Location of tap hole.

[spud]

I was wondering if PMRC has done any research on tapping a tree inches above or below the lateral line? I know the drops are supposed to not have lats of bends but does it really hurt the vacuum?

Spud

[DrTimPerkins]

I was wondering if PMRC has done any research on tapping a tree inches above or below the lateral line?

I did a study last year comparing tapping above and below the lateral line with used tubing and new spouts or new CV spouts. I tapped 2' above or 2' below the lateral line with 5/16" droplines, so a total of 4' of difference in tapping height.

Tim Wilmot (UVM Maple Extension -- retired) did a similar study, but he used new 3/16" tubing and his drop length was 18'.

In short, there were no differences in sap yield or sugar content when tapping above or below the lateral line. I believe Tim is presenting this work at Verona. I'll be presenting it at the Vermont Maple Conferences.

The other thing that was very apparent was that when we did hit an old taphole wound (compartmentalized zone/brown wood), the sap yield from that taphole was GREATLY reduced. Even with those tapholes were excluded from the study, there was no difference in sap yield. When we tap, we look at the drill shavings for each taphole.

I intend to repeat the study for the 2016 season to verify (or not) the results, hopefully in a more typical/longer season. We are also setting up one area (in an older section of our woods with very mature, slow-growing trees that were tapped for decades with multiple 7/16" spouts) where ALL the trees will be tapped below the lateral line.

As for tapping a few inches above or below.....shouldn't matter as long as the droplines have a gentle sweep and aren't kinked.

[sapman]

It would seem to me that you should lose a little flow at the start of a run, due to frozen sap in the dropline below the lateral?

And another question: When tapping below laterals, are you leaving the tee in the normal position, or flipping it over so the dropline is heading down at the start? Probably another one of those "doesn't matter" issues, but I try to envision exactly how it looks.

Thanks

[DrTimPerkins]

It would seem to me that you should lose a little flow at the start of a run, due to frozen sap in the dropline below the lateral?

That could happen during a very brief flow, however with is likely to be pretty marginal. Keep in mind that there is a relationship between pressure and flow. When one taphole starts flowing, it will run fast for a time, then slow down as the pressure dissipates. Another hole that remains frozen for a hour longer will run faster when it first thaws than the taphole that opened up an hour or two earlier, so in a short time the total yield will pretty similar to the first hole (just slightly behind). In a season that was composed of a lot of very short flow periods, this might add up to be a reasonable amount.....that is one reason that we like to do studies over 2 or more years....hoping to get different flow conditions in each year. Sometimes we'll keep doing a study for even longer to be sure we've captured several different flow regime years. 2013 and 2014 were very similar (at least for us), so some of our studies will be repeated in hopes we get something different just to be sure our results hold up.


And another question: When tapping below laterals, are you leaving the tee in the normal position, or flipping it over so the dropline is heading down at the start? Probably another one of those "doesn't matter" issues, but I try to envision exactly how it looks.

In this case, we flipped the tee so that it was pointed downward. This was primarily (in our case) to be able to get close to exactly 2' up and 2' down. As you say, it probably wouldn't matter much, as long as there was no kinking of the line.