124 DRY LAND FARMING 



soil in semi-arid areas that are properly cultivated is 

 much more moist than it was before the land had been 

 broken. 



But breaking up the land admits the air as well as 

 the moisture. This of course aids in preparing the soil 

 for becoming a suitable home for the roots of plants. 

 When air penetrates a moist soil, it aids in bringing about 

 mechanical and chemical changes that prepare food for 

 plants. These processes come practically to a standstill 

 when the soil is virtually destitute of moisture, or when 

 it has an excess of the same. In semi-arid regions ex- 

 cessive aeration is to be carefully guarded against. It 

 is excessive when it aids in the removal of moisture 

 that is needed from the top soil. To prevent this as far 

 as it may be possible, the soil is usually compressed or 

 firmed soon after it has been plowed. 



On land that has never been plowed, it would not 

 be easy to form a seed bed. It could of course be done 

 with the disc, but to make it thus would involve much 

 labor, and it would not be satisfactory when made. The 

 plow alone does not form a seed bed, but it puts the 

 land in a condition so that the work can be completed 

 with the aid of other implements. A good seed bed in 

 dry areas should be: (1) fine and mellow on the top two 

 or three inches of soil and firm but not hard below ; (2) 

 as free as possible from weed seeds and the presence 

 of perennial weed growth, and (3) moist enough to ger- 

 minate the seeds of crops that are planted on the soil. 

 To insure these ends the plowing must be done at a cer- 

 tain time and in a certain way, but after the land has 

 been plowed the roller, the harrow and sometimes the 

 disc must usually be more or less used. 



After ground has been broken with the plow, the 

 seed bed is frequently prepared by the aid of the disc 

 and harrow only. This plan is generally followed after 

 cultivated crops, and for the reason chiefly that moisture 



