73 



spots where brush was biirjicd and without the contin- 

 ued areation above referred to. Heat, therefore, seems 

 to accomplish in the soil effects similar to those brought 

 about by areation. The application of fertilizers pro- 

 duces no such effects." Since heating by burning brush 

 on Hawaiian soils seemed to accomplish the same re- 

 sults as aeration, Kelley made a study of the effect of 

 heating on the solubility of the constituents of soils; 

 and found that in most soils, heating increased the 

 amount of soluble manganese. Also it is of special in- 

 terest to note his results on the unheated soils. Work- 

 ing with both normal and abnormal types, he reports 

 water soluble manganese, iron, and aluminum in each 

 of the unheated soils. 



While no definite statement was made as to the acidi- 

 ty of the soils used, it is evident that each was acid, 

 else these water soluble compounds were not likly to 

 have been found. In all probability, water soluble 

 iron, aluminum, and manganese found in these soils 

 would be sufficient to account for poor plant growth, 

 Kelley states that his samples No. 416 and 417 are repre- 

 sentative of a type of soil abundant in the islands. 

 Soil No. 416 was taken from cultivated land, and No. 

 417 from a near-by sod. Since these sod lands are non- 

 productive when first put under cultivation, it is inter- 

 esting to note that much more manganese and iron, 

 and approximately equal amounts of aluminum were 

 recovered from the sod land. The point is stressed 

 that cultivation and aeration reduce the solubility of 

 manganese. With regard to productivity, aeration and 

 heating b}'^ the burning of brush seem to accomplish the 

 same beneficial results. The results reported above 

 suggest that the increased fertility found where brush 

 was burned on these soils was due to the alkaline ash 

 which would tend to precipitate manganese, iron, and 

 aluminum, rather than to any direct effect of the heat- 

 ing. 



From ammonification and nitrification studies on 

 these soils Kelley (11) concludes that while both the 

 cultivated and the uncultivated support ammonifica- 

 tion, only the cultivated soils support a vigorous nitri- 

 fication. 



Kelley says "Soine of the inert virgin soils appear to 

 contain soluble substances which inhibit nitrification. 

 Sterilization in the autoclave affected both cultivated 

 and uncultivated soil in such way as to render them 

 practically equal in regard to subsequent ammonifi- 

 cation and brought about conditions toxic to nitrifica- 



