51 



Marshall Silt Loam. The i)li<)si)horic acid in soils from the for- 

 ested fields, 1, II and III (Tabic 48) shows the same irregularity as 

 that on tile other forest type, the Carrin.q^ton loam. The cleared fields, 

 T\' and V, :.re in .i^eneral more like those on the i)rairie types, the 

 amounts beiiis;" considerably higher than those found on the other 

 three, /.s pointed out above (p. 24), the thickness of loessial deposit 

 on the three forested fields is not great, the till being encountered in 

 the third foct on two of them so that it is not improbable that these 

 have been souewhat modified. The cleared fields, on the other hand, 

 appear to be more typical of this type, the thickness of the deposit here 

 being sulficient to remove any chance of inter-mixing with boulder clay 

 from belDw. 



Table 48. — FItosplioric acid from the different sections from the five fields on 

 Marshall silt loim. 



A vcrage 

 1—36 0.132 0.142 0.155 0.183 0.186 0.160 



Discussion. The averages for the five fields from the diflferent 

 types on the two drifts are shown in table 49. The amounts found on 

 the Kansan, on each type and in every field, are greater than those on 

 the Latti Wisconsin. The vertical distribution on the prairie types, 

 viz., the Canington silt loam and the Fargo silt loam, show^s a steady 

 decrease from the surface downward while that on the forest types is 

 irregular. 



Tabid 49. — Phosphoric acid in the different sections. The data arc the aver- 

 ages for the five fields reported in tables 43 to 4S inclusive. 



