168 REPORT OF THE COMMlsSIOIS^ER OF AGRICULTURE. 



Table II. — Nitrogen and carlon in various soils — Continued. 

 VAKIOUS AKABLE SOILS IN GREAT BRITAIN. 



UNITED STATES AND CANADIAN PRAIRIE SOILS. 



RUSSIAN SOILS. 



FERTILITY DEPENDS ON THE MINIMUM QUANTITY OF ANY NECES- 

 SARY CONSTITUENT PRESENT. 



As the soil is the source whence plants derive their mineral food, 

 all the elements required for this nourishment have, in a certain sense, 

 equal value, for if one of them is wanting in the soil, or is present in 

 a form not readily available by the roots, the plant will not flourish ; 

 and so its fertility depends on the minimum quantity of any necessary' 

 constitutent present. 



WEIGHT OF A SOIL PER ACRE. 



The weight of soil on an acre of land is so enormous that even small 

 proportions of plant food may amount to every considerable quantities. 

 The weight varies with the porosity and the amount of sand and gravel 

 the soil contains. 



The following table gives the specific gravity, the weight of 1 cubic 

 foot of different soils, dry and wet, taken from the table in Professor 

 Schtibler's article "On the physical properties of soils," in the Journal 



