260 SOILS AND FERTILIZERS 



fertility necessitates a balanced condition of the physi- 

 cal and chemical properties of a soil. Some soils are 

 of good texture and have all of the necessary physical 

 requisites for crop production but fail to produce good 

 crops because of a scant supply of the essential ele- 

 ments of plant food. Other soils contain the neces- 

 sary plant food but are unproductive because of poor 

 physical conditions. Soils may be unproductive on 

 account of either chemical or physical defects causing 

 an unbalanced condition of the various factors of soil 

 fertility. In the cultivation of a soil it should be the 

 aim to discover any defect and then to apply the 

 necessary corrective measures. Soil problems are ex- 

 tremely varied in character and the cultivator of the 

 soil should seek aid jointly from the sciences of chem- 

 istry, physics, biology and geology, and also from prac 

 tical experience founded upon observations in the 

 cultivation of soils and the production of crops. The 

 utilization and maintenance of the fertility of the soil 

 necessarily form the basis of any rational agricultural 

 system. 



