22 A/IASS. EXPERIMENT STATION BULLETIN 378 



complete lactations while the other eight receive a grain mixture in which 

 urea has been substituted for the usual protein concentrates (cottonseed 

 meal, soy bean oil meal, and gluten feed). The maximum amount of urea 

 which it is planned to feed is 3 percent of the grain allowance (60 lbs. 

 per ton). This amount has now been fed for over six months without 

 untoward results. Cornstarch is being used to balance the energy con- 

 tent of the grain mixture which contains urea. 



The first season's work with the eight cows on the double reversal 

 experiment has been completed and summarized, and results from the 

 first twenty-two weeks with the sixteen cows on the continuous feeding 

 trial are also available. While final conclusions must await the outcome 

 of another year's work, results to date indicate that, except for a slight 

 superiority in the general condition of tlie cows receiving the regular 

 ration, the two rations have had apparently similar effects. 



The Effect of Feeding Irradiated Dry Yeast on Reproduction and Gen- 

 eral Health in Dairy Cows. (J. G. Archibald and A. E. Conklin.) This 

 practice, established some years ago for the production of metabolized 

 vitamin D milk, is being investigated for its possible beneficial eflfect on 

 the cows themselves. The work is being done in cooperation with Stand- 

 ard Brands, Inc., of New York City and the Massachusetts State Depart- 

 ment of Healtli. Sixty cows in the herd of the Gardner State Hospital 

 have been divided into two groups, one of which receives the regular 

 herd ration while the other receives in addition irradiated yeast (Y^ pound 

 per ton of grain) for a period of two years. Careful records of milk pro- 

 duction, reproductive function, and general herd healtli are being kept. 

 The work has not yet been in progress long enough to yield any substan- 

 tial amount of data or to warrant drawing any conclusions. 



DEPARTMENT OF BACTERIOLOGY 

 Leon A. Bradley in Charge 



Nitrification in Soils Containing Plant Residues of High Lignin Con- 

 tent. (James E. Fuller.) This experiment is being carried on in co- 

 operation with the Agronomy Department. In 1939 a number of plots 

 were planted with crops having high lignin content. For comparison, 

 some low-lignin crops were planted, and some plots were left fallow. In 

 the fall the crops were plowed under. In 1940 tobacco was grown over 

 the whole area. Soil samples were collected in the spring, in mid-season, 

 and in fall. The ability of the soils of the samples to nitrify their own 

 nitrogen and to nitrify dried blood was studied. The experiment is based 

 on the theory that if it can be shown that certain crops plowed into the 

 soil hamper the process of nitrification, it might follow that growth of 

 plants (tobacco, for instance) would also be interfered with; and stunted, 

 or even diseased crops, would result. 



To date, no differences observed in the nitrifying capacities of the soils 

 can be attributed to the crops plowed under. The experiment will be 

 continued another year. 



Bacteriological Study of Spices and Spice Oils. (James E. Fuller and 

 Frederick J. Wishart.) Several standard brands of packaged spices were 

 studied, including cinnamon, cloves, nutmeg, allspice, black pepper, red 



