Final report for ONE19-347
Project Information
The premise underlaying this research was that a scientific investigation into walnut sap flow and syrup making would lead to more farmers utilizing their walnut tree resource to make and sell walnut syrup. This project tackled what we saw as the most pressing knowledge gaps inhibiting the expansion of a walnut tapping industry. The project was comprised of four independent investigations, each with their own objective, methodology, results, and conclusions.
Objective #1 looked at the proper time to tap walnut trees. In this study we did a literature survey of walnut sap flow physiology along with a field study that staggered the timing of tapping by two-week intervals. While the field study did not yield the results we expected, the literature review alerted us to the possibility of root pressure as a secondary initiator of sap flow, causing us to tap much later and observed a copious sap flow event. We have plans to further investigate root pressure sap flow in the coming season.
Objective #2 investigated the effects of vacuum and sap flow. We collected walnut sap from 20 taps relying on gravity flow and 20 taps under relatively low vacuum. We found a highly significant increase in sap flow from the trees under vacuum. Eight inches of vacuum increased sap flow from 0.37 qt./hr. to 0.74 qt./hour. This is highly useful information. Two major West Virginia walnut producers are now running vacuum on their lines.
Objective #3 investigated a spile specifically designed for walnut trees and improved tapping procedures. It included a preliminary study of compartmentalization of sapwood around a taphole, which relates to tapping sustainability. In three of the four study sites the new taps and procedures significantly increased sap flow. The compartmentalization study showed that 8 times the volume of the taphole is killed in walnut, which compares favorably to the 27 times the volume of the taphole killed in maple. The above studies also pointed to another walnut tapping problem, where over time the spouts are pushed out of the tree. We are working with the Robert C. Byrd Institute of Advanced Manufacturing to design of a second generation “stickier” walnut spile.
Objective #4 was the development of a small sap evaporator based on rocket stove principles. We successfully designed and tested an energy efficient evaporator that boils away 6.3 gallons of sap/hour, is inexpensive to build, and uses readily available materials. This has created a lot of interest. We have 16 people building and testing this design in the coming sap flow season. The plans will soon be on Future Generations University’s website. It will be very useful in encouraging farmers to start a new maple of walnut syrup production operation.
Outreach this year was limited due to COVID restrictions. We have published research reports on all of our studies that are available on the Future Generations University's website and on www.mapleresearch.com. An article on the project is due to come out in The Maple Digest and we have had articles in The Pendleton Times (WV) and the Roanoke Times, (VA).
1) This project seeks to discover the proper time to tap walnut trees to maximize the volume and sweetness of the sap collected. This will allow farmers to increase yield and quality of this specialty crop and thereby increase potential sales.
2) This project seeks to answer the question of whether vacuum applied to sap collection lines will substantially increase walnut sap flow. Answering this question will allow farmers to develop superior sap collection strategies that improve the reliability of this crop.
3) This project seeks to develop and test a sap collection spout designed specifically for walnut, a semi-ring porous species. It will be designed to reduce sap leakage and increase yield, thus increasing the amount of syrup farmers can produce and sell from their walnut tapping operations.
4) This project seeks to adapt “rocket stove” technology to improve the walnut sap evaporation process, creating a small-scale evaporator. This model will reduce sap spoilage and achieve greater processing efficiency. This will benefit farmers by minimizing losses and allowing them to start making walnut syrup with a small number of trees and a minimal investment.
