CULTIVATION IN DRY AREAS 157 



the conditions present, but usually it is not less than 

 four. (5) On nearly all kinds of small grain, after the 

 blades begin to show and until the plants are ready to 

 shoot, to keep the soil from encrusting, to destroy weeds 

 and to prevent moisture from escaping from below. The 

 number of the harrowings given to a grain crop may 

 run from 1 to 5. In some instances harrowing may not 

 be called for, owing to peculiarities of season and soil. 



The steel harrow is sometimes used, but not in all 

 instances: (1) On fall-plowed land to aid in its pul- 



ONE SECTION OF THE AJAX STEEL LEVER HARROW. 

 Courtesy Deere & Webber Co., Minneapolis, Minn. 



verization. (2) On several of the small grains between 

 the season of sowing and the appearance of the plants, 

 the object being to destroy weeds and to prevent en- 

 crustations. (3) On winter grain autumn and spring, 

 to hold moisture and to loosen and aerate the land. 



The harrow should not be used: (1) On cloddy 

 land until the clods are first crushed with roller or 

 planker, as on such land it will not do effective work. 

 (2) On breaking or overturned sod until the sods have 

 been pressed down with disc, roller or planker, lest 

 many of the sods should be left with the grass on the 



