Aug. 19, X91S Availability of Potash in Soil-Forming Minerals 
313 
Table X .—Active potash of soil after two years ’ cropping 
Treatment. 
Potash 
carriers 
applied 
per pot. 
Calcium 
carbonate 
applied 
per pot. 
Potash 
recovered 
(p. p. m. of 
potassium 
oxid). 
Gain or 
loss due to 
calcium 
carbonate. 
Potassium sulphate. 
Gm. 
3 * 57 
7. 14 
7. 14 
7. 14 
21. 49 
42. 98 
42. 98 
42. 98 
19. 87 
39 - 74 
39 - 74 
39 * 74 
i 3 * 55 
27. 01 
27. ox 
27. OX 
12. 55 
25.10 
25.10 
25.10 
Gm. 
34*7 
55*9 
53*2 
$ 7-6 
24. 5 
32.6 
26. 6 
31*8 
21.8 
35-9 
33*4 
28.6 
13. 2 
15*2 
12. 5 
14. 6 
13. 0 
14. 8 
10. 8 
16. 0 
12. 9 
14. 2 
10. 8 
2 potassium sulphate. 
2 potassium sulphate plus calcium carbonate. 
2 potassium sulphate plus 2 calcium carbonate 
Riotite. 
16. 71 
33 * 42 
- 2.7 
+*•7 
2 biotite. .. 
2 biotite plus calcium carbonate. 
2 biotite plus 2 calcium carbonate. 
Muscovite. 
16. 71 
33 - 42 
—6. 0 
—0. 8 
2 muscovite. 
2 muscovite plus calcium carbonate. 
2 muscovite plus 2 calcium carbonate. 
Orthoclase... 
16. 71 
33 * 42 
“2. 5 
- 7*3 
2 orthoclase. 
2 orthoclase plus calcium carbonate. 
2 orthoclase plus 2 calcium carbonate. 
Microcline... 
16. 71 
33 * 42 
-2. 7 
—0. 6 
2 microcline. 
2 microcline plus calcium carbonate. 
2 microcline plus 2 calcium carbonate. 
Control (no potash). 
16. 71 
33 * 42 
-4.0 
+1.2 
Control (no potash) plus calcium carbonate.. 
Control (no potash) plus 2 calcium carbonate. 
16. 71 
33 * 42 
+ i *3 
- 3*4 
SUMMARY 
The chief points brought out by this investigation are as follows: 
(1) Little difference in the solubility of potash in water is found among 
the common soil-forming minerals: Biotite, muscovite, orthoclase, and 
microcline. 
(2) Biotite and muscovite give up considerably more of their potash 
to solutions of carbonic acid than do orthoclase or microcline. The 
order in which potash is removed by this solvent is biotite, muscovite, 
orthoclase, and microcline. 
(3) Lime as calcium bicarbonate does not increase the solubility of 
potash in any of the above minerals. 
(4) Pot experiments which include the growth of four crops—oats, 
soybean, rye, and cowpea—that have had potash supplied in the form of 
♦minerals show that these plants can extract different amounts of this 
element from them. Biotite is able to produce four times the amount 
of dry matter of oats as microcline and 66 per cent as much as potassium 
sulphate. Muscovite produces nearly twice as much dry matter as 
orthoclase. The same general effect is caused from these carriers of 
potash with rye. 
(5) Lime in the form of precipitated carbonate has not materially 
increased the dry matter or the potash removed from the soil by oats or 
