254 SOILS AND FERTILIZERS 



Corn. Phosphoric acid first, then nitrogen and 

 potash. 



Potatoes. General manuring, reenf orced with pot- 

 ash. 



Mangels. Nitrogen. 



Turnips. Phosphoric acid. 



Clover. Lime and potash. 



Timothy. General manuring. 



306. Commercial Fertilizers and Farm Manures. - 



Commercial fertilizers should not replace farm manures, 

 but simply reenforce them. Although commercial fer- 

 tilizers are called complete manures, they fail to supply 

 organic matter. It is more important in some soils 

 than in others that the organic matter be maintained, 

 because in some soils the organic matter takes a more 

 important part in crop production than does the food 

 applied in commercial forms. When a rich prairie soil 

 is reduced by grain cropping and is allowed to return to 

 pasture, heavier yields of grain are afterward obtained 

 than from similar land which has received only appli- 

 cations of commercial fertilizers. This is due to the 

 action of the humus in the soil. At the Canadian Do- 

 minion Experimental Farms, where comparative trials 

 have been made for eighteen years with farm manures 

 and commercial fertilizers, it has been found that farm 

 manures, even on new lands, give better results than 

 commercial fertilizers for the production of wheat and 

 corn. 93 



