PRINCIPLES OF AGRICULTURAL CHEMISTRY 



the field. In the laboratory the apparent specific gravity will vary 

 with the method used for determining it. 



The apparent specific gravity of a soil is determined by weigh- 

 ing the dry soil that occupies a given volume. In the field this is 

 accomplished by driving a tube of definite size, not less than 2 

 inches in diameter, into the soil, so as to remove a core of known 

 volume. The core is removed, dried and weighed, and the weight 

 divided by the volume is the apparent density. 



Apparent density is determined in the laboratory by packing 

 200 to 1000 cc. of the soil into a glass cylinder, and weighing it. 

 This method to a certain extent is applicable to incoherent soils, 

 but is not well suited to clay soils, in which the action of water 

 has a decided effect upon the apparent density. It represents the 

 weight of the soil when in condition of good tilth. 



The apparent specific gravities of different kinds of soils are 

 as follows, according to Schubler i 1 



Sandy soils, usually termed "light," are the heaviest of all, 

 while clayey land, termed "heavy" weighs less than ordinary soils. 

 The terms "light" and "heavy" refer to the readiness with which 

 the soils are worked by the plow, light soils requiring much less 

 labor than heavy ones. 



The actual weight of the soil in the field varies with the quantity 

 of water present. A peaty soil saturated with water is very 

 heavy. 



Since soil analyses are made by weight, differences in the 

 apparent specific gravity of soils must be taken into consideration 

 in interpreting the results. 



1 Stockbridge, Rocks and Soils, p. 153. 



