it must be run over the soil so many times that the result is 

 the much talked of "dust mulch." In our volcanic ash and 

 heavy clay soils, this dust mulch is not at all desirable as it too 

 readily encrusts again when more rain falls. The disk harrow, 

 by breaking the crust with a single operation, leaves the 

 surface, not as a dust mulch, but in a well pulverized, well 

 firmed condition. 



On the unirrigated lands of Idaho it is a common practice 

 to summer fallow every other year. The summer fallow is 

 frequently so infested with weeds and volunteer grain that a 

 great deal of difficulty is met. It is often impossible for a 

 farmer to cultivate his fallow when the weeds are just beginning 

 to emerge from the soil. After the weeds have gained a rea- 

 sonably good start a spike-toothed harrow is not effective in 

 eradicating them. The disk harrow here is very effective. The 

 object in all the summer cultivation of fallowed soil is to keep 

 the surface pulverized and to keep down weeds. The more shal- 

 lowly this cultivation can be done the smaller will be the 

 quantity of soil moisture lost through evaporation. It is always 

 desirable, therefore, to be as effective as possible, in accomplish- 

 ing the desired object and at the same time to avoid going too 

 deeply into the soil. An ordinary plow would eradicate the 

 weeds but the operation would be expensive and large quantities 

 of soil moisture would be unnecessarily lost. The use of a spike- 

 toothed harrow would probably pulverize the surface soil and 

 it would avoid going too deeply, but it would not be effective 

 in most cases in eradicating the weeds. The disk harrow is 

 found in such cases to be the happy medium. It is very widely 

 and very successfully used in Idaho for this purpose. 



In preparation of seed beds for all field crops in this state, 

 the disk harrow has its uses. The desirable seed bed contains 

 from four to six inches of well pulverized surface soil, reason- 

 ably firm, without being too compact. This zone of pulverized 

 soil should be uniform all over the field in depth, moisture con- 

 tent and tilth. Comparatively few fields are prepared for plant- 

 ing on the best farms of this state without the use of a disk 



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