194 Fertilizers 



deficient element may be either phosphoric acid or lime; 

 and if these are supplied in abundance, the plant will be 

 able to secure the necessary potash. In a limy soil, the 

 lime and phosphoric acid, and perhaps the potash, may be 

 in sufficient abundance to cause a normal growth of plant, 

 yet the nitrogen may be so deficient as to prevent a normal 

 growth. 



Physical imperfections of sandy soils. 



If it were possible distinctly to classify soils in respect 

 to their lack of one or more of the essential constituents, 

 it would be an easy matter to formulate rules for our 

 guidance in the fertilization of these soils ; but such is not 

 the case. Even sandy soils vary widely in their chemical 

 composition, as well as in their mechanical or physical 

 properties, and certain of them possess such a physical 

 character as to make it impossible to grow maximum crops 

 even though the essential elements are all supplied in 

 sufficient abundance. The constituent particles are too 

 coarse, and thus make the soils so open and porous that 

 they too freely admit the air, water and warmth, and thus 

 results a very rapid drying and heating of the soil, with a 

 premature ripening and burning of the crops. The phos- 

 phates or the potash compounds applied are not readily 

 fixed, and suffer an immediate loss as soon as rain falls in 

 such amounts as to cause a leaching from them. 



Physical imperfections of clay soils. 



In clay soils, the physical conditions are quite the reverse. 

 All clay soils do not have the same general composition, 

 and they differ widely in their physical qualities. Certain 

 of them possess a reasonably good texture, and permit the 

 absorption of the food applied, as well as its gradual dis- 