This research worked to increase the tapping of Black Walnut (Juglans nigra) for syrup production by developing techniques for more effective sap collection and syrup processing. Diversifying within the maple syrup industry to alternative tree syrups is a priority for farmers with the available resource. By tapping walnut trees farmers will be able to enter the highly profitable niche market for specialty syrups. Walnut trees are plentiful in West Virginia and the Mid-Atlantic states, occurring in bottomland forests and farm fields. West Virginia—with an estimated 63,123,000 trees—and Pennsylvania—with an estimated 57,381,000 trees—are two of the top 10 states in number of walnut trees (Schmidt, USFS, 1992). Of those, only handful of producers are presently tapping walnut trees. The problem is a lack of knowledge about walnut sap flow and sap collection. The only active research on walnut sap and syrup production is being conducted by Cornell University, Catawba Sustainability Center of Virginia Tech, and Future Generations University (the lead investigator of this project). Unlike with maple sap flow, there has been little prior research. Walnut and maple are anatomically and physiologically different species. The differences in the springtime development of trunk pressure and the large size of the walnut vessels requires a different strategy for maintaining sap flow. Based on the preliminary work completed in the 2019 sap flow season, we tested the hypothesis that walnut sap flow can be substantially increased using artificial vacuum with 3/16-inch sap lines and a vacuum pump sized to remove the excess gasses in the sap due to the large vessels of the semi-ring porous species during the 2020 sap flow season. We also tested whether tapping later in the season will increase sap flow by having tap holes active when tree pressures reach their maximum.
Also investigated in this study were the effectiveness of specially designed walnut sap collection spouts and the development of an energy efficient sap evaporator for small scale production. Working with West Virginia’s Robert C. Byrd Institute of Advanced Manufacturing, the research team developed a prototype for a walnut-specific sap collection spout and designed a small-scale sap evaporator using “rocket stove” design principles. Working with participating farmers, we tested both in the 2020 sap flow season.
Cooperators
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Research
Sap pressure builds in trees as they prepare for bud break in the spring. The 2020 sap flow season began in late January and ran through mid-March. Sap flow research began the third week of January on Elton Bower’s farm as well as with our partner farmers: Chip Matheny, Steve Czarnik, and Karen Milnes.
Up through the initiation of sap flow in late January, the project team, made up of Primary Investigator, Mike Rechlin, and Research Associate, Kate Fotos, have been developing research tools, working with partnering farmers, consulting with project researchers at The Robert C. Byrd Institute (RCBI), and conferring with our advisory board members Mike Ferrell and Abby van den Berg.
Activities by objective were as follows:
Objective #1 – Timing of tapping study. The hypothesis that walnut sap runs later in the season than maple sap has help up. We have continued our literature review to better understand the physiological and anatomical characteristics of walnut trees as they relate to sap flow. The following articles were reviewed, and ideas incorporated in our proposed methodologies:
- Gross influences on heartwood formation in black walnut and black cherry trees. USDA FOREST SERVICE RESEARCH PAPER FPL 268, 1976.
- Water relations in walnut during winter, F. Ewers et. al. Michigan State Univ. Dept. of. Botany and Plant Pathology.
- Winter stem xylem pressure in walnut trees: effects of carbohydrates, cooling and freezing. Thierry Ameglio, et.al. Tree Physiology 2001.
- Winter embolism, mechanisms of xylem hydraulic conductivity recovery and springtime growth patterns in walnut and peach trees. Thierry Ameglio, et.al. Tree Physiology 2002.
- Temperature effects on xylem sap osmolarity in walnut trees: evidence for a vitalistic model of winter embolism repair. Thierry Ameglio, et.al. Tree Physiology 2004.
- JrSUT1, a putative xylem sucrose transporter, could mediate sucrose influx into xylem parenchyma cells and be up- regulated by freeze–thaw cycles over the autumn–winter period in walnut tree (Juglans regia ) Melanie Decourtex, et.al. Plant, Cell and Environment. 2006.
- Seasonal variation in xylem pressure of walnut trees: root and stem pressures. Frank W, Ewers. Tree Physiology. 2001. Sugars Exchanges Between Vessels Associated Cells and Xylem Vessels, in Relation with temperature, in walnut. V. Valentin, Proc. IV Int. Walnut Symp.
- Making syrup from black walnut sap. Gary Naughton. Transactions of the Kansas Academy of Science. 2006.
