ABSORPTION OF SALTS BY SOILS. 



157 



is no reason to question the original ainiount present in the solu- 

 tion. Moreover, the amount of potassium nitrate added was 

 made an indefinite amount more than one gram by adding 

 enough to quickly tip a Springer Torsion balance against a gram 

 weight. More potash, in every case but one, has been absorbed 

 than is required to represent the chemical equivalent of the nitric 

 acid disappearing from the solution. 



The retention of phosphoric acid has not been very different 

 with the different soils, but this, too, was the case in the in- 

 stances cited from Voelcker. The solution contained phosphoric 

 acid enough to represent 29.55 parts per million of the dry soil. 

 In no case has this amount been absorbed ; and the amounts left 

 in the solution ranged between 10 and 22 parts per million of 

 the soil, as may be seen from the general table, p. 155. 



Comparatively large amounts of SO 4 were also fixed by the 

 four poorer soils, the Janesville Loam being the only one which 

 corresponds with the observations of earlier investigators. 



Chlorine is the only negative radicle, existing in the solution 

 used, which does not appear to have been fixed by the soils. 



COMPARISON OF YIELDS WITH THE AMOUNTS OF ABSORBED AND 

 DISSOLVED SALTS. 



In the last two lines of the last table there are given the foot- 

 ings of the absorbed and dissolved salts for each soil type. In 

 the next table these amounts are brought into comparison with 

 the yields from the same soil types. 



Comparison of yields with the amounts of snlts absorbed by 8 soil 

 types from <t manure solution. 



