676 



Journal of Agricultural Research 



Vol. XII, No. 10 



Chaniberland-Pasteur filters. Nitrate, calcium, and phosphoric acid 

 were determined in the filtrates by the methods already referred to. 

 Nitrite, when present, was also determined by the Greiss-Ilosovay method. 

 The calcium determinations for the 98-day period have been omitted 

 from the table, owing to an error in the analytical procedure. The 

 average results from duplicate incubations are recorded in Table III. 



Table III. — Effects of nitrification on the solubility of fricalcium phosphate in sand 



cultures 



[Results expressed in parts per million) 



DISCUSSION OF EXPERIMENTAL RESULTS 



Soil series. — The data submitted in Table 11 show that active nitri- 

 fication took place in the soil series. For example, the nitric nitrogen 

 increased in the control portions from 8.5 p. p. m., originally present, to 

 20 p. p. m. in 28 days. Where ammonium sulphate was added, the con- 

 centration increased to 98.5 p. p. m., while dried blood yielded 91.0 

 p. p. m. of nitric nitrogen. The addition of calcium carbonate and tri- 

 calcium phosphate either singly or together produced very slight, if any, 

 effects on nitrification in this series.^ After subtracting the amounts of 

 nitric nitrogen in the controls, it is found that 78 per cent of the am- 

 monium sulphate and 71 per cent of the dried-blood nitrogen were 

 oxidized in 28 days. 



When allowance is made for the soluble calcium found at the beginning 

 of the experiment (Table I), the data show that in every case nitrification 



1 In other experiments with this soil the addition of calcium carbonate has slightly stimulated the nitri- 

 fication of ammonium sulphate, but not of dried blood. 



