166 COBir CROPS 



harrows, rollers, and cultivators, is essential to keeping the 

 soil in. good mechanical condition. 



SUBSOILING 



116. The subsoiler is a tool for loosening the subsoil 

 without bringing it to the surface. While tools for this 

 purpose have been in use for many years and have been 

 generally tried out in all the principal agricultural regions, 

 yet subsoiling is nowhere in general practice. General 

 experience has confirmed results obtained at the Nebraska 

 station, where, in a cooperative test with fifty-nine farmers 

 for three years, beneficial results were obtained on soils 

 having a heavy or impervious subsoil, but on loam sub- 

 soils the results were indifferent or injiu-ious. 



PEEPAKATION OF PLOWED LAND 



116. The amount of fitting that must be given to land 

 after plowing depends on the soil and the seasonal condi- 

 tions. A good loam soil, plowed when in just the proper 

 condition, may need very little fitting with the simplest 

 tools, as harrow and float, in order to bring it to a proper 

 mechanical condition. On the other hand, the same soil if 

 plowed when too wet, or if when wet it had been tramped 

 by stock in pasturing, would require more labor and a 

 greater variety of tools for proper fitting. This emphasizes 

 the importance of plowing only when the soil is thoroughly 

 pulverized by the plow. Also, further pulverizing of the 

 soil, with harrow or cultivator, is most easily accomphshed 

 within twenty-four hours or less after plowing, and one 

 harrowing at this time may accomplish several times as 

 much as a few days later, when the clods have dried. 



There are certain heavy clay soils that always require a 



