The only research available (http://www.uvm.edu/~pmrc/vacsap.pdf) has shown that there is no trend of decreasing sugar content with increasing vacuum level....at least up to 25" Hg. There really isn't a whole lot of possible physiological reason for there to be a difference. I could see this being a possibility during a long extended thaw, but for any single, relatively normal sap run, there shouldn't be any significant difference.
vac vs sugar.JPG
Dr. Tim Perkins
UVM Proctor Maple Research Ctr
http://www.uvm.edu/~pmrc
https://mapleresearch.org
Timothy.Perkins@uvm.edu
If he got the same yield as you did with 10" Hg vacuum less, then there is some other difference accounting for the yield and sugar content you are observing. Very small differences in tree size (mostly volume) can result in fairly strong differences in sap or syrup yield. For every 1" in stem diameter increase, trees will produce roughly 0.5 lbs syrup more (on high vacuum with good sanitation). That is why we randomize our treatments and use replication in doing our experiments. It is also why I don't pay a lot of attention to producers saying they compared two spouts in two different sections of their woods and got different results. It would be very surprising if they didn't see different results....the statistical degree of freedom in that comparison is 1 (the lowest you can have).Originally Posted by spud
Dr. Tim Perkins
UVM Proctor Maple Research Ctr
http://www.uvm.edu/~pmrc
https://mapleresearch.org
Timothy.Perkins@uvm.edu
Every scientific publication or presentation that i've heard from scientists or producers says that higher vacuum is better for total yield. I think a lot of the 'well I got this yield with this setup this year' type of stories are only so helpful, just like Dr. Tim is saying. Small variations between producers makes using other people's experiences as the basis for your decisions not the best idea sometimes. We try to use scientifically researched methods when tapping, installing tubing, storing sap, boiling etc. as most producers do and I think this is a good route to take, although sometimes science turns out to be wrong about something. I don't personally know anything more about vac. level vs. yield than what is available in local seminars and on websites like PMRC's website. But until we understand otherwise we'll try to have vacuum at 28.4" which is what we sat at for most of last year.
Dr. Perkins- Have you completed studies that show the increase in syrup yield in relation to tree diameter? Surely there has to be a small range that this holds true. Would this mean that an 18" tree would yield 5 lbs more syrup then an 8" tree with high vacuum and good sanitation?
Jeremy
Buffalo Creek Sugar Camp
Somerset County, PA
22000 taps on vacuum and counting
4x14 Leader Max pans oil fired with steam-away, 2-1000gph RO's, 2-4000gph RO's
Lowell Vt.: Tapped yday and have sap to boil. Leaving aside the spring of 2012, this is about a week earlier than my average early sap run. we usually expect to be boiling on Easter here, but I wonder if that holds true this year.
Yes, that is exactly what I was trying to say. Producers can definitely do their own comparisons, but when 1" vacuum difference in two different sections makes a 5-75 difference in yield, or 1" dbh difference in trees makes a 0.5 lb difference in syrup produced, it still takes controlled studies with replication over a few years to tease out the real differences.
Don't misunderstand....scientists certainly can and do go down the wrong path sometime, but more than often it is because of something that is very unusual or unknown. Even more commonly, people (including scientists) try to take the results of one study and apply it to everything.
Dr. Tim Perkins
UVM Proctor Maple Research Ctr
http://www.uvm.edu/~pmrc
https://mapleresearch.org
Timothy.Perkins@uvm.edu
What is somebody from PA doing on the Vermont thread?
Yes, we do have data and we are investigating this relationship further. Keep in mind that that what I said was a rough approximation. I'm not going to go into a lot of detail here because it is a study that is ongoing, but you would be surprised how little sap a tree 8" in diameter produces in relation to a tree that is 18" in diameter. The strength of the relationship between diameter and yield is VERY high (correlation of better than 70%).
Going back to the simplified "pipe" model of a tree.....the amount of liquid in a pipe doesn't double as the diameter of the pipe double....it goes up MUCH faster than that. This is why thinning trees to encourage strong growth of the remaining crop trees is so important in producing good yields. Bigger trees produce more sap (and are able to compensate for wounding better).
We will talk about this subject more later on....perhaps as early as the end of this current season, but the study is largely to look at the economy of tapping different sized trees and where the line should be drawn (tapping guidelines) in relation to tree size, wounding, yield, and economics of production.
Dr. Tim Perkins
UVM Proctor Maple Research Ctr
http://www.uvm.edu/~pmrc
https://mapleresearch.org
Timothy.Perkins@uvm.edu
Good stuff Dr. Tim. Sounds like a very interesting study. Good forest management certainly is the key to higher yields and I'm sure the high yields that PMRC achieves and that we all strive for are related to good forest management. Just hooking a maple tree up to a vacuum tubing system doesn't mean it will produce well.
Made over 30 gallons of syrup yesterday from sap collected over the weekend, and from the ice that is slowly thawing from Jan. and early Feb. The first 10 gallons or so were dark and strong flavor, likely due to the sap sitting in the pans since last boil in late Jan. But it quickly lightened up and we got almost to GD for the last 10 or so. Going to clean the front pans today and get ready to boil again tomorrow. Sap has been running ok and sugar is now up to 2%.
About 750 taps on High Vac.
2.5 x 8 Intens-O-Fire
Airtech 3 hp LR Pump
Springtech Elite 500 RO
14 x 24 Timber Frame SugarHouse
16 x 22 Sap Shed w/ 1500 gal. + 700 gal. tanks
www.littlehogbackfarm.com
Started tapping Saturday after seeing the forecast for this week. I finished all my pipeline yesterday with the help of my Wife and my Brother. (600ish) Turned on the vacuum pump around 3:00pm yesterday, collected about a 100 gallons in two hours to clean the lines and tanks. Dumped that and left the pump running all night, I had 130 gallons this morning when I headed to work. I checked the vacuum and it was way down 12.5" I usually can pull 16" or 17" I must have a lot of leaks. Needless to say I have some work to do and I still have about 50 buckets to hang this weekend. The full time job is getting in the way of the full time hobby.
Unexpectedly got down to 28 last night and stayed there for a good ten hours. I suspect it's running nicely today.
173 on 3/16 natural vac for 2023
36 buckets
2 x 5 Smoky Lake Hybrid pan on a custom arch
RB25 from RO Bucket
12x24 salvaged sugarhouse built by wife's grandpa
1965 Massey Ferguson 165 tractor to haul sap.
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