ANNUAL REPORT,, 1929 33y' 



Four definitely planned experLmental conditions were established for 

 the defined agronomic work: 



1. Units planted with legumes and receiving fertilizer. 



2. Units planted with legumes and not receiving fertilizer. 



3. Units receiving fertilizer but not planted with legumes. 



4. Units not receiving fertilizer and not planted with legumes. 



From this summary there appears to be sufficient nitrogen-fixation in 

 the soil of Field A to account for the nitrogen reserve. The nitrogen- 

 fixation in the experimental field is correlated with the presence of a 

 strain of Azotobacter capable of fixing substantial quantities of nitrogen 

 when cultivated in pure culture in a nitrogen-free medium. Nitrogen- 

 fixation and the distribution of the Azotobacter appear to have remained 

 reasonably constant over a three-year period. The growth of the legume 

 and non-legume crops has not influenced nitrogen-fixation or the distri- 

 bution of the Azotobacter. The hydrogen-ion concentration of the soil 

 of the experimental field does not^ appear to be the controlling factor 

 in the nitrogen-fixation or the distribution of the Azotobacter. The data 

 as accumulated in this study have furnished considerable information 

 which may later be placed on a basis for the establishment of practical 

 methods by which the nitrogen-fixation organisms naturally present in soil 

 may be stimulated to greater activity. 



Laboratory Service. (Ralph L. France). More than one thousand 

 examinations of samples were made by the department during the past 

 year. Of this number, seven hundred were control tests of various town 

 milk supplies in the Connecticut Valley. In many cases monthly control 

 tests are made, and in other cases the testing is done at different times 

 during the month. At the present time the activities in this phase of the 

 laboratory work are somewhat limited because samples can be transported 

 only short distances. Then, too, the Massachusetts State Department of 

 Health carries on activities especially for those dairies and town health 

 departments located in the Boston or metropolitan district. Many samples 

 from private water supplies have been submitted to the laboratory for 

 examination. These have been for complete bacteriological and chemical 

 examination, for the most part, to determine the purity of the water in 

 question. It is of some interest to us from the standpoint of public 

 health to note that nearly 50 per cent of the private supplies were found 

 to be unsafe. This indicates the need of more active education in the 

 construction and location of private water supplies. It also indicates the 

 need of a sanitary survey of water supplies as regards those located on 

 private property. 



The sale of legume cultures has materially decreased during the year. 

 This is no doubt due to the activities of certain commercial concerns which 

 are supplying cultures free to purchasers of legume seeds in bushel lots. 



Other services rendered by the laboratory are: 



1. Bacteriological analyses of food and food products, milk and milk 

 products, and water. 



2. Chemical analyses of milk and water. 



3. Preparation and distribution of viable and efficient cultures of 

 nitrogen-fixing bacteria for leguminous crops. 



4. Testing of nitrogen-fixing bacteria for quality. 