Objective #1 – Timing of Tapping Study activity
- Early tapping - Tap 10 trees – Research Associate, Kate Fotos – Third week of January 2020
- Installed pressure gauges on 10 trees – Research Associate, Kate Fotos – Third week of January 2020
- Late tapping – Tap 10 trees – Research Associate, Kate Fotos – 2nd week of February 2020
- Checked buckets, recording volume in each bucket by tree throughout the season – Partner Farmer, Steve Czarnik
- Checked and recorded gauge readings in the afternoon during sap runs – Partner Farmer, Elton Bowers
- Data analysis – Research Associate, Kate Fotos
Objective #2 – Vacuum & Sap Flow study. We continued to investigate whether artificial vacuum will increase walnut sap flow. Ongoing discussions were held with project advisory board members Mike Ferrell (The Forest Farmers Inc) and Abby Van den Berg (UVM Proctor Maple Research Center) on the proposed research methodology. These discussions led to the re-thinking of some of our research methodologies. The decision was made to experiment with 3/16-inch tubing and a diaphragm vacuum pump. The decision was also made to combine the controlled two-line (15-20 tap) experiment with a system wide (100 plus tap) vacuum experiment. This was done so that research results will be more applicable to commercial walnut tapping. The research trees for this objective were also identified on Elton Bower’s farm.
Objective #2 - Vacuum & Sap Flow Study activity
- Ran two lines (A line and B Line) 20-30 trees per line that were flagged by PI, Mike Rechlin – Research Associate, Kate Fotos
- Tapped trees – Research Associate, Kate Fotos – First week of February
- Monitored 10 sets daily total flows on each line. Twenty measurements total running from morning to freeze-up. –PI, Mike Rechlin, and Research Associate, Kate Fotos
- One flow with pump on line A
- Next flow with pump on line B
- Put approximately 100 walnut trees on tubing. Monitored sap flow throughout the season using a Mountain Maple diaphragm pump and controller.
- Data analysis – PI, Mike Rechlin, and Research Associate, Kate Fotos
Objective #3 – Tapping Study #1. Hypothesis: Special walnut 7/16 spouts and revised walnut tapping guidelines will yield more sap than 5/16 maple spouts using maple tapping guidelines. We explored whether special walnut 7/16 spouts and revised walnut tapping guidelines would yield more sap than 5/16 maple spouts using maple tapping guidelines. Working with the researcher Arley Carpenter at the Robert C. Byrd Institute of Advanced Manufacturing (RCBI) we designed a walnut specific sap spout that included considerations of a longer barrel to accommodate the thicker bark of walnut trees and that had more taper than a maple spout, allowing it to seal without penetrating the tap hole as far as a standard low tapered maple spout. After consultations with the project advisors, and based on observed walnut tree growth rates, it was decided to develop a 7/16-inch spout as opposed to the widely used 5/16- inch maple spouts.
Related to spout size is the amount of injury the tree sustains due to tapping. Part of the third project objective was to dissect previously tapped walnut trees to look at that injury, referred to as compartmentalization, of the injury. Injured xylem, which is no longer productive, along with growth rates will allow us to develop sustainable walnut tapping guidelines. Working with collaborating researcher Adam Taylor of Virginia Tech’s Catawba Sustainability Center, we dissected the first of ten trees. Research Associate Kate Fotos is developing a mathematical model that will factor growth rate and tissue loss into recommended tapping guidelines.
Objective #3 – Tapping Study #1 activity completed third and fourth weeks of January.
