Aug. i 9t 1918 Availability of Potash in Soil-Forming Minerals 
305 
a porpss/oyy scrip/Mra 
a porpss/otf sc/ip/zpra+ca co 3 
a s/or/rs 
a a/or/ra+ca co 3 
a sft/scowrs 
a/wscowra+oz co 3 
These data show quite conclusively that the oat plant is capable of 
extracting potash from the soil minerals at different rates. When the 
greatest yield, 2 potassium sulphate and 2 calcium carbonate, is given 
the rank of 100, the following order of plant growth is obtained: Two 
biotite plus 2 calcium carbonate reaches 69; 2 muscovite alone 53; 2 
orthoclase alone 31.8; 2 microcline plus calcium carbonate 15.8; and 
no potash without cal¬ 
cium carbonate 11.3. 
This soil responds 
markedly to potash 
fertilization, as shown 
by the oat yields. Sol¬ 
uble potash produces 
growth to the extent 
of 44.8 gm. per pot; 
where no potash mate¬ 
rial is applied only 5.1 
gm. per pot is secured. 
To judge from the 
plant growth, lime has 
not made available 
any of the insoluble 
potash applied in the 
form of minerals. In 
many instances the 
yield has been slightly 
reduced where the car¬ 
bonate has been used. 
The results of plant 
growth fertilized with 
double applications of 
potash and lime are 
shown graphically in 
figure 1. 
Considerably more potash has been recovered in the crop when applied 
in the soluble form. The order of potash recovery follows the same 
order as crop yield, biotite showing the greatest and microcline the least. 
Time has not increased this recovery in any of the treatments (PI. 49, A). 
2 OPr//OCLPSS 
20 Pr//0ClPS£+Cct co 3 
2 M/CPOCL//VS 
2ff/CPOCl/A!£+Ca co s 
COA/TPOl 
\ooA/rpoL +ca co 3 
Fig. i.—R ate of growth of oats under similar conditions fertilized with 
double applications of potash minerals and calcium carbonate. 
Soybean Crop 
After harvesting the oats the quartz mulch was removed; the roots of 
the oats were finely ground and mixed thoroughly with the soil. 
All pots were inoculated with as nearly the same number of a pure 
culture of Bacillus radicicola as could be done. 
On June 19, 10 seeds of Mammoth Yellow variety of soybean were 
seeded to each pot. These were drawn down after germination to a 
