Black Walnut tapping, does vacuum improve sap volume?

[Illinois]

We're in our third year of experimenting with tapping walnut trees using buckets.
We have noticed a huge difference from tree to tree in the amount of sap.
Some will have a generous amount of sap but many others very little. Just read in the Maple News about birch tree tapping that they will not run by gravity only on vacuum. Any experience on this would be appreciated.

Illinois Maple producer all on vacuum
250 walnut taps with buckets

[Trends]

Yes I'm finding it does increase the amount collected.
I'll add to this later I'm just heading out

[DrTimPerkins]

Just read in the Maple News about birch tree tapping that they will not run by gravity only on vacuum.

Maples generate internal stem pressure during thaws following a freeze which creates sap flow through any open wound. Vacuum increases the gradient substantially and increases the rate and amount of flow. https://mapleresearch.org/pub/m1007sapcollectionvacuumlevel/

Birches produce root pressure. They will run without gravity, but likely will run somewhat better with vacuum.

Beech trees will not generate stem or root pressure (the physiology is different than maple, birch or walnut), so no sap is produced UNLESS you use vacuum.

Walnuts typically produce modest amounts of sap flow on gravity, but more on vacuum.

[Illinois]

Thank you. That makes sense. We just have to figure out how to link some walnut trees together with vacuum as our trees are scattered widely across a predominantly hard maple forest. In 2022 we tapped 120 trees and made 5.5 gallons of nice tasting walnut syrup. Still refining our boiling methods now using an old 2 x 6 CDL syrup pan on an LP burner. Cheers.

[DrTimPerkins]

Most of the new research on walnut is coming from WV (Dr. Mike Rechlin). Watch for news from that group.

[Trends]

I'm very new at the tapping Walnut tree's game (3rd yr) and I'm also trying to maximize my sap yields.
i came across some information from Future Generations University "MAPLE INITIATIVE" on The Effect of Vacuum on Walnut Sap Flow which proved to be a very interesting and enlightening read (link attached)

https://projects.sare.org/wp-content/uploads/Attachment-2-Walnut-2020-Vacuum-_Final_Formatted-1.pdf

My take was that a vacuum system should increase the sap and this year I'm giving it a try. Much to early season for proper #'s but to date (considering only about - sap producing days) my totals of 7 trees on gravity vacuum is sitting at 15gal or 2.1gal per tree average while the 28 tree total on vacuum pump is sitting at 83gal or 3gal per tree. So early data shows the mech vacuum is doing better.
With the sap brix varying from 1 to 2.4% this 98 gal of sap has finished up at 1.6 gal of syrup to date.

I'll post a pic of my vacuum cooler as soon as I find my phone.

23046

23045

I expect good flows going forward from this weekend into April and hopefully we can do much better then the 145 total gallons of sap from last years 30 trees tapped.