AVAILABILITY OF POTASH IX GROUND ROCK. 



19 



1 niilliniotor in diameter to an inijalpaltle powder. Tliis was mixed with 

 pure (luartz sand. Hone ash was used to snpidy lime and pliesplioric acid. 

 The sample used contained n<» potasli. Nitrate of lime furnished the nitrogen. 

 Chlorine was furnished l>,v a minute »iuantit.v of calcic chloride. Distilled 

 water was used throujrhout the experiment. 



The plants grew healthily in this mixture until the Hoors of the huilding were 

 oiled and the room in which the plants wcn> growing was shut up and hecame 

 too warm; these two things together gave them a decided setback, and later 

 a thrips. 7'7(r//>.s striata according to Professor (lillette, attack(»d the plants and 

 did them mucli damage. Some of the ]»lants. however, seeded. 'I'hey were 

 harvested, though in had condition and very uneven in the degree of their de- 

 velopment. The root system was well developed, the sand being tilled with the 

 roots. The weight of the toi)s as harvt'sted was I'.tS.,") grams; that of the roots 

 as washed out was 4t> grams. Tlie tops and roots were iiicinerati'd together 

 and yielded ri.T'.)."; jxt cent of solulile and D.SO.*? per cent of insoluble ash. a total 

 of 15..WS ]>er cent. 



Examination of the feldspars used showed the jtresence of 11.993 per cent of 

 potash and I'.'.iSS per cent of soda. I'hosiiiioric and sulphuric acids were present 

 in very small (luantities; the former e(inaled 0.041 i)cr <cnt and the lattei' 0.003 

 per cent of the feldspar. 



The nitrogen in the oat hay. roots inc 

 The ash gave the following analysis: 



l'(>r cent. 



Carban __ o. IT 



Sand S. 1.'. 



Silicic acid 1."). 7."1 



Sulphuric acid 4.41 



Phosphoric acid 3. 98 



Carbonic acid 15. 3r> 



Chlorine 2. 73 



Potassic oxide 15.95 



Sodic oxide 4.62 



udcd. was ."..2.54.". per cent. 



I'pi- cent. 



Calcic oxide 21.70 



Magnesic oxide 3.90 



Ferric oxide .96 



Ahmiinic oxide .31 



Manganic oxide . 16 



Ignition 2. 61 



100. 71 



This ash is very anomalous in its composition as well as. in the quantity 

 present in the plants. The plants were not evenly matured at the time of gath- 

 ering and were in l)ad condition. The question we endeavored to investigate, 

 however, is perfectly answered by the results, i. e.. the oat plant can use the 

 finely divided feldspar as a source from which to obtain potash, for in this 

 experiment, made under very adverse conditions, we found that the oat plants 

 took from the feldspar 1.4417 grams of potash. The potash added in tlie seed 

 has been deducted. The silicic acid appropriated by the plant indicates the 

 decomposition of the silicate. 



In 1905 Prianischnikow,* a Russian investigator, published the 

 results of a series of pot tests using feldspar and mica as sources of 

 potash. The feldspar used was ground so that it was less than 0.25 

 mm. in diameter, corresponding to an 80-mesh sieve. The material 

 was mixed with sand and the other foods added in the form of phos- 

 phates and nitrates of lime and soda. The cultures used were tobacco, 

 buckwdieat, flax, peas, sunflowers, and barley. The tabulated results 

 are too voluminous for insertion here, but they appear to show that 



o Landw. Vers. Stat., 1905, 63, 151. 



104 



