SOILS FEBTILIZERS. 323 



opposite effect. Calcium sulphate and chlorid reduced loss solely by their 

 direct action on the ammonium carbonate. 



The chlorid was the only salt of magnesium which reduced loss of ammonia. 

 Potassium and sodium chlorids, sulphates, and carbonates, as well as Ivainit and 

 Thomas slag, reduced the absorptive power of the soil. Treatment with alcohol 

 was without effect. On the other hand steaming, and especially igniting, had 

 a marked effect. 



The effect on absorption was dependent not only upon the bases but upon 

 the nature of the acids with which they were combined. The absorptive power 

 of the soil appears to be dependent mainly upon the exchange of bases in the 

 zeolite compounds. The more rapid the aeration the greater was the loss of 

 ammonia. The character of the soil exerts a great influence not only on the 

 absorption of anunonia but on the action of lime on the absorption, rendering 

 the addition of lime favorable, unfavorable, or without effect. See also pre- 

 vious notes (E. S. R.. 21, p. 417; 26, p. 320). 



The active potash of the soil and its relation to pot experiments, G. S. 

 FRAPS (Texas Sta. Bui. tJ,5, pp. 39, figs. 3).— The results of studies of the active 

 potash in soils as measured by the solubility in fifth-normal nitric acid are 

 reported, and the analytical data compared with crop yields in pot experiments 

 with different crops on a large number of Texas soils. During the course of 

 the work a study was made of the solubility of potash of a number of minerals 

 which may be present in the soil. The method of conducting the pot exi)erimen!s 

 was substantially the same as that employed in studies of the active phosphoric 

 acid (E. S. R., 23, p. 423). The author summarizes his results as follows: 



"The potash of nephelite, leucite, glauconite, biolite is completely extracted 

 by strong hydrochloric acid. About one-third of the potash of muscovite is ex- 

 tracted and only a small percentage of the potash of microcline and orthoclase. 

 Practically no potash is removed from orthoclase and microcline by fifth-normal 

 nitric acid, less than 10 per cent from glauconite and biotite, and from 15 to 60 

 per cent from muscovite, nephelile, leucite, apophyllite, and phillipsite. 



" Potash dissolved by fifth-normal nitric acid from soils represents a portion 

 of the potash in the easily decomposed minerals. From 36 to 100 per cent of 

 the potash absorbed from aqueous solution by certain minerals was extracted 

 by fifth-normal nitric acid. Two per cent ammonia dissolved from 9 to 45 per 

 cent of the potash absorbed by minerals. 



" Tlie potash extracted represents the difference between the potash dissolved 

 and that fixed from the solution. The fixation of potash from fifth-normal 

 nitric acid Is much less than the fixation of phosphoric acid from the same 

 solvent. The potash extracted from the soil by successive treatments with 

 fifth-normal nitric acid at first represents easily soluble potash, and is finally 

 reduced to the small amount of potash dissolved from highly insoluble minerals. 

 Increasing the quantity of potash mineral to a fixed amount of solvent increases 

 the quantity of potash extracted, but the percentage of the potash extracted 

 decreases. 



" The quantity of potash extracted by fifth-normal nitric acid below 50 parts 

 per million represents 1 to 2 per cent of the potash of highly insoluble silicates. 

 The quantity extracted in excess of approximately 50 parts per million repre- 

 sents a comparatively large percentage of a much smaller quantity of more 

 easily soluble potash. 



" The potash extracted by fifth-normal nitric acid from the soil is not neces- 

 sarily in the same form of combination in different soils and does not neces- 

 sarily have the same value to plants. . . . 



56022°— No. 4—12 3 \ 



