57 » 



There is a wide difference in the amounts of nitroj^eii found in the 

 surface foot on the two drifts, those on the Kansan heintj', on the aver- 

 age, 76 per cent the higher in the surface six inches and 32 per cent the 

 higher in the second section. The conditions mentioned ahove (p. 53) 

 under which the soils of this type were developed furnish an explana- 

 tion for this difference, the accumulation of organic matter and nitro- 

 gen heing parallel. 



The average amount of nitrogen found in the second and third 

 foot-sections on the two drifts are, on the other hand. (|uite similar. 



Carringtoti Loam. The amounts of nitrogen found in a forest type 

 are naturally not as high as those found on the prairie types. The 

 variation (Table 56) within the same field and from field to field, as 

 well as the distribution from the surface downward, are much the same. 

 There is little dift'erence between the averages for the two drifts. 



Marshall Silt Loam. The three forested fields, I, II and Til. show 

 little variation within the same field, but a wider one from field to field 

 (Table 57). In the amounts present these resemble the fields on the 

 Carrington loam, a forest type. 



The cleared fields, IV and V, resemble the ])rairie types in both 

 the amounts of nitrogen and its distiHbution. 



Discussion. The averages for the five fields on the different types 

 are shown in tal)le 58. Both the Carrington silt loam and the Carring- 

 ton loam are very similar on the two drifts. The latter shows the 

 lowest percentage of all four types, but this is to be explained by the 

 fact that the areas sampled were all forested while prairie conditions 

 prevailed on the other types, with the exception of three fields on the 

 Marshall silt loam. 



Tabic 38.— Nitrogen in the different sections. The data arc averages for the 

 five fields reported in tables 54 to 57 inclusi7'c. 



Carrington silt loam Fargo silt loam Carrington loam Marshall 



Depth Kansan I.ate Wis. Kansan Late Wis. Kansan Late Wis. silt loam 



Inches per cent per cent per cent per cent per cent per cent per cent 



1—6 383 .364 .786 .445 .243 .263 .254 



7—12 .292 .278 .466 .305 .122 .117 .173 



13_'?4 ■■ 166 .164 .152 .\4S .072 .084 .109 



25—36 .058 .066 .044 .065 .039 .044 .057 



\veraffe 



1-36 187 .184 .274 .196 .0^)8 .106 .126 



With the Fargo silt loam the two upper sections are much richer 

 in nitrogen on the Kansan than on the T-ate Wisconsin, the fomier 

 being 76 per cent higher in the first 6-inch section and 52 ])er cent in 

 the second. This corresponds to the organic carbon (Table 53). The 

 averages for the second and third foot-sections f.n this type are very 

 similar. 



The average for the three feet on the Marshall silt loam is quite 

 similar to both of those on the Carrington loam, the difference being 

 due to the relatively large amounts found in the two cleared fields on 

 the former. 



