NITRIFICATION IN ARABLE SOIL. 



493 



NITRIFICATION IN AUVERGNE AND GRIGNON SOILS AFTER PULVERI- 

 ZATION AND AERATION IN AUTUMN. 



In the latter part of November, 1892, 50 kg. lots of Palbost and 

 Marmilhat soils were taken to the station buikliug at Grignon. These 

 soils had been selected for experimental purposes in 1890, and had 

 remained unmanured since that time. At the same time a sample of 

 Grignon soil was collected which had remained unfertilized since 1875, 

 except that in the spring of 1891 it had received an application of 

 manure leachings, the effects of which had almost entirely disappeared. 

 As checks Palbost, Marmilhat, and Grignon soils manured in 1891 and 

 remaining in place were used. 



The unfertilized soils were spread out on the paved floor of the sta- 

 tion building and stirred at various times during about six weeks. The 

 temperature in the building was generally quite low, although when 

 the temperature outside fell below zero the building was heated. In 

 the latter part of December the soils were placed in pots, Where they 

 were allowed to remain for some time, a sample of 500 gm. being 

 retained. Of this sample 100 gm. was saturated with water and kept 

 in a closet of the laboratory. Another 100 gm. was kept without 

 being moistened. One hundred-gram lots of the Palbost, Marmilhat, 

 and Grignon soils which had remained in place without being disturbed 

 were submitted to the same manipulation. 



In the early part of January, 1893, the samples of soil which had 

 been treated in the laboratory were leached with water to remove the 

 nitrates, the water being applied in 25 cc. lots, until the whole quantity 

 used amounted to 250 cc. This extract was evaporated and nitrates 

 determined in the residue by the ferrous- chlorid and hydrochloric acid 

 method. The following results were obtained : 



Nitric nitrogen formed in stirred and unstirred soils {December 20 to January 7). 



Soils saturated with water. 

 Grignon : 



Unstirred 



Stirred 



Marmilhat: 



Unstirred 



Stirred 



Palbost: 



Unstirred 



Stirred 



Unmoixtened soils. 

 Grignon : 



Unstirred 



Stirred 



Marmilhat 



Unstirred 



Stirred 



Palbost : 



Unstirred 



Stirred 



Nitrogen 

 dioxid ob- 

 tained. 



Cc. 



4.0 



70.5 



3.5 

 82.0 



3.7 

 114.5 



5.0 

 62.0 



4.2 

 74.5 



4.3 

 90.2 



Nitric ni- 

 trogen in 100 

 gm. of soil. 



Grams. 

 0.002 

 .044 



.002 

 .051 



.002 

 .071 



.002 

 .039 



.002 

 .043 



.002 

 .057 



