200 MASS. EXPERIMENT STATION BULLETIN 280 



The plots maintained in cooperation with the United States Golf Association 

 continue to furnish interesting data, and the value of complete fertilizers with 

 high nitrogen content is very obvious on the closely clipped putting green turf. 



On the eight-year campus lawn plots with Kentucky blue grass, cottonseed 

 meal continues to produce such a healthy stand of grass that weeds find no room. 



DEPARTMENT OF BACTERIOLOGY 

 Leon A. Bradley in Charge 



Nitrogen Fixation in tlie Presence of or as a Result of Legumes versus 

 Non-Legumes. (.J. E. Fuller). Nitrogen fixation .studies comparable with 

 those previously published (L. A. Bradley and J. E. Fuller, Soil Sci. 30: 49-57, 

 1930) were made. Samples were taken from the various sections of the experi- 

 mental plot in the spring (1931) before the crop was planted, and in the fall 

 after the crop was harvested. Nitrogen fixation at both seasons appeared to be 

 reasonably constant and generally distributed over the plot. There was no sig- 

 nificant difference noted between the legume and non-legume strips. This agrees 

 with findings of 1926 and 1928, reported in the publication mentioned above. 

 In order to estimate the quantitative distribution of nitrogen-fixing microorgan- 

 isms through the plot, studies were made of the various soil samples by a dilution 

 method. The dilutions employed were 1 in 100, 1 in 1000, and 1 in 10,000, and 

 1-cc. quantities were inoculated in Ashby's solution. In soil samples taken in the 

 spring there was no nitrogen fixation from any except the 1 in 100 dilution. 

 The samples taken in the fall gave definite nitrogen fixation from all dilutions, 

 indicating an increase in the number of the nitrogen-fixing microorganisms dur- 

 ing the season. There was no difTerence between the legume and non-legume 

 strips. 



The activity of the soil in nitrifying dried blood and ammonium sulfate, and 

 in decomposing cellulose, was studied. Both functions were active and generally 

 distributed over the whole field. There was no difference between the legume and 

 non-legume strips. These studies were made on the soils collected in the spring. 

 Studies on the samples collected in the fall have not been completed. 



The fertilizer treatment of the plot, and the crop planted on it, are reported 

 under the same title as that above by the Department of Plant and Animal 

 Chemistry (F. W. Morse). 



Utilization of Mannite by Azotobacter. (J. E. Fuller.) The practice of 

 reporting the amount of nitrogen fixed by bacteria as milligrams of nitrogen per 

 gram of consumed mannite appears to be faulty. The mannite rarely is entirely 

 consumed; and in 100 cc. quantities or less of culture media, it is impractical to 

 estimate the amount of residual mannite. Experiments showed that soil inocu- 

 lum and pure cultures of Azotobacter, each supplied with 10-gram quantities 

 of mannite, fixed only slightly more than twice as much nitrogen as was fixed 

 when 2-gram quantities of mannite were supplied. 



Influence of Temperature on the Nitrate Content of Soil in the 

 Presence of Decomposing (Cellulose. (.J. E. Fuller and L. H. Jones.) Com- 

 post soil -uath one per cent added cellulose (filter paper) was incubated for 6 

 weeks at temperatures of from 10° C. to 35° C, at intervals of two and three 

 degrees. Nitrate tests were made each week. At temperatures of 25° to 35° 

 there seemed to be sufficient nitrification to replace the nitrate loss in the presence 



