PT NOTION OF D&NITRlFlERS 



247 



Russell, commenting upon the results, states: 'The experiment 

 is not fine enough to justify any discussion of the missing 1 10 pounds, 

 but it shows that the loss of nitrogen is mainly due to leaching out 

 of nitrates." 



It is even doubtful if denitrification goes on to any appreciable 

 extent in a well aerated soil even though it contains considerable 

 nitrates. The nitrates, however, may disappear as seen from the 

 following results in which the author mixed 2 grams of dried blood 

 and M724.S parts per million of various nitrates with 100 grams of 

 soil made the moisture up to 18 per cent, and after twenty-one 

 days' incubation at 30 C. recovered the various percentages of 

 nitric nitrogen. The untreated soil was taken as 100 per cent. 



This indicates a loss of nitrates where sodium, potassium, calcium, 

 magnesium, and manganese nitrates had been applied to the soil. 



An analysis of the soil for total nitrogen showed a loss only where 

 the potassium nitrate was applied to the soil, and in this case it 

 was only 5.96 mgrns. in place of 41.2 per cent., as was indicated by 

 the first results. 



Treatment. 



Dried blood + no nitrate 



+ 84 . 06 mg. N.N. as KNO 3 



+ 84.06 mg. N.N. as NaNOs . 



+ 84 . 06 mg. N.N. as Mg (NO 3 ) 2 



+ 84.06 mg. N.N. as Fe(NO 3 ) 3 . 



+ 84 . 06 mg. N.N. as Ca(NO 3 ) 2 



+ 84. 06 mg. N.N. as Mn(NO 3 ) 2 



Gain ( +) or loss ( ) in 

 nitrogen over soil receiving 

 no nitrate. 



. . 0.00 



. -5.96 mgs. 



. . 1 . 34 



. . 25.14 



. . 37.04 



. . 42.54 

 48.54 



Function of Denitrifiers. Huge quantities of organic and inorganic 

 nitrogen find their way into the septic tanks of large cities, and 

 much of this is returned to the atmosphere by these bacteria. More- 

 over, that which reaches the lakes and oceans is also acted upon by 

 denitrifying bacteria; hence, they play a part, although of minor 

 importance in the nitrogen cycle. 



REFERENCE. 



Voorhees, Edward B., and Lipman, Jacob G.: "A Review of Investigations in 

 Soil Bacteriology." U. S. Dept. Agr. Off. Exp. Sta. Bui. 194. New Jersey Exp. Sta. 

 Ann. Rpts. 1901 and 1902. 



