REPORT OF THE CHEMIST. 129 



SOILS. 



The investigation into the composition of certain Canadian soils has been con- 

 tinued, and the results of the analyses of sixteen samples obtained during the past 

 year are now given. 



Since the amount of work involved in soil analysis in very considerable, the 

 chemical examination is renLricted to those samples which either represent the 

 virgin soils covering large areas in the Dominion or, on account of supposed barrenness, 

 present themselves as woi-thy of special examination. 



In previous reports (1890 and 1891) the factors upon which the fertility of a 

 soil depends have been enlarged upon, the constituents of soils enumerated, and the 

 limits between which the elements of the plant food vary in soils given. It will 

 only be necessary, therefore, to insert the following abstracts, which afford sufficient 

 information to render intelligible the chemical data in the subjoined table: 



Factors op a Soil's P'ertility. — "The factors upon which the fertility of the 

 soil depend are many. The amount of plant food and its degree of solubility, the 

 mechanical texture or tihh and the climate (temperature, amount of rainfall, &c.) 

 are the chief of these. 



" Soil, to be fertile, must contain the elements of plant food in such forms that 

 they can be readily used for the nutrition of vegetation. At the same time its con- 

 dition must not be too loose, else a firm hold will not be afforded to the roots of plants, 

 and there will be too much drainage and evaporation ; nor must it be too heavy and 

 plastic, for then air and water could not freely permeate it nor the roots extend 

 themselves bej'^ond a very limited area. Generally speaking, light, loose soils are 

 not as rich in plant food as those in which clay predominates ; yet, on account of 

 their excellent condition of tilth, they often yield, in favourable seasons, heavier 

 crops than the latter. Stiff, heavy clays, though I'ich in inorganic plant food (potash 

 and phosphoric acid) are often poor in nitrogen, while their condition is such as to 

 prevent thoi-ough aeration and the penetration of the roots. It is these soil« espe- 

 cially that are benefited by drainage. By a system of drainage the water which 

 saturates the surface soil is carried off, air allowed to permeate, the whole rendered 

 more friable and easily worked, and much plant food is converted into assimilable 

 forms. 



** Where sand largely preponderates, the soil is not retentive of moisture and 

 fertilizing material, especially if the subsoil be light, and though easily worked, is 

 not so dei^irable in dry seasons as a heaviec soil. 



" A proper proportion of sand and clay, therefore, for many reasons, makes the 

 best soil. 



"With the clay and sand, vaiying amounts of peaty matter or humus (derived 

 from the decomposition of vegetable matter), and of calcaieous matter (principally 

 carbonate of lime) are usually associated, and a right proportion of the two latter 

 exerts a beneficial influence upon the tilth of a soil. From the pi'csence of these pre- 

 dominating materials, soils are known respectively as clay, sandy, peaty and calcare- 

 ous, according as one or the other is in excess. 



" By the slow decomposition of the clay and the peaty and calcareous matter, 

 plant nutrients are liberated in a soluble form, and therefore the function of these 

 soil fundamentals is not only mechanical but chemical. 



The Essential Elements op Plant Food. — "The most important inorganic 

 constituents of a soil are potash and phosphoric acid. These, together with nitrogen, 

 are known as the essential elements of plant food. 



" Fotash — derived principally from the decomposition of felspathic rocks, e.g., 

 granite — exists chiefly in combination with silica in a more or less soluble condition. 

 The limits of potash in a soil lie between a mere trace and about 2 per cent. A 

 good agricultural soil contains between -25 per cent and 1 per cent. Clay soils, 

 usually, are the richest in potash. 

 8c— 9 



