In a previous posting we started looking at some issues of how we determine how far apart we space our vines. Some traditional knowledge from other regions is that the tighter the spacing the more vigor was reduced in the vineyard. The one study we looked at did not confirm that.
Now we are going to take a look at some other information that has been published in the well known publication from the American Journal of Enology and Viticulture. To view entire articles online from this journal you need to become a member, but a short abstract (summarization) of them is available free online.
Dr. Andrew Reynolds has done a lot of interesting research in viticulture. A lot of his studies have looked at the impact of vine spacing, training systems, and so forth. In 4 of them, Am. J. Enol. Vitic. 55:1 (2004), Am. J. Enol. Vitic. 46:1 (1995), Am. J. Enol. Vitic. 47:1 (1996), Am. J. Enol. Vitic. 45:4 (1994), they found some similar trends that were observed in the previous posting: increasing vine spacing reduced vine vigor per unit of row.
Part of these studies included having Chancellor, Riesling, and Seyval vines planted at different vineyard densities. While we won’t look specifically at the yield, fruit chemistry, and so forth, we will look at the observations on vigor. In all of those 4 studies, planting vines closer together lead to higher pruning weights per unit of space (meters, feet, yards, or what ever system you want to use). Planting vines farther apart lead to lower pruning weights per unit of space. The following figure shows an example of this.
This graph shows what might be an example of the impact of vine spacing on vine vigor. Note that there are no values on this chart, because the relationship will change depending in the vineyard and region. In some there may be a more drastic impact as seen in the blue versus the red line.
In some regions that are dry, it might be that vines planted closer together have less vigor since they may be ‘competing’ for water. However in regions that get more than enough rain to sustain grape production, it is likely this trend will be similar.
So, back to the graph. When you first plant a vineyard you can’t precisely guess what vigor level it might be, but you can get a rough guess based on the cultivar and by looking at other vineyards.
Where is the ideal on this chart? First of all it depends on what you think is considered vigorous or not and what you producing. In juice grape vineyards we want vigorous vines to produce high yields. In wine grape vineyards we likely are looking at moderate vigor as being ideal. Too high of vigor can cause shading problems and reduce fruit quality and too low of vigor is likely not profitable and may not be able to ripen commercial yields of fruit.
So what is the best spacing? Once again my answer is ‘it depends’. I would look at vineyards near you and adjust based on their experience (assuming your conditions are similar), also look at the cultivar that you are growing since they vary in vigor as well. The training system you are using will also impact your vine spacing, as well as your equipment.
It sounds overwhelming, but in reality the attentive grower will always see how they would have possibly done something different. In your original planting go with what you think will work based on what we have looked at in this posting, and then adjust accordingly for new ones.
We’ll look at the impact training systems might have in vine spacing in future postings.
If you have any questions or comments, feel free to contact me (firstname.lastname@example.org).