- Selected study trees at each partner’s farm. Two taps per tree (Collaborating Research Adam Taylor at Catawba Sustainability Center and Partner Farmers Karen Milnes, Steve Czarnik, and Chip Matheny)
- Each farmer tapped trees just like he/she did last year or last time they tapped walnut – Partner Farmers
- Installed a second tap in each tree using 7/16 walnut taps and revised tapping guidelines – PI, Mike Rechlin
- Partners monitored and recorded sap flow and brix, and the date on both taps throughout the season. Note – each tap ran into a separate bucket. – Partners
- Data analysis – PI, Mike Rechlin
Injury compartmentalization study (completed after 2020 growing season)
- Harvested 5 trees tapped with new walnut spouts and dissect to determine volume of xylem compartmentalization. – PI, Mike Rechlin and Collaborating Researcher, Adam Taylor of Catawba Sustainability Center
- Harvested 5 trees tapped with maple spouts and dissect to determine compartmentalization – PI, Mike Rechlin and Collaborating Researcher, Adam Taylor of Catawba Sustainability Center
- Developed tapping sustainability model, based on volume of compartmentalization and tree growth rate – Research Associate, Kate Fotos
Objective #4. - Design and build an advanced rocket stove design-based evaporator. The goal is to create an inexpensive small-scale evaporator that will allow farmers to begin tapping without a major investment.
On October 10th a project organizational meeting was held at RCBI. That was followed up on November 11th with a design charrette where specific stove design features were identified. The design parameters agreed upon were that the evaporator:
- Should incorporate “rocket stove” principles.
- Rocket stoves are energy efficient, they burn relatively little wood
- They are clean burning, producing low emissions, and
- They are efficient at transferring heat from the fire box to the cooking vessel.
- Should be easy and relatively inexpensive to build. The goal is to design an evaporator that can be constructed with locally available materials, needing the services of no more than a local welder, and cost less than $500 to construct.
- Obtain a sap evaporation rate of 5 gallons/hour.
Darren Booth was designated the lead fabricator, with design assistance from Arley Carpenter, RCBI engineer. Other members of the rocket evaporator team include: Greg Christian (mechanical and electrical engineering) Evan Nelson (quantitative analysis) and Mike Rechlin (project PI and walnut sap flow specialist).
Design is an iterative process. The rocket evaporator team met a third time, on January 9th, to test an initial prototype. After firing up and analyzing the stove, the following changes are recommended for the second iteration:
- The addition of stove gasket to make a better seal between the pan and the stove
- Lowering the grate on the firebox to raise the point where flame is sucked into the heating chamber
- Adding an air intake port with damper to the firebox to maintain laminar air flow across the flame
- Additional sealing of the firebox to the heat exchange chamber
- Encompassing the firebox with insulation (vermiculite and a housing) to reduce heat loss
- Redesigning the bottom of the pan to include raised flues to increase surface area
- Adding handles to make removing the pan easier.
Objective #4 - Design and build an advanced rocket stove design-based evaporator activity completed fall 2020. Darren Booth (collaborating researcher), Arley Carpenter (RCBI), and Mike Rechlin (PI)
- Iterative Design Process – Arley Carpenter (RCBI), Darren Booth (collaborating researcher)
- Build Prototypes – Darren Booth (collaborating researcher)
- Coordinate Testing – Mike Rechlin (PI)
- Evaporation rate
- Fuel efficiency
We worked under the assumption that the softer wood of walnut would allow the spout to be driven in further before it “stuck,” as indicated by the tapping hammer bouncing off the spout and the pitch of the tap ringring. These are commonly used metrics of a properly inserted spout in maple trees. To test this assumption, we conducted a study in which we compared commonly used low taper maple spouts to our newly designed high taper walnut spouts.
Pre-season field testing of New walnut spouts
Study dates: 12/10/19 and 1/8/20
Taps seat when the pitch rises, and the hammer bounces off the spout when hit. Seating is important to seal the tap hole and to have the spouts stick in the tree. The further in the tap hole that the spout is driven before seating, the less exposed xylem for sap flow. Based on preliminary studies during the 2019 sap flow season we hypothesized that commonly used 3/16-inch maple spouts were being driven too far into the hole before seating. We then designed and built new stainless steel 7/16-inch walnut spouts that have a greater barrel taper. Average taper on the maple spouts was .05 inches while the taper on the new walnut spouts was .15 inches. These new walnut spouts also had a .75 inch longer barrel than the maple spouts to compensate for the thicker bark on walnut trees.
