PLOWING IN DRY AREAS 139 



to promote excessive leaching. It will not avail in un- 

 drained soils until they are drained, if they hold an ex- 

 cessive amount of water for any considerable period. 

 The necessity for subsoiling in dry areas and the benefits 

 to be derived from it have called forth opinions that are 

 more or less conflicting. Many authorities look upon it 

 as a necessity in nearly all the semi-arid region. They 

 lose sight, apparently, of the cost of subsoiling. In much 

 of the semi-arid region the limited rainfall does not call 

 for a great depth of stirred soil to take in all that falls. 

 When once thus absorbed, the water can usually go 

 downward with sufficient readiness in the average west- 

 ern soils. If the connection between the upper and lower 

 soils is too much disturbed, the upward movement of 

 moisture will be hindered until the disturbed soil has 

 time to settle again. 



As a rule, the most effective subsoiling mechanical 

 in character is that which stirs the soil more and more 

 deeply by a gradual process, rather than by stirring it to 

 a very considerable depth at once. Usually the neces- 

 sity for going more deeply than 12 to 18 inches would 

 not seem necessary for ordinary cropping. For alfalfa 

 and also for field roots, it may sometimes prove helpful 

 to go more deeply. 



When alfalfa comes to be generally grown in dry 

 areas, subsoiling mechanically would seem to be un- 

 necessary. It would be difficult to conceive of subsoil- 

 ing more complete than that furnished by the roots of a 

 good stand of alfalfa in their decay. They burrow deeply 

 in the subsoil during the process of growth. In their 

 decay they leave it honeycombed with avenues leading 

 downward. Moisture can readily go down in these and 

 form a reserve for later growth. The process does not 

 cost the grower anything. 



The frequency of the plowing. The frequency with 

 which land should be plowed will depend to some extent 



