902 Journal of Agricultural Research vol. vi.no. 23 



in all cases to increase the nitrogen gained. It will thus be observed that 

 the manure applied increases the bacterial activities measured, while the 

 water increased ammonification, nitrification, and nitrogen fixation, but 

 depressed the number of colonies developing upon synthetic media. 

 This would seem to be a very vital point against the count method. 

 For we thus find a soil treatment increasing the main bacterial activities 

 of a soil, but at the same time depressing the number developing in the 

 laboratory. It would thus appear that the media used to make counts 

 was better adapted for the development of organisms other than those 

 which take the greatest part in the nitrogen transformation in the soil. 

 On the other hand, it is quite possible that the increase in number may 

 not keep pace with the increased physiological efficiency due to the 

 application of water and manure. But this latter explanation would not 

 account for the less number developing on the synthetic media. 



FIELD EXPERIMENT ON FALLOW PLOTS 



The fallow plots used in the field experiments were 7 feet wide and 

 24 feet long with a 4-foot walk between each two. The land was plowed 

 in the fall, left over until spring, when a mixture of fairly well-rotted 

 horse and cow manure was applied to the various manured plots. This 

 was thoroughly disked or plowed into the soil. Water was applied to 

 the plots from flumes as described in Utah Experiment Station Bulletins 

 115 to 120. They were kept free from weeds throughout the year. 

 The quantities of water and manure applied to the various plots were as 

 follows : 



Four plots received no water and no manure. 



Two plots received 5 inches of water, but no manure. The water was 

 in two equal applications. 



Two plots received 10 inches of water, but no manure. The water was 

 applied in two equal applications. 



Two plots received 20 inches of water, but no manure. The water was 

 applied in four equal applications. 



Two plots received 30 inches of water, but no manure. The water was 

 applied in six equal applications. 



Three plots received 40 inches of water, but no manure. The water was 

 applied in eight equal applications. 



All of the above were repeated with plots receiving 5 and 15 tons of 

 manure to the acre. Hence, the series includes soils without manure, 

 with 5 tons per acre, and with 15 tons per acre. The water applied 

 varied from none up to 40 inches both with and without manure. This 

 does not, however, represent the entire water reaching the soil, for there 

 was an average annual precipitation of about 18 inches, most of which 

 fell between the months of October and May. The precipitation from 

 May to November did not exceed 5 inches, which, of course, would be 



