Introduction. 17 



Fermentation. A process of decomposition, often accompan- 

 ied by the oxidation of carbonaceous matter, and produced by the 

 life processes of bacteria, yeasts and molds. When the process 

 occurs out of free access of air and bad smelling gases are formed, 

 the process is called putrefaction. 



The constituents of plants. All agriculture depends upon the 

 growth of plants and consequently all profit for the farmer de- 

 pends upon the value of the crop his farm produces. This is 

 true whether the crop is sold directly from the farm or whether 

 it is fed to animals and the products such as live stock, beef, pork, 

 wool, eggs, or milk, used as the source of revenue. If the crops 

 now produced on two hundred acres of land could be grown on 

 one hundred without a great increase of labor and other expense, 

 the profit would be greater. Successful farmers have demon- 

 strated that the present average of crops can be doubled, and that 

 at a cost per acre scarcely more than is now required for the one- 

 half crop. 



To accomplish this requires a broader knowledge of the food 

 requirements of plants than is possessed by most of our farmers. 

 A thorough understanding of the subject of plant food and plant 

 nutrition by our forerunners in agriculture would have rendered 

 it unnecessary to emphasize constantly the relation of the con- 

 stituents of the plant to soil exhaustion. 



It is common experience that continued cropping results in a 

 loss of fertility. The productiveness of a virgin soil seems un- 

 limited, for large crops are produced from year to year with no 

 apparent decrease. But sooner or later they begin to diminish 

 in size, gradually to be sure, but unceasingly, until at last the 

 yield becomes so small as to make the cost and labor of produc- 

 tion unprofitable. 



At the Experiment Station at Rothamsted, England, barley 

 grown continuously on the same plot for forty-three years with- 

 out the use of fertilizers of any kind, yielded in the forty-third 

 year 10 bushels of dressed grain per acre, the average for the 

 last eight years being 1134 bushels. Wheat grown for fifty years 



