IO SOILS AND FERTILIZERS 



cal, bacteriological, and chemical changes occur, many 

 of which are only imperfectly understood. The fun- 

 damental principles of soil fertility are, however, rea- 

 sonably well established, and it is now possible to 

 intelligently conserve the fertility of soils and to pro- 

 duce maximum yields of crops. Since the soil wealth 

 is the greatest and the most important form of wealth 

 of a nation, intelligent effort should be made for its 

 conservation and development. 



