220 THE PRINCIPLES OF SOIL MANAGEMENT 



penetration of roots. This condition may be largely 

 corrected by subsoiling. 



Coupled with deep plowing and subsoiling, subsur- 

 face packing is often very beneficial. Particularly is 

 this true in early fall and late spring plowing, where 

 the soil is likely to be cloddy and to make poor capillary 

 contact with the subsoil. Spring crops may be greatly 

 injured by this condition. The subsurface packer crushes 

 the clods, presses the furrow slice down more firmly 

 on the subsoil without compacting the surface soil. 



Fig. 71. "Clod crasher" and sub-surface packer. 



It leaves a light mulch on the top to hold moisture. 

 Not only is it useful in improving the soil structure 

 under the conditions just mentioned, but it promotes 

 the decay of organic manures and assists plant roots 

 in penetrating into the subsoil below, where they may 

 have a larger moisture and food supply. 



Increase in the humus content stands next to modifi- 

 cation in texture and structure as a means of increasing; 

 the water capacity of the soil in accordance with the prin- 

 ciples explained on pages 144 and 153. It accomplishes 