Various maple spouts and our new walnut spout were tested, to determine depth to seating, on a black walnut bolt of freshly cut maple bolt. Depth to seating, minus the bark thickness, was then measured. Spouts were considered seated when the pitch went up and the hammer bounced off the spout.
Results
Fig 1.1 Black walnut (Depth in inches)
|
Trial |
New 7/16 walnut spouts |
Maple spouts |
3/16 maple spouts tested |
Barrel taper |
Inches |
|
1 |
0.37 |
0.81 |
Polycarb stubby adapter |
.36-.29 |
.07 |
|
2 |
0.46 |
0.66 |
Nylon stubby adapter |
.31-.29 |
.02 |
|
3 |
0.47 |
0.62 |
Polycarb CDL |
.34-.30 |
.04 |
|
4 |
0.34 |
0.79 |
White plastic CDL |
.35-.28 |
.07 |
|
Mean |
0.41 |
0.72 |
7/16 walnut spout taper |
.56-.41 |
.15 |
Fig 1.2 Sugar Maple
|
Trial |
Seating depth |
3/16 spout type |
|
1 |
.5 |
Polycarbonate stubby adapter |
|
2 |
.5 |
White plastic CDL |
|
3 |
.5 |
Nylon stubby adapter |
|
4 |
.25 |
Polycarb CDL |
|
Mean |
.44 |
|
Analysis: As shown in Figure 1.1, the average depth to seating in walnut was 0.72 inches for the maple spouts and only 0.41 inches for the new walnut spouts, a statistically significant decrease (t-test p=.002). That means that the maple spouts are being driven 0.31 inches further into the tree, sealing off an approximately third of an inch more xylem, which could potentially reduce sap flow.
To be sure that wood harness was the cause of the difference we also tapped the maple spouts into a bolt of Sugar Maple (Figure 1.2). The average depth to seating for maple spouts in maple was 0.44 inches. This is almost the same as the depth of the new walnut spouts in walnut (0.44 inches vs 0.41 inches), indicating that the added taper in the walnut spout was compensating for the softer wood and achieving spout seating without sealing off more xylem than necessary. It is also worth noting that the Polycarbonate CDL spout seated at half the depth of the other spouts tested.
Final Results Summary and Research Conclusions
Objective #1 - Timing of Tapping Study
The study report, Walnut – Observations of the Timing of Tapping, is attached (Attachment #1 Timing of Tapping).
We tapped our walnut trees starting two weeks after the initial maple run, with staggered tappings on February 8th, February 23rd, and March 18th. Our hypothesis was that walnut trees run later in the season, and we expected to see heavier sap flows in the later tappings. For a variety of reasons, we were not able to show this expected relationship. Then, quite serendipitously, we drilled some holes in a walnut tree on April 16, a full two weeks past our last data collection date and had, by far, the best walnut sap flow of the season. This was well after we assumed the season was over. The paper reviewed for this research: Seasonal variation in xylem pressure in walnut trees: root and stem pressures, by Frank W. Ewers sheds light on this observation. Ewers found that, unlike maple, walnut builds stem pressure due to freeze/thaw cycles and root pressure. Like birch, root pressure builds after the end of the seasonal freeze/thaw cycles as the soil warms.
The study report is titled “Observations of the Timing of tapping,” because we collected only one very late season data point. In the 2021 sap flow season, we plan on conducting a series of very late season tappings to verify this single observation and to see if the presumed root pressure-initiated sap flow significantly increases yield. It is possible that a walnut tapping strategy could involve early season tapping to catch the freeze/thaw that initiated sap flow followed by a second very late season tapping to catch sap flow due to root pressure.
