A Study of Colorado Wheat 
27 
eighth, eighteenth and twenty-fifth were chosen. The method of 
extraction was with hydric chlorid, specific gravity 1.115, for ten 
hours. Two samples out of each four were treated a second time, 
namely, samples 8 and 18 of each block. The second extraction 
takes up a further quantity of each of these substances, but particu¬ 
larly of the potash. We were aware of this fact before we made 
these analyses. The new portion of potash unquestionably comes 
from the progressive decomposition of the felspar. This fact puts 
every potash determination made in our soils by this method in more 
or less doubt. I do not believe, however, that it is a serious matter, 
for the amount of potash involved is so large that a considerable 
mistake will matter but little, besides, even fresh felspar yields pot¬ 
ash to plants or even to water, so that a mistake of 10 to 15 percent 
of the total potash involved does not in this case seem to me a very 
serious matter. For the sake of clearness and brevity, I shall give 
only the twelve'results obtained by the double extraction as suffi¬ 
cient to show the variation in the amounts of phosphoric acid and 
potash within small, consecutive areas to a depth of one foot. It 
has already been explained that each block is five feet square and 
contains twenty-five square feet, which are numbered from left to 
right, beginning at the upper left-hand corner. 
VARIATION OF PHOSPHORIC ACID AND POTASH IN CONSECUTIVE AREAS 
Phosphoric Acid 
Potash 
Block 
Sample 
Percent 
Percent 
1 
8 
0.140 
0.775 
1 
18 
0.140 
0.736 
2 
8 
0.143 
0.745 
2 
18 
0.143 
0.785 
3 
8 
0.132 
0.751 
O 
O 
18 
0.157 
0.713 
4 
8 
0.134 
0.722 
4 
18 
0.145 
0.787 
5 
8 
0.147 
0.743 
5 
18 
0.145 
0.745 
6 
8 
0.131 
0.698 
6 
18 
0.153 
0.739 
The variation in these results for the phosphoric acid extracted 
from the soil by this method is 0.026 percent, and for the potash 
0.089 percent. The absolute amounts of phosphoric acid and potash 
indicated by these percentages are sufficient to have, possibly, some 
influence, but we can scarcely think that we are justified in laying 
any stress upon them, because we know that their common source is 
the felspar and we cannot regulate the extent to which the solvent 
shall act upon it in a given time. The quantities actually involved 
are, for the phosphoric acid, 1040 and, for the potash, 3560 pounds 
for the acre-foot of soil sampled; whereas the total quantities solu¬ 
ble in the solvent used, are about 5600 pounds for the phosphoric 
