This project has developed guidelines to determine a tap hole size that maximizes sap production while minimizing the damage caused by drilling.
The maple sugar industry removes sap from maple trees by drilling holes into the trunk of the tree. Energy spent by the tree on wound-response to a large tap hole may reduce the tree?s longevity and therefore the amount of sap that can be harvested from the tree. Thus, there is a direct economic value to optimizing the balance between sap yields and tree damage.
We conducted research on the relation between hole size and sap yields in vacuum sap collection systems. The results show that tap hole size can be reduced from the standard 11 mm to 7.5 mm without significant reduction in sap yields. Reducing the hole size to 4 mm seems to produce less sap, but not always.
Our analysis of fluid flow in the tree has allowed us to predict how sap yields will vary based on the size of the tap hole and the length of the sap flow period. We were also able to explain how vacuum systems improve sap yields, a matter which has puzzled researchers and producers. These results have been published and presented to maple producers in public presentations.
Drilling 7.5 mm tap holes takes less time and effort, produces less internal tree damage, and avoids significant reduction in sap yields. As a result, many producers have adopted the 7.5 mm standard. More than half of the current producers are now using this standard, and more are converting as they upgrade their equipment.
Manufactures are now introducing taps that produce holes smaller than the 7.5 mm standard. Yet, depending upon the environmental conditions in each particular forest, these taps may potentially reduce sap yields. By explaining how tap hole size, vacuum systems, and temperature conditions affect sap yields, our research has allowed producers to make more informed decisions regarding the purchase of equipment that would further reduce hole sizes and potentially decrease yields.
Our research will also benefit the longevity and health of maple trees and thus contribute to forest sustainability.
- Federal Formula Funds - Research (e.g., Hatch, McIntire-Stennis, Animal Health)
- Private (e.g., commodity groups, foundations, companies)
- North American Maple Syrup Council
- Brian F. Chabot, Department of Ecology and Evolutionary Biology