212 



THE PRINCIPLES OF SOIL MANAGEMENT 



furrow slice be brought into close contact with the 

 subsoil as soon as possible, in order, (1) that the' best 

 possible capillary contact with the subsoil may be estab- 

 lished; (2) that there may be sufficient moisture to 

 promote the rapid decay of the organic matter; (3) to 

 increase the moisture capacity and cut down loss by 

 percolation and evaporation. This may be accomplished 



Fig. 67. The Campbell subsurface packer 



by rolling the plowed land, but in particularly dry 

 regions the practice of sub-surface packing is advan- 

 tageous. The aim of sub-surface packing is to pack the 

 soil and still leave a loose mulch on the surface. The sub- 

 surface packing may very well be applied to land sub- 

 soiled in the spring. Land subsoiled in the fall will not, 

 as a rule, require this treatment, certainly not in the 

 humid sections of the country. To accomplish sub- 

 surface packing, a special group of implements have 

 been devised, one of which consists of small wheels 



