[shutt-smith] 



'ALKALI" CONTENT OF SOILS 



89 



parts of the field the grass was of good growth. Samples collected 

 July 6th, 1917. 



Native Prairie Grass. 

 Series II. Sec. 9, Tp. 11, R. 25, W. of 3rd Meridian. 



Discussion of Results. In this, as in Series I, the alkali is chiefly 

 sodium sulphate, but magnesium sulphate is also present in notable 

 amounts, especially in Group 1604, characterized by "no growth." 



Group 1606. Good growth. The sodium sulphate in A (O'-O — 

 0'-5) is present in negligible amounts, but in the lower members of 

 this group it reaches percentages ranging from -541 (in D) to -731 

 (in C), accompanied by small amounts of magnesium sulphate. 



It might be inferred from these facts that provided the alkali 

 in the first 6 inches of soil were negligible and that it did not exceed 

 • 7 per cent from 1' • 5 — 5' • that native prairie grass might be expected 

 to make a good growth, without any marked distress. 



Group 1605. Poor and meagre growth. The concentration of 

 sodium sulphate in A (O'^O — 0'-5) is -432 per cent, but increases 

 markedly in the lower members of that group, amounting to 1 • 662 

 per cent in D. 



This distribution of alkali probably represents the limits of 

 tolerance for native prairie grass under irrigation. An amount 

 approaching -5 per cent in the first 6 inches, underlaid by soil con- 

 taining 1 per cent or more of alkali would seem to be the extreme con- 

 ditions under which the native grass might be expected to yield a crop. 

 It is interesting to note, comparing the two series discussed, that the 

 native prairie grasses are more alkali-resistant than Western Rye 

 grass. 



