Oct. 14, 1918 Fertilizer Potash Residues in Hagerstown Silty Loam 73 



We may safely conclude from these studies that, although the clays 

 are not so rich as the nonclays in total potash, weight for weight, they 

 yield to weak solvents from six to eight times as much of this element 

 during a short period of time. It is also clear that, while both fractions 

 of the potash-dressed soil are richer in soluble potash than the corre- 

 sponding fractions from the unfertilized soil, the clays differ in this par- 

 ticular much more than the nonclays. 



The percentages of the total potash in these washed clays and non- 

 clays that are removed by the ammonium-chlorid solution are: 



Potash dissolved from — 



Clay, washed o. 761 i. 306 



Nonclay, washed 102 . 132 



That is, whether the amount dissolved be expressed in terras of the 

 respective soil fractions or of their total potash contents, the solubility 

 of the clay potash is much greater than that of the nonclay. 



RELATION OP AMOUNTS OF POTASH DISSOLVED FROM CLAY AND NONCLAY TO THE 

 COLLECTIVE SURFACE AREAS OF THEIR PARTICLES 



Since one of the important factors detennining the quantity of a given 

 solid that can be dissolved by a given solvent is the amount of surface 

 which the solid exposes to the liquid, it is worth while to attempt an 

 approximation of the surface areas exposed to the solvent by the clays 

 .and nonclays of these soils, and to the amount of potash dissolved from 

 unit areas respectively exposed to the solvent. 



In the following tabular statement are given the areas, in square 

 meters, of the clay and nonclay fractions in 100 gm, of the respective 

 air-dry soils, as calculated by the conventional method (7, p. 118), 

 using the formula 



Surface area- J<^ 



0X2.65 



in which "w" is the weight in grams of the group of soil particles for 

 which the surface area is to be computed; "J," the mean diametei, in 

 centimeters, of the particles of the group; and "2.65" the assumed 

 specific gravity. The areas stated for the nonclays are the sums of 

 those separately computed for the particles of each class as to fineness, 

 other than the clays. Owing to the practical identity in mechanical 

 composition of the soils of the two plots, the same percentages of 

 mechanical composition were used in the calculations for both soils. 

 With these areas (expressed in square meters in the table) are given the 

 corresponding quantities in milligrams of the potash dissolved by the 

 ammonium-chlorid solution from i square meter of the particle surface 

 of the respective fractions. 



.If we accept without qualification these results of the conventional 

 computation of the surface areas of the respective groups of soil particles, 



