352 Bacteria in Relation to Country Life 



manure heap, but also in the soil. The sour manure, 

 even though thoroughly incorporated with the soil, does 

 not decay as rapidly as similar manure not treated with 

 acid. Its nitrogen becomes available more slowly, and 

 the maturing of the crop is delayed. 



When smaller quantities of sulfuric acid are employed, 

 the losses of nitrogen from the manure pile are not 

 materially reduced. The denitrifying bacteria in the 

 manure itself may be injured to some extent, yet the 

 manure scarcely loses any of its denitrifying power. 

 This is not difficult to understand, in view of the fact 

 already noted, that denitrification in the soil is caused 

 by manure in virtue of the organic matter it supplies. 

 In other words, in virtue of the food it provides for the 

 denitrifying bacteria. The soil itself contains an abun- 

 dance of the latter and the destruction of nitrates can 

 be accomplished by them in the presence of excessive 

 quantities of organic matter, such as is supplied in the 

 manure. 



Value of chemical methods. — The use of chemicals 

 for the conservation of the organic matter, of the nitro- 

 gen, and of other constituents in the manure, has not 

 given, on the whole, satisfactory results. The chemicals 

 that are mild in their action, as gypsum, t)r small 

 amounts of superphosphate, prevent, to some extent, 

 the loss of ammonia by changing it to more stable com- 

 binations. They do not prevent, on the other hand, the 

 loss of nitrogen in the free state. These losses are more 

 serious than those due to the volatilization of ammonia. 

 The chemicals more or less injurious to the bacteria, 

 for example, large quantities of superphosphate, kainit, 



