DRY-FARMING 



disc harrow, the Acme harrow, the spike- 

 tooth and spring-tooth harrow. The disc 

 harrow is an absolutely indispensable tool 

 for dry-farming. Under ordinary con- 

 ditions discs of fourteen inches diameter 

 do much better work than those of eigh- 

 teen or twenty inches. The disc should 

 be used to break up the surface-sod or 

 stubble immediately after the harvest, for 

 where this is done it will be found that 

 plowing will produce a much better seed- 

 bed. Turning under the disked surface 

 also leaves less air space and the seed-bed 

 is made more compact and mellow. The 

 disc is also useful in killing weeds on 

 summer fallow lands, but it must be used 

 when the weeds are small, for it will 

 merely stimulate the growth of the larger 

 weeds. Always lap the disc one half, 

 which double-discs the ground and leaves 

 it level. The disc is especially useful in 

 cleaning old alfalfa (lucerne) fields; and 

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