12 SOILS AND FERTILIZERS 



2. Physical Properties Defined. The physical prop- 

 erties of a soil are : 



1. Weight and volume. 



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



3. The relation of the soil to air, water, heat, and 

 cold. 



4. Color. 



5. Odor and taste. 



6. The relation of the soil to electricity. 



3. Weight and Volume. Soils vary in weight with the 

 composition and size of the particles. Fine sandy soils 

 weigh heaviest, while peaty soils are the lightest. 

 But when saturated with water, a cubic foot of peaty 

 soil weighs more than a cubic foot of sandy soil. A 

 given volume of clay soil weighs less than the same 

 volume of sandy soil. The larger the amount of or- 

 ganic matter, the less the weight. Pasture land, for 

 example, weighs less than arable land. A cubic foot 

 of soil from a field which has been well cultivated 

 weighs less than that from a field where the soil has 

 been compacted. Weight is an important property to 

 consider when the total amounts of plant food in two 

 soils are compared. A peaty soil containing i per cent 

 of nitrogen and weighing 30 pounds per cubic foot has 

 less total nitrogen than a soil containing 0.40 per cent 

 of nitrogen and weighing 80 pounds. 



The weight of soils per cubic foot as determined from 

 apparent density is approximately as follows : 6 



