AVAILABILITY OF PCTTASH IN GROUND ROCK, 21 



mixture containing red clover, bastard clover (alsike), white clover, 

 and timothy grass. Even in the first year the grass developed vigor- 

 ously and produced vegetable matter, as shown in the table. An 

 average of 1 square meter of each of the two parallel plats was 

 taken. Fifty-four pounds of phosphoric acid were used on each plat. 



Plat 

 □um- 

 ber. 



Kind hikI inmiitily of fertilizer per acre. 



Without potash and with 357 pounds of basic slaj,'. 

 With 89 pouiKls of potash as potash manure salt . . . 



With 89 pounds of potash as ground feldspar 



With 17S pounds of potash as ground feldspar 



Greenvege- T,,prp„,p 

 'f™o"'- <1"eTopot- 



du*c%71°av. ^±:>iT 



crage of 2 

 plats. 



age of 2 

 plats. 



These figures show that this soil responded very weW to the appli- 

 cation of the soluble potash salts. "While it must be admitted that the 

 ground feldspar was somewhat available, the effect appears to have 

 been inconsiderable. 



It is hard to reconcile such contradictory results as these which 

 are given at length in the preceding pages. The only thing that can 

 be said at the present time is that careful and systematic tests are 

 required in order to determine finally to what extent and under what 

 conditions ground feldspar can be economically used in agriculture. 

 The inference to be drawn would seem to be that under certain 

 conditions finely ground feldspar is at least partially decomposed, 

 so that its potash becomes sufficiently available to be made use of by 

 certain crops. Under other conditions we are forced to the con- 

 clusion that ground feldspar is of little value as a potash fertilizer. 



Before proceeding Avith the description of experiments carried on 

 by the Department of Agriculture it will be necessary to define, as 

 briefly as possible, total and available potash, as the terms are com- 

 monly used. Potash is the name given to the oxid of the metallic 

 element potassium. The name is derived from the fact that potash 

 at one time was principally obtained by leaching wood ashes in large 

 iron pots. The letter K is used by chemists as the symbol for potas- 

 sium, the German name for which is Kalium. The oxid is written 

 KoO, which signifies that two atomic weights of potassium unite 

 with one atomic weight of oxygen to form potash. Potash as such is 

 a strongly caustic substance which unites with water to form a com- 

 pound technically known as lye. Fertilizers, both natural and arti- 

 ficial, contain potash, invariably combined with some acid to form a 

 compound or salt, such as sulphate, chlorid, carbonate, nitrate, phos- 

 phate, or silicate. Although potash (K.O) does not exist free 

 in a fertilizer, the potassium present in whatever, form is figured 

 and reported as total potash (KoO). Owing to the belief that has 



104 



