FARM MACHINERY 



215 



system of disposing of the stalks and cultivating the soil be- 

 fore plowing cannot be too highly commended. Many 

 weeds are destroyed and a better seed bed is obtained upon 

 plowing. 



Construction of the Disk Harrow. The standard disk 

 harrow has full round disk blades, sixteen inches in diam- 

 eter and about sixteen in number, spaced six inches apart. 

 This is the four-horse machine. Smaller disk blades do 

 not give sufficient clearance, and larger sizes do not do 

 as effective work. The sixteen-inch disk rotates faster than 

 a larger disk and so pulverizes the ground more, and it also 

 has less bearing surface under the working edge, insuring 

 greater penetration. 



Disk harrows have one lever by means of which both 

 disk gangs are adjusted at the same time, or two levers, one 

 for each gang, permitting individual adjustment. The two 

 levers are almost essential when "lapping half," or allowing 



Fig. 123. A full-blade, two-lever disk harrow with tongue truck. 



