32 



this excessive aniotiiit of nitrate, when the soil was washed continuously 

 for about one month until no nitrate was contained in the drainage, 

 only 18 per cent of the nitrate added was recovered. 



AVhile the samples of soil examined in this work have not l)oen numer- 

 ous, extreme types have been included from ditferent islands, and the 

 data obtained are sufficient to warrant the assertion that a widespread 

 characteristic of Hawaiian soils is that when they are at or near the 

 saturation point with respect to water, there is a chang-e of nitrates and 

 an apparent fixation of a portion of the nitric nitrogen in a form not 

 easily soluble. 



In this connection the question naturall}" arises: If a portion of the 

 nitric nitrogen is fixed in the soil, in what form is it; and is it, or does 

 it become, available for plant growth? A study of this question and 

 a further study of the factors influencing the change will be carried on 

 during the coming year. 



On the completion of the new laboratory work was resumed on the 

 study of the constitution of the nitrogenous compounds in Hawaiian 

 soils. The considerations which led to taking up this work have been 

 stated in the last report. It was decided to work on a soil or soils, 

 fairlv high in nitrogen, for the obvious reason that smaller quantities 

 of soil would have to be handled to obtain amounts of nitrogenous 

 bodies sufficient for identification; and also for the reason that the 

 majority of soils, especially on Hawaii, suitable or available for crops 

 other than cane are of this nature. 



The work done has, for the most part, been on soil from one locality, 

 viz, Pohakea, Hawaii, where this station is experimenting with tobacco. 

 Along certain lines the work has been carried on with other soils,, but 

 the data from these is as yet fragmentary, and the results given below 

 apply to the single soil mentioned above. Mechanical and partial 

 chemical analyses of this soil have been published in Press Bulletin 

 No. 12 of this station and are as follows: 



Anali/sis of Pohakea xoil. 



Mechanical analysis, soil dried at 100° C. 



Combined -water and organic 



Fine gravel 1-2 mm 



Coarse sand 1-0.5 mm 



Medium sand 0.5-0.25 mm . . . 



Fine sand 0.2.5-0.1 mm 



Verv tine .«and 0.1-0. 05min. . . 



Silt 0.05-0.0005 mm 



Clav O.OO.T-0.0001 mm 



35. 935 

 16. .511 

 11.337 

 G.716 

 14.002 

 8.339 

 5. 848 

 .940 



Chemical analy.sis. 



Water 



Organic and combined water 

 Insoluble 



^V-*y' iron and alumina 



Cab lime 



MgO magnesia 



SO.'i sulphuric acid 



PjOj phosphoric acid 



KoO potash 



Nitrogen total 



Humus total 



Humic nitrogen 



Nitrogen in humus 



540 

 360 

 320 



TOO 

 631 

 343 

 703 

 077 

 728 

 470 

 560 

 490 



