34 MASS. EXPERIMENT STATION BULLETIN 449 



Frost Experiments. (C. E. Cross.) Burlap and cotton cloth were used on 

 bogs to determine what degree of frost protection they would afford as covers 

 over cranberry vines. Temperatures on frosty nights ranged from 4 to 8 degrees 

 F. warmer under the coverings — the more severe the frost, the greater the pro- 

 tection. Paper was tried as a cheaper material. Though it apparently afforded 

 good protection from low temperatures, it could not be anchored even in light 

 winds, and is therefore considered impractical. 



Soil Water Studies. (F. B. Chandler.) Studies of soil water made with wells 

 and with tensiometers (instruments to measure the tension required to move 

 water in the soil) show that one section of a bog is not uniform in water move- 

 ment for drainage or irrigation. Some bog sections or parts of sections may be 

 poorly irrigated although the ditches are filled with water. During the coming 

 year, several growers are cooperating and more data will be available later. 



Fertilizer Requirements of Cranberry Plants. (F. B. Chandler and William G. 

 Colby.) The plots previously started have been continued and about 100 new 

 plots added, for the purpose of studying the different sources of nitrogen (nitrate 

 of soda, sulfate of ammonia, cyanamid, Urea-form and tankage), sources of 

 phosphorus (rock phosphate, normal superphosphate, and triple superphosphate)^ 

 amounts of nitrogen per acre (10, 20, 40, and 80 pounds of nitrogen per acre), 

 and ratio of nitrogen to phosphorus (1-1 and 1-2.) Time of application and minor 

 elements are also being studied. The results so far do not justify any recom- 

 mendations. 



DEPARTMENT OF DAIRY INDUSTRY 

 D. J. Hankinson in Charge 



Sanitizing Agents for Dairy Use. (W. S. Mueller.) The newer sanitizing 

 agents for dairy use have in common a quaternary ammonium salt of one form 

 or another which is the active bactericidal material. A new development is a 

 cleaner-sanitizer combination. These new products are now available in both 

 liquid and powder form. 



Some of the results of this study, "Testing Quaternary Ammonium Sani- 

 tizers and Their Use in the Dairy Industry" were published in Soap and Sanitary 

 Chemicals, September, 1947 issue. 



The following progress has been made: 



1. A Method for Evaluating the Sanitizing Efficiency of Quaternary Ammonium 

 Compounds ajid Other Germicides Proposed for Sanitizing Food Utensils. (W. S. 

 Mueller and E. P. Larkin.) The method is described in the last annual report. 

 During the past year more data have been obtained on several technical steps, 

 for the purpose of improving the standardization of the suspension of test organ- 

 isms as used in the test. A hand homogenizer was used for breaking up clumps 

 of bacteria in suspension. A spectrophotometer was used for measuring the 

 turbidity of the bacterial suspension and this value was correlated with the num- 

 ber of bacteria present as determined by the plate count. Three distinct types of 

 bacteria were used in the study: a gram-negative organism, E.coli; a gram-posi- 

 tive organism, S. aureus; and a sporeformer, B. cereus. The different organisms 

 were variously affected by homogenization. The plate count of S. aureus was 

 increased 70 percent; that of B. cereus was slightly decreased. No significant 

 effect was noted on E. coli. 



