30 



THE ELEMENTS AND THE SOIL 



Weight of soils. 



Soils vary widely in weight according to their composition and the 

 size of the particles. Humus soils are the lightest, and sand}' soils are 

 the heaviest. Clay soils weigh less per cubic foot than arable soils or 

 sandy soils. The larger the amount of organic matter in a cubic foot 

 of soil, the less it weighs. For this reason, surface soils are lighter, as a 

 rule, than subsoils (Stevenson). 



The weight of a cubic foot of dry soil is given by Shubler as 

 follows : 



Silicious sand 



Half sand and half clay 



Common arable soil 



Heavy clay 



Garden mold rich in vegetable matter 

 Peat soil . 



LB. 



110 



96 

 80 to 90 



75 



70 

 30 to 50 



Warington gives the following data regarding the weight of soil per 

 acre : 



1. Old pasture, Rothamsted, loam with clay subsoil 



2. Arable land, Rothamsted, loam with clay subsoil 



