24 



Campbell s 1902 Soil Culture Manual. 



the handling of fields for summer culture there is no tool that can take the 

 place of the disc harrow, cost of labor and value of work considered; and 

 while it is not a tool that can be continuously used, we do not see how a man 

 can successfully handle an orchard without it. The disc harrow cannot alone 

 be used to prepare a field for a crop, but in connection with the plow its 

 work is most valuable. The complete pulverizing and thorough separat- 

 ing of the particles one from another in its rotating action, when proper 

 diameter of disc is used, is perfect. 



SIZE OF DISC. 



When disc harrows first came in use the common size was 14 inches 

 in diameter and this size we still prefer, but the demand seems to be for 

 larger discs, the farmers conceiving the idea that they draw lighter. 

 While this is true the pulverizing effect of the 16 inch is not as good as the 

 14, the 18 inch even less, and a 20 inch we would not have on a farm. Just 

 a moment's thought on this point and you will readily see the reason. The 

 larger the disc the slower it revolves, consequently the pulverizing effect is 

 decreased as the size of the disc is increased. I have noticed 20 inch discs 

 rolling along when soil was somewhat dry, and simply slice the soil, raising 

 it up a little and letting it fall back in exactly the same position it was be- 

 fore the disc passed over. The process simply made these little crevices 

 and actually increased the evaporation of moisture, instead of decreasing 

 as it should do. A 14 inch disc moving along at the same rate of speed 

 would revolve faster, therefore, pulverize and completely reverse the soil. 



Don"t buy a disc too large in diameter. The smaller the diameter of 

 the disc the finer and more completely it pulverizes the soil. 



A large diameter disc draws easier but does not do as good work. 

 Always double-disc by lapping half; this leaves your field level. 



CULTIVATION. 



There is probably no question connected with soil culture that has 

 received more attention, and has been more thoroughly discussed than 

 that of cultivation of corn, potatoes, and other growing crops. In the past 

 few years we have heard much about shallow cultivation. In fact it seems 

 to be the prevailing idea. It needs no argument with the average farmer 

 to-day to persuade him that deep cultivation with the old long pointed 

 shovels is not the thing. Shallow cultivation is not, however, well under- 

 stood. There are many important points not generally observed. In cut 



