AVAILABILITY OF POTASH IN GROUND ROCK. 



17 



feldspars. TIk' itots used for the exiK-riinciits were like those used in the 

 phosphate experiments. They were also tilled la the same manner, havinf; 

 first a layer of gravel at the bottom and above this 0;j pounds of quartz sand, 

 with the last i{5 pounds of which were mixed the experimental fertilizers. 



Three pots. 1. 5, and 0. were supplied ea<-h with 10 •grains of feldspar carry- 

 ing 11.1)1 per cent of potash, 10 grams of nitrate of soda, and 10 grams of acid 

 South Carolina rock. Three other pots, 13, 17, and 20, were fertilized with 20 

 grams of feldsi)ar and the same amount of nitrate of soda and acid phosphate 

 as was supplied to 1, .">. and J). In these pots were i»Ianted oats. When the oats 

 were 2 or '.i inches high they were thinned out to IS plants per pot. The 

 pots were watered in the same manner as were those in which the exi)eriment 

 with phosphates was conductetl. 



In the table below art' shown the results of substituting muriate of potash 

 for feldspar as a source of potash : 



Kind and quantity of fertilizers. 



10 grams feldspar 



10 grams nitrate of soda 



10 grams acid Soulh Carolina rock 



20 fjrams feldspar 



10 grams nitrate of soda 



10 grains acid South Carolina rock 



3 grains muriate of potash 



10 grams nitrate of soda 



10 grams acid South Caroliua rock 



Yield of 



straw, in 



grams. 



47 

 43 

 47 

 47 

 47 

 52 

 07 

 72 

 65 



The pots receiving 10 grams of feldspar produced, on the average, about 79 

 per cent of the average of the grain produced by those pots receiving 3 grams 

 of uuuiati> (if potash having 50 per cent of actual potash. The amount of 

 grain was not increased by increasing the feldspar to 20 grams, though there 

 was a slight gain in straw. 



The conclusion to be drawn from the experiment is that the oats were able 

 to draw from the feldspar potash enough for a large crop of grain. If this 

 conclusion is verified by future work, some of our feldspars nia.v prove a cheap 

 source of ijotash to the farmers of the State. 



Examination of the figures given in the above table shows that 

 the potash from the feldspar iindonbtedly became available, but was 

 not as efficient as that from the more soluble muriate. 



In 1889, the same year that the results of these experiments were 

 made public, Xilson " in Sweden published an investigation in which 

 fine-ground feldspar prepared for the potteries Avas tested in com- 

 parison with potassium sulphate. Oats were used, and the experi- 

 ments were carried out on the Swedish moor soils, which, in a dry 

 condition, already contained 0.5 per cent of potash, although only 

 0.03 per cent of this was soluble in dilute acid. There w^ere 300 

 kilograms (660 pounds) of slag phosphate, 50 kilograms (110 

 pounds) of nitrogen in the form of Chile saltpeter, and 80 kilo- 

 grams (176 pounds) of potash as sulphate or 200 to 300 kilograms 



« Landtbr. Akad. Haudliugar och Tidskr., 1889. 

 1889, 18, 608. 

 104 



See also Centbl. Agr. Chem., 



