38 THE PRINCIPLES OP AGRICULTURE 



structure: as, mellow, hard, loose, compact, open, 

 porous, shallow, deep, leachy, retentive, lumpy, 

 cloddy, fine in good tilth. 



51. Texture and structure must not be con- 

 founded with the physical forces or operations in 

 the soil, as the fluctuations of temperature, move- 

 ments of water, circulation of air. They refer to 

 condition or state, and are passive, not to forces 

 or movements, which are active; but it is upon 

 this passive condition that the operation of both 

 physical and chemical forces chiefly depends. 



2. Wliy Good Texture and Structure are Important 



52. A finely divided, mellow, friable soil is 

 more productive than a hard and lumpy one of 

 the same chemical composition, because: It 

 holds and retains more moisture; holds more 

 air; promotes nitrification; hastens the decom- 

 position of the mineral elements; has less varia- 

 ble extremes of temperature; allows a better 

 root-hold to the plant; presents greater surface 

 to the roots. In all these ways, and others, the 

 mellowness of the soil renders the plant-food 

 more available, and affords a congenial and 

 comfortable place in which the plant may grow. 



53. Good structure (as understood by the far- 

 mer) not only facilitates and hastens the physi- 

 cal and chemical activities, but it also presents 



