SOIL SURVEY OF BAXNER COUNTY, NEBRASKA. 21 



The Mitchell soils are deriv^ed from terrace material and do not dif- 

 fer in profile in an}' essential respect from the Bridgeport soils. They 

 are differentiated from the latter on the assumed basis of derivation 

 from terraces whose material came chiefly from the Brule clay. 

 The Bridgeport material is to a considerable extent colluvial in its 

 process of accumulation, Avhile the Mitchell material was accumu- 

 lated by larger streams. Since the material, however, in both cases 

 came from the same ultimate source, the various crj-stalline and 

 sedimentary rocks of the Rockj^ Mountains, there would seem to be 

 very slight reason for maintaining them as separate series of soils. 

 This is done, however, pending the accumulation of more specific 

 data. For all practical purposes the soils of the two series seem to 

 be essentially identical. 



The soils of the Valentine series have been developed from accu- 

 mulations of wind-blown sand that has ceased to move and has be- 

 come covered with grass. The soil material is almost entirely 

 quartz. The carbonate content, even in the subsoil, is too low to 

 cause effervescence in acid. The profile is immature, the horizons 

 consisting of a surface soil darkened by accumulated organic matter 

 and a subsoil of the unweathered parent sand. 



The Scott silt loam, the only member of the series mapped in 

 Banner County, has developed under imperfect drainage conditions. 

 As would be expected, it occurs in small areas only in depressions 

 in which water accimiulates during periods of high rainfall. In 

 wet seasons some of the areas fill with water and become temporary 

 lakes. The surface soils are dark brown in color, while the subsoils 

 are usualh- grayish in color and rather heav}'. 



The Dunlap soils have a profile differing from that of the Rose- 

 bud in one important respect. The lower part of horizon 2 consists 

 of a heavy clay that as fully developed becomes very intractable, and 

 does not permit the ready passage of capillary water. It seems to 

 be the only soil in the area whose course of development has been 

 influenced by the presence of soluble salts. It occurs on fiat sur- 

 faces, where surface drainage has not been rapid, and where such 

 salts as were developed by weathering processes would tend to accu- 

 mulate. It is well known that the presence of certain salts, even in 

 quantities too small to influence the growth of plants by their pres- 

 ence, may influence the character of the soil by the deflocculation of 

 the surface horizons, thus allowing percolating water to carry the 

 finer particles into the subsoil, where they accumulate, forming a 

 heavy clay horizon. It is apparent that this process has been at 

 work in this area to produce the soils mapped as Dunlap. 



The Laurel soils have a profile marked by the absence of well- 

 develo])ed horizons, except a darkish surface horizon. They consist 

 of recently accumulated alluvial material. 



