NITRIFICATION OF SAMPLES IN SOLUTION. 



19 



explained, however, by the original high nitrate content of the soil, 

 as there is often a tendency for the nitrifying power of a soil to 

 decrease as nitrates accumulate. 



NITRIFICATION OF SAMPLES IN SOLUTION. 



In order to further test for the presence of nitrifying bacteria and 

 also to study some of their characteristics, inoculations were made 



Fig. 12.— Diagram showing the nitrification of ammonium snlphate in samples of soil from different depths 

 from plats 2G0 and 270, Truckee-Carson Experiment Farm. Original nitrate present in samples from 

 plat 200- Depth, to inches, 02 parts per million; 6 to 12 inches, 30; 12 to 18 mches, 18.75; 18 to 24 

 inches, 35.7; 24 to 30 inches, 30. From plat 270: Depth, to inches, 100 parts per million; 6 to 12 

 inches, 27.7; 12 to 18 inches, 50; 18 to 24 inches, 40; 24 to 36 inches, 50. 



into media consisting entirely of inorganic material wliich is not suit- 

 able for the growth of saprophytic bacteria. ^ Curves have not been 

 plotted from the data thus obtained, as the conditions were too 

 abnormal to warrant considering the difl'erences from a quantitative 



' A\'inogi-adsky and Omelianski's Fluid Culture-Medium for Isolating the Nitrate 

 Bacteria from Soils, and Winogradsky and Omelianski's Fluid Cultiu-e-Medium for 

 Isolating the Nitrite Bacteria from Soils. Centrall)latt fur Bakteriologie, Parasiten- 

 kunde und Infektionskrankheiten, vol. 5, pt. 2, 1899, pp. 537-549. 

 211 



