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THE PRINCIPLES OF SOIL MANAGEMENT 



like the leaves of a book, when the pages are bent. This 

 disturbance of the existing arrangement of particles 

 starts in motion two forces: (1) The surface tension 

 of the water films, which must now readapt themselves 





Fig. 35. Clay soil plowed when very wet. Condition indicated by the slickened 

 soil surfaces and coarse, dense structure 



to the new arrangement, and which, by opening larger 

 spaces, may lose some moisture by evaporation into 

 the arger interstitial spaces. (2) The cohesive forces 

 between particles, some of which have been forced 

 closer together and some farther apart. The strength 

 of cohesion between small particles, like clay, can be 



