30 



The influence of varying amounts of water is shown roughly by the 

 following ligurcs. The soil treated contained 38 parts of nitrogen as 

 nitrate per million and required 75 cubic centimeters to saturate it. 



Parts per 

 million. 



75 cubic centimeters water added, let stand 24 hours, nitrogen as 



nitrate ^-^ 



65 cubic centimeters water added, let stand 24 hours, nitrogen as 



nitrate ^-^ 



55 cubic centimeters water added, let stand 24 liours, nitrogen as 



nitrate ^^- ^ 



45 cubic centimeters water added, let stand 24 hours, nitrogen as 



nitrate -^^-^ 



The addition of a small amount of chloroform to the soil, or heating 

 after saturation with water to 125° C. for live minutes, prevented 

 this change of nitrates in the case of all the soils examined. 



As was to be expected, this denitrification took place equally as 

 rapidly with nitrates added as with that naturally in the soil. In 

 working on this phase of the question larger quantities of soil were 

 used, usually 500 or 1,000 grams. A number of soils were studied from 

 this standpoint, and in a number of different ways, but the statement 

 of one case will probably be sufficient at present. One thousand grams 

 of soil containing 15 parts of nitrogen as nitrate were placed in a glass 

 percolator of such size that the soil was about 8 inches in depth, and 

 after saturation with water was allowed to stand 2-1 hours. Three 

 hundred cubic centimeters of water containing 1 gram of potassium 

 nitrate was then added, the drainage caught, and the total nitrogen, 

 nitrate, ammonia, and nitrites determined in aliquot portions. This 

 was repeated, at intervals of 2-1 or 48 hours, until 1.-12 grams of 

 nitrogen as potassium nitrate had been added. The soil was then 

 washed until the drainage was free from nitrate, the drainage being 

 analyzed as before. The figures obtained were as follows: 



Grams. 



Total nitrogen added as nitrate 1-42 



Total nitrogen recovered in drainage 56 



Difference •'^'^ 



The total nitrogen recovered in the drainage was distributed as 

 follows : 



Grams. 



Recovered as nitrate 0. 268 



Recovered as ammonia 257 



Recovered as nitrite ^"^ 



Recovered as other forms 027 



The difference between the amount of nitrogen added as nitrate, and 

 the total nitrogen recovered, can bo explained in one of two ways— 

 either 0.86 gram of nitrogen as nitrate had been changed to free nitro- 

 gen and had escaped, or it had been fixed in the soil in some form 



