CHAPTER VII 

 SOME PHYSICAL PROPERTIES OF THE SOIL 



While texture is of great importance in the determina- 

 tion of the physical and chemical nature of a soil, it is 

 evident that the arrangement of the particles also exerts 

 considerable influence. The term texture refers to the 

 size of the soil particles; the term structure is used in 

 reference to their arrangement, or grouping. It is at 

 once apparent that certain conditions — such, for ex- 

 ample, as air and water movement, heat transference, 

 and the like — will be as much affected by structure 

 as by texture. As a matter of fact, the great changes 

 wrought by the farmer in making his soil better suited 

 as a foothold for plants are structural changes rather 

 than changes in texture. The compacting of a light 

 soil or the loosening of a heavy soil is merely a change 

 in arrangement of the soil grains. It is of interest, there- 

 fore, to ascertain the probable arrangement of the particles 

 in any soil. 



80. Arrangement of soil particles (Fig. 17). — In any 

 consideration it is the easier way to advance from the 

 simple to the complex. Therefore in the explanation of 

 structural relationships a theoretical condition will be dealt 

 with first, after which the discussion will proceed to the 

 intricate condition existing in the soil. Assuming that 

 this theoretical condition consists in spherical particles 

 aU of the same size, we find these particles susceptible 



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