366 SOILS 



gardening and in the culture of special crops and 

 on certain soils; but the indications are that their 

 use in general farm practice as a chief source of 

 fertility is on the wane, while the use of the more 

 natural resources, green-manuring and farm ma- 

 nures, is on the increase. Often artificial fertilisers 

 have been used to remedy temporarily the effects 

 of poor texture, due to mismanagement. Com- 

 mercial fertilisers, if used at all in general farming, 

 should be applied sparingly and as a supplement 

 to natural resources, not as the main source of 

 fertility. 



WHAT COMMERCIAL FERTILISERS ARE MADE OF 



The term is usually applied simply to materials 

 which contain the essential plant foods nitrogen, 

 potash and phosphoric acid. These are found in 

 many materials: some are mineral products, as 

 nitrate of soda, muriate of potash, phosphate rock; 

 some are animal products, as dried blood and 

 tankage, which are wastes from the slaughter 

 houses, and boneblack, which is a refuse in refining 

 sugar. These raw materials are combined in 

 various ways, and in different proportions, per- 

 haps treated with acids. One brand of commercial 

 fertiliser may be made of two or three of these raw 

 materials ; another may contain many kinds. 



Complete and Incomplete Fertilisers. Com- 

 mercial fertilisers are either "complete" or "in- 

 complete." A complete fertiliser contains all three 

 of the essential plant foods ; an incomplete fertiliser 

 contains but one or two. Most fertilisers sold in 

 this country are complete. The reason for this, 

 from the manufacturer's point of view, is obvious. 

 He knows little or nothing of the kind of soil upon 



