100 



FIG CULTURE 



clods, which require repeated harrowing to wear 

 down into anything like comfortable beds for culti- 

 vated plants. Farm implements, aided by frost, 

 rain and sunshine, work land into friable conditions 

 in three or four years. At first the lumps are so 



How soil particles look un- 

 der a microscope, showing 

 air spaces. 



Clay soil that has "ce- 

 This cut shows the par- mented" and become im- 



ticles partly run together pervious to ordinary roots 



with some air spaces left. from packing rains. It 



needs humus between the 

 soil grains. 



large there is no capillarity, air circulates in the 

 interstices too freely, promoting excessive dryness, 

 while the clods are impenetrable to roots in search 

 of food. If new soil is plowed deep, and fined with 

 a disk, or harrow, it will often deceive an observer 



