THE ANALYSIS OF VIRGIN SOILS. 357 



of phosphoric acid in soils and doubtless also in fertilizers. The verj 

 unusually high content of phosphoric acid in the Hawaiian soils, ex- 

 ceeding all others on record, so far as known to the writer, emphasize 

 the effects of ferric hydrate upon soluble phosphates ; while the fact 

 that these very soils are greatly benefited by the use of phosphate fer- 

 tilizers, proves that the Dyer (citric acid) method for the determination 

 of available phosphoric acid which in soils Nos. 21 to 26 yielded results 

 largely in excess of the established limit in European soils, cannot be 

 successfully applied to these highly ferruginous soils. It should also be 

 noted that the amounts of phosphoric acid found in the humus extracted 

 by the Grandeau method is in the first two Hawaiian soils over ten 

 times the amount extracted by citric acid, but that while they rise and 

 fall together, no definite quantitative ratio exists between the two. 



It is obvious that in such soils, fertilization with water-solu- 

 ble phosphates would be likely to result in the quick partial 

 withdrawal of the same from useful action, and that any ex- 

 cess not promptly taken up by the crop, is likely to become 

 inert and useless. It will evidently be desirable to use the 

 phosphates in the form of bone-meal or basic slag (Thomas 

 Phosphate), which because of their difficult solubility will be 

 acted upon but very slowly, if at all, by the ferric and aluminic 

 hydrates. 



Nitrogen. In determining the nitrogen-content of the soil, 

 a great variety of methods has been followed. Some include 

 all that can be obtained by the combustion of the organic mat- 

 ters of soil and from the nitrates present in the same; while 

 others, the writer among the number, believe that the mainly 

 important source of nitrogen to the plant being the nitrifica- 

 tion of the humus-nitrogen, the determination of the humus 

 by the method of Grandeau, and of the nitrogen contained in 

 it, should be the standard; the unhumified vegetable matter 

 being of no definitely ascertainable value, and the nitrates 

 varying from day to day and being liable to be lost by leach- 

 ing at any time ; therefore forming no permanent feature of the 

 soil. Considering the variety of methods, the unanimity with 

 which about one-tenth of one per cent (.10) has been assumed 

 as the ordinarily adequate percentage is remarkable. In view 

 of the extremely variable amount of nitrogen in the humus 

 (ranging from 1.7 to nearly 22%), the amount of the latter 



