116 THE PRINCIPLES OF SOIL MANAGEMENT 



which most influences the structure of the soil. All 

 these processes promote the development of lines of 

 weakness upon which the water may act. In this way 

 organic matter promotes granulation. 



49. Soluble salts. In the action of certain salts, 

 a different process from the previous ones is introduced. 

 When lime is mixed with water containing fine particles 

 in suspension, there is almost immediately a change in 

 the arrangement of the particles. They appear first 

 to draw together in light fluffy groups or floccules, 

 which then rapidly settle to the bottom, so that the 

 supernatant liquid is left clear or nearly so. This phe- 

 nomenon is termed flocculation, because of the groups 

 of particles. It is not an action limited to lime, but in 

 greater or less degree results from the use of many 

 substances. Lime is about the most active flocculating 

 agent, and a very small amount is required. Acids, 

 especially the mineral acids, are strong flocculating 

 agents. Many of the common fertilizing materials have 

 a flocculating power. Some substances, however, pre- 

 vent or break up flocculation. Such, for example, is the 

 effect of carbonates of the alkalies. From an agricul- 

 tural point of view, the various forms of lime are the 

 most important in this connection because their use 

 on the soil is practical for the farmer. When introduced 

 into _ the soil, this flocculating action occurs whereby 

 granules are formed, the stability of which may be 

 further increased by other favoring conditions. 



The effect of lime on this process and the relative 

 rapidity of the action for different forms, as shown by 

 its influence on the cohesion of a puddled soil, is shown 



