THE SOILS OF THE CANE-GROWING REGIONS 



73 



availability of the fertilizing elements. Very remarkable is the presence, rare in 

 arable soils, of a large quantity of magnesia, from i per cent, to 3 per cent. 

 The fertilizing elements, properly so called, were found per kilogram : — 



Phosphoric acid 

 Potash . . 

 Organic nitrogen 

 Nitric nitrogen, trace to 



1-44 to 2-30, mean, I • 75 grms. 

 1-56 to 3-68, „ 2-28 „ 



0-37 to 1-40, ,, 0-72 ,, 



— 0-040, ,, 0-004 '" 



Finally, the quantities of chlorine and sulphuric acid which have so great an 

 influence on the formation of efflorescent salts injurious to vegetation were found in 

 healthy soils. 



Chlorine .. .. o-io to o-o6 per 1000. 



Sulphuric acid .. 0-25 to i- 6c per 1000." 



The average composition of 2S samples of sugar cane soils is thus given 

 bv these authors : — 



The quantities are the percentages soluble in nitric acid, according 

 to the oiftcial French method. 



The mean of seven analyses of Egyptian soils made by Mackenzie and 

 Burns^^ with h\'drochloric acid as solvent gave the following results : — 



The Soils of the Hawaiian Islands. — As this sugar-producing district has 

 yielded, and continues to yield the greatest return of sugar per acre, 

 its soils are of peculiar interest. They have been examined in great detail 

 by ^laxwell, Eckart, and Kelly, and to a less extent by Crawlej', Shorey and 

 Hilgard. Recently Burgess- has made a very detailed study of the soils 

 under cane cultivation in the island of Hawaii. 



The dominant factor in the formation of these soils has been the decom- 

 position of basaltic lavas, the product of very recent vulcanism. They are 

 characterized by the presence of large quantities of iron, alumina and lime, 

 with smaller quantities of potash. Phosphates are also present in quantity 

 mainly in the form of apatite. 



MaxwelP ^ thus classifies these soils : — 



3- 



A. — Geological Formation. 



Dark red soils : — Soils formed by the simple weathering of normal lavas in 

 climatic conditions of great heat and drj-ness. 



Yellow and light red soils : — -Soils derived from lavas that underwent great 

 alteration, under the action of steam and sulphurous vapours, at the time of 

 or after emission from craters. 



Sedimentary soUs : — Soils derived from the decomposition of lavas at higher 

 altitudes, and removal and deposition by rainfall at lower levels. 



♦Schloesing's method. 