Objective #2 – Vacuum and Sap Flow Study
The study report, The Effect of Vacuum on Walnut Sap Flow, is attached (Attachment #2 Walnut 2020 Vacuum).
In this study, we established two sap lines with 20 taps on each line and used a small diaphragm pump to pull approximately 8-inches of vacuum on one line, while the other was on gravity flow. With 8 experimental runs we found that the application of low vacuum doubled sap flow (p=0.038).
Walnut sap has an excessive amount of gasses in the sap, limiting the ability of a diaphragm pump to pull higher levels of vacuum. We were able to bring in a high CFM vacuum pump and releaser for a one-day trial on 300 plus taps, bringing the end line vacuum up to only 10 inches of mercury. Once again, it showed a doubling of sap flow. Our research plans for the coming season include replicating this study with a system that has the capacity to bring the vacuum up to 24 inches Hg and allow us to monitor sap flow on multiple trials at various vacuum levels. Results from the 2020 season show that relatively low levels of vacuum dramatically increase walnut sap flow.
Objective #3 – Tapping study #1
The Study Report, Research into Designing a Walnut Specific Spile, is attached (Attachment #3 Walnut tapping).
In this study, we worked with 4 partnering farmers tapping black walnut trees to trial a new walnut specific spile and assess tapping methods to increase walnut sap production. The walnut specific spile was designed and built by the Robert C. Byrd institute of advanced manufacturing. It incorporated a longer barrel to accommodate the thick walnut bark, more taper to seat better, and a larger 7/16-inch tap hole. The modified tapping procedures called for drilling a deeper tap hole, cutting through the entire depth of the sapwood of the tree. The 2006 study by Gary Naughton found that sapwood thickness correlated most highly with sap yield. In three of the four partner studies the walnut specific spile and new tapping guidelines significantly outperformed the practices the farmers had used in past years.
In the process of doing this study and the previous vacuum study, we began to identify specific and unique issues related to walnut tapping. The first of those was the excessive gasses in the sap, which is most likely related to the semi-ring porous nature of the wood. In a 3/16-inch sap tube, walnut has an average of 5% sap (95% gasses), whereas maple has an average of 85% sap (15% gasses). The second is that the nylon 7/16-inch spouts used in these studies tended to back out of the tree. We found that 25% of spouts had to be reseated each day. This compares to maple’s reseating rate of 1% of spouts over the course of the season. During the 2021 sap flow season, we plan on using polycarbonate spouts, which stick much better. We are also continuing our work with RCBI in refining the walnut specific spout to incorporate design characteristics that make it stick better in the soft wood.
The study report, Preliminary Walnut Staining Pattern is attached (attachment #4 Preliminary Walnut Staining Pattern).
The second part of this objective was looking at the area of compartmentalization caused by tapping walnut trees. This is important in determining walnut tapping guidelines. Although very preliminary, it looks like walnut trees are able to efficiently contain the death and staining of sapwood. In the two samples analyzed, the stained volume was contained within 8 times the taphole volume as opposed to the 75 times the volume of the taphole in maple. We have plans to continue analyzing more taphole compartmentalization this coming year.
Objective #4 – Design and build an advanced rocket stove design-based evaporator
Fabrication instructions for The Rocket Sap Evaporator are attached (Attachment #5 RSE plans)
Working with RCBI and based on the manual Design Principles for Wood Cook stoves, by the Aprovecho Research Center, we designed and built an energy efficient rapid boiling sap evaporator for “backyard” syrup makers with 20 or fewer trees tapped. Our objectives in this project were to design and build a stove that would:
- Evaporate 5 gallons of sap per hour; what you can get out of good commercial hobbyist evaporator. The Rocket Sap Evaporator will evaporate 6.3 gallons of sap/hour.
- Be energy efficient – The Aprovecho design principles are used worldwide to increase wood burning efficiency to decrease deforestation.
