ABSORPTION OF SALTS BY SOILS. 153 



same solution, and with the- admitted dependence of crops upon 

 soluble matter in soils, it is, perhaps, not strange that Voelcker 

 should describe his least absorptive samjple as token .from a 

 "very infertile soil.' 7 



ABSORPTION OF SALTS BY EIGHT SOIL TYPES FROM A DILUTE 

 MANURE SOLUTION. 



After having washed the samples of 8 soil types eleven times 

 in distilled water, as described in Bulletin "B," p. 81, the same 

 samples were washed with a prepared manure solution to which 

 a quantity of potassium nitrate was added in order to have (1) 

 a considerable amount of potash in the solution, and (2) to study 

 the effect of these soils upon nitric acid in the presence of other 

 ingredients of such a solution. The potassium nitrate was not 

 added until everything was ready to make the washing, this pre- 

 caution being taken to avoid denitrification. 



The manure solution was prepared by choosing such an 

 amount as would be equivalent to a dressing of 15 tons of stable 

 manure per acre, allowing the surface foot of soil to weigh 

 3,000,000 Ibs. ; the manure to be incorporated with one-half the 

 surface foot of soil ; and the manure to contain 70 per cent, of 

 moisture. The amount of water-free manure used was 14.396 

 grams, the solution being prepared in the manner of plant solu- 

 tions, making it up first in 3 liters which, after straining, were 

 diluted to 12 liters. 



The solution was prepared on October 7 and used the next 

 day, when it was analyzed after adding the potassium nitrate, 

 giving, by the colorimetric method, the amount stated in the 

 table. 



Amounts of ivater-soluble salts in a manure solution to which po- 

 tassium nitrate was added. 



