917 



That the ferment is aerobic is iudicated by the fact that reduction 

 goes on more rapidly in flasks supplied Avith oxygen. 



The ferment reduces the nitrates of the soil. If when the soil is dry- 

 ing and the nitrates rising to the surface it is covered with wet straw 

 which is allowed to dry out slowly, nitrates are not found either in the 

 surface soil or in the straw. 



While a part of the nitrogen of the nitrates is set free a certain por- 

 tion is combined with organic substances. In one experiment a third 

 of the nitric nitrogen was lost, while the straw and the water in which 

 it was soaked tripled its organic nitrogen. In a second experiment G7 

 per cent of the nitric nitrogen was lost. 



To observe the evolution of nitrogen two series of experiments were 

 carried out. In one series the moist straw was placed in test tubes 

 {eprouvettes), which were filled with 1 per cent nitrate of potash solu- 

 tions and inverted in the same solution. The second series was carried 

 out in the same manner, substituting pure water for the nitrate of potash 

 solution. Into each test tube there was introduced 24.5 c. c. of air con- 

 taining 19.6 c. c. of nitrogen. The gas obtained was analyzed with the 

 following results : 



Reduction of nitrates to free nitrogen Tnj the aerohic ferment. 



No nitrogen was evolved in the tubes containing pure water, and it 

 should be explained that in Nos. 1 and 3 of the first series the oxygen 

 of the air introduced was not completely exhausted, a further evidence 

 that the ferment is aerobic. 



It is believed that the reduction of nitrates in arable soils by this 

 ferment need not be feared, because such soils retain only a small 

 amount of water and consequently do not present favorable conditions 

 of development. In meadows and forests it is otherwise. The vegeta- 

 ble residues of such soils furnish the ferment in abundance and retain 

 the moisture necessary to its free development. Tliis furnishes a proba- 

 ble explanation of the fact observed by Boussingault more than 40 

 years ago — that such soils do not contain nitrates. 



The comparative effect of sulphate of iron and sulphate of lime 

 on the conservation of nitrogen in bare soils, and on nitrification, 

 P. Pichard [Ann, de Chim. et de Phys., 25 {lf<r)-J), pi^. ;^;i-.?N;).— Hav- 

 ing observed in earlier experiments the beneficial effect on nitrification 



