 5 Acre and 7 Acre planted in 1982 and 1983. Darker blocks represent higher vigor, lighter show lower vigor, as measured by several parameters.