overtapping with vacuum

[handtapper]

Ive been reading some threads and people keep saying vacuum increases production. If your sucking out more sap with a vacuum pump do you have to be more conservative with how many taps your putting in each tree? Doesn't make much sense to this tubing/vacuum newbie to have three buckets on one field tree and say its maxed out and have three vacuumed taps on a similar tree.

[wiam]

Very few trees should have 3 taps. Most should only have one. There have been studies with vacum gauges on opposite side of tree from tap and vac transfers through the tree.

[GeneralStark]

There are certainly different schools of thought on this matter, but producers using vacuum are generally using 1-2 taps per tree. I generally only use two taps if the tree is over 18" and has a large crown. Using vacuum you can access sap throughout the tissue of the tree so there is really no point in over-tapping (more than one or two taps).

There are several studies related to this and many threads here on this subject. Search for "tapping guidelines" and you will find lots of info.

One of the most significant advantages to using vacuum IMO is less impact on the tree (assuming it is healthy and vigorous) while increasing production dramatically.

It is kind of baffling to me that there are sugarmakers that will hang 3 or 4 buckets on 7/16" spouts on one tree while claiming that vacuum "hurts" a tree.

[markcasper]

It is kind of baffling to me that there are sugarmakers that will hang 3 or 4 buckets on 7/16" spouts on one tree while claiming that vacuum "hurts" a tree.

Even more baffling is when you see someone who is putting 2-3 taps in 8 and 10" trees with vacuum and warn them of the ramifications and then they turn and say that you are jealous or envious or some other B.S.

[Thompson's Tree Farm]

Most damage to the tree is from the tap hole, not the removal of sap, so usually those using vacuum drill less holes in each tree.

[GeneralStark]

Even more baffling is when you see someone who is putting 2-3 taps in 8 and 10" trees with vacuum and warn them of the ramifications and then they turn and say that you are jealous or envious or some other B.S.

That is indeed baffling, though probably less common than overtapping with buckets.

[handtapper]

If the thought process is damage to the tree via the tap hole then wouldnt a guy using tree saver taps put in say 4 while a guy using 7/16 should put 1to2. Seems fairly basic to me. I take all information from uvm or other research places with appreciation and as gospel. I do want to say my grandpa tapped 5 taps in some trees and 2minimum on all trees 10" plus for 50 years (lived in same old house for 57 years) and the trees in his yard look healthy as could be. His spiles were homemade from dowels and we used a 1/2" paddle bit everyone will scream when I post some pictures of these hydrants

[GeneralStark]

A guy can do whatever he would like to his own trees. On leased land, that may be a very different situation depending upon the nature of the lease agreement. Tapping guidelines are just that, guidelines, and are intended to maximize production over many decades. I have tapped some old field edge trees that were tapped for many years, typically with 4 or 5 1/2" taps and buckets. On may of these trees it was quite difficult to find good wood to tap and I would often drill into rotten or questionable wood. More conservative guidelines are intended to maximize the growth potential of the tree so that a producer can tap it for many years with no major negative impact to the tree, and so the producer can continue to tap healthy wood. Just because your grandpa's trees are still doing well does not mean one could continue to tap these trees with 4-5 taps sustainably for very long. Sugar Maples are extremely resilient and can compartmentalize to wall off injured parts of the tree very well.

The following are from the "Maple Syrup Producers Manual"

Traditional Tapping Guidelines:

10-15 Inch Diameter - 1 Tap
15-20 Inch Diameter - 2 Taps
20 - 25 Inch Diameter - 3 Taps
25+ Inches Diameter - 4 Taps

Conservative Tapping Guidelines:

12-18 Inch Diameter- 1 Tap
18+ Diameter - 2 Taps

It is ultimately up to the sugarmaker to determine their own tapping strategies.

[BreezyHill]

We started tapping in '71 and vacuum shortly there after to lift sap up to the sap sap house. We did buckets for a few years. Not once have I hit an old tap hole and we have some monster trees on the state line that are well over 200 yrs+. It can be confussing but think of it as rules to have a productive tree in the future; after following the guidelines. The large old time spiles left a huge hole that would heal in a couple of season or sometimes one. The 5/15 health spiles are a season and the hole is healed.

Vacuum allows us to have a fair run on days that buckets would be dry. On days that would be a slow flow, we are running good. On good days we are flowing well also.

We run high vac...28"+. Our trees have never looked better. We did not tap one year that the gypsy moths ravaged the foliage and another year that we had a bad drought and the trees turned the end of Sept.

Vacuum does increase production relative to the amount of vacuum you apply. I have not witnessed any tree damage as a result of running high vacuum and producing nearly 1/2 gallon of syrup per tap.

Ben

[DrTimPerkins]

Several converging topics/subtopics here, so difficult to hit them all in any detail.

As someone said, these are guidelines....not rules. Current guidelines are, in some cases, not firmly grounded in science, but have instead evolved from practice or been interjected by rules that may or may not make sense. There are no maple police, so unless you're organic certified, tapping on State or Federal land, or are leasing and have an agreement with the landowner on the number of taps and size of trees, you can do whatever you like with your own trees. That said, it is beneficial to ensure that you do not overtap and possibly threaten the sustainability of the practice or reduce your yield by overtapping.

From the onset I should state that we don't have all the answers yet, and that a comprehensive "Tapping Guidelines" manual is in the works, but is still a few years away. We began a series of studies looking at some of these issues several years ago, and have been plugging away at them. Many we have good answers for. Some are still a few years away.

There are two areas of concern with respect to tapping: 1) the wound created by tapping and 2) the carbohydrate (sugar) extracted from the tree. Most of what people talk about, and the guidelines were created for deal with #1. That is probably a bigger issue when either tapping suppressed or subdominant trees or when tapping very large slow-growing trees. The idea behind tapping guidelines is to never render non-functional (through the stain created....which no longer can move sap through this zone) more wood than can be regrown in the subsequent growing season. There are several recent papers on the UVM PMRC website http://www.uvm.edu/~pmrc/ (right column, under "Recent Publications", "Tapping Guidelines") dealing with this subject. Specifically there is an Excel-based model that allows you to estimate the effect of your tapping practices on the degree of compartmentalization/stained wood formation. The short story here is that tree growth has to be sufficient to sustain your tapping practices (taphole size and depth and dropline length/tapping band dimensions). If not, consider changing your practices to reduce the wound you produce.

In terms of carbohydrate removal, this is a considerably more difficult subject to deal with. There are relatively few studies that have looked at it. Mark Isselhardt (UVM PMRC) completed his Master's degree a few years ago on this subject, and we have a couple of papers that will be out within the next 6 months about it. In general, it appears that tapping typically removes only a small fraction (< 3-4%) of the available carbohydrate from trees, and thus sap collection practices are not generally problematic. The one exception to this is, again, for small, suppressed or subdominant trees (<6" dbh), especially when collecting with high vacuum. In that case, removal of 10% or more of the available carbohydrate reserves may occur, which would likely impact the growth and survival of those trees. These types of trees are very limited in the amount of sugar they can make due to lack of crown exposure to light. Now if you're intention is to thin them out in a few years, tapping that cohort isn't a problem. The better practice however might be to thin them out and allow the remaining trees to grow better (and thus produce more and sweeter sap).

As people here have noted, there are different approaches that may be valid in different situations. The question of one tap vs two taps, or deeper or shallower tapholes all influence yield as well as wounding and carbohydrate removal. There are benefits and drawbacks of each practice, and knowing the trade-offs and making an informed decision as to what practice to use is the best approach. Unfortunately, we just aren't quite ready to write the book yet.

In work done by Tim Wilmot (UVM Maple Extension), we do know that deeper tapholes produce more sap, although the effect isn't linear. We also know that two taps under gravity will produce considerably more sap in larger trees (nearly double), but that a second tap under vacuum won't produce nearly as big a percentage increase as found under gravity. So your sap collection practice should affect/influence your tapping practices to some degree.

