172 BOARD OF AGRICULTURE. [Pub. Doc. 



century ago, is now a connnon household word. We, of 

 course, used bacteria al)undautly in the past, but it is only 

 recently that we were aware that we were doing so. We 

 now know that the common processes, such as bread making, 

 brewing, making vinegar, ripening of cream, the developing 

 of flavor in cheese, and hundreds of other every-day matters, 

 are dej^endent upon bacteria or other very low forms of 

 life. Through bacteriological research it has been foiuid 

 that the soil is filled with micro-organic life, so that there 

 may be from 100 to 200 millions of germs present in a single 

 ounce of soil. 



While as yet we know but little of this soil life, sufficient 

 progress has been made so that certain bacteria, particularly 

 in their relations to nitrogen, may be classified. While it 

 is possible that the relations of the I)acteria are as important 

 to siilphm', phosphorus and other mineral constituents, the 

 problem of the nitrogen transformations are prol)ably far 

 more significant to the fertility of the soil. Because of the 

 rapid loss of nitrogen from the soil under faulty manage- 

 ment, it is more important for us to acquaint ourselves with 

 the results of bacterial action upon nitrogen and its various 

 compounds than upon other soil and plant constituents. 



Kinds of Bacteria. 



This is not the place nor is there time to enter into a dis- 

 cussion of the nature of bacteria and their natural history, 

 but a few points must be noted in order to guide our practice 

 in the handling of soils and manures. Not only are there 

 millions of bacteria in an ounce of soil, but there are very 

 many kinds of bacteria. Not all of these by any means 

 have been isolated, and of many of those that have been 

 separately studied little is known as to what they do. 



Some bacteria live without oxygen (air) ; others can live 

 only with an abundant sui)])ly of oxygen. Some bacteria 

 are parasitic, living within and feeding upon the tissues of 

 animals or j^lants ; others use the dead tissues of plants or 

 animals for their food, thereby breaking complex chemical 

 compoimds into much sim})ler ones ; and still others l)uild 

 up complex comjiounds out of simpler ones. All of these 

 dillerent kinds of bacteria arc concerned in the nitrogen 



