CULTIVATION. 105 



may be avoided by making the deepening of the soil a 

 gradual process, plowing each time a little deeper than 

 before. 



Some sandy or alluvial soils are naturally so loose as 

 to admit air and roots freely. Such soil, on the one 

 hand, is not so much in need of deep plowing ; and, on 

 the other hand, if the lower portions are brought to the 

 surface, they can do no harm, since they have become 

 adapted for plants by the presence of air and the fertil- 

 izers which have been washed downward. 



It may not always be wise to plow deeply. In the 

 varied processes of cultivation, there may be occasions 

 when shallow plowing will, for the time being, better 

 accomplish the particular end desired ; as, for example, 

 when the lower soil is already sufficiently loose, and we 

 simply wish to destroy weeds or mix fertilizers with the 

 surface soil. 



Subsoil Plowing. The subsoil plow follows in the bot- 

 tom of the furrow made by the ordinary plow, stirring 

 the lower soil and allowing it to remain in the same 

 position. By its use some of the advantages of deep 

 tillage are gained without the necessity of bringing the 

 poor subsoil to the surface. 



The Time to Plow. It is an important question at 

 what time plowing should be done ; whether as long as 

 possible before the seed is planted or just before, in 

 the fall or in the spring. 



There are two sides to the question. After land is 

 plowed, and exposed loosely to the atmosphere, chemical 

 changes go on more rapidly, converting the elements of 

 fertility into a soluble form. On the other hand, the soil 

 is more exposed to the washing of rain. 



As all vegetation has been destroyed by plowing, de- 



