SOIL MANAGEMENT 



11 



organic matter. This in turn reacts on tlie physical and drain- 

 age condition of the soil in a way which is doubly injurious. 

 The maintenance of humus in the soil is one of the most effective 

 means of improving the tilth. This applies to sandy land quite 

 as much as to clay land, but in sand the mode of action is dif- 

 ferent from the process of granulation. 



4. Lime has a peculiar effect on clay soils. The tine particles 

 are thrown together in groups or floccules and when the soil 

 dries these become granules. Clay soils rich in lime carbonate 

 have sometimes been mistaken for sandy soils because of this 

 action. Clay soils that have been granulated w^ork more easily 



Fig. 5. — These figures represent two pans of clay soil which had been puddled and 

 molded with a smooth surface. While still wet, pan No. 2 was permitted to 

 freeze. Both pans were permitted to dry out. The cracks formed where the 

 structure of the soil was most open. The pattern in Xo. 2 shows the influence 

 of the ice crystals, and this soil was much more friable and crumbly than the 

 soil that was dried without freezing. 



than those that have not. An English farmer is reported to 

 have said that liming his clay land enabled him to plow mth 

 two horses. 



5. Alternate freezing and thamng breaks up hea\^^ soils. As 

 water freezes in the soil, long, needle-like crystals are formed 

 that cut through, the soil in many directions. So complete is this 

 network of crystals and so effective is their cleavage action that 

 the hardest clod rarely fails to fall to pieces after two or three 

 severe freezes. Nothing is more effective in breaking up sub- 

 soils than deep fall plowing which leaves them exposed to the 

 action of frost during the M^nter. To be most effective, how- 

 ever, the fall plowing should be accompanied by good drainage, 



