30 



THE ELEMENTS AND THE SOIL 



Weight of noils. 



Soils vary widely in weight according to their composition and the 

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

 the heaviest. Clay soils weigh less per cu))ic foot than aral^le 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 : — 



LB. 



Silicious sand 110 



Half sand and half clay 96 



Common arable soil 80 to 90 



Heavy clay 75 



Garden mold rich in vegetable matter 70 



Peat soil 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 



