526 



EXPERIMENT STATION RECORD. 



the composition of unaltered lavas with the average of about 600 soils 

 derived from them (calculated to the basis of mineral matter): 



On the basis of the studies made the soils of the islands are classi- 

 fied geologically as follows: 



"(1) Dark red soils formed by the simple weathering of normal lavas, in climatic 

 conditions of great heat and dryness. 



"(2) Yellow and light red soils derived from lavas that underwent great alteration 

 under the action of steam and sulphurous vapors at the time of or after emission 

 from the craters. 



"(3) Sedimentary soils derived from the decomposition of lavas at higher altitudes 

 and removal and deposition by rainfall at lower levels. 



"In addition to the classihcation based on geological differences in the lavas the 

 soils have been further considered in classes dictated by the results of climatic con- 

 ditions as follows: 



"(1) Upland soils formed under lower temperatures and greater rainfall, and dis- 

 tinguished by a large content of organic matter and nitrogen and by a low content 

 of the elements of plant food in an available state, these elements having been 

 removed by rainfall. 



"(2) Lowland soils formed under higher temperature and smaller rainfall, and 

 characterized by a lower content of organic matter and nitrogen and by a higher 

 content of the elements of plant food in a state of immediate availability, which is 

 due in part to the receipt of some soluble constituents from the upper lands and to 

 a smaller rainfall over the lower levels." 



The composition of some of these soils is shown in the following table, 

 which gives the average of over 1,300 analyses. The mineral constit- 

 uents reported were determined by digesting the soils in hydrochloric 

 acid of 1.115 specific gravity for 10 hours in a boiling water bath. 



Composition of different classes of Hawaiian soils. 



Insoluble matter 



Moisture 



Combustible matter. 



Titanic oxid 



Phosphoric acid 



Sulphuric acid 



Carbonic acid 



Ferric oxid 



Aluminic oxid 



Calcium oxid 



Magnesium oxid 



Manganese oxid 



Potassium oxid 



Sodium oxid 



Total 



Insoluble silica (calculated to mineral matter) 



Soluble silica (calculated to mineral matter) 



Total nitrogen 



Nitrogen soluble in 3 per cent KOH in 30 hours. . . 

 Nitrogen insoluble in 3 per cent KOH in 30 hours 

 Water absorptive power 



