68 THE ROYAL SOCIETY OF CANADA 



The chief differences from the chemical point of view between 

 surface soil and its subsoil are the higher percentages of nitrogen and 

 organic matter in the former; this well-established fact may be 

 legitimately used as a diagnostic factor in the consideration of the 

 present problem. 



An inspection of the data of the foregoing table shows that the 

 nitrogen content of 1683 " A" isdecidedly lessthan thatof "A" in any 

 of the other groups; it is but little higher than that of "B" of 1681 and 

 1682 and almost identical with that of "B" of 1684 and 1685. The 

 evidence, in our opinion, is satisfactory as indicating that the burn- 

 out represents an area from which the surface soil has been removed. 



The surface soil of the area represented by Groups 1684 and 1685 

 is somewhat richer in organic matter and its concomitant nitrogen 

 than that represented by Groups 1681 and 1682, and we consequently 

 find that "B" and "C" of the former groups (1684 and 1685) possess 

 higher percentages of these constituents than 1681 and 1682. In 

 " D " throughout the whole five groups the nitrogen content approaches 

 the same figure. 



In accordance with our practice in the examination of .soils from 

 irrigable areas the water-soluble content of these samples was deter- 

 mined. Groups 1683, 1684 and 1685 were found entirely free from 

 alkali. Group 1682 is free to a depth of 3 feet; in D (3'.0-5'.0) a 

 small percentage of soluble matter which proved to be calcium 

 sulphate was observed. As in the other groups, "A" of 1681 contains 

 no saline matter, "B," "C" and "D" of this Group, however, show 

 a notable but not serious impregnation, which is chiefly sulphate of 

 soda. In "D" there is a marked percentage of calcium sulphate, a 

 characteristic feature of certain subsoils in Southern Alberta. 



When these burn-outs are large, say several feet in diameter, 

 it is noticed that, for a few years after breaking, the crops upon them 

 are lighter than those on the surrounding unaffected soil. This dis- 

 parity tends to disappear with a few years' tillage, a fact which is in 

 accord with our observation that the subsoils of semi-arid areas are 

 rich in available plant food and, as compared with those of humid 

 districts, are more or less readily brought into a condition of economic 

 productiveness. 



