Advancing black walnut syrup production through research and report on optimal tapping practices and promotion of findings at a field day.

View the project final report

Commodities

• Miscellaneous: syrup

Practices

• Crop Production: agroforestry
• Education and Training: on-farm/ranch research
• Energy: energy conservation/efficiency
• Farm Business Management: budgets/cost and returns, feasibility study
• Sustainable Communities: urban agriculture

This project aimed to advance black walnut (Juglans nigra) syrup production by testing sustainable tapping practices and collecting performance data through parallel maple and black walnut tapping operations.  By running parallel operations on the same sugarbush, the timing and production of the maple and black walnut can be compared.  This offers insight into the degree that black walnut should use maple tapping practices.

The project contemplated tapping with both buckets and vacuum tubing. With buckets, data can be analyzed at each tree. With vacuum tubing, higher yields can be drawn.  Black walnuts produce substantially less sap than maples, and increasing sap production is one of the biggest challenges for black walnut syrup producers.

Sap was collected and measured daily during each run.  A digital refractometer was used to measure sugar content.  A graduate student from Purdue University, Jean Fritz Saint Preux, analyzed the data and created a report with charts and calculations included below.  Another report with pictures and descriptions of the tapping process was also created.  Additionally, a best practices guide and business plan for a small operation was compiled.

The findings of the research were presented at a Field Day at the Rusted Flatbed Farm, which include a presentation of results, the best practices guide and business plan, a tour of the sugarbush, a black walnut syrup tasting, and large and small group discussions.

The major research conclusion is that most maple guidelines should also apply to black walnuts as the timing of trunk pressure and sap flows in relation to changes in temperature are quite similar.  It was also learned that stainless steel taps should not be used on black walnuts.  Poly taps work well, and the tapholes should be drilled between the ridges of the black walnut bark and not through them.  Because sugar content seems to diminish over the course of the season, which is dissimilar to maples, black walnuts should be tapped earlier in the season. 

These lessons learned have been put into practice and shared with other black walnut producers.  Based on observations between the maple and black walnut on 5/16" tubing, the next season will incorporate 3/16" tubing on the black walnut lines in hopes of achieving a higher level of vacuum through a natural grade gravity effect.

The solution proposed in this project is to increase the body of research on black walnut tapping by sustainably collecting and processing black walnut sap in tandem with maples and compiling data from each step in the process.

Timeline:

• May-December 2023: Sourcing and assembling equipment, selecting trees, mapping tube lines.
• January-April 2024: Tapping, boiling, and compiling data.
• May-August 2024: Draft article on findings and conclusions with assistance of grad student.
• September 2024: Circulate article among interested organizations; invitations to Field Day.
• October 2024: Field Day, survey.
• November-December 2024: Draft and submit report on grant.

This project will tap approximately 60 black walnut trees and 60 maple trees.  Around 40 of each tree type will be tapped with vacuum tubing and 20 will be tapped with buckets.  Tapping on both trees will begin at the same time (in Indiana, maple season starts in late January or early February).  The trees will be numbered and trunks measured.  Trees on buckets will be measured daily for sap production and sugar content.  The bulk tank for the trees on tubing will be measured daily for sap production and sugar content.  A spreadsheet with these measurements will be maintained, and daily high and low temperatures will be noted.  Sap production for the maple trees will be noted as well.  Daily fail rates of taps will be noted.  Adjustments to tubing vacuum pressure, types of taps, and re-tappings will be tracked.  After 3 weeks, bucket taps will be checked daily for the degree of closing of the taphole.  Hours expended in labor will be tracked.  

The walnut sap will be boiled as sufficient quantities are collected.  For each session, the amount of sap, the rate of boil, and quantity of pre-filter final product will be recorded.  The sap will be processed with industry-standard high-efficiency equipment: wood-fired arch, drop flue pan, continuous flow, arch fan, finishing pan, and steam hood.  

The Rusted Flatbed Farm, for its maple syrup operation, utilizes buckets rather than vacuum lines.  Likewise, it uses a single-batch flat pan for the evaporator.  This set-up is ideal for a maple syrup operation geared toward darker, more robust-flavored maple syrup (which tends to happen with the longer boils on flat-bottomed pans).  This is not sustainable for black walnut syrup, which requires vacuum tubing and higher efficiency pans to compensate for the lower sap production and sugar content of black walnut trees.  Accordingly, the project requires the acquisition of specific equipment and materials.

After the tapping season, a grad student with an appropriate skill set will be retained to help create graphs and charts and analyze trends in the data.  An article will be created with sections on research findings, best practices learned, and an analysis of the costs, labor, and potential ROI for the black walnut syrup operation.

The article will be presented at an open house at the Rusted Flatbed Farm in the fall of 2024.  The event will include a tour of the facility, tastings during lunch, and afterwards a discussion of the findings of the report.  The invitees will be drawn through outreach, and particularly among the members of the Indiana Maple Syrup Association (IMSA) and the Indiana Nut and Fruit Growers Association (INFGA).  A survey among the attendees will assess the flavor, degree of interest in purchasing, producing, or selling (per size of bottle, and blend), and feedback regarding the report and its conclusions.

The final report will include an updated article, summary of the open house, and survey results.  The final report will be submitted for posting on the websites and newsletters of IMSA, INFGA, and their national organizations.