- Cost less than $500. The stove we build cost $240, compared to a commercial hobbyist evaporator costing over $1,500
- Able to be made from readily available materials and fabricated by a local welder. We now have 4 people using the Fabrication instructions to build their own Rocket Sap Evaporator.
With an efficient and inexpensive evaporator, more people will be able to make their own maple syrup and experiment with walnut syrup production. This will allow people to start making these valuable syrups on a small scale. Some of them will just enjoy their syrup on their breakfast pancakes. Some will expand to become commercial syrup producers.
Objective #1 looked at the proper time to tap walnut trees. In this study we did a literature survey of walnut sap flow physiology along with a field study that staggered the timing of tapping by two-week intervals. While the field study did not yield the results we expected, the literature review alerted us to the possibility of root pressure as a secondary initiator of sap flow, causing us to tap much later and observed a copious sap flow event. We have plans to further investigate root pressure sap flow in the coming season.
Objective #2 investigated the effects of vacuum and sap flow. We collected walnut sap from 20 taps relying on gravity flow and 20 taps under relatively low vacuum. We found a highly significant increase in sap flow from the trees under vacuum. Eight inches of vacuum increased sap flow from 0.37 qt./hr. to 0.74 qt./hour. This is highly useful information. Two major West Virginia walnut producers are now running vacuum on their lines.
Objective #3 investigated a spile specifically designed for walnut trees and improved tapping procedures. It included a preliminary study of compartmentalization of sapwood around a taphole, which relates to tapping sustainability. In three of the four study sites the new taps and procedures significantly increased sap flow. The compartmentalization study showed that 8 times the volume of the taphole is killed in walnut, which compares favorably to the 27 times the volume of the taphole killed in maple. The above studies also pointed to another walnut tapping problem, where over time the spouts are pushed out of the tree. We are working with the Robert C. Byrd Institute of Advanced Manufacturing to design of a second generation “stickier” walnut spile.
Objective #4 was the development of a small sap evaporator based on rocket stove principles. We successfully designed and tested an energy efficient evaporator that boils away 6.3 gallons of sap/hour, is inexpensive to build, and uses readily available materials. This has created a lot of interest. We have 16 people building and testing this design in the coming sap flow season. The plans will soon be on Future Generations University’s website. It will be very useful in encouraging farmers to start a new maple of walnut syrup production operation.
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Education & Outreach Activities and Participation Summary
Participation Summary:
Walnut tapping was included in presentations gave by Dr. Mike Rechlin (PI) at the following events:
- 9/19 Laurel Fork Sapsuckers Forest Management for Sap Production Workshop (Sept. 2019)
- 11/19 Catawba Sustainability Center Tapping Workshop (Nov. 2019)
- 11/19 Southwest Virginia Maple School (Nov. 2019)
- Lake Erie Maple Expo (Nov. 2019)
- Scheduled presentations on walnut tapping that were cancelled due to COVID
- Southern Syrup Research Symposium, June 2020
- West Virginia Maple Syrup Producers Association Annual Meeting, May 2020
Walnut tapping was also included in the curricula of Future Generations University’s Certificate in Maple Sap Collection & Syrup Processing, which includes online instruction.
