Mar. 1, 1925 
Effect of Sulphur and Gypsum on Palouse Silt Loam 455 
These data reveal some interesting 
facts. Considering first, the results of 
experiment 1, it may be noticed that 
after three months there was only a 
slight oxidation of the elemental sul¬ 
phur, owing possibly to the cold tem¬ 
peratures prevailing during this time. 
From February to June the tempera¬ 
ture was more favorable for the activity 
of soil organisms, and a considerable 
portion of the elemental sulphur from 
both the small and large applications 
was changed to the sulphate form. 
Practically the same amount of sul¬ 
phates was produced from the small 
applications of uninoculated and in¬ 
oculated sulphur. Slightly more sul¬ 
phates were formed from the large 
application of inoculated sulphur than 
from the same amount of uninoculated 
sulphur. 
It was realized that the amount of 
rainfall percolating through the soil in 
the pots was not sufficient to remove 
all of the sulphur which had been 
changed to sulphates. Therefore, at 
the conclusion of the experiments, 
soil extracts were made from a com¬ 
posite soil sample from each pot in 
order to throw more light on the 
changes that the elemental sulphur 
had undergone in the soil. The data 
obtained from these extracts were 
added to the amount of sulphur re¬ 
covered in the drainage in order to 
get the total water-soluble sulphur. 
By examining the latter data it is 
noted, first, that after seven months 
approximately 200 lbs. of sulphate 
sulphur was obtained from the low- 
sulphur pots Nos. 3, 4, 5, and 6, and, 
second, that a little more than one- 
half of the 1,000 pounds of sulphur 
added to pots Nos. 7, 8, 9 and 10 was 
recovered as sulphates. 
These facts indicate that this soil 
has a very marked sulphofving power, 
which probably explains why the 
inoculated and uninoculated sulphur 
treatments produced almost the same 
quantity of sulphates. 
It may be well to recall that the soil 
in the pots in the greenhouse was 
maintained at optimum moisture con¬ 
ditions for a period of 72 days. Dur¬ 
ing this time conditions should have 
been extremely favorable for optimum 
microorganic activity, and the data 
given for experiment 2 show that such 
conditions did exist. The results for 
the small sulphur treatments agree 
almost perfectly with the data obtained 
from experiment 1. In the case of the 
larger sulphur additions it is surprising 
to note that the total 1,000 lbs. of 
sulphur which was originally added 
was recovered as sulphates after two 
and one-half months. The large 
sulphur treatments seemed to have 
had a marked influence also on sulpho- 
fication, as is shown by the increase in 
sulphur obtained over the amount 
added and the amount recovered from 
the untreated soils. These data also 
show that for this soil the uninoculated 
sulphur is just as effective as the inocu¬ 
lated sulphur in producing available 
sulphur for plants. 
A striking feature of the December 
analysis is that practically one-half of 
the sulphur added in the 1,000 lbs. of 
gypsum leached through the surface 
soil at the end of one month. After 
three months all of the sulphur 
originally added, and an appreciable 
quantity besides, appeared in the 
drainage water. By June the gypsum- 
treated soil showed a still further 
increase in sulphur in the drainage 
water when compared with the control. 
These results would seem to indicate 
that gypsum greatly increased sulpho- 
fication in this soil. The results 
obtained in the greenhouse for the soil 
treated with gypsum, however, do not 
agree with these findings, but show on 
the other hand that gypsum did not 
increase sulphofication. The data 
obtained from the field pots treated 
with gypsum present a strong argu¬ 
ment for the spring application of 
gypsum, because if applied in the fall 
it may be largely lost through leaching 
before the crop has a chance to make 
use of it. 
EFFECT OF SULPHUR AND GYPSUM ON 
POTASSIUM 
The results of the analyses of the 
drainage water and leachings for potas¬ 
sium are given in Table IV. 
An examination of the amount of 
potassium leached from the control 
soil indicates that the Palouse silt 
loam is not deficient in available potas¬ 
sium. All of the sulphur treatments 
caused small but decided increases in 
the amount of potassium appearing in 
the drainage water. The results of 
both experiments confirm this state¬ 
ment, although it is not known why so 
much more water-soluble potassium 
was present in the drainage water and 
water extracts from the field soils than 
was the case in the soils in the green¬ 
house. The process of making potas¬ 
sium available is certainly correlated 
with sulphofication, because, as shown 
by the analyses of the drainage water 
obtained during the different months, 
no effect on soil potassium was pro¬ 
duced until the end of June, or after 
appreciable quantities of sulphur had 
been oxidized. This statement is very 
