38 



The Ottawa Naturalist. 



[June 



Plant Food and its Sources. 



To understand and appreciate the full sij^nificance of my sub- 

 ject, the improvement and recuperation of soils by the j^rowth of 

 lep^umes, it will be necessary for us to first consider the sources of 

 plant food, the nature of soils, and the manner in which soils are 

 affected by cultivation. 



The analysis of plants shows that they are composed of some 

 thirteen chemical elements, present, as might be expected, in vary- 

 ing proportions, according to the nature of the plant and the part 

 of it examined. Though these are built up by the plant into 

 numerous combinations, we can readily recognize in all vegetable 

 structure three distinct classes of compounds, viz.: water, mineral 

 or ash compounds, and organic compounds. The elements com- 

 prising these are drawn from two sources, the atmosphere and 

 the soil, both of which, as we shall see, furnish this food in forms 

 or compounds suitable to plant life, for it is well to remember that 

 the uncombined elements are practically valueless, considered as 

 plant foods for farm crops. 



The following scheme permits one to see at a glance the con- 

 stituents of plant food, their sources and products ; 



Plant Constituents. 



2 Soils 



r 



Carbon ^ 

 THE V 



Oxygen j ) 

 ORGANIC ^Hydrogen} 



ELEMENTS 



Nitrogen 



I 



f Calcium 

 Magnesium 

 Potassium 



Carbonic Acid 

 Water 



THE 



INORGANIC ^ 



ELEMENTS 



Sodium 



Iron 



Manganese 



] St; 



arch 

 gar 



Hbre 



Oil 



■J) 



T3 



'5 



c 



Xi 



) 



Phosphorus 

 Silicon 

 Sulphur 

 Chlorine 



AIR 

 DERIVED 



< ELEMENTS 



1 



SOIL 



DERIVED 



ELEMENTS 



