RELATIONSHIPS BETWEEN TUBING SYSTEM COMPONENT AGE AND SAP YIELD A Preliminary Assessment

INTRODUCTION Although a number of factors affect maple sap flow in vacuum tubing systems, it has become increasingly apparent that sap yields are largely a function of two major influences: vacuum level at the taphole and taphole and tubing sanitation. Vacuum controls sap yield by heightening the pressure differential between the inside of the tree and the inside of the tubing system, therefore causing more sap to flow than otherwise would without vacuum (Heiligmann et al. 2006, Chapeskie and Staats 2006, Wilmot et al. 2007). Good vacuum is primarily a matter of proper tubing system design and installation, vacuum pump capability, and the control of leaks. Taphole drying, the slowdown or cessation of sapflow, is the direct result of microbial contamination (Naghski and Willits 1955). A multi-year study at the UVM Proctor Maple Research Center demonstrated that tubing systems show fairly rapid reductions in sap yield as they age, and that these reductions are due to the level of tubing system contamination (Perkins, Stowe, and Wilmot 2010). Numerous research studies and abundant maple producer practice have adequately demonstrated that a wide variety of microbes rapidly colonize maple tubing systems (Lagace et al. 2004, Figure 1), and that changes made in the tubing system aimed at improving sanitation in the immediate vicinity of tapholes (annually changing spout adapters, new droplines, Check-valve adapters, silver antimicrobial spouts) significantly increase sap yield (Perkins 2009, Perkins 2010, Childs 2010). The objective of this study was to determine the strength of the relationship between the age of the major components of maple tubing systems and sap yield. Eventually a predictive model could be constructed to allow maple producers to evaluate their own tubing systems in order to judge potential improvements and determine the cost versus the benefits of making various changes.