CONCENTRATION OF POTASSIUM IN ORTHOCLASE 

 SOLUTIONS NOT A MEASURE OF ITS AVAILABILITY 

 TO WHEAT SEEDLINGS 



By J. F. BreazealE, Associate Biochemist, and Lyman J. Briggs, Physicist in Charge, 

 Office of Biophysical Investigations, Bureau of Plant Industry, United States Depart- 

 ment of Agriculturt 



The object of the experiments described in this paper was to deter- 

 mine the availability of the potassium in solution of orthoclase by growing 

 wheat seedlings in aqueous orthoclase solutions, analyzing the seed- 

 lings for potassium, and comparing the results with those obtained from 

 suitable controls. The results show that the potassium present in solu- 

 tions of orthoclase is not appreciably absorbed by young wheat plants. 

 The conclusion is reached that potassium may be present in soil solu- 

 tions in such combination with other elements that it is not available to 

 plants. 



The orthoclase used in our experiments was obtained near Riverside, 

 Calif., and contained a total of 12.5 per cent of potassium oxid (K 2 0). 

 It was ground to pass a 60-mesh sieve. Different samples when brought 

 into equilibrium with water and analyzed 1 contained from 2 to 9 parts 

 per million of soluble potassium, the saturation concentration not being 

 definite. There was, however, always some potassium present in the 

 aqueous solutions, the average concentration being about 4 parts of po- 

 tassium oxid per million of solvent. 



The wheat was germinated on perforated aluminum disks floated on 

 water. When the plumules were about ]/ 2 inch long the seedlings were 

 transferred to other aluminum disks in the pans containing the culture 

 solutions. This early transfer prevents the young seedling plants from 

 absorbing the potash which exudes form unsprouted seeds. 



The method of experimentation was, in general, to compare the potas- 

 sium content of wheat seedlings grown in orthoclase solutions with that 

 of similar seedlings grown in distilled water or other suitable control 

 solution free from potassium. 



SOLUBLE POTASSIUM IN ORTHOCLASE NOT AVAILABLE TO WHEAT 



SEEDLINGS 



Wheat cultures were grown in orthoclase solution with and without 

 the addition of gypsum and were compared with cultures grown in dis- 

 tilled water alone and in distilled water to which gypsum had been added. 

 (See Table I, series a.) Although the orthoclase solutions were known 



1 The J. Lawrence Smith method was used in the analysis. 



Journal of Agricultural Research, Vol. XX, No. 8 



Washington, D. C Jan, is, 1921 



win Key No. G-216 



(615) 



