Aug. 19.1918 Availability of Potash in Soil-Forming Minerals 
3 ” 
Table) IX .—Weight of cowpea crop and potash removed from soil —Continued 
Dry matter (grams). 
Treatment. 
Whole 
plant. 
Aver¬ 
age 
total. 
Rela¬ 
tive 
rank of 
aver¬ 
age. 
2 othoclase. 
0. 6 
Do. 
y 
11. 2 
10. I 
23. 0 
Do. 
0. 4 
2 orthclase plus calcium carbonate... 
Do. 
14. 6 
16. 6 
16. I 
36.4 
Do. 
17. 8 
i 5 *o 
16. 0 
2 orthoclase plus 2 calcium carbonate. 
Do. 
16. 3 
3 6 -S 
Do. 
17.9 
4. 8 
Microcline. 
Do. 
e. 6 
- 3 . 3 
12.4 
Do. 
6. 2 
0 D 
2 microcline. 
4.0 
Do. 
4.0 
4.6 
10. 5 
Do. 
5-9 
9*4 
ID. 2 
2 microcline plus calcium carbonate.. 
Do. 
9*4 
21. 4 
Do. 
8. 6 
2 microcline plus 2 calcium carbonate. 
Do. 
10. 0 
IO. 2 
Q. 6 
21. 8 
Do. 
8. 6 
1 
Control (no potash). 
5 * 0 
{ 
Do.t.'.. 
\ 4. 6 
Do. 
A* 0 
f 
Control (no potash) plus calcium car¬ 
bonate . 
10. 0 
Do. 
7.2 
00 
C/l 
19*3 
Do. 
8 3 
Control (no potash) plus 2 calcium 
carbonate. 
8. 3 
Do. 
0. 6 
8.3 
18.6 
Do. 
y 
7.2 
Potash removed (grams). 
Whole 
plant. 
0*153 | 
. 160 > 
• 142 1 
. 202 1 
• i 74 | 
. 210 J 
. 222 ] 
•i 97 \ 
.184 J 
.081 | 
.091 } 
.094 J 
.068 } 
. 084 [ 
. 082 J 
.108 ] 
.110 !• 
.096 J 
• 113 ] 
. 114 \ 
.092 j 
.090 1 
. 084 } 
.078 J 
.108 ] 
. 102 > 
• 105 J 
. 101 ] 
• 103 f 
.096 J 
Average 
total. 
Aver¬ 
age gain 
over 
no 
potash. 
O. 152 
O. 068 
•195 
. Ill 
. 201 
. 117 
.088 
. 004 
. 078 
None. 
. 105 
. 021 
. 106 
. 022 
. 084 
.105 
. 021 
. IOO 
. 016 
Though the results are not as pronounced from cowpeas as with soy¬ 
beans, the same general effect is produced Biotite and muscovite lead 
the insoluble minerals as carriers of potash. Orthoclase still seems to 
show a slight lead over microcline and where potash-carrying minerals 
were applied. 
Lime has produced large increases where soluble potash is added, but 
its effect is not so great with the micaceous material as when soybeans 
were grown. This would indicate that, through the forces of weathering, 
a protective covering had formed around the particles of mica, preventing 
the plant roots from extracting as much potash as was done when the 
preceding legume was grown. 
The rates of growth of cowpeas of the double applications of potash 
and lime are graphically given in figure 4. 
