146 SOILS 



the teeth of entangled weeds. The implement 

 is now made with a steel or iron frame, usually 

 rectangular, and should be provided with a shoe. 

 The more the teeth slant backward the more 

 shallow do they work and the greater is the smooth- 

 ing effect of the tool. The teeth should be set 

 straight only when it is desired that they work 

 deeply and tear up the soil. 



The size of the spike-tooth harrow varies from 

 a single six-foot section to the forty-foot wide 

 smoothing harrow of many sections that is used 

 on prairie grain fields. The latter are drawn by 

 four to six horses and cover thirty to forty acres a 

 day. The width of all harrows has increased in 

 recent years and is still increasing in obedience to 

 the same demand that has given us gang plows. 

 The wider a harrow is the steadier it runs. 



Usefulness of the Spike-tooth Harrow The 

 spike-tooth harrow is seldom used now to tear 

 up rough-plowed ground, as it was some years 

 ago before improved harrows were available. 

 The old time spike-tooth harrow had a few long, 

 heavy teeth which tore up sod quite effectively, 

 especially when weighted with rocks, or pro- 

 vided with a" platform for the driver. At the 

 present time most spike- tooth harrows are of the 

 type called "smoothing harrows," having numerous 

 small and short teeth. When the teeth are so 

 short that the bar in which they are set scrapes the 

 ground when it is in use, the implement is often 

 called a "drag." This type of harrow is chiefly 

 valuable for one purpose to put the finishing 

 touches on a piece of land tnat needs to be 

 made very mellow and very level for seeding. 

 It is usually preceded by a stronger and deeper- 

 working tool, as a disk or spring-tooth harrow. 



