NITRIFICATION IN ARABLE SOIL. 



497 



Average amounts of nilric niiro<ien in the drauiaf/c water, i>cr hectare, duriiif/ the ijcars ISDO, 



1S91, avd IS92. 



Spring 



Summer 



Autiimu 



Winter 



Whole year 



Kilograms. 



We thus see that it often happens that samples collected from soils 

 in i)lace and afterwards repeatedly handled furnish very large amounts 

 of nitrates. This is shown in the analyses of the drainage waters of the 

 soils of Seine-et-Marne and of Limagne. We see further that soils col- 

 lected at the end of autumn and exposed to the air in thin layers for six 

 weeks show an extremely active nitritication, but that when this aera- 

 tion and pulverization is repeated on hard frozen soils collected in winter 

 the production of nitrates is very slow. Finally it appears that nota- 

 ble amounts of nitrates are formed in samples collected during the 

 month of March, although nitrification is not as active as in the samples 

 collected in autumn. In spite of certain irregularities in detail we may 

 draw the general conclusion that i)nlverization and aeration of the soil 

 usually result in the formation of considerable quantities of nitrates. 



NITRIFICATION IN SOILS STIRRED AT THE SURFACE AND IN THOSE 



LEFT UNDISTURBED. 



The preceding experiments were made in the laboratory. The soils 

 were exposed to the air, stirred and pulverized in a most thorough 

 manner. In order to determine the action under conditions which more 

 nearly approach those of ordinary culture, observations were made dur- 

 ing the year 1893 on nitrification in soils in experiment pots, some of 

 which were cultivated while others were left undisturbed. 



The year 1893 was particularly unfavorable to this kind of observa- 

 tions in France on account of the exceptionally severe drought of the 

 spring in the vicinity of Paris, and especially at Grignon. It rained, 

 however, during July, and drainage water was also collected in abun- 

 dance during the autumn. The table below shows the results obtained 

 on two Grignon soils, one of which was cultivated at the surface on 

 February 17, and frequently thereafter during the year, while the other 

 remained undisturbed. 



12982— No. G 2 



