328 Bacteria in Relation to Country Life 



42 days old were a,dded to the solution, half of the 

 nitrate was reduced in 14 days, and 30 days were re- 

 quired for the complete reduction. 



When the manure employed in the experiments 

 was thoroughly stirred at frequent intervals, its nitrate- 

 reducing power decreased more rapidly than that of 

 the unstirred manure. 



Similarly, portions of manure whose decomposition 

 had been retarded by additions of gypsum, superphos- 

 phate, and kainit, retained their denitrifying power to 

 a more marked degree. Lime, which hastened the de- 

 composition of the manure, caused, in some of the ex- 

 periments, a more rapid decline of its denitrifying power. 

 The various samples of treated or untreated manure 

 which had been thus kept for 112 days, reduced at the 

 end of that period the following amounts of nitrate out 

 of every 100 parts present in the solution: 



Manure without addition of conserving materials, reduced . . 8 parts 



Manure with gypsum, reduced 39 parts 



Manure with gypsum and phosphate, reduced 40 parts 



Manure with kainit, reduced 66 parts 



Manure with lime, reduced 9 parts 



In another experiment, in which samples of manure 

 70 days old were added to the nitrate solutions, all of 

 the nitrate was destroyed in 64 days when the untreated 

 manure was employed. When, however, manure treated 

 with lime was used, it required 83 days to complete the 

 destruction of the nitrate. The conservation of the or- 

 ganic matter in the manure by means of chemicals, or 

 by merely compacting the heap and excluding the air, 

 is equivalent, therefore, to the conservation of its de- 



