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Chili the nitrate of soda, and the Canadian hardwood 

 forests furnish wood ashes. The introduction of these 

 and still other sources of plant food marks an important 

 era in the history of agriculture. Hitherto the farmer was 

 greatly handicapped in his operations. He could not in- 

 crease his business at will, simply because sufficient fer- 

 tilizer was not to be had at any price, whereas now sup- 

 plies being practically unlimited, he can increase his oper- 

 ations to such extent as he finds it profitable. 



In considering chemical manures or commercial fertil- 

 izers we have to think of the three main elements of plant 

 food, nitrogen, potash and phosphoric acid. These are all 

 the farmer has to concern himself about. Nitrogen is the 

 most costly element as well as the one most easily lost, 

 since it readily escapes into the air or is washed away into 

 the subsoil. Therefore a nitrogeneous fertilizer is only to 

 be applied in spring or summer during the period of active 

 plant growth. Potash and phosphoric acid on the other 

 hand, being of mineral composition, may be applied to the 

 soil in the fall, as well as spring. They will make the 

 land just so much better put on at any season, and can 

 safely be relied upon to remain in the soil until removed 

 by the growth of crops. 



The materials now employed in the manufacture of fer- 

 tilizers are very numerous ; and, as to what selection the 

 farmer will make, that will depend upon the comparative 

 cost of the elements of plant food in one substance and in 

 another. A slight computation will reveal to any farmer 

 at any time where the cheapest source of fertility for him 

 is to be found. All he needs as a basis upon which to 

 work is the guaranteed percentage of nitrogen, potash, or 

 phosphoric acid, which each manurial material contains. 



Ready mixed fertilizers are used very largely. Whether 

 it is cheaper for the farmer to purchase fertility by buying 

 these, or rather by securing the original chemicals and mix- 



