AI R WATER SOILS. 



527 



The following table compares the composition of two of the above 

 soils with that of the lavas from which they were derived: 



Comparison of lavas and soils. 



Silica. 



Ferric Aliimi- Calcium 

 oxid. mini oxid. oxid. 



Normal lavas (solid) 



Normal lavas (weathering) 



Dark-red soils 



Tufa lavas 



Yellow and light-red soils. 



Per cent. 

 47. 58 

 40.35 

 31. 45 



32.84 

 23.(53 



Per cent. 

 15.02 

 20. 52 

 29.78 

 33. 92 

 43.11 



Per cent. 

 19. 92 



25. 23 



26. 94 



29. 1 1 

 18.33 



Per cent. 

 8.88 

 8.11 



.57 

 1.74 



.37 



The analyses show that Hawaiian soils are strongly basic. As a 

 rule the dark-red soils and the sedimentary soils are distinguished by 

 a greater and more permanent fertility than the yellow or light-red soils. 



"A comparison of American rocks with Hawaiian lavas, and of the soils respec- 

 tively derived from them, have shown that the soils of these islands are totally 

 different in type from the soils of the United States, which is set forth hy the 

 great differences in physical properties and chemical composition. Relatively 

 speaking, the soils of these islands are in their youth, and the soils of the United 

 States and of Europe in a state of old age." 



Availability and loss of the elements of plant food in Hawaiian soils. — 

 For the purpose of ascertaining the availability of the fertilizing con- 

 stituents in Hawaiian soils the solubility in water and in 1 per cent 

 citric acid of the lime, potash, and phosphoric acid in samples of 30 

 typical soils was determined. 



"In the estimation of elements soluhle in water 200 gm. of the field sample (not 

 fine earth) was put into a closed funnel, with a ground-glass cover, and treated with 

 1,000 cc. of water for 48 hours, the water percolating through slowly, and then 

 returned upon the soil and continued for the time stated. 



"In determining the elements soluhle in 1 per cent citric acid solution 200 gm. of 

 the field sample was put into a 2-liter bottle with 1,000 cc. of the 1 per cent citric 

 acid solution ; the bottle was gently shaken every 15 minutes during the day portion 

 of 24 hours, and at the end of this time filtered off." 



The average results in percentages and pounds per acre are as follows : 



Solubility of soil constituents in water and in 1 per cent citric acid. 



Soluble 

 in water. 



Soluble 



in citric 



acid. 



Upland soil: Percent. 



Lime 0.0032 



Potash 0031 



.0001 



.0054 

 .0047 

 . 0003 



Phosphoric acid 

 Lowland soil: 



Potash 



Phosphoric acid. 



Per cent. 



0. 0940 

 . 0250 

 .0035 



. 1330 

 .6380 

 .0046 



"By far the most striking result from the action of a 1 per cent solution of citric 

 acid upon the soil is the enormous proportion of the lime and also of the potash 

 dissolved." 1 



1 In connection with the tests of availability of the fertilizing constituents in the 

 soils a series of observations was made on the relative sensibility of plants to acidity 

 in soils, an account of which has already been given (E. S. R. ; 10, p. 128). 

 12342— No. 6 3 



