70 THE MANURE HEAP AND SEWAGE. 



contains the nitrogen which has been actually metabolized by ani- 

 mals, and which can now be brought back readily into a condition 

 available for plant life. The liquid manure contains three-fourths 

 of the total nitrogen of the whole heap, and four-fifths of the total 

 potash. But farmers frequently fail to realize this, and allow this 

 material to waste by soaking into the ground. In addition to these 

 ingredients manure always contains a large amount of water and 

 an unknown number of species and varieties of bacteria in very 

 great abundance. 



In this manure the bacteria find plenty of food and moisture 

 and their growth is rapid. There is a great struggle for existence 

 among them and, in the weeks of fermentation, first one and then 

 another species may gain mastery. If the bacterial contents of 

 such a mass be studied at intervals, the number and variety of species 

 which are most abundant are found to be constantly changing. 

 At first the ordinary intestinal bacteria abound; later the putrefactive 

 bacteria become most abundant, and finally the denitrifying and 

 nitrifying bacteria are in the majority. All of this indicates faintly 

 the wonderful complexity of bacterial life and the intensity of the 

 struggle for existence among the numerous species originally present 

 in the manure. 



Losses from the Manure Pile. The result of this bacteria 

 growth is an extensive and profound series of chemical changes 

 by which the manure is profoundly modified. These are partly 

 useful and partly injurious, but, taken as a whole, they are neces- 

 sary. Most of the material in the manure is in a form not capable 

 of being used by plants, and must be greatly transformed before it is 

 available for vegetation. The transformations are much the same 

 as those we have already considered in the soil, but they take place 

 under different conditions, which somewhat modify them. In our 

 study of the subject it should be borne in mind that the most im- 

 portant feature of manuring is the furnishing of nitrogen to the crops, 

 and the first care should be to protect this material and avoid its 

 loss. 



The losses from manure are due to two causes, i. Leaching. A 

 considerable portion of the nitrogen is in a soluble form, including 



