GEOLOGICAL CLASSIFICATION OF SOILS 63 



spar, mica, hornblende, augite, caleite and other minerals 

 are found. 



A few typical analyses are given below which show the 

 variability that may be expected, especially in the nitrogen, 

 phosphoric acid, potash, and lime. 



Table X 



ANALYSES OP AMERICAN LOESS SURFACE SOILS^ 



(JONSllTDENTS 



1 



2 



3 



4 



SiO^ 



71.30 



81.13 



86.96 



69.66 



TiO, 



.60 



.78 



.69 



1.72 



AlA 



11.47 



8.52 



4.69 



12.71 



Fe.Os 



4.05 



2.92 



2.86 



4.89 



MgO 



1.10 



.39 



.43 



1.28 



CaO 



1.38 



.31 



.71 



1.09 



Na,0 



1.95 



.52 



1.07 



1.17 



K,0 



2.40 



1.78 



.91 



2.42 



PA 



.23 



.08 



.07 



.15 



N 



.22 



.11 



.11 



.23 







Whenever moisture relations are favorable, loess is an 

 exceedingly fertile soil. Under heavy cropping, especially 

 when little in the way of organic or mineral matter is re- 

 turned, this soil shows a need of phosphoric acid and lime, 

 the application of which is becoming part of good farm prac- 

 tice in the Central West. Considering the wide extension of 



=^1. Marshall silt loam, Pottawattamie Co., la. 



Bennett, H. H., Soils and Agriculture of the Southern States, 

 p. 332; New York, 1921. 



2. Memphis silt loam, G-renada Co., Miss. 



Eobxnson, W. 0., et at, Variation in tJi^ Chemical Composition 

 of Soils; U. S. Dept. Agr., Bui. 551, Jnne, 1917. 



3. Cherokee silt loam, Cherokee Co., Kan. 



Bennett, H. H., Soils and Agriculture of the Southern States, 

 p. 332; New York, 1921. 



4. Silt loam, Weeping Water, Neb. 



Alway, F. J.^ and Rost, C. 0., The Loess Soils of the Nebraska 

 Portion of the Transition Megion, Part IV; Boil Sci., Yol. I, 

 No. 5, p. 431, May 1916. 