The biggest outstanding issue is how does carbohydrate extraction (gravity or vacuum) affect long-term growth of trees. Obviously sugaring is a practice that has gone on for long periods of time and is, in general, considered sustainable. However with modern techniques (high vacuum, good sanitation) we are removing 2-4X the amount of sap (and sugar) from the tree. Does sap removal affect growth? Does too much sap removal affect it more? Does it really matter (if we slow growth down somewhat)? The answer so far is, "we don't think it impacts growth detrimentally." Some researchers sap removal does slow growth (taphole closure) down somewhat (~10%). Others think it doesn't affect it that much. We (UVM PMRC) have done some work that shows that there may be some effect, but it tends to be fairly modest. As it turns out, the best way to know is to test it directly. With that in mind, we recently (last fall) started a study looking at the long-term effects of sap removal on growth. We found 90 (10-12" dbh) trees at UVM PMRC that had never been tapped. 1/3 of these remained untapped, 1/3 were tapped by gravity (5/16" spouts) in 2014, 1/3 were tapped with vacuum (5/16" spouts). We will collect sap from them each year in the same way. Each fall we will measure dbh. After 5 yrs we will see if there is any difference in the amount those trees have grown. We will also assess shoot growth and seeding (if any occurs). After 5 and 10 yrs we will core the trees to check growth more directly. What this means is that it'll be at least another 4 yrs, and maybe 9 yrs before we have a good answer to the question. This study is being wholly funded by the UVM Agricultural Experiment Station. To set it up required an investment of $25k in chambers alone (with many thanks to Lapierre Equipment who supplied these chambers at cost), about 1/2 mile of new mainline, and a several hundred hours of technician time.

So at this time, the best estimate I have is that we're about 4 years away from a comprehensive "Tapping Guidelines" manual.

[ennismaple]

Thanks Dr Tim! I'm really interested in the 10 year study so please keep us informed!

[DrTimPerkins]

Thanks Dr Tim! I'm really interested in the 10 year study so please keep us informed!

Ask me for an update about 9 yrs from now. :D

[Mooneybc]

Several converging topics/subtopics here, so difficult to hit them all in any detail.

As someone said, these are guidelines....not rules. Current guidelines are, in some cases, not firmly grounded in science, but have instead evolved from practice or been interjected by rules that may or may not make sense. There are no maple police, so unless you're organic certified, tapping on State or Federal land, or are leasing and have an agreement with the landowner on the number of taps and size of trees, you can do whatever you like with your own trees. That said, it is beneficial to ensure that you do not overtap and possibly threaten the sustainability of the practice or reduce your yield by overtapping.

From the onset I should state that we don't have all the answers yet, and that a comprehensive "Tapping Guidelines" manual is in the works, but is still a few years away. We began a series of studies looking at some of these issues several years ago, and have been plugging away at them. Many we have good answers for. Some are still a few years away.

There are two areas of concern with respect to tapping: 1) the wound created by tapping and 2) the carbohydrate (sugar) extracted from the tree. Most of what people talk about, and the guidelines were created for deal with #1. That is probably a bigger issue when either tapping suppressed or subdominant trees or when tapping very large slow-growing trees. The idea behind tapping guidelines is to never render non-functional (through the stain created....which no longer can move sap through this zone) more wood than can be regrown in the subsequent growing season. There are several recent papers on the UVM PMRC website http://www.uvm.edu/~pmrc/ (right column, under "Recent Publications", "Tapping Guidelines") dealing with this subject. Specifically there is an Excel-based model that allows you to estimate the effect of your tapping practices on the degree of compartmentalization/stained wood formation. The short story here is that tree growth has to be sufficient to sustain your tapping practices (taphole size and depth and dropline length/tapping band dimensions). If not, consider changing your practices to reduce the wound you produce.

