38 



stroyers." They completely undo the work of the other bacteria, 

 or " nitrate formers." The " nitrate destroyers" live on the non- 

 nitrogenous constituents of the straw and leaves and the oxygen 

 of the nitrates. This liberates the nitrogen in the form of gas, 

 which escapes into the air and is lost to the farmer. The process 

 also consumes the non-nitrogenous portion, which is chiefly the 

 remainder of the litter. It is formed into water and carbonic acid 

 gas, which escape into the air and thus diminish the bulk of the 

 pile. While the "nitrate formers" live near the surface of the 

 manure and require air for their work, the "nitrate destroyers" 

 live away from the air and do not need it. They are dependent, 

 however, on food of a certain kind, and must have plenty of it, 

 otherwise they become inactive and can do no damage, though 

 millions of them may exist in the interior of the manure pile. 

 One of their principal foods, the non-nitrogenous material of the 

 litter, they cannot use as food until it has been made soluble by a 

 third class of bacteria, which causes the rotting of the litter. 

 Nitrates are also indispensable for their nourishment. If, there- 

 fore, they are deprived of either one of these constituents of their 

 diet they either die or at least become harmless. 



The work of the "nitrate formers" is beneficial; it converts 

 organic nitrogen into nitrate, a most available form of plant food. 

 Half-rotted manure contains nitrogen largely in this form. The 

 work of " nitrate destroyers" is destructive. It removes the sol- 

 uble nitrates from the manure. It converts half-rotted manure 

 into well-rotted manure. In this way the different effects pro- 

 duced by manure in the three different conditions are explained. 

 The nitrogen in fresh manure is largely organic and not imme- 

 diately available. It, therefore, has a slower and less effect than 

 half-rotted manure. The nitrogen in half-rotted manure is largely 

 in the form of nitrates, and this is available. The nitrogen in 

 well-rotted manure has all been converted into nitrates also, and was 

 once available, but has subsequently been lost in the air. This is 

 why the well-rotted condition is the least valuable of the three. 



Of the three common conditions of barnyard manure, half- 

 rotted manure is the most valuable, and well-rotted manure the 

 least, because of their relative amounts of nitrates. 



Manure should be kept packed away from the air as tightly as 

 possible, and, if rotted, should be ploughed under just before 

 planting, otherwise, several months before that time. 



The more litter used in the manure, the greater liability to loss 

 of nitrogen. 



The use of bedding material free from decomposable organic 

 matter is a means of protection against loss of nitrogen. 



