224 SOILS AND FERTILIZERS 



Potatoes. — General manuring ; reenforced with pot- 

 ash. 



Mangels. - r - Nitrogen. 

 Turnips. — Phosphoric acid. 

 Clover. — Lime and potash. 

 Timothy. — General manuring. 



289. Commercial Fertilizers and Farm Manures. 



— - Commercial fertilizers should not replace farm ma- 

 nures, but simply reenforce them. Although com- 

 mercial fertilizers 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. For 

 example, when a rich prairie soil is reduced by grain 

 cropping and is allowed to return to pasture, heavier 

 yields of grain are afterwards obtained than from sim- 

 ilar soils which received applications of commercial 

 fertilizers. 



