In the Vineyard
What is ‘precision viticulture’, precisely ?
A vineyard’s location, contours and soil composition are key factors to consider —and deal with.
By Gary Strachan
get twitchy in the fall when I look at a vineyard that displays shades of green, amber and brown like a patchwork quilt. If the boundaries of the quilt are clearly defined squares, it makes sense to me because each variety of grape has its own unique timing to achieve maturity. If the patches have irregular boundaries, I can’t help but wonder what went wrong this year. If it’s conducted properly, precision viticulture starts before there is a vineyard. Think first about site selection and preparation. Let’s walk the site, look at the soil, look at the slope and orientation, check historic regional weather records, and check the Grape and Wine Atlas and the Provincial Soil Surveys (both posted on line). Based on average heat unit accumulation and length of frost-free season we should be able to select a few grape varieties sustainably suited to the site. Is the slope uniform or is it undulating? Slopes have better air drainage. Let the cool air accumulate on your neighbor’s property or use the bottom of the slope for your service road or utility buildings (so long as air flow isn’t interrupted.). It may seem inconsequential that the site has small depressions, but even a small depression can interrupt the flow of air on a slope and result in a temperature difference of (say) one Celsius degree.
I GARY STRACHAN
Autumn mosaic of colors in a vineyard. Precision treatment of weak areas can improve yield and quality.
When that small increment is accumulated over (say) a 180-day frost- free season, the result is depressed accumulated heat units of 180 growing degree days. If you are pushing the season to ripen a particular grape variety, the depression will likely be visible in the fall colour mosaic. Grapes from that area will have a composition different from the uniform areas. It isn’t easy to recontour a vineyard. This can seriously mess up the soil biome and structure — to the point at which it can take decades to recover. Obviously it is best to carefully remove the surface soil, recontour and restore.
Even this is not a perfect solution, but the site will recover more quickly than if it is simply graded without regard for changes inflicted on the site. The compromise is to do nothing and tolerate the localized handicap of reduced yield and quality during the next (say) 50 years of vineyard production. Your choice.
The geological history of the site will determine soil composition. Granitic soils tend to be low pH and the easiest way to adjust them is by adding powdered limestone. Calcareous soils tend to have high pH and can be
British Columbia FRUIT GROWER • Winter 2015-16
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