Oct. 14. 1918 Fertilizer Potash Residues in Hagerstown Silty Loam 65 



FiyASK METHOD. — A lo-gm. portion of the soil was heated with i ,000 cc. 

 of freshly boiled and cooled distilled water in an electric oven at 40° C. 

 for five hours, with vigorous shaking at hourly intervals. At the end of 

 the heating period the solution was filtered quickly away from the undis- 

 solved soil, and freed from suspended silt and clay by repeated filtration. 

 The entire filtrate, after it had been freed from visible suspended matter, 

 was concentrated by evaporation. To destroy the dissolved organic 

 matter, the solution was evaporated to dryness, ignited, and the residue 

 taken up with dilute acid. The determinations of potash were made 

 gravimetrically as in the preceding solutions, but with highly variable 

 results. Although the results from the respective soils, obtained by 

 five repetitions for plot i and eight for plot 4, were — 



Percentage of 

 potash (K2O). 



Plot I, untreated o. 0032 ±0. 0003 



Plot 4, dressed with potash 0049 ± • °<3o6 



the ranges of variation were, for plot i, from 15 to 46 parts of potash per 

 million of the soil, and for plot 4, from 17 to 75 p. p. m. 



PERCOiyATiON MBTHOD. — For this method 50-gm. composites for each 

 plot were gradually filled into "J/i-mch. percolation tubes, closed below by 

 means of a double paper filter reenforced by a linen filter firmly bound 

 around the lower end of the tube. The soil was lightly tamped as it was 

 filled into the tubes, so thot in each case the dry soil column had a final 

 depth of 2)H inches. The distilled water was delivered from a Bunsen 

 bottle suspended over the tube at such rate as to maintain a i-inch water 

 head above the level of the light, acid-extracted asbestos wad placed over 

 the soil to secure uniform entry of the liquid into the soil column and to 

 prevent spattering and superficial packing of the soil. Four such tubes 

 containing duplicate portions of the two soils were supported side by side 

 at room temperature (about 21° C), under like evaporation conditions, 

 and the percolation was continued until 500 cc. of percolate had been 

 obtained from each. The times required for the percolation differed 

 somewhat. 



The percolates were filtered until free from clay, and potash was then 

 determined as in the preceding solutions, with the following results: 



