48 



7. Magnesia. 



There is very little difference between the amounts of magnesia 

 (Table 43) found on the two drifts on any given type. The largest 

 amount is found, as in the case of lime, on the Fargo silt loam, the 

 average being, respectively, 1.25 per cent for the Kansan and 1.27 per 

 cent on the Late Wisconsin. The averages for the Carrington loam are 

 slightly lower than those for the Carrington silt loam, which are 0.8? 

 per cent and 0.94 per cent, respectively, for the two drifts. 



Table 43. — Magnesia in the different scctiotts. 



The ratio of total lime to magnesia (Tal)le 44, pt. 1) falls between 

 1.0 and 1.8, averaging 1.4 for the three-foot section on all types. It is 

 very similar for each type on both drifts, the greatest difference being 

 shown on the Carrington silt loam, where, on the Kansan, it is 1.2 as 

 compared with 1.5 on the Late Wisconsin. The optimum ratio varies 

 with different plants (26), but in general the lime must equal or exceed 

 the magnesia if the most satisfactorv cultural results are to be obtained 

 (24, p." 33). 



Table 44. — Relation of lime to magnesia in the different sections. 



Carrington silt loam Fargo silt loam Carringrton loam 



" Late Wis. 



per cent 



1.8 

 1.4 

 1.1 

 1.3 



1.3 



1.6 

 1.3 

 1.0 

 1.2 



1.2 



On both prairie types the ratio of the portion of the lime in the 

 form of silicate to magnesia (Table 44, pt. 2) decreases from the sur- 

 face downward, as was the case with the amounts of lime in the form 

 of silicate on these, while on the forest type it decreases through the 

 first three sections, rising slightly again in the third foot. On both 

 drifts the average ratio for each type is very similar with the exception 

 of the Fargo silt loam, where that for the Kansas is the higher. 



