SOILS OF THE ARID AND HUMID REGIONS. 



393 



ingredient, phosphoric acid, the indication in the table that 

 there is no characteristic difference in the average contents in 

 soils of the arid and humid regions, respectively, is doubtless 

 correct. This substance is so tenaciously retained by all soils 

 that there is no obvious reason why there should be any ma- 

 terial influence exerted upon its quantity by leaching, or by 

 any of the differences in the process of weathering that are 

 known to exist between the two climatic regions. Moreover, 

 it is apparent that the average for the arid region is made up 

 out of very widely divergent figures; that of California excep- 

 tionally low (lower than any of those for the states of the 

 humid regions), while those for Washington and Montana are 

 exceptionally high. The latter is due to country rocks 

 ("basalts") showing abundance of microscopic crystals of 

 apatite, which in some cases raise the contents of the soils in 

 phosphoric acid to nearly twice the average given for the 

 states. 



The forecast that for most California soils, fertilization with 

 phosphates is of exceptional importance, has already been 

 abundantly confirmed by cultural experience. Few definite 

 data are as yet available from other arid states, where fertil- 

 ization is thus far sporadic and unsystematic. But it is pre- 

 dicable that in view of the presence of an excess of lime carbon- 

 ate in the arid soils, and the unfavorable effect of this com- 

 pound on the rapid solubility of tricalcic phosphate demon- 

 strated by Schloesing, Jr., 1 by Bottcher and Kellner 2 and 

 Naganka, :i fertilization with readily available phosphate fertil- 

 izers will be found necessary among the first, all over the arid 

 region, especially in view of the scarcity of humus in arid soils. 



A curious instance of the effects of continued warm maceration in 

 rock decomposition is afforded by the highly ferruginous soils derived 

 from the black basaltic lavas of the Hawaii Islands. These lavas, like 

 the basalt sheet of the Pacific Northwest, contain a large amount of 

 crystallized phosphate minerals, notably apatite and vivianite. A cor- 

 respondingly large proportion of phosphoric acid is found in the soils 



1 Ann. Sci. Agronomique, tome i, 1899. 



3 Landw. Presse, 1900, No. 52 ; ibid. 1901, Nos. 23 and 24. 



" Hull. Univ. Tokyo, Vol. 6, N'o. 3. Production was diminished to less than one 

 half when lime was used with bone meal, and actual assimulation of phosphoric 

 acid to one fifth. 



