CONSERVATION OF FERTILITY 



321. Manures Necessary for Conservation of Fer- 

 tility. — In order to conserve the fertility of the soil, 

 not only must a systematic rotation be practiced, but 

 a proper use must be made of the crops produced. 

 When they are sold from the farm and no restoration 

 is made soils are gradually depleted of their fertility. 

 No soil has ever been found that will continue to pro- 

 duce crops without the use of manures. Many prairie 

 soils give large yields for long periods without manur- 

 ing, but they are never able to compete in productive- 

 ness with similar soils that have been systematically 

 cropped and manured. With a fertile soil the decline 

 of fertility is so gradual that it is not observed unless 

 careful records are kept of the yields from year to year. 



322. Use of Crops. — The use made of crops whether 

 as food for stock or sold directly from the farm, deter- 

 mines the future crop-producing power of the soil. 

 W T ith different systems of farming different uses are 

 made of crops. When exclusive grain farming is fol- 

 lowed no restoration of fertility is made, while in the 

 case of stock farming, the manure produced contains 

 fertility in proportion to the crops consumed. If 

 good care is taken of the manure, and in place of the 

 grains sold, mill products are purchased and fed, there 

 is no loss of fertility. Between these two extremes, 

 exclusive grain farming and stock farming, there are 

 found in actual practice, different systems of farming, 