In terms of carbohydrate removal, this is a considerably more difficult subject to deal with. There are relatively few studies that have looked at it. Mark Isselhardt (UVM PMRC) completed his Master's degree a few years ago on this subject, and we have a couple of papers that will be out within the next 6 months about it. In general, it appears that tapping typically removes only a small fraction (< 3-4%) of the available carbohydrate from trees, and thus sap collection practices are not generally problematic. The one exception to this is, again, for small, suppressed or subdominant trees (<6" dbh), especially when collecting with high vacuum. In that case, removal of 10% or more of the available carbohydrate reserves may occur, which would likely impact the growth and survival of those trees. These types of trees are very limited in the amount of sugar they can make due to lack of crown exposure to light. Now if you're intention is to thin them out in a few years, tapping that cohort isn't a problem. The better practice however might be to thin them out and allow the remaining trees to grow better (and thus produce more and sweeter sap).

As people here have noted, there are different approaches that may be valid in different situations. The question of one tap vs two taps, or deeper or shallower tapholes all influence yield as well as wounding and carbohydrate removal. There are benefits and drawbacks of each practice, and knowing the trade-offs and making an informed decision as to what practice to use is the best approach. Unfortunately, we just aren't quite ready to write the book yet.

In work done by Tim Wilmot (UVM Maple Extension), we do know that deeper tapholes produce more sap, although the effect isn't linear. We also know that two taps under gravity will produce considerably more sap in larger trees (nearly double), but that a second tap under vacuum won't produce nearly as big a percentage increase as found under gravity. So your sap collection practice should affect/influence your tapping practices to some degree.

The biggest outstanding issue is how does carbohydrate extraction (gravity or vacuum) affect long-term growth of trees. Obviously sugaring is a practice that has gone on for long periods of time and is, in general, considered sustainable. However with modern techniques (high vacuum, good sanitation) we are removing 2-4X the amount of sap (and sugar) from the tree. Does sap removal affect growth? Does too much sap removal affect it more? Does it really matter (if we slow growth down somewhat)? The answer so far is, "we don't think it impacts growth detrimentally." Some researchers sap removal does slow growth (taphole closure) down somewhat (~10%). Others think it doesn't affect it that much. We (UVM PMRC) have done some work that shows that there may be some effect, but it tends to be fairly modest. As it turns out, the best way to know is to test it directly. With that in mind, we recently (last fall) started a study looking at the long-term effects of sap removal on growth. We found 90 (10-12" dbh) trees at UVM PMRC that had never been tapped. 1/3 of these remained untapped, 1/3 were tapped by gravity (5/16" spouts) in 2014, 1/3 were tapped with vacuum (5/16" spouts). We will collect sap from them each year in the same way. Each fall we will measure dbh. After 5 yrs we will see if there is any difference in the amount those trees have grown. We will also assess shoot growth and seeding (if any occurs). After 5 and 10 yrs we will core the trees to check growth more directly. What this means is that it'll be at least another 4 yrs, and maybe 9 yrs before we have a good answer to the question. This study is being wholly funded by the UVM Agricultural Experiment Station. To set it up required an investment of $25k in chambers alone (with many thanks to Lapierre Equipment who supplied these chambers at cost), about 1/2 mile of new mainline, and a several hundred hours of technician time.

So at this time, the best estimate I have is that we're about 4 years away from a comprehensive "Tapping Guidelines" manual.


Did the Tapping Guidelines Manual ever come out? Where might I find the results of these studies done 9 years ago (if they are available)?

[DrTimPerkins]

Did the Tapping Guidelines Manual ever come out? Where might I find the results of these studies done 9 years ago (if they are available)?

A number of studies on this subject have been published over the last several years https://mapleresearch.org/

There are revised guidelines in the new maple manual available here https://mapleresearch.org/pub/manual/

The ten year study looking at how sugar removal from maples at different levels (none, gravity collection, vacuum collection) will be finished after this coming (2023) growing season, but might take a year or so before it hits the printed page.