INSTITUTE AND COLLEGE, PUSA, FOR 1909-10. 49 



months of March, April, May and June. It is hoped that 

 it may be found possible in the future to establish a hill 

 station laboratory, where this difficulty may be eliminated 

 during the hot season. 



(b) The distribution and activity of the nitrifying 

 organisms has been studied closely in samples taken from 

 various depths and localities. The value of the inform- 

 ation acquired has been considerably discounted by the 

 contamination of some of the cultures owing to the absence 

 of a suitable room for carrying out inoculations and with- 

 drawing samples. During the dry hot months the air is 

 charged with dust particles carrying innumerable bacteria 

 and the periodical withdrawal of samples from the culture 

 flasks is attended with great risk of infection of the latter, 

 when conducted in the open laboratory. A suitable room, 

 capable of being isolated from the general laboratory and 

 kept free from dust and currents of air, was selected early 

 in February, and arrangements are being made to have it 

 converted for this purpose. 



Active nitrification has been observed in borings from 

 the plots attached to the pot culture house down to a 

 depth of 24 inches, the greatest amount taking place in the 

 second six inches. The samples were taken in February, 

 when the dryness of the surface soil would naturally 

 depress the general level of bacterial activity. 



It is of interest to observe that salts of magnesia have 

 been found to inhibit nitrification entirely in Pusa soils 

 when the latter are seeded into liquid media. This effect 

 is being further investigated with a view to determining 

 its underlying causes. Samples have been obtained from 

 borings to a depth of nine feet and it has been of interest 

 to discover the relatively enormous numbers of bacteria 

 present in the Pusa soils and their occurrence in the 

 samples taken from the lowest depth, it having been found 

 necessary to use dilutions of one in one hundred thousand 

 in order to obtain a workable number of colonies in 

 plating. 



E 



