AGRICULTURE HANDBOOK 134, U.S. DEPT. OF AGRICULTURE 



PN-4706 



Figure 9. — Measuring the density of sap C Brix) with a 

 precision hydrometer cahbrated in 0.1°. If the bucket 

 contains too little sap to provide the necessary depth 

 for the measurement, transfer the sap to a hydrometer 

 can. 



of the sap so the hydrometer reading can be 

 corrected. (The sap should contain no ice.) Sub- 

 tract 0.4° Brix for temperatures of 32f to 50° F., 

 0.3° Brix for temperatures of 51° to 59°, and 0.1° 

 Brix for temperatures of 60^ to 68". 



The sap hydrometer is usually calibrated 

 from 0° to 10° Brix, with divisions of 0.5°. A 

 more accurate measurement can be obtained 

 by using a hydrometer with divisions of 0.1° (fig. 

 9). 



The amount of sugar in sap is of great eco- 

 nomic importance. A taphole that produces 15 

 gallons of sap with a sugar content of 2° Brix 

 yields 2.5 pounds of sugar, or one-third gallon of 

 sirup; whereas a taphole that produces 15 gal- 

 lons of sap with a sugar content of only 1° Brix 

 yields only 1.3 pounds of sugar, or less than one- 



fifth gallon of sirup. The cost of producing the 

 sirup from both tapholes is approximately the 

 same. Trees producing sap with a sugar content 

 of 10° Brix are especially profitable, as 15 gal- 

 lons of sap from 1 taphole yields nearly P/4 

 gallons of sirup, or more than five times as 

 much as the 2°-Brix sap. Trees that produce sap 

 low in sugar (1° Brix or less) should be culled. 



Research is being conducted at the Universi- 

 ties of Vermont and New Hampshire, at the 

 Ohio Agricultural Experiment Station, and by 

 the U.S. Forest Service on the propagation of 

 maple trees from selected high-yielding trees 

 (20, 32, 33, 3U, U5). This research should eventu- 

 ally make it possible to set out maple orchards 

 or roadside trees that will produce sap with a 

 high sugar content. 



Use of a germicidal pellet to prevent prema- 

 ture drying up of a taphole may increase sap 

 yields as much as 50 percent. Since the results 

 obtained by using the pellet are due to its 

 germicidal action, it will not increase the sap 

 crop in sugar groves where sanitary measures 

 are already being practiced. 



Summary' 



(1) Consult your State extension forester, farm 

 forester, and county agricultural agent and 

 work with them to develop a management 

 plan for your sugar grove. Aim for 160 

 tapholes per acre (160 trees 10 inches d.b.h. 

 or 40 trees 25 inches d.b.h.). 



(2) Remove all defective, diseased, and weed 

 trees. 



(3) Check the yield and sugar content (° Brix) of 

 the sap from each tree. Cull trees that yield 

 sap low in sugar (1° Brix). 



(4) For maximum sap yields use germicidal 

 taphole pellets. 



TAPPING THE TREE 



The sap of the sugar maple, from which sirup 

 and sugar are made, differs in composition from 

 the circulatory sap of a growing tree. We know 

 little concerning this sap, or sweet water as it is 

 called in western Pennsylvania. Intensive 

 study of maple sap at the University of Ver- 

 mont (3U, 35, 57-59) should lead to a better 



understanding of its nature, function, and 

 source, and of the factors responsible for sap 

 flows. 



Sap will flow any time from late fall after the 

 trees have lost their leaves until well into the 

 spring, each time a period of below-freezing 

 weather is followed by a period of warm 



