238 THE ROYAL SOCIETY OF CANADA 



The absence of all growth here clearly proves that the limit of 

 endurance for wheat has been passed. This toxic effect is due chiefly 

 to the large amounts of sodium sulphate present, although it is prob- 

 able that the .687 per cent, magnesium sulphate is to some degree 

 an additional injurious factor. 



It is desirable that more work should be done upon this problem 

 before the limits of tolerance are fixed definitely and finally. Further 

 evidence confirming results obtained with respect to the alkali toler- 

 ance of the crops already investigated must be obtained but it seems 

 justifiable, however, at this point to sum up the work accomplished 

 to date and tentatively to adopt limits of tolerance for the crops 

 examined. In this we have regarded an area of distressed growth as 

 representing soil impregnated with an amount of alkali approaching 

 the limits of safety for the crop in question and the following 

 data from such areas, extracted from results published in former 

 papers, have been tabulated with a view to presenting the evidence 

 to date. 



Wheat — Distressed Growth 



It seems apparent from a study of the above table that for 

 wheat the limit of sodium sulphate in the chief root feeding zone 

 (0'.0-l'.5) is between .5 and 1.0 per cent., for sodium carbonate from 

 .06 to .07 per cent. It is not evident why the "limit" in Group 1661 

 appears so much lower and in all probability its sickly crop was in 

 part due to some cause other than alkali. 



Western Rye Grass — Distressed Growth 



Group No. Na2S04 NaaCOa 



1602 A .117 



B .254 



1658 A .227 



B .038 



Western Rye grass seems to be a comparatively non-resistant 

 crop; .2 per cent sodium sulphate is apparently the toxic limit. 