Following the 2020 sap flow and research season we plan on the following outreach activities:
- West Virginia Small Farms Conference – panel presentation by Research Associate Kate Fotos (February 2020)
- West Virginia Maple Syrup Producers Association Annual Meeting – Demonstration and Presentation of Results by Research Associate, Kate Fotos (May 2020)
- Second Annual Southern Syrup Research Symposium – presentation by PI, Mike Rechlin (June 2020)
- Second Annual Southern Syrup Research Symposium – presentation by Research Associate Kate Fotos (June 2020)
- Articles for Maple News – PI, Mike Rechlin (July/August 2020)
- Articles for Maple Syrup Digest – PI, Mike Rechlin and Research Associate Kate Fotos (July/August 2020) Digest final 5_26
- Article about Walnut Syrup Production in the Roanoke Times 'Liquid gold' from walnut trees brings new attention to Highland County | Business | roanoke.com
- Article in Pendleton County Times about Alternative Syrups Alternative syrups
- Creation of Walnut Syrup Facebook Group A New Sweet Presence on Facebook
Learning Outcomes
Walnut tapping procedures, the potential for marketing specialty syrups
Project Outcomes
As more data about best practices for syrup production has been made available, the partner farmers, as well as additional producers interested in walnut syrup, have been able to improve the efficiencies in their systems (walnut-specific spiles/spouts, tapping practices, small-batch evaporative efficiencies) and the rocket sap evaporator is applicable for new maple syrup producers, making entry into the market easier and less expensive.
The research approach worked well, although flexibility was needed as partnering farmers dropped out of the program and had to be replaced by others to complete the activities.
This is the final report on the NE SRE Partnership Grant ONE19-347. All objectives have been reached and the project funds expended. However, the work initiated in this grant is not over. As often happens, research answers questions, and those answers lead to other questions. With funding from the Claude Worthington Benedum Foundation, Future Generations University will be able to continue research into walnut sap flow and syrup production over the 2021 sap flow season. Secondary questions identified in the reporting under Objectives 1,2, and 3 will be investigated this year.
Objective #1: Timing of Tapping Study
- Install a sensitive pressure gauge and a spout and bucket on a walnut tree. Monitor pressure during the normal sap flow season and during the root pressure late season flow through use of a wildlife camera programmed to take a picture every 30 minutes. This will correlate sap flow to pressure during the stem pressure and the root pressure season. This will also help let us know when to put in the second tap at Tonoloway Farm.
- Baseline walnut sap flow study: We will develop a data sheet where walnut sap producers could enter key sap flow and syrup production parameters throughout the season. This will be online, and open to walnut syrup Facebook members. It would allow us to begin to determine who is tapping, how much syrup is being made, and the timing of their tappings. It woud also link FGU to the walnut sap and syrup world of producers.
Objective #2: Vacuum and Sap Flow Study
- Sap flow and vacuum level. Using trees on the A and B lines established last year but now with 5/16-inch tubing, we propose to tap into Elton’s vacuum lines to conduct 10 trials in which 10 inches of vacuum are applied to one line and 20 to the other line.We would then monitor sap flow and the gas to sap ratio in each line.
- Walnut sap flow under vacuum from 3/16-inch vs 5/16-inch tubing. Run a new 3/16-inch line and a 5/16-inch line with approximately 20 trees each up Elton’s hillside where we had 3/16-inch tubing last season. Monitor sap flow in 10 trials of equal length recording end of line vac levels.
Objective #3: Tapping Study
- Conduct the “Cornell 2 tap” study at Christoph’s. We would use one tap during the regular sap flow season and one tap late in the season to catch the root pressure-initiated run. This would require running 2 sap lines to each of approximately 20 trees.One line would be tapped in early February sap collected and measured. This trial would continue throughout the sap flow season. The second line, with a second tap in each tree would be tapped late in the season to collect only the late season flow. Measuring total sap collected from each line would indicate when tapping would be most effective.
- Analyze walnut compartmentalization on the tree we set up for this study last spring. Harvest tree, section, measure staining, and calculate volumes.
- Analyze walnut compartmentalization on the tree we set up for this study a year ago. Harvest tree, section, measure staining, and calculate volumes. Feeds data into the compartmentalization study.
Information Products
- Walnut – Observations of the Timing of Tapping (Article/Newsletter/Blog)
- Research into Designing a Walnut Specific Spile (Article/Newsletter/Blog)
- The Effect of Vacuum on Walnut Sap Flow (Article/Newsletter/Blog)
- The Rocket Sap Evaporator (Manual/Guide)