May, '14] 



GRANITIC SOIL POTASSIUM. 



21 



These data show that dilute solutions of sodium nitrate, sodium 

 chloride, sodium carbonate, and acid phosphate, in contact with 

 these soils, liberate potassium in considerable amounts. The date 

 in Table XV was secured to determine the effect of commercial 

 acid phosphate on the solubility of the soil potassium. A sample 

 was found which contained no potassium, and the soluble phos- 

 phate extracted with water. The free acid was neutralized with 

 lime, the solution filtered and standardized. 



As already stated, these data could not be obtained from field 

 work because of the relatively small amounts of fertilizer generally 

 used. There is, however, no reason to believe that these same 

 reactions do not take place under field conditions. The solu- 

 tions used in these experiments, while dilute, are much more 

 concentrated than soil solutions, excepting under special condi- 

 tions. Nitrate of soda and acid phosphate solutions are very 

 active in their effect on potassium. This has a very practical 

 bearing in relation to crops grown in connection with nitrate and 

 acid phosphate fertilizers. In order to determine the effect of 

 calcium carbonate and calcium sulphate, these salts were mixed 

 dry with the soil at the rate of 1 gram per 100 grams of soil. 

 Distilled water was percolated through and the percolate exam- 

 ined for potassium. 



The data in Table XVI as well as other observations made 

 in this laboratory show that calcium oxide and calcium carbon- 

 ate do not liberate potassium from these soils. Some observa- 

 tions have indicated a decreased solubility. A limited number 



