THE PHYSICO-CHEMICAL INVESTIGATION OF SOILS. 331 



rains moisten the parched soil, is in part at least accounted for 

 by this immediate availability of a large supply of plant-food. 

 Composition of Janesville loam. In connection with the 

 above data given by King, it is interesting to note the compo- 

 sition of the soil in the above table yielding the highest pro- 

 portions of soluble matter, when analyzed according to the 

 method practiced by the writer (see chap. 19, p. 343). This 

 analysis was made under the supervision of Professor Jaffa 

 in the laboratory of the California Experiment Station by 

 Assistant Charles A. Triebel. 



Loam Soil from Janesville, Wisconsin ; sample sent by Prof. F. H. 

 King, Madison, Wis. 



This soil is a light friable loam, resembling the northern Loess in 

 color and texture ; it is highly productive. It is underlaid at 5 feet by 

 the drift gravel of that region, enclosing much calcareous material, 

 which evidently has had a large share in the formation of this soil, just 

 as is the case in southern Michigan. 



The soil, when dried at 1 10 C., consisted of 



CHEMICAL ANALYSIS OF FINE EARTH. 



Insoluble matter 69.35 



Soluble silica 10.89 



Potash (KOn) 59 



Soda (NaaO) 04 



Lime (CaO) 83 



Magnesia ( MgO) .51 



Br. ox. of Manganese (Mn 3 O 4 ) .08 



Peroxid of Iron (Fe^Oa 3.60 



Alumina (AljOs) 5.26 



Phosphoric acid (P 3 O 3 ) ... 06 



Sulfuric acid (SOi) 10 



Water and organic matter. 8.72 



Total 1 00.03 



It will be noted that in accordance with the interpretation of analyses 

 of soils as given in the next chapter, this is a high-class soil in every 

 respect, except that its content of phosphoric acid is only just above 

 the lower limit of sufficiency. But as is also shown below, in presence 

 of a large supply of lime even lower percentages of phosphoric acid are 

 adequate for long-continued production (see chap. 19, pp. 354, 365). 

 by rendering the substance more freely available ; and that this is true 

 in this case is shown by the result of King's leachings, in which this 

 soil yields a maximum of 419 parts per million as against 80 and 64 

 parts in the poor soils, which at the same time yield only one fourth as 

 much of lime. Unfortunately we have no full analyses of these other 



