CHAPTER I 



PHYSICAL PROPERTIES OF SOILS 



1. Soil. Soil is disintegrated and pulverized rock 

 mixed with animal and vegetable matter. The rock 

 particles are of different kinds and sizes, and are in 

 various stages of decomposition. If two soils are 

 formed from the same kind of rock and differ only in 

 the size of the particles, the difference is merely a 

 physical one. If, however, one soil is formed largely 

 from sandstone, while the other is formed from lime- 

 stone, the difference is both physical and chemical. 

 Hence it is that soils differ both physically and chem- 

 ically. It is difficult to consider the physical proper- 

 ties of a soil without also considering the chemical 

 properties. The chemical and physical properties, 

 when jointly considered, determine largely the agri- 

 cultural value of a soil. 



2. Physical Properties Defined. The physical 

 properties of a soil are : 



1. Weight. 



2. Color. 



3. Size, form, and arrangement of the soil particles. 



4. The relation of the soil to water, heat, and cold. 



5. Odor and taste. 



6. The relation of the soil to electricity. 



3. Weight. Soils differ in weight according to the 

 composition and size of the particles. Fine sandy 

 soils weigh heaviest, while peaty soils are lightest in 



