330 



SOILS. 



WATER EXTRACTION OF SOILS OF LOW AND HIGH PRODUCTION, 

 BY F. H. KING. 



PARTS PER MILLION. 



King's observations show strikingly both the continuous 

 solubility of the soil, and the differences between the solutions 

 derived from soils of low and high productiveness; wholly 

 negativing the contention of Whitney that the solutions 

 from different soils are of practically the same composition. 1 

 King also calls attention to the fact, shown in other experi- 

 ments made in the extraction of soils without intermediate 

 dryings, that the amounts extracted were very much less in sub- 

 sequent than in the first extraction ; doubtless because the evap- 

 oration from the soil particles had carried a large proportion of 

 soluble matters to the surface, whence it was readily abstracted 

 by the first touch of the solvent water. At each drying not 

 only are the soluble matters again drawn to the surface, but 

 heating a soil even to 100 renders additional amounts of soil 

 ingredients soluble both in water and in acids. It can scarcely 

 be doubted that the intense heating which desert soils undergo 

 during the warm season is similarly effective; and thus the 

 great productiveness of these soils under irrigation, and the 

 marvelously rapid development of the native vegetation when 



1 Bulletin No. 22, Bureau of Soils, U. S. D. A. 



