We had two objectives in the study of sugar maples which showed signs of decline and stress on a roadside where deicing salt was used in the winter. One goal was to determine if tree stress is related to the levels offsodium and chloride in their sap and in the groundwater and soil around their roots; and, if so, to develop methodology approved by the Association of Official Analytical Chemists (AOAC) that would allow any laboratory to use a standard method to assess maple tree decline due to sodium and chloride effect. The second goal was to evaluate the quality of the syrup processed from sap aseptically collected from maples in decline. We are updating here the later objective of the project that is of interest to the sugar maple producers.
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Dr. Abby van den Berg, Research Associate Professor with UVM’s Department of Plant Biology and Proctor Maple Research Center, shares the results of a multi-year experiment conducted by the University of Vermont Proctor Maple Research Center to determine the net yields and impacts of fall and early-winter tapping, with and without subsequent “freshening” of the tapholes by re-drilling them wider and/or deeper.
During the 2011 maple sap season a variety of research trials were conducted at the Arnot Forest of Cornell University and in the woods of a number of cooperators both with vacuum and gravity systems. Research conducted over the last five years has shown that significant increases in sap yield can be obtained by keeping the tap hole from contamination by bacteria and yeast.
In 2012 a variety of spout and tubing cleaning and replacement options were tested to determine the extent of sap yield changes. These tests were done at the Cornell Arnot Research Forest.
In 2013 a variety of spout and tubing cleaning and replacement options were tested to determine the extent of sap yield changes that would result. Most of these tests were done at the Cornell Arnot Research Forest.
In 2014 and 2015 the focus of the tubing and taphole sanitation research changed dramatically. Tests conducted in 2013 showed that if the spout and drop line were adequately sanitized sap yield comparable to a new spout and drop could be obtained. With the assistance of a grant from the Northeast Sustainable Agriculture Research and Extension program of the USDA and in cooperation with the Proctor Maple Research Center in Vermont, a variety of spout and drop cleaning and replacement options were tested to determine the extent of sap yield changes.
During the 2015 maple sap season the Cornell Maple Program conducted a small trial, testing sap yield from 5/16″ tubing vs. 3/16″ tubing. This trial was not conducted at the Arnot Research forest but with a small maple operation cooperator. The tubing system consisted of six lateral lines, three 5/16″ and three 3/16″ alternating between the two treatments across the hillside.
Documents experiments conducted by Cornell researchers involving re-tapping mid-season.
During the 2019 maple season the Cornell Maple Program conducted replicated trials on 5/16Ó and 3/16Ó tubing looking at a variety of tubing options for taphole sanitation and tapping. This report will focus on the 5/16Ó results.
In a normal sap flow event, trees exude sap during the above freezing period and replenish that lost water by ÒsuckingÓ it up from the roots during the below freezing period. If on a tubing system, during this negative pressure period they tend to draw sap back into the tree from the dropline. Sap, once it enters the droplines, is quickly contaminated with microbes. When they are drawn back into the tree, tap hole closure is initiated. The problem is compounded in 3/16- inch tubing because, unlike 5/16-inch tubing, the smaller diameter collection tube remains full of sap. A Cornell study found that up to 12 feet of sap in a 3/16-inch tube can be drawn back into the tree during this recharge time. CV spouts are one proven method of limiting this drawback with 5/16 inch tubing. The question was: will they also be effective with 3/16-inch tubing that is full of sap?