1.5.2 In which direction should the rows face?

What is the topographic profile of the plot?

Erosion is a major concern when running a vineyard. If there is a strong incline, the vines should be planted following the contours of the slope to avoid significant water flow. If the incline is slight to moderate, the vines should be planted in the same direction as the slope.
When the slope is too sharp to plant following the contour of the land, terracing should be considered and tractors avoided. If impossible to do so, other methods exist to help protect against erosion, but they are not without compromise or risk.
Finally, neighboring plots and their aspect should be taken into account. This will benefit the overall work organization and facilitate mechanization if the rows of different plots are aligned.

What is the plot’s climate?

Three factors need to be taken into consideration: sun exposure, if the varietal is early-ripening, and the orientation.
The Huglin index (HI) is used to define whether the climate is hot or cold. It is an index using two variables: temperature and the day’s length in the region between April and September 30th.

IH=k.∑_01.04^30.09▒((Tmed-10)+(Tmax-10))/2

Variables:
Tmed=Average air temperature in °C
Tmax: Maximum air temperature in °C
K= « day length » coefficient, for our purposes -1,04

Very hot	IH+3	3000
Hot	IH+2	2400<IH<3000
Temperate warm	IH+1	2100<IH<2400
Temperate	IH	1800<IH<2100
Cool	IH-1	1500<IH<1800
Very cold	IH-2	IH<1500

It should be kept in mind that this index will evolve with global warming. In the Côte d’Or, for example, the HI went from approximately 1700 in the 1980s to 1900 in 2010. This phenomenon raises a lot of questions for the future of the world’s vineyards, as there are very few ways to limit the progression.
When we know where our location is on the scale, we must examine the needs of the grape variety we want to plant. The following values are given to produce a wine with a sugar concentration between 180 and 200 g per liter.

Huglin Index Values	Varietals
1600	Pinot Blanc / Gamay
1700	Pinot Noir / Chardonnay / Sylvaner
1800	Cabernet Franc
1900	Cabernet Sauvignon / Chenin Blanc / Merlot / Sémilion / Riesling
2000	Ugni Blanc
2100	Cinsault / Grenache / Syrah
2200	Carignan
2300	Aramon

This chart gives an idea of the ripeness levels a varietal can potentially reach in a given climate. If planted in a hotter climate, the vines will mature earlier.
By taking into consideration these elements, we can work out required sunshine levels. The orientation of the vines is crucial in this aspect.
Two steps are important to evaluate:
Firstly, if on a hillside, the plot’s orientation is correlated to the amount of direct sunshine on the vines.
Secondly, it stands to reason that the row’s orientation is the only means of action to control the amount of sun exposure.
Examples: On a hillside with a northerly aspect there will be less sunshine, so it is recommended to plant with a slight North/South angle or a North/West angle or lastly a South/East angle.
Inversely, when the goal is to limit sunshine exposure, it is best to plant East / West.
The combination of all these criteria enable us to best choose the plot’s orientation.

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