[shutt-smith] "ALKALI" CONTENT OF SOILS 97 



The impregnation of this series is sodium carbonate, black alkaH, 

 other salts being present in traces only. 



In group 1628, the best growth, the concentration of alkali 

 in the first 6 inches amounts to • 135 per cent, which somewhat exceeds 

 the usually accepted limit of tolerance for farm crops in general. 

 It would seem, therefore, that onions might be classed with those 

 crops which are more or less alkali resistant. 



The concentration, as in the other groups of the series, diminishes 

 with depth of sampling, evidently a characteristic of areas impregnated 

 with black alkali. 



Group 1627 , representing the poor and distressed growth, prob- 

 ably marks the extreme limit of toxicity which this crop can bare. 

 The amount in "A," -224 per cent, is certainly much higher than 

 crops in general could endure. In its lower members the alkali 

 content corresponds very closely to that of group 1628, showing that 

 it is the concentration in the immediate surface soil that is the crucial 

 factor in determining growth. 



The percentages of sodium carbonate in group 1626 are not much 

 higher than in 1627, yet they are sufficient to inhibit all growth. 

 In this series we have an illustration of the fact that in the case of 

 black alkali slight differences in the concentration are of very con- 

 siderable significance. With "white alkali" the differences which 

 mark the limit of toxicity are of much greater magnitude. 



It is proposed to continue these studies for a number of seasons, 

 obtaining further evidence as to the limits of tolerance for various 

 farm crops and at the same time ascertaining to what extent and in 

 what manner the distribution of alkali is affected by irrigation with 

 and without drainage. The work here recorded is to be regarded 

 as merely the first step towards the establishment of standards for 

 Canadian conditions. 



Sec. Ill, Sig. 7